Leatherback aggregation and feeding on the Southwest Shelf Edge and Slope

Transcription

1 Leatherback aggregation and feeding on the Southwest Shelf Edge and Slope Potentially Harmful Activity (X) Potentially Harmful Stressor (X) Bottom trawl X Oil pollution X Fishing (groundfish, shrimp) Scallop dredges Marine Industrial effluent Clam dredges pollution Fishplant effluent Midwater trawl X Sewage Gillnets (bottom) X Historic military waste Gillnets (pelagic) Long range transport of nutrients Long line X Acid rain Scottish seining X Persistent Organic Pollutants (POPs) Purse seining X Eutrophication Recreational cod fishery Ghost nets X Crab pots X Litter X Lobster pots Other contaminants (specify) Whelk pots Ice distribution Otter trapping Climate Temperature change Other Change Seal hunt Sea-level rise harvest Seabird hunt Ocean acidification Seaweed harvest Current shifts Anchor drops/drags Increased storm events Seabed Ore spill Increased UV light alteration Fish offal dumping Oxygen depletion Finfish aquaculture Changes in freshwater runoff Dredge spoil dumping Other (specify) Dredging Green crab Mining/Oil & gas drilling Harmful Membranipora species Cables Golden Star Tunicate Freshwater diversion Violet Tunicate Subtidal construction Vase Tunicate Coastal Intertidal/coastal Codium fragile alteration construction Clubbed Tunicate Other (specify) Didemnum Vessel traffic X Toxic Algal Blooms Disturbance Ship strikes X Disease organisms (human waste) Ecotourism Disease organisms (aquaculture) Marine construction Other (specify) Seismic surveys X Other Navy sonar X Other (specify) 1

2 Background Information Three species of sea turtles are known to occur on the Grand Banks. They are the leatherback, the loggerhead, and the Kemp s Ridley turtle. The leatherback and Kemp Ridley turtles are listed as endangered and the loggerhead turtle is listed as threatened (Templeman & Davis, 2006).The leatherback turtle is officially listed by COSEWIC as endangered and Leatherback turtles are listed as Endangered under Schedule I of SARA, which results in legal protection and mandatory recovery requirements a priority species under the 2003 Species At Risk Act (SARA) (Atlantic Leatherback Turtle Recovery Team, 2006). The leatherback turtle is classified as critically endangered by the International Union for the Conservation of Nature ( and listed as a depleted and rare species in the CP document. The leatherback turtle is the world s largest reptile, the only sea turtle with no claws on their flippers, and the only sea turtle that does not have a hard shell or scales (Under Water World). Although they do not nest in Canada (Templeman & Davis, 2006), Canadian waters support one of the highest summer and fall densities of leatherbacks in the North Atlantic, and should be considered critical foraging habitat for this endangered species (James et al., 2006). The Atlantic population appears to be more stable, but shows dramatic fluctuations in the number of nesting females from year to year. There are no good population estimates for leatherbacks in Canadian waters (COSEWIC & James, 2001). From , fishers and other mariners reported 851 geo-referenced sightings of free-swimming or entangled leatherback turtles in Atlantic Canada. Sightings principally corresponded to the Scotian Shelf, mainly reflecting reporting by fishers in Nova Scotia. However, smaller number of sightings was also reported outside of the principal study area, including coastal Newfoundland and slope waters south of Nova Scotia (James et al., 2006). Leatherbacks depend on prey with very little nutritive content and since this species diet of jellyfish is high in water and low in organic content, they must consume large quantities of food (Lutcavage, 1996) to fulfil their food energy requirements. This is the only known biological limiting factor in Canadian waters (Atlantic Leatherback Turtle Recovery Team, 2006). Leatherbacks breathe air, and also spend time basking, resting and feeding at the sea surface. In Canadian waters satellite tracking studies have shown that leatherbacks spend between 1-35% of their time on the surface (James et al., 2005a). The primary determinant of movement and behaviour of leatherbacks is the spatial and temporal distribution of their primary prey, gelatinous plankton generally known as jellyfish. In general jellyfish abundance is lower in pelagic vs. coastal waters, however, physical transport of jellyfish can create local aggregations, particularly at physical discontinuities such as shelf breaks and upwelling zones (James et al., 2005b). Jellyfish are planktonic, generally floating in surface waters, but in deep offshore areas may be occur at considerable depths, and leatherbacks foraging in shelf waters off Canada appear to search for and capture much of their prey at depth, before returning to the surface to consume it (James et al., 2005a). 2

3 Figure 1. Diving behaviour of two leatherback turtles tagged in coastal waters off Nova Scotia, Canada: Proportion of time (per 6 h sample) spent in different depth ranges (James et al., 2005a). This pattern of foraging behavior is consistent with the high proportion of time spent at the surface in northern waters (Figure 1). Increased surface time at northern latitudes may also reflect basking, as we have routinely observed turtles resting at the surface during the middle part of the day and evening with both front and rear flippers extended and their heads lowered in the water. There is evidence that leatherbacks do not feed exclusively at the surface. In fact turtles equipped with time-depth recorders have been recorded diving beyond 1000m. This deep diving behavior may reflect nocturnal foraging for jellyfish and other softbodied invertebrates within the deeper water layers (COSEWIC & James, 2001). Leatherbacks will readily consume a variety of edible and inedible slow-moving and buoyant objects. Though this behavior is adaptive in exploiting large concentrations of jellyfish, these turtles regularly mistakenly ingest plastic bags and other floating marine debris. Marine debris accumulates at convergence zones, where prey is also naturally concentrated. Ingestion of plastics, styrofoam and other waste can be fatal (COSEWIC & James, 2001). The leatherback s insatiable appetite and foraging curiosity also may lead to entanglement in fishing gear. Front flipper entanglement in ropes and cables is common, and this may result from turtles approaching buoys and biting at them. Leatherbacks may also become entangled after being attracted to the jellyfish that foul fishing gear (COSEWIC & James, 2001). Of all Atlantic sea turtle species, leatherback seem to be most vulnerable to entanglement in fishing gear such as pelagic longlines, lines associated with fixed ear (pots, traps, gillnets), buoy anchor lines and other ropes and cables (Atlantic Leatherback Turtle Recovery Team, 2006). Their specialized diet may make leatherbacks vulnerable to ingestion of plastics and other buoyant marine debris. Whether or not such ingestion is deliberate, since these materials may resemble their soft-bodied prey the magnitude of the threat that ingestion of marine debris poses may be grossly underestimated (James & Herman, 2001). A new study looked at necropsy reports of more than 400 leatherbacks that have died since 1885 and found plastic in the digestive systems of more than a third of the animals. Besides plastic bags, the turtles had swallowed fishing lines, balloon fragments, spoons, candy wrappers and more (Discovery News online). 3

4 The leatherback's diet of jellyfish may help conserve fish species. Leatherbacks help keep the jellyfish population under control. This is significant not only because jellyfish compete with larval fish for food (both eat zooplankton), but because jellyfish are also known predators of larval fish (James et al., 2005a) (James et al. 2005). Figure 2.Occurrence of the leatherback turtle, Dermochelys coriacea, off eastern Canada. Shaded areas show the location of concentrations of observations (Atlantic Leatherback Turtle Recovery Team, 2006) (Atlantic Leatherback Turtle Recovery Team, 2006) 4

5 Table 2. A summary of natural and anthropogenic impacts on sea turtles(noaa, 2003). In Canada, aerial surveys are required to assess regional patterns and long-term trends in leatherback abundance, to help identify areas of turtle concentration at smaller scales, and to evaluate the spatial and temporal overlap between leatherbacks and the human activities that impact them (James et al., 2006). Scoping Bottom trawl: Bottom trawl fisheries are the single greatest human threat to leatherback sea turtles. In the USA, (estimates for the Mid-Atlantic) an average of 770 sea turtles are captured each year in trawl fisheries (Griffin et al., 2008). There are currently no legally-binding measures in place by any IGO that require fishing vessels to implement sea turtle avoidance methods (Gilman et al., 2007). On average, an estimated 770 sea turtles are caught annually in Mid-Atlantic bottom trawl fisheries in the USA. Of these fisheries, only the summer flounder fishery is currently required to use TEDs (turtle excluding devices) (Griffin et al., 2008). In addition to the TED regulations, the U.S. also established a leatherback turtle Conservation Zone in 1995 to restrict trawl activities on the Atlantic coast during periods when leatherbacks are concentrated (Atlantic Leatherback Turtle Recovery Team, 2006). Of all the Atlantic sea turtle species, leatherbacks seem to be the most vulnerable to entanglement in fishing gear such as pelagic longlines, lines associated with fixed pot gear and gillnets, buoy anchor lines, and other ropes and cables. The leatherback has never 5

6 developed the ability to swim backwards. This poses some difficulty when it encounters fishing nets and lines in the ocean because it has no hope of backing out of them (Underwater World). Leatherback interactions have been observed in the shrimp trawl and other bottom trawl fisheries (Atlantic Leatherback Turtle Recovery Team, 2006). There is evidence of only one leatherback turtle entanglement in otter trawl gear in the Northwest Atlantic in Ledwell & Huntington (Ledwell & Huntington, 2007). The Recovery Strategy for the Leatherback Turtle in Atlantic Canada (2006) does not list bottom trawl as one of the gear types with high potential for sea turtle interaction (Table 1), and the 2006 Whale and leatherback sea turtles incidental entrapment in fishing gear in Newfoundland report only listed one entanglement. Screened out. Gillnets (bottom): Gillnets are fixed gear, and consist of vertical walls of mesh, with mesh openings sized such that target species in the desired size range are caught as they attempt to swim through the webbing, entangling their gills. Bottom gillnets are secured in direct contact with the seafloor by weights and have a high incidence of bycatch. Within the EBSA, offshore license holders are limited to nets that are 91m in length and are usually joined together (Appendix A, Table 5). This amounts to a maximum of 36.4 km of net per license holder. Gillnets are used extensively in the area of the EBSA, moreso than anywhere else in the LOMA, and are responsible for 30% of landings by weight in this EBSA over the period (Fisheries and Oceans Canada, 2008). Edinger et al. (2007) state that peak areas of gillnet use in the Newfoundland Region were found along the Southwest Grand Banks (Edinger et al., 2007). The main directed fisheries using gillnet in the EBSA targeted monkfish, Greenland halibut, skate and white hake. Leatherbacks may become entangled after being attracted to the jellyfish that foul fishing gear (COSEWIC & James, 2001). These incidents can result in serious injuries (rope or cable cuts on the shoulders and front flippers) or death by drowning. The leatherback has never developed the ability to swim backwards. This poses some difficulty when it encounters fishing nets and lines in the ocean because it has no hope of backing out of them. Entanglement in fishing gear at any time can result in serious injuries to the turtles, including severe cuts and necrosis (death) of the tissue, which could lead to the loss of a flipper; entanglement can also lead to death by drowning. Unlike other smaller species of sea turtles, leatherbacks are sometimes strong enough to drag large amounts of fishing line and gear to the surface of the water, where they are discovered and released (Fisheries and Oceans Canada, 2004). There are currently no legally-binding measures in place by any IGO that require fishing vessels to implement sea turtle avoidance methods (COSEWIC & James, 2001). An estimated 3000 leatherback interactions with artisanal gillnet fishing gear occurred off Trinidad in 2000, with reported mortality rates of 28 34%. Turtles that forage in northern waters of the western Atlantic are among those at risk in these southern coastal areas (James et al., 2005b). 6

7 Although the fine scale distribution and movements of turtles on the Grand Banks are not well known, data indicates that the edge of the shelf is an important area for sea turtles (Atlantic Leatherback Turtle Recovery Team, 2006). During a two-year programme of enhanced observer coverage levels, 22% of the records involved mooring or buoy lines associated with bottom gillnets, bait nets and pound nets of other fish traps. Screened in. Longline: Bottom longlines are fixed gear, and consist of a single mainline to which shorter lines armed with baited hooks, are attached (maximum of 6,000). Anchors attached to the longline secure the gear to the ocean floor. The directed fisheries using longlines in the EBSA target skate, white hake, Atlantic halibut, Greenland halibut and large pelagics. Longlines are often deployed deeper than trawls (>500m), precisely targeting rough-bottom ( un-trawlable ) areas. Longline fisheries are concentrated on the Southwest Shelf Edge and Slope and are deployed in a range of depths throughout much of the EBSA, precisely targeting roughbottom areas. Based on observer data for the Newfoundland and Labrador region, average depths fished with longline in the offshore are 867m for Atlantic halibut and 1,070m for Greenland halibut (Wareham & Edinger, 2007), although annual Conservation Harvest Pans may include specific depth provisions for a given fishery or area. Longline is responsible for only 7% of landings by weight over the period within the EBSA, with an annual average landing of 343t (Appendix A, Table 16). Leatherbacks are one of the world's deepest-diving vertebrates. The maximum recorded dive depth for a leatherback is 1,270 metres (Fisheries and Oceans Canada, 2004). Turtle interactions are well documented in longline fisheries targeting swordfish and tunas. Leatherbacks become entangled in longlines, buoy anchor lines, and other ropes and cables. These incidents can result in serious injuries (rope or cable cuts on the shoulders and front flippers) or death by drowning. Leatherback turtles are known to be present in the area of the EBSA between June and November, although some literature reports sightings all year round (Templeman & Davis, 2006). Several longline fisheries overlap with leatherback feeding. Swordfish longlines snare turtles at 10 times the rate of those targeting tuna, as the latter are set deeper than depths turtles frequent. Marine biologists at Duke University estimate that if longlining continues unabated, there is a 50 percent chance of turtle extinctions in the next 10 to 30 years, notably the leatherback turtle and their decline is strongly linked with longline fisheries (Wildlife Conservation Society, 2005). Estimates of incidental capture of leatherback turtles in the entire Atlantic Ocean range from 30,000 to 60,000 for offshore pelagic longline fleets in 2000 (Atlantic Leatherback Turtle Recovery Team, 2006). Turtle interactions do not appear to occur in Canadian pelagic longline fisheries targeting shark, but are well documented in longline fisheries targeting swordfish and tunas (28 individuals swordfish 2001; 33 individuals swordfish 2002; 4 individuals offshore tuna 2002) (Atlantic Leatherback Turtle Recovery Team, 2006). There are currently no legally-binding measures in place by any IGO that require fishing vessels to implement sea turtle avoidance methods (Gilman et al., 2007). As fixed gear fisheries receive relatively little observer coverage, the magnitude of the threat they pose to leatherbacks has not been adequately recognized nor addressed (James et al., 2005b). Screened in. 7

8 Scottish seine: This gear could result in cetacean entanglement, but Scottish seines are not used in this EBSA. Over the period there were no reported landings with Scottish seine in the EBSA. Screened out. Purse seine: This gear is not currently utilized in the EBSA. No landings are reported for the period Screened out. Crab pots: There are intermittent landings of crab reported for the EBSA- ranging from a maximum of 44 tons in 1999 to a low of 2 tons in Some years had no landings of crab. Over the total period from crab landings (by weight) in this EBSA amounted to less than 1% of the total EBSA landings (Fisheries and Oceans Canada, 2008). Crab pots are attached by ropes to surface buoys, and may be set singly or in strings. In Newfoundland waters, crab pots are generally linked together in a long chain by groundlines which float in the water column many meters off the bottom. Both ground lines and lines to surface buoys are responsible for frequent entanglement of large marine animals such as leatherback turtles. 92 leatherbacks were entangled in fixed pot gear from New York through Maine for the period (Atlantic Leatherback Turtle Recovery Team, 2006). The use of lead (heavy) groundlines is a potential mitigation which can minimize entanglement in crab pots, but this mitigation is not widely adopted. Although crab pots can impact leatherback turtles, there is minimal crab fishing effort in this EBSA. Screened out. Ship strikes: The Southwest Shelf Edge and Slope has between ,799 total vessel transits in an average year. This is considered low within the LOMA. In an average year, of those vessel transits are tankers, which rank among the medium density of tanker traffic in the LOMA. Vessel traffic is highest from April June (400 1,199 transits), and leatherback turtles are known to be present in the area of the EBSA between June and November, although some literature reports sightings all year round. Vessel transit densities vary according to fishing vessel traffic, but commercial shipping does not vary significantly over the year (Pelot & Wootton, 2004). Leatherback turtles breathe air, and feed on planktonic jellyfish, and so spend much of their time near the sea surface where they are vulnerable to ship strikes. Leatherback turtles are known to bask at the surface for extended periods of time when foraging in temperate waters and, therefore, may be vulnerable to collisions with marine traffic. While no incidences of collisions with boats are documented in Atlantic Canada, they have been known to occur in some areas of the U.S. and may have an impact on the leatherback turtle population that also uses Canadian waters. In areas where recreational boating, commercial fishing and ship traffic are concentrated, propeller and collision-related injuries may represent a source of mortality. Between 1986 and 1988, 7.3 percent of all sea turtle strandings documented in U.S. Atlantic and Gulf of Mexico waters sustained some type of propeller or collision injuries (NOAA, 2003). However, in situations where there is evidence of a collision, it is difficult to infer whether the collision itself led to the death of the turtle in question, or if the 8

9 turtle was hit after it died of other causes (Atlantic Leatherback Turtle Recovery Team, 2006). Vessel traffic is considered low in this EBSA. Screened out. Vessel traffic: The Southwest Shelf Edge and Slope has between ,799 total vessel transits in an average year. This is considered low within the LOMA. Vessel traffic is highest from April June (400 1,199 transits). Little is known about the hearing ability of the leatherback turtle and its response to acoustic disturbance. Studies involving adult green, loggerhead and Kemp s ridley turtles suggest that sea turtles detect sounds in the low frequency sound range, with the greatest hearing sensitivity between Hz (Atlantic Leatherback Turtle Recovery Team, 2006). Studies on sea turtles have shown that certain levels of exposure to low frequency sound may cause displacement from the area near the sound source and increased surfacing behaviour. This raised the concern that turtles may be displaced from preferred foraging areas (Atlantic Leatherback Turtle Recovery Team, 2006). There are a range of sources of anthropogenic noise in the marine waters of Atlantic Canada that produce underwater sounds within the frequency range detectable by sea turtles. These include oil and gas exploration and development, shipping, fishing, military activity, underwater detonations, and shore based activities (Atlantic Leatherback Turtle Recovery Team, 2006). There is currently no oil and gas exploration areas in this EBSA (CNLOPB, 2008). Because vessel traffic is considered low within this EBSA it is not considered a stressor, however, leatherbacks are thought to have a small population and every encounter may be significant. Screened out. Seismic exploration: The South Whale Basin was the first area to be drilled in the Newfoundland offshore area. Fifteen wells were drilled in the South Whale Basin between 1966 and One well was drilled in this are in July 2005, but there is no longer an Exploration licence for the South Whale Basin (CNLOPB, 2008). There are no current plans for seismic exploration in the South Whale Basin. Studies have described behavioural responses of exposure to seismic airguns used in exploration to include increased swimming speed, increased activity, change in swimming direction and avoidance(fisheries and Ocean Canada, 2004). Startle responses and erratic swimming behaviour was observed. Another study noted a temporary reduction in hearing capability and temporarily increased physiological parameters (e.g., glucose, white blood cells and creatinine phosphokinase) which is suggestive of damaged tissues or altered physiology. Overall, based on the available information, it is considered unlikely that sea turtles are more sensitive to seismic operations associated with oil and gas exploration than cetaceans or some fish (Atlantic Leatherback Turtle Recovery Team, 2006). Screened out. Oil pollution: The South Whale Basin was the first area to be drilled in the Newfoundland offshore area. Fifteen wells were drilled in the South Whale Basin between 1966 and Although good reservoirs and several oil and gas shows were indicated, there were no commercial discoveries. The South Whale Basin Property was comprised of three exploration licences 9

10 (1060, 1061, 1062) covering 1,644,255 acres. In July 2005, the first Jack-up rig on the Grand Banks, drilled a well on Husky Energy s Lewis Hill prospect in the South Whale Basin. This was the first well drilled since The South Whale Basin is an area which overlaps the Southwest slope edge and shelf EBSA. This exploration licence is expired, and no further drilling plans have been reported for the area. Most reports of oil impact are anecdotal or based on small sample sizes, but there is no question that contact with oil negatively impacts sea turtles. The earlier life stages of living marine resources are usually at greater risk from an oil spill than adults. Sea turtles diving behaviour also puts them at risk. They rapidly inhale a large volume of air before diving and continually resurface over time. Adults doing this in an oil spill would experience both extended physical exposure to the oil and prolonged exposure to petroleum vapours, the most acutely harmful phase of a spill. Olfactory impairment from chemical contamination could represent a substantial indirect effect in sea turtles, since a keen sense of smell apparently plays an important role in navigation and orientation. Impairing the turtle s ability to properly orient itself can result in a population impact as significant as direct toxicity perhaps even greater. Even if sea turtles avoid direct contact with oil slicks, eating contaminated food is a direct exposure path, and reduced food availability is an indirect exposure route, but is a greater risk for other sea turtle species which feed primarily on crustaceans and molluscs (NOAA, 2003). The leatherback is relatively resistant to the effects of oil due to its thick leathery hide and lack of sensitive features such as fur, feathers or gills, and its high mobility. The Southwest shelf edge and slope has between ,799 total vessel transits in an average year. This is considered low within the LOMA, but includes tanker transits per year. Vessel traffic is highest from April June (400 1,199 transits). The effect of marine pollution on sea turtles is not well quantified, and therefore the magnitude of pollution-related mortality is unknown. Screened out. Ghost nets: Ghost nets are fishing gear that have been lost or discarded at sea. Since the 1960s, fishing nets have been constructed from highly durable plastic materials such as nylon which do not biodegrade. Unlike their natural predecessors, the new materials can last for years or decades in the marine environment, are largely impervious to biodegradation, are resistant to chemicals and abrasion (National Academy of Sciences, 2008). Sun exposure can lead to photodegradation of some synthetic materials, but on the sea bottom, protected from UV radiation, there is no evidence that these nets weaken or degrade over time and as a result, lost gear can continue to fish for decades. Gillnets, traps, trawls and line fisheries are considered the most harmful in relation to derelict fishing gear (National Academy of Sciences, 2008). Bottom trawl are responsible for 62% of the landings in the EBSA, gillnets for 30% and long line for 7% over the period (Appendix A, Table 15). Due to high intensity of fishing activity in the area and the dynamic nature of the environment, loss of gear is likely significant. Gillnets are responsible for 30% of landings by 10

11 weight in this EBSA over the period Gillnets that are lost or abandoned by fishermen continue to catch fish and other organisms. Most ghost nets are about 100 metres long and three metres deep. They're anchored to the bottom and float upward. When the nets are full they sink to the ocean floor. The dead fish rot away or get eaten by scavengers. Then the nets refloat themselves and the process of trapping fish starts all over again. It's a cycle that can go on for 10 years, until the nets fall apart (CBC News, 2000). We have no statistics of what proportion of gillnets are lost in an average year, but we do know it is a common occurrence. Ghost nets may catch jellyfish and attract turtles. Leatherback turtles are unable to swim backwards, making it more difficult to avoid encounters with ghost nets; however they feed mainly on the surface. Ghost nets are not expected to have a significant impact on leatherback aggregation and feeding. Screened out. Litter: The main prey of the leatherback turtle are jellyfish, which float in the upper water column where plastic debris accumulates. Floating plastic bags, balloons, condoms and sheeting resemble jellyfish and ingestion of plastic debris is a thought to be significant threat to leatherback recovery. Leatherbacks are known to ingest a variety of anthropogenic marine debris, including plastic bags, balloons, plastic and Styrofoam pieces, tar balls, plastic sheeting, and fishing gear (Atlantic Leatherback Turtle Recovery Team, 2006). Ingestion of such materials may interfere with metabolism or gut function and lead to blockages in the digestive tract, which could result in starvation or in the absorption of toxic by-products (Plotkin & Amos, 1989). A new study looked at necropsy reports of more than 400 leatherbacks that have died since 1885 and found plastic in the digestive systems of more than a third of the animals (Sohn, 2009). The effect of marine pollution on sea turtles is not well quantified, and therefore the magnitude of pollution-related mortality is unknown. Leatherback sea turtles may be more susceptible to marine debris ingestion than other turtle species due to their pelagic existence and the tendency of floating debris to concentrate in convergence zones that adults and juveniles use for feeding areas and migration (Atlantic Leatherback Turtle Recovery Team, 2006). Jellyfish are the leatherback's principal prey, but the turtles will also eat other softbodied creatures, such as salps. Salps are soft-bodied (gelatinous) free-swimming marine invertebrates with a transparent barrel-shaped body. The primary reason that leatherbacks migrate north is to feed on jellyfish (Fisheries and Oceans Canada, 2004). Sources of plastic debris within the EBSA include fishing vessels and some shipping traffic through EBSA. Ocean gyres are known to accumulate plastic debris from distant sources. This area has vertical and horizontal mixing, creating areas of high productivity. Currents can also form temporary rings and eddies which also affect ocean circulation. In particular, eddies are a feature of the Southwestern and tail of the Grand Banks (Coughlan, 2002). Of all of the PBGB EBSAs, the Southwest Slope and Edge is most directly affected by the Gulf Stream. Because of the currents along the shelf edge and slope, it is unlikely that litter is retained in the EBSA. Screened in. 11

12 Persistent organic pollutants: Leatherbacks may serve as an indicator of the degree of contamination of the oceanic food web by bio-accumulating substances such as heavy metals and polychlorinated biphenyls (PCBs) found in plankton-feeding jellyfish. Metal and PCB levels in the leatherback are expected to represent a biomagnification of concentrations found in their prey; however, to date, tissue samples derived from leatherbacks in European waters have not revealed evidence of significant chemical contamination (Atlantic Leatherback Turtle Recovery Team, 2006). Leatherback turtles are large, but feed very low on the food chain, with jellyfish being their preferred prey. As a result the do not tend to accumulated POPS to any significant extent, unlike the smaller piscivorous whales and fish such as belugas and tunas. Screened out. Temperature change: Drinkwater (UNEP & UNFCCC, 2002) predicts a temperature increase of 2-4 o C in Southern Newfoundland waters by 2100 based on IPCC 2001 models. Temperature rise will likely not be linear, but is expected to accelerate over time. Even given the worst case scenario, an increase in 0.4 o C is likely the most we can expect from this prediction over the next ten years. Leatherbacks can survive in water that is much too cold for other marine turtles. A combination of adaptations makes this possible, including their dark body colour, thick layer of fat, and high volume-to-surface-area ratio. Leatherbacks also have "countercurrent" heat exchangers in their flippers. This means that the veins and arteries are closely bundled next to one another, so that the warmer blood carried away from the heart in the arteries helps to warm the cooler blood returning to the heart from the veins. All of these factors help the leatherback maintain a core body temperature (the temperature inside the turtle) that is as much as 18 C warmer than the surrounding water temperature. Some scientists even hypothesize that the leatherback might have some capacity to generate its own body heat, like a mammal, even though reptiles are ectotherms - or "cold-blooded" - which means that their body temperature depends upon the temperature of the environment in which they find themselves (Fisheries and Oceans Canada, 2004). Global warming is predicted to have deleterious effects on marine turtles, as it could potentially influence temperature-dependent sex determination (Atlantic Leatherback Turtle Recovery Team, 2006). In addition, effects of temperature change will indirectly affect turtles through seasonal abundance of prey, particularly Cyanea sp, their principle jellyfish prey (Atlantic Leatherback Turtle Recovery Team, 2006). The mean SST corresponding to reports of leatherbacks in James et al. (2006) was 16.6 o C. 20% of sightings were associated with SSTs below 15 o C, attesting to this species capacity to exploit cold, temperate waters. Frequency of reported sightings increased with warmer water temperatures, suggesting that water temperature may affect seasonal distribution and abundance of leatherbacks (James et al., 2006). Colder average annual SST could partially account for what appears to be much lower density of leatherbacks in coastal Newfoundland versus Nova Scotia (James et al., 2006).Temperature rise expected over the next ten years is 12

13 not expected to significantly impact this CP, but may be a serious threat in the future. Screened out. Current shifts: Climate change models project a slow-down in the thermohaline circulation, the large-scale ocean circulation driven by fluxes of heat and salinity at the ocean surface. Cold water is denser than warm water and tends to sink, but saline water is denser than freshwater and also tends to sink. The strength of this circulation depends on a subtle balance between the rate of cooling and the input of less dense freshwater from melting ice sheets, precipitation and river runoff in sub-polar regions and the rate of heating and evaporation in the tropics. Currently, thermal forcing dominates and circulation is driven by the sinking of cold water in polar regions, but without the temperature effects, circulation would reverse, with sinking in the tropics and rising in the sub-polar regions (Drijfhout, 2008). Global models generally show that Atlantic thermohaline circulation weakens by 15% to 50% with a doubling of atmospheric CO 2 (as predicted in moderate climate change scenarios by 2100), but the weakening will not occur in a simple linear manner. The actual amount of CO 2 is less important than the rate of increase little happens at first as the circulation rapidly removes the freshwater, but there is a well-defined threshold beyond which the thermohaline circulation cannot cope with additional freshwater and breaks down (Rahmstorf, 1997). As a result, the thermohaline circulation can be subject to sudden transitions (linked to melting sub-polar ice sheets) which could lead to abrupt climate change, but this is not anticipated during the century (Drijfhout, 2008). Leatherbacks normally inhabit areas where prey productivity is high, along oceanic frontal systems and along vertical gradients located at oceanic fronts In eastern Canada, the distribution and movements of leatherback are thought to be closely associated with seasonally abundant prey, particularly Cyanea sp, their principle jellyfish prey (Atlantic Leatherback Turtle Recovery Team, 2006). Therefore, adult leatherback habitat may be determined by prey abundance, with turtles moving from offshore waters into coastal areas to exploit the seasonal production of jellyfish (Atlantic Leatherback Turtle Recovery Team, 2006). Although the Labrador Current clearly does not act as an absolute thermal barrier to leatherbacks, their association with this current may principally be limited to areas where it meets warmer water masses, such as on the Grand Banks or the east coast of Newfoundland. Such frontal zones are known to concentrate gelatinous zooplankton, and, therefore, may create favorable foraging conditions for leatherbacks (James et al., 2006). These changes may affect the production or distribution of jellyfish within shelf edge and slope waters, and consequently may affect leatherback abundance and distribution, but any affects are not expected to be significant over the next ten years. Screened out. Key Activities/Stressors: Gillnets (bottom) Longline Litter 13

14 Reference List 1. Atlantic Leatherback Turtle Recovery Team (2006). Recovery Strategy for Leatherback Turtle (Dermochelys coriacea) in Atlantic Canada (Rep. No. Species at Risk Act Recovery Strategy Series ). Ottawa: Fisheries and Oceans Canada. 2. CBC News (2000). Ghost nets litter Newfoundland waters. [Online]. Available: 3. CNLOPB (2008). Canada-Newfoundland and Labrador Offshore Petroleum Board. Internet [On-line]. Available: 4. COSEWIC & James, M. C. (2001). COSEWIC Assessment and Update Status Report on the Leatherback Turtle Dermochelys coriacea in Canada Ottawa: Committee on the Status of Endangered Wildlife in Canada. 5. Coughlan, G. (2002). The Southeast Shoal Area of the Grand Banks of Newfoundland, Potential as a Marine Protected Area: A Biophysical and Socio-economic Area Examination. Faculty of Environmental Design, University of Calgary. 6. Drijfhout, S. (2008). Changes in the Atlantic Meridional Overturning Circulation (Rep. No Biennial Reports). KNMI (Royal Netherlands Meteorological Institute). 7. Edinger, E., Baker, K., Devillers, R., & Wareham, V. (2007). Coldwater Corals off Newfoundland and Labrador: Distribution and Fisheries Impacts Halifax, Canada: World Wildlife Fund. 8. Fisheries and Ocean Canada (2004). Review of Scientific Information on Impacts of Seismic Sound on Fish, Invertebrates, Marine Turtles and Marine Mammals. 9. Fisheries and Oceans Canada. (2004). Underwater World Aquatic Species at Risk - The Leatherback Turtle. Ottawa, Ont. Ref Type: Pamphlet 10. Fisheries and Oceans Canada. (2008) LMNOP4R Effort and Catch. Policy and Economics Branch. [Newfoundland and Labrador Region Catch and Effort]. Fisheries and Oceans Canada. Ref Type: Data File 11. Gilman, E., Moth-Poulson, T., & Bianchi, G. (2007). Review of Measures Taken by Intergovernmental Organizations to Address Sea Turtle and Seabird Interactions in Marine Capture Fisheries (Rep. No. FAO Fisheries Circular No. 1025). Rome: Food and Agriculture Organization of the United Nations. 12. Griffin, E., Miller, K. L., Harris, S., & Allison, D. (2008). Trouble for Turtles: Trawl Fishing in the Atlantic Ocean and Gulf of Mexico Washington, DC: Oceana. 14

15 13. James, M. C. & Herman, T. B. (2001). Feeding of Dermochelys coriacea on Medusae in the Northwest Atlantic. Chelonian Conservation and Biology, 4, James, M. C., Myers, R. A., & Ottensmeyer, C. A. (2005a). Behaviour of leatherback sea turtles, Dermochelys coriacea, during the migratory cycle. Proceedings of the Royal Society B, 272, James, M. C., Ottensmeyer, C. A., & Myers, R. A. (2005b). Identification of high-use habitat and threats to leatherback sea turtles in northern waters: new directions for conservation. Ecology Letters, 8, James, M. C., Sherrill-Mix, S. A., Martin, K., & Myers, R. A. (2006). Canadian waters provide critical foraging habitat for leatherback sea turtles. Biological Conservation, 133, Ledwell, W. & Huntington, J. (2007). Whale and leatherback sea turtles incidental entrapment in fishing gear in Newfoundland and Labrador and a summary of the Whale Release and Strandings Program during 2006 A Report to the Department of Fisheries and Oceans, St. John's, Newfoundland and Labrador, Canada. 18. National Academy of Sciences (2008). Tackling Marine Debris in the 21st Century. 19. NOAA, U. S. D. o. C. (2003). Oil and Sea Turtles: Biology, Planning and Response U.S. Department of Commerce, National Oceanic and Atmospheric Administration. 20. Pelot, R. & Wootton, D. (2004). Maritime traffic distribution in Atlantic Canada to support an evaluation of a Sensitive Sea Area proposal (Rep. No ). Maritime Activity & Risk Investigation Network. 21. Rahmstorf, S. (1997). Risk of sea-change in the Atlantic. Nature, 388, Sohn, E. (2009). Plastic Found in One-Third of Leatherback Tutles. Discovery News Discovery Channel. Ref Type: Generic 23. Templeman, N. D. & Davis, M. B. (2006). Placentia Bay-Grand Banks Ecosystem Overview and Assessment Report (DRAFT) Newfoundland & Labrador: Fisheries and Oceans Canada. 24. UNEP & UNFCCC (2002). Climate Change Information Kit UNEP and UNFCCC. 25. Wareham, V. E. & Edinger, E. N. (2007). Distribution of deep-sea corals in the Newfoundland and Labrador region, Northwest Atlantic Ocean. Bulletin of Marine Science, 81, Wildlife Conservation Society (2005). State of the Wild 2006: A global portrait of wildlife, wildlands, and oceans. Washington, D.C.: Island Press. 15

16 Leatherback aggregation and feeding on the Southwest Shelf Edge and Slope Gillnets (bottom) Magnitude of Interaction Areal extent: Leatherback turtles have not been systematically surveyed around Newfoundland and distribution maps rely largely on opportunistic reporting and tracking of small numbers of individual leatherbacks. The primary determinant of movement and behaviour of leatherbacks is the spatial and temporal distribution of their primary prey, gelatinous plankton generally known as jellyfish. In general jellyfish abundance is lower in pelagic vs. coastal waters, however, physical transport of jellyfish can create local aggregations, particularly at physical discontinuities such as shelf breaks and upwelling zones (James et al., 2005a). James et al., (2005) identified spatial use of leatherbacks in the western Atlantic through satellite tracking tags on 38 turtles (Figure 1) Figure 1. Identification of high-use habitat and threats to leatherback sea turtles in northern waters. (James et al., 2005b). This information indicates that leatherbacks are broadly distributed throughout the EBSA. The area occupied by the CP is therefore considered to be the entire EBSA, an area of 16,580 km 2. 1

17 Figure 2. Total fishing effort density (All fisheries, Gillnet gear, 2004 & 2005) (Edinger et al., 2007). Gillnet fishing occurs throughout much of the EBSA. We have calculated an areal extent of 10,949 km 2 based on gillnet fishing data from Figure 3. Gillnet fishery areal extent, Newfoundland Region fisheries, (Fisheries and Oceans Canada, 2008). Based on this information we have estimated the area of overlap (10,949/16,580) = 66%. Score 6.6 Contact: Quantitative Fishing Gear Scores (Fisheries and Oceans Canada, 2007) for contact between bottom gillnets and leatherback, offshore are low (occasionally 1-25%). 2

18 The main directed fisheries using gillnet in the EBSA targeted monkfish, Greenland halibut, skate and white hake, most of which occur all year long (Appendix A, Table 5). Offshore license holders are allowed nets that are 91m in length and are usually joined together (Appendix A, Table 5). This amounts to a maximum of 45.5km of net per license holder. Within the offshore area, average depths fished with gillnets are 218m for white hake, 439m for skate, 331m for monkfish and 995m for Greenland halibut (Wareham & Edinger, 2007). Leatherbacks breathe air, and also spend time basking, resting and feeding at the sea surface. In Canadian waters satellite tracking studies have shown that leatherbacks spend between 1-35% of their time on the surface (James et al., 2005a). Although leatherbacks feed mainly of jellyfish, and are generally thought of as surface feeders, there is evidence that leatherbacks do not feed exclusively at the surface. In fact turtles equipped with time-depth recorders have been recorded diving beyond 1000m. This deep diving behavior may reflect nocturnal foraging for jellyfish and other softbodied invertebrates within the deeper water layers (COSEWIC & James, 2001). Jellyfish are planktonic, generally floating in surface waters, but in deep offshore areas may be occur at considerable depths, and leatherbacks foraging in shelf waters off Canada appear to search for and capture much of their prey at depth, before returning to the surface to consume it (James et al., 2005a). Figure 4 below shows the proportion of time two leatherbacks tagged off Nova Scotia spent in different depth ranges: Figure 4. Diving behavior of two leatherback turtles tagged in coastal waters off Nova Scotia, Canada: Proportion of time (per 6 h sample) spent in different depth ranges (James et al., 2005a). Although diving behavior may lead to increased incidents of entanglement in offshore waters, surface buoy lines appear to be most problematic (Atlantic Leatherback Turtle Recovery Team, 2006). In the offshore, a series of nets are generally set as a fleet, tied together at the headrope and footrope. Buoy lines are attached at the ends of the fleet, rather than at the ends of each net, and therefore contact with the surface is relatively low. Based on this information we have selected a score at the high end of the low range since entanglement in fishing gear has been identified as a significant threat to leatherbacks in the region (Atlantic Leatherback Turtle Recovery Team, 2006; Griffin et al., 2008; Ledwell & Huntington, 2007). 3

19 Score 3 Duration: Leatherbacks are typically present in the EBSA from June to October (Atlantic Leatherback Turtle Recovery Team, 2006). Bottom gillnet fishing is open within the EBSA for one or more fisheries all year round (100% of the time). Score 10 Intensity: Halpern et al. (2008) have developed maps showing the global intensity of several anthropogenic stressors including demersal non-destructive fishing with high bycatch, which includes bottom gillnet fisheries (Figure 5). This map can be used to provide guidance in scoring the intensity of a stressor in relation to maximum (Fisheries and Ocean Canada, 2007) intensity in a global context in accordance with the scale provided below This map shows a medium (yellow) intensity relative to global levels for a score range of 40% to 60% for the LOMA, but a lower score of 1-20% for the EBSA. Halpern s fishing maps are based on data from , and better represent NAFO fisheries, which are notoriously variable year to year, than Canadian fisheries, and are not as spatially precise on a local scale, as long term local data. Map colour Red Orange Yellow Light Blue Dark Blue Intensity % 60-80% 40-60% 20-40% 0-20% Figure 5. Global intensity of demersal non-destructive fishing with high bycatch (Halpern et al., 2008). Gillnet fisheries within the EBSA represent an average of 30% of the landings from (Fisheries and Oceans Canada, 2008). Since gillnet fisheries within the LOMA are concentrated in this EBSA, we have selected a moderate score within the range indicated for the LOMA. Score 5 Magnitude of Interaction: (6.6 x 3 x 10 x 5)/1000 = 1.0 4

20 Sensitivity: Sensitivity of the CP to acute impacts: Quantitative Fishing Gear Scores (Fisheries and Oceans Canada, 2007) for harm resulting from an interaction between bottom gillnets and sea turtles in 3NO are low (occasionally 1-25%), but in Atlantic wide bottom gillnet fisheries, scores are high (> 75% of the time). Of all the Atlantic sea turtle species, leatherbacks seem to be the most vulnerable to entanglement in fishing gear (Atlantic Leatherback Turtle Recovery Team, 2006). Since inshore gillnets are set closer to the surface and generally have more buoy lines/nets, incidents in the EBSA are likely to be lower than those inshore areas, as indicated by the Quantitative Fishing Gear scores. Incidental capture in fisheries is considered as a leading cause of population decline (James et al., 2006). The susceptibility of leatherbacks to entanglements may result from their large body size, long pectoral flippers and soft shell. Acute impacts due to entanglement may vary in severity from trivial to lethal depending the extent of the entanglement. Entanglement of leatherbacks beneath the surface generally leads to death through drowning since the turtle is unable to reach the surface to breath. Even if the turtle is able to free themselves, serious injuries may be sustained, or gear may remain attached to the turtle leading to chronic impacts (Atlantic Leatherback Turtle Recovery Team, 2006). Based on this information we have selected a score at the high end of the low range. Score 3.5 Sensitivity of the CP to chronic impacts: A long lifespan, very high rates of egg and hatchling mortality, and a late age of maturity makes this species unusually vulnerable to even small increases in rates of mortality of adults and older juveniles (COSEWIC & James, 2001). Generation time is estimated at <30 years (NOAA, 2003). The leatherback turtle is classified as critically endangered by the International Union for the Conservation of Nature and as endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Leatherbacks have experienced a dramatic population decline of more than 60 per cent since Since male turtles do not return to land, it is not possible to accurately count them. So, scientists determine the population of sea turtles by counting nesting females. Currently, the total number of nesting females is thought to be less than 35,000 worldwide (Fisheries and Oceans Canada, 2004). The Atlantic population appears to be more stable, but shows dramatic fluctuations in from year to year. The relative density of leatherbacks in Canadian waters has been estimated at turtles (during summer), but this is likely low, as there are no accurate population estimates for leatherbacks in Canadian waters (COSEWIC & James, 2001). Chronic impacts of entanglement can range from minor rope scars, to debilitating injuries, or moderate to severe morbidity due to gear remaining attached or imbedded in the turtle. In these cases, the ability of the animal to move and feed may be compromised by injuries, infection, interference with vital body functions (rope/netting confining limb, neck or mouth movement) or by the weight of gear. In severe cases death may occur months or even years later as a result of starvation or chronic infection (Atlantic Leatherback Turtle Recovery Team, 2006) 5

21 Turtles towing gear for any length of time are unlikely to free themselves, and are more likely to become entangled again. Given the poor recovery rate for serious interactions, and low reproductive rates of leatherbacks, we have selected a moderate score (5.5) for chronic sensitivity. Leatherbacks are listed as a depleted species for the LOMA (add 1 point). Score 6.5 Sensitivity of ecosystem to harmful impacts to the CP: Leatherbacks depend on prey with very little nutritive content and since this species diet of jellyfish is high in water and low in organic content, they must consume large quantities of food to fulfill their food energy requirements (Atlantic Leatherback Turtle Recovery Team, 2006). Jellyfish are generally considered a nuisance species, which can foul fishing gear and force the closure of swimming beaches. Jellyfish also compete with larval fish for food (both eat zooplankton), and are also known predators of larval fish (James et al., 2005b). Leatherbacks help keep the jellyfish population under control, and may therefore help conserve fish species, as well as contributing to pest control within the LOMA. Despite their relatively small numbers, leatherbacks represent a significant biomass due to their large size, and contribute significantly to the energetics of the marine ecosystem. Leatherbacks are highly mobile, and their large scale movements contribute to the transfer of energy and biomass from seasonally productive areas to distance marine systems. Dead leatherbacks also contribute significantly to the productivity of the marine ecosystem, with their large carcasses providing food for fish, sharks, birds and decomposers. Due to their large size and habit of basking on the sea surface, leatherbacks have long attracted interest, and their presence within the LOMA contributes to ecotourism opportunities. Canadian waters support one of the highest summer and fall densities of leatherbacks in the North Atlantic, and should be considered critical foraging habitat for this endangered species (James et al., 2006). Although the EBSA has been identified as an important area for leatherback aggregation and feeding, leatherbacks are widely distributed within the LOMA during the summer months and other areas may be of equal or greater importance. The Atlantic Leatherback Turtle Recovery Team identified areas of leatherback concentration off eastern Canada which did not include the EBSA (Figure 6). 6

22 Figure 6.Occurrence of the leatherback turtle, Dermochelys coriacea, off eastern Canada. Shaded areas show the location of concentrations of observations (Atlantic Leatherback Turtle Recovery Team, 2006) Based on this information we have selected a score in the medium range to reflect the importance of the species in the LOMA, and have selected a score at the low end of the medium range to reflect the relatively low importance of leatherback aggregation and feeding within the EBSA in relation to the LOMA as a whole. Score 4 Sensitivity: ( )/3 = 4.7 Risk of Harm: 1.0 x 4.7 = 4.7 7

23 Certainty Checklist Answer yes or no to all of the following questions. Record the number of NO s to the 9 questions, and record certainty according to the scale provided below: 1 No s = High certainty 2-3 No s = Medium certainty > 4 No s = Low certainty Y/N N Is the score supported by a large body of information? N Is the score supported by general expert agreement? N Is the interaction well understood, without major information gaps/sources of error? N Is the current level of understanding based on empirical data rather than models, anecdotal information or probable scenarios? Y Is the score supported by data which is specific to the region, (EBSA, LOMA, NW Atlantic? Y Is the score supported by recent data or research (the last 10 years or less)? N Is the score supported by long-term data sets (ten years or more) from multiple surveys (5 years or more)? Y Do you have a reasonable level of comfort in the scoring/conclusions? N Do you have a high level of confidence in the scoring/conclusions? Certainty Score: Low For interactions with Low certainty, underline the main factor(s) contributing to the uncertainty Lack of comprehensive data Lack of expert agreement Predictions based of future scenarios which are difficult to predict Other (provide explanation) Suggest possible research to address uncertainty: More comprehensive observer coverage in offshore 8

24 Reference List 1. Atlantic Leatherback Turtle Recovery Team (2006). Recovery Strategy for Leatherback Turtle (Dermochelys coriacea) in Atlantic Canada (Rep. No. Species at Risk Act Recovery Strategy Series ). Ottawa: Fisheries and Oceans Canada. 2. COSEWIC & James, M. C. (2001). COSEWIC Assessment and Update Status Report on the Leatherback Turtle Dermochelys coriacea in Canada Ottawa: Committee on the Status of Endangered Wildlife in Canada. 3. Edinger, E., Baker, K., Devillers, R., & Wareham, V. (2007). Coldwater Corals off Newfoundland and Labrador: Distribution and Fisheries Impacts Halifax, Canada: World Wildlife Fund. 4. Fisheries and Ocean Canada (2007). Conservation Harvesting Plan (CHP), Atlanticwide for Mobile Gear Vessels ', February 8, 2007 (unpublished) Fisheries and Oceans Canada, Newfoundland & Labrador Region. 5. Fisheries and Oceans Canada. (2004). Underwater World Aquatic Species at Risk - The Leatherback Turtle. Ottawa, Ont. Ref Type: Pamphlet 6. Fisheries and Oceans Canada (2007). Placentia Bay-Grand Banks Large Ocean Management Area Conservation Objectives (Rep. No. 2007/042). Canadian Science Advisory Secretariat Science Advisory Report. 7. Fisheries and Oceans Canada. (2008) LMNOP4R Effort and Catch. Policy and Economics Branch. [Newfoundland and Labrador Region Catch and Effort]. Fisheries and Oceans Canada. Ref Type: Data File 8. Griffin, E., Miller, K. L., Harris, S., & Allison, D. (2008). Trouble for Turtles: Trawl Fishing in the Atlantic Ocean and Gulf of Mexico Washington, DC: Oceana. 9. Halpern, B. S., Walbridge, S., Selkoe, K. A., Kappel, C. V., Micheli, F., D'Agrosa, C. et al. (2008). A Global Map of Human Impact on Marine Ecosystems. Science, 319, James, M. C., Myers, R. A., & Ottensmeyer, C. A. (2005a). Behaviour of leatherback sea turtles, Dermochelys coriacea, during the migratory cycle. Proceedings of the Royal Society B, 272, James, M. C., Ottensmeyer, C. A., & Myers, R. A. (2005b). Identification of high-use habitat and threats to leatherback sea turtles in northern waters: new directions for conservation. Ecology Letters, 8,

25 12. James, M. C., Sherrill-Mix, S. A., Martin, K., & Myers, R. A. (2006). Canadian waters provide critical foraging habitat for leatherback sea turtles. Biological Conservation, 133, Ledwell, W. & Huntington, J. (2007). Whale and leatherback sea turtles incidental entrapment in fishing gear in Newfoundland and Labrador and a summary of the Whale Release and Strandings Program during 2006 A Report to the Department of Fisheries and Oceans, St. John's, Newfoundland and Labrador, Canada. 14. NOAA, U. S. D. o. C. (2003). Oil and Sea Turtles: Biology, Planning and Response U.S. Department of Commerce, National Oceanic and Atmospheric Administration. 15. Wareham, V. E. & Edinger, E. N. (2007). Distribution of deep-sea corals in the Newfoundland and Labrador region, Northwest Atlantic Ocean. Bulletin of Marine Science, 81,

26 Leatherback aggregation and feeding on the Southwest Shelf Edge and Slope Longline Magnitude of Interaction Areal extent: Leatherback turtles have not been systematically surveyed around Newfoundland and distribution maps rely largely on opportunistic reporting and tracking of small numbers of individual leatherbacks. The primary determinant of movement and behaviour of leatherbacks is the spatial and temporal distribution of their primary prey, gelatinous plankton generally known as jellyfish. In general jellyfish abundance is lower in pelagic vs. coastal waters, however, physical transport of jellyfish can create local aggregations, particularly at physical discontinuities such as shelf breaks and upwellings zones (James et al., 2005a). James et al., (2005) identified spatial use of leatherbacks in the western Atlantic through satellite tracking tags on 38 turtles (Figure 1). Figure 1. Identification of high-use habitat and threats to leatherback sea turtles in northern waters. (James et al., 2005b). This information indicates that leatherbacks are broadly distributed throughout the EBSA. The area occupied by the CP is therefore considered to be the entire EBSA, an area of 16,580 km 2. Longline fisheries within the LOMA are concentrated on the Southwest Shelf Edge and Slope and are deployed in a range of depths throughout much of the EBSA, precisely 1

27 2. Figure 2. Areal extent of longline use, Newfoundland Region fisheries (Fisheries and Oceans Canada, 2008) (Fisheries and Oceans Canada, 2008). Figure 3. Distribution of bycatch of leatherback and loggerhead turtles caught in United States longline fishery from 1985 to 1999 (Fuller & Myers, 2004). 2

28 Based on this information we have estimated an area of overlap of 11,660 km 2 /16,580 km 2 = 70%. Score 7 Contact: Quantitative Fishing Gear Scores (Fisheries and Oceans Canada, 2007) for contact between bottom longline and leatherback, offshore are low (occasionally 1-25%). Although leatherbacks feed mainly of jellyfish, and are generally thought of as surface feeders, there is evidence that leatherbacks do not feed exclusively at the surface. In fact turtles equipped with time-depth recorders have been recorded diving beyond 1000m. This deep diving behavior may reflect nocturnal foraging for jellyfish and other softbodied invertebrates within the deeper water layers (COSEWIC & James, 2001). Jellyfish are planktonic, generally floating in surface waters, but in deep offshore areas may be occur at considerable depths, and leatherbacks foraging in shelf waters off Canada appear to search for and capture much of their prey at depth, before returning to the surface to consume it (James et al., 2005a). Figure 4 below shows the proportion of time two leatherbacks tagged off Nova Scotia spent in different depth ranges: Figure 4. Diving behavior of two leatherback turtles tagged in coastal waters off Nova Scotia, Canada: Proportion of time (per 6 h sample) spent in different depth ranges (James et al., 2005a). Of all Atlantic sea turtle species, leatherbacks seem to be most vulnerable to entanglement in fishing gear such as pelagic longlines, lines associated with fixed gear (pots, traps, gillnets), buoy anchor lines and other ropes and cables (Atlantic Leatherback Turtle Recovery Team, 2006). The leatherback s insatiable appetite and foraging curiosity also may lead to entanglement in fishing gear. Front flipper entanglement in ropes and cables is common, and this may result from turtles approaching buoys and biting at them (COSEWIC & James, 2001). Although diving behavior may lead to increased incidents of entanglement in offshore waters, surface buoy lines appear to be most problematic (Atlantic Leatherback Turtle Recovery Team, 2006). Longlines may also be problematic while they remain near the surface while being set or tended. 3

29 Based on this information we have selected a score at the high end of the low range since entanglement in fishing gear has been identified as a significant threat to leatherbacks in the region (Atlantic Leatherback Turtle Recovery Team, 2006; Griffin et al., 2008; Ledwell & Huntington, 2007). Score 3 Duration: Leatherbacks are typically present in the EBSA from June to November (Atlantic Leatherback Turtle Recovery Team, 2006). Longline fishing is open within the EBSA for one or more fisheries all year round (100% of the time). Score 10 Intensity: Halpern et al. (2008) have developed maps showing the global intensity of several anthropogenic stressors including demersal non-destructive fishing with low bycatch, which includes longline fisheries (see Figure 5). This map can be used to provide guidance in scoring the intensity of a stressor in relation to maximum intensity in a global context, in accordance with the scale provided below. It shows a medium to low (light blue) intensity relative to global levels for a score range of 20% to 40%. Map colour Red Orange Yellow Light Blue Dark Blue Intensity % 60-80% 40-60% 20-40% 0-20% Figure 5. Demersal, non-destructive, low bycatch fisheries (Halpern et al., 2008). Halpern s fishing maps are based on data from , and better represent NAFO fisheries, which are notoriously variable year to year, than Canadian fisheries, and are not as spatially precise on a local scale, as long term local data. Longline fisheries within the LOMA are concentrated on the SW Shelf Edge and Slope and represent 7% of the landings. Since longline fisheries are concentrated in the EBSA, we have selected the highest score within the range, 40%. Score 4 4

30 Magnitude of Interaction: (7 x 3 x 10 x 4)/1000 = 0.8 Sensitivity Sensitivity of the CP to acute impacts: Quantitative Fishing Gear Scores (Fisheries and Oceans Canada, 2007) for harm resulting from an interaction between longline and sea turtles range from low (occasionally 1-25%), to high (> 75% of the time). Of all the Atlantic sea turtle species, leatherbacks seem to be the most vulnerable to entanglement in fishing gear (Atlantic Leatherback Turtle Recovery Team, 2006). Incidental capture in fisheries is considered as a leading cause of population decline (James et al., 2006). The susceptibility of leatherbacks to entanglements may result from their large body size, long pectoral flippers and soft shell. Acute impacts due to entanglement may vary in severity from trivial to lethal depending the extent of the entanglement. Entanglement of leatherbacks beneath the surface generally leads to death through drowning since the turtle is unable to reach the surface to breath. Even if the turtle is able to free themselves, serious injuries may be sustained, or gear may remain attached to the turtle leading to chronic impacts (Atlantic Leatherback Turtle Recovery Team, 2006). Based on this information we have selected a score in the moderate range. Score 5 Sensitivity of the CP to chronic impacts: A long lifespan, very high rates of egg and hatchling mortality, and a late age of maturity makes this species unusually vulnerable to even small increases in rates of mortality of adults and older juveniles (COSEWIC & James, 2001). Generation time is estimated at <30 years (NOAA, 2003). The leatherback turtle is classified as critically endangered by the International Union for the Conservation of Nature and as endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). Leatherbacks have experienced a dramatic population decline of more than 60 per cent since Since male turtles do not return to land, it is not possible to accurately count them. So, scientists determine the population of sea turtles by counting nesting females. Currently, the total number of nesting females is thought to be less than 35,000 worldwide (Fisheries and Oceans Canada, 2004). The Atlantic population appears to be more stable, but shows dramatic fluctuations from year to year. The relative density of leatherbacks in Canadian waters has been estimated at turtles (during summer), but this is likely low, as there are no accurate population estimates for leatherbacks in Canadian waters (COSEWIC & James, 2001). Chronic impacts of entanglement can range from minor rope scars, to debilitating injuries, or moderate to severe morbidity due to gear remaining attached or imbedded in the turtle. In these cases, the ability of the animal to move and feed may be compromised by injuries, infection, interference with vital body functions (rope/netting confining limb, neck or mouth movement) or by the weight of gear. In severe cases death may occur months or even years later as a result of starvation or chronic infection (Atlantic Leatherback Turtle Recovery Team, 2006; Wildlife Conservation Society, 2005). 5

31 Turtles towing gear for any length of time are unlikely to free themselves, and are more likely to become entangled again. Given the poor recovery rate for serious interactions, and low reproductive rates of leatherbacks, we have selected a moderate score (5.5) for chronic sensitivity. Leatherbacks are listed as a depleted species for the LOMA (add 1 point). Score 6.5 Sensitivity of the ecosystem to harmful impacts to the CP: Leatherbacks depend on prey with very little nutritive content and since this species diet of jellyfish is high in water and low in organic content, they must consume large quantities of food to fulfill their food energy requirements (Atlantic Leatherback Turtle Recovery Team, 2006). Jellyfish are generally considered a nuisance species, which can foul fishing gear and force the closure of swimming beaches. Jellyfish also compete with larval fish for food (both eat zooplankton), and are also known predators of larval fish (James et al., 2005b). Leatherbacks help keep the jellyfish population under control, and may therefore help conserve fish species, as well as contributing to pest control within the LOMA. Despite their relatively small numbers, leatherbacks represent a significant biomass due to their large size, and contribute significantly to the energetics of the marine ecosystem. Leatherbacks are highly mobile, and their large scale movements contribute to the transfer of energy and biomass from seasonally productive areas to distance marine systems. Dead leatherbacks also contribute significantly to the productivity of the marine ecosystem, with their large carcasses providing food for fish, sharks, birds and decomposers. Due to their large size and habit of basking on the sea surface, leatherbacks have long attracted interest, and their presence within the LOMA contributes to ecotourism opportunities. Canadian waters support one of the highest summer and fall densities of leatherbacks in the North Atlantic, and should be considered critical foraging habitat for this endangered species (James et al., 2006). Although the EBSA has been identified as an important area for leatherback aggregation and feeding, leatherbacks are widely distributed within the LOMA during the summer months and other areas may be of equal or greater importance. The Atlantic Leatherback Turtle Recovery Team identified areas of leatherback concentration off eastern Canada (Figure 6) and did not include the EBSA. 6

32 Figure 6.Occurrence of the leatherback turtle, Dermochelys coriacea, off eastern Canada. Shaded areas show the location of concentrations of observations (Atlantic Leatherback Turtle Recovery Team, 2006). Based on this information we have selected a score in the medium range to reflect the importance of the species in the LOMA, and have selected a score at the low end of the medium range to reflect the relatively low importance of leatherback aggregation and feeding within the EBSA in relation to the LOMA as a whole. Score 4 Sensitivity: ( )/3 = 5.2 Risk of Harm: 0.8 x 5.2 = 4.2 7

33 Certainty Checklist Answer yes or no to all of the following questions. Record the number of NO s to the 9 questions, and record certainty according to the scale provided below: 1 No s = High certainty 2-3 No s = Medium certainty > 4 No s = Low certainty Y/N N Is the score supported by a large body of information? N Is the score supported by general expert agreement? N Is the interaction well understood, without major information gaps/sources of error? N Is the current level of understanding based on empirical data rather than models, anecdotal information or probable scenarios? Y Is the score supported by data which is specific to the region, (EBSA, LOMA, NW Atlantic? Y Is the score supported by recent data or research (the last 10 years or less)? N Is the score supported by long-term data sets (ten years or more) from multiple surveys (5 years or more)? Y Do you have a reasonable level of comfort in the scoring/conclusions? N Do you have a high level of confidence in the scoring/conclusions? Certainty Score: Low For interactions with Low certainty, underline the main factor(s) contributing to the uncertainty Lack of comprehensive data Lack of expert agreement Predictions based of future scenarios which are difficult to predict Other (provide explanation) Suggest possible research to address uncertainty: More comprehensive observer coverage in offshore 8

34 Reference List 1. Atlantic Leatherback Turtle Recovery Team (2006). Recovery Strategy for Leatherback Turtle (Dermochelys coriacea) in Atlantic Canada (Rep. No. Species at Risk Act Recovery Strategy Series ). Ottawa: Fisheries and Oceans Canada. 2. COSEWIC & James, M. C. (2001). COSEWIC Assessment and Update Status Report on the Leatherback Turtle Dermochelys coriacea in Canada Ottawa: Committee on the Status of Endangered Wildlife in Canada. 3. Fisheries and Oceans Canada. (2004). Underwater World Aquatic Species at Risk - The Leatherback Turtle. Ottawa, Ont. Ref Type: Pamphlet 4. Fisheries and Oceans Canada (2007). Placentia Bay-Grand Banks Large Ocean Management Area Conservation Objectives (Rep. No. 2007/042). Canadian Science Advisory Secretariat Science Advisory Report. 5. Fisheries and Oceans Canada. (2008) LMNOP4R Effort and Catch. Policy and Economics Branch. [Newfoundland and Labrador Region Catch and Effort]. Fisheries and Oceans Canada. 6. Fuller, S. D. & Myers, R. A. (2004). The Southern Grand Bank: a marine protected area for the world Halifax: World Wildlife Fund Canada. 7. Griffin, E., Miller, K. L., Harris, S., & Allison, D. (2008). Trouble for Turtles: Trawl Fishing in the Atlantic Ocean and Gulf of Mexico Washington, DC: Oceana. 8. Halpern, B. S., Walbridge, S., Selkoe, K. A., Kappel, C. V., Micheli, F., D'Agrosa, C. et al. (2008). A Global Map of Human Impact on Marine Ecosystems. Science, 319, James, M. C., Myers, R. A., & Ottensmeyer, C. A. (2005a). Behaviour of leatherback sea turtles, Dermochelys coriacea, during the migratory cycle. Proceedings of the Royal Society B, 272, James, M. C., Ottensmeyer, C. A., & Myers, R. A. (2005b). Identification of high-use habitat and threats to leatherback sea turtles in northern waters: new directions for conservation. Ecology Letters, 8, James, M. C., Sherrill-Mix, S. A., Martin, K., & Myers, R. A. (2006). Canadian waters provide critical foraging habitat for leatherback sea turtles. Biological Conservation, 133, Ledwell, W. & Huntington, J. (2007). Whale and leatherback sea turtles incidental entrapment in fishing gear in Newfoundland and Labrador and a summary of the 9

35 Whale Release and Strandings Program during 2006 A Report to the Department of Fisheries and Oceans, St. John's, Newfoundland and Labrador, Canada. 13. NOAA, U. S. D. o. C. (2003). Oil and Sea Turtles: Biology, Planning and Response U.S. Department of Commerce, National Oceanic and Atmospheric Administration. 14. Wildlife Conservation Society (2005). State of the Wild 2006: A global portrait of wildlife, wildlands, and oceans. Washington, D.C.: Island Press. 10

36 Leatherback Aggregation and Feeding in the Southwest Shelf Edge and Slope Litter Magnitude of Interaction Areal extent: Leatherback turtles have not been systematically surveyed around Newfoundland and distribution maps rely largely on opportunistic reporting and tracking of small numbers of individual leatherbacks. In eastern Canada, the distribution and movements of leatherbacks are thought to highly correlate with distributions of jellyfish, their principle prey (Atlantic Leatherback Turtle Recovery Team, 2006; Templeman & Davis, 2006). In general jellyfish abundance is lower in pelagic vs. coastal waters, however, physical transport of jellyfish can create local aggregations in pelagic waters, particularly at physical discontinuities such as shelfbreaks and upwelling zones (James et al., 2005a; James et al., 2006). James et al., (2005) identified spatial use of leatherbacks in the western Atlantic through satellite tracking tags on 38 turtles (Figure 1). Figure 1. Identification of high-use habitat and threats to leatherback sea turtles in northern waters (James et al., 2005b). This information indicates that leatherbacks are broadly distributed throughout the EBSA, but are concentrated where prey is most abundant. There is little data on marine litter available for the EBSA. Plastic debris comes from many sources, occurring chronically throughout the LOMA, but is not restricted to any specific area. Therefore we have estimated areal extent (high, medium, low) based on the 1

37 Major sources of marine litter in the EBSA include boat traffic (fishing and shipping) and ocean currents. Average annual marine traffic density in the EBSA is considered low. Surface currents can carry significant quantities of floating litter, and islands such as Sable Island (Lucas, 1992) accumulate significant quantities of plastic debris. Although the EBSA is most directly affected by a branch of the deep Labrador Current, prevailing southwest winds may carry significant quantities of debris towards the EBSA, and as marine debris tends to accumulate at convergence zones, where prey is also naturally concentrated, area of overlap may be amplified. Based on this information we have estimated the areal extent in the medium to low range. Score 4.5 Contact: Marine debris accumulates at convergence zones, where prey is also naturally concentrated. Floating plastic debris has a high degree of contact with leatherbacks which spend much of their time on the sea surface, both feeding and resting. Score 9 Duration: Leatherbacks occur in the EBSA from June to November (Atlantic Leatherback Turtle Recovery Team, 2006; James et al., 2006). Litter is considered a chronic stressor which occurs every year, and so is given a moderate (30-70%) score. Since marine litter is persistent, consisting largely of plastic debris, and sources of litter (fishing boats, ships and winds/currents) are present throughout the year, we have selected a score at the top of the medium range. Score 7 Intensity: Global maps (Halpern et al., 2008) for ocean pollution, shows a medium-low (yellowlight blue) intensity relative to global levels for a score range of 20% to 60%. 2

38 Map colour Red Orange Yellow Light Blue Dark Blue Intensity % 60-80% 40-60% 20-40% 0-20% Figure 2. Global intensity of ocean pollution, adapted from (Halpern et al., 2008). We have selected the medium score within the range. Score 4 Magnitude of Interaction: (4.5 x 9 x 7 x 4)/1000 = 1.1 Sensitivity Sensitivity of the CP to acute impacts: Leatherbacks depend on prey with very little nutritive content and since this species diet of jellyfish is high in water and low in organic content, they must consume large quantities of food to fulfill their food energy requirements (James et al., 2005b). This is the only known biological limiting factor in Canadian waters (Atlantic Leatherback Turtle Recovery Team, 2006). Their specialized diet may make leatherbacks vulnerable to ingestion of plastics and other buoyant marine debris. This behavior is adaptive in exploiting large concentrations of jellyfish, and leatherbacks will readily consume a variety of inedible buoyant objects such as plastic bags, styrofoam, balloons, condoms and plastic sheeting. Whether or not such ingestion is deliberate, since these materials may resemble their softbodied prey, and marine debris accumulates at convergence zones, where prey is also naturally concentrated, the magnitude of the threat that ingestion of marine debris poses may be grossly underestimated (James & Herman, 2001). Acute impacts of ingestion of plastics, styrofoam and other waste can lead to both acute and chronic impacts. Acute impacts leading to mortality include blockage of the throat or digestive tract and physical injury from ingestion of hard objects. In general chronic impacts are of greatest concern. Score 4 Sensitivity of the CP to chronic impacts: A long lifespan, very high rates of egg and hatchling mortality, and a late age of maturity makes this species unusually vulnerable to even small increases in rates of mortality of 3