The Bycatch Problem Effects of Commercial Fisheries on Non-Target Species in India Aaron Savio Lobo This article provides a general overview of the effects of commercial fishing on non-target/bycatch species, with special relevance to the Indian scenario. It discusses the possible detrimental implications of the removal of organisms from the marine ecosystem and suggests possible measures to mitigate this problem. Aaron Savio Lobo is at Nature Conservation Foundation, Mysore. His interests are in marine biology and more specifically the impacts large-scale commercial fishing operations on species and their environment. He is presently conducting research along the Coromandel Coast of Tamil Nadu. Keywrds Bycatch problem, shrimp trawler, marine protected areas. Commercial fishing affects not only the species targeted, but also several other species that are caught incidentally. This is commonly referred to as bycatch. Bycatch generally include species of little commercial importance, which in most cases is dumped overboard either into the sea or after reaching the fish landing sites. A recent estimate (2006) suggests that 7.3 million tonnes of the global catch is discarded annually as bycatch [1]. In most of the large scale commercial fishing operations, this constitutes a higher percentage of the catch than the target species. The issue of bycatch first captured public attention in 1960 s and 1970 s because of the threat to the charismatic dolphins in the eastern tropical Pacific that were being trapped in purse seines (nets designed to encircle and trap large shoals of fish) which were targetting yellow finned (Thunnus albacares), bigeye (Thunnus obesus) and skipjack (Katsuwonus pelamis), that are varieties of Tuna. The dolphins being restrained in these nets for prolonged durations during the hauling process subsequently died of asphyxiation [2]. This is a topic of concern because bycatch from large-scale fishing can threaten several other species which not only constitute fish, but also those from several other higher taxa such as reptiles, birds and mammals. Bycatch occurs in all possible fishing methods; however its quantum varies from low in traditional fishing methods to very high in 60 RESONANCE May 2007
commercial methods such as shrimp trawling, gill netting, purse seining, etc. Even sea birds such as the albatross and petrels are caught as bycatch on hooks of the long lines designed to catch large fish. The Shrimp Trawler Case The highest levels of bycatch are known to come from shrimp trawlers. Shrimp trawling is a highly efficient fishing technique, wherein a long funnel shaped net (~ 30m) with a wide mouth and small mesh size (steadily decreasing from the mouth to the tapering portion called the codend) is dragged along the sea floor by a mechanized boat (Figure 1). Anything in the path of the net is captured, with a very bleak chance of escape. Shrimp trawlers are known to catch over 400 marine species. Estimates suggest that 10:1 bycatch to shrimp ratios have been recorded in the tropics. Shrimp trawlers are responsible for one third of the world s total bycatch, despite producing less than 2% of global sea food. Besides contributing to huge amounts of bycatch, persistent trawling also brings about changes in the habitat complexity and thus biodiversity. Shrimp trawling started in India during the latter half of the 20th century and is presently considered the most effective and widespread method of fishing in the country. There are several categories of bycatch obtained from shrimp trawlers. Some of these are: Shrimp trawlers are responsible for one third of the world s total bycatch, despite producing less than 2% of global sea food. Figure 1 (left). A shrimp trawler towing its net. Figure 2 (right). A shrimp trawler hauling its net. RESONANCE May 2007 61
Besides the small, low priced and unwanted species, larger more charismatic species such as dolphins, porpoises and sea turtles also sometimes constitute bycatch of shrimp trawlers in India. Bycatch of no commercial value include species of coelenterates, echinoderms and several species of gastropods, crustaceans such as small inedible crabs, mantis shrimp, etc., and sometimes smaller inedible species of fish and eels. Seasonal bycatch include species which are of commercial importance in a certain season if caught in large quantities, but in small proportion is of little commercial value and is usually dumped overboard. For example, oil sardines (Sardinella longiceps) in Goa are of commercial importance when caught in large quantities and are used for the production of oil which is extracted from them, but when caught in small numbers along with shrimp as a bycatch and are of little use. Area specific bycatch where in the bycatch of one area may not necessarily be the bycatch of another. For eg., The Bombay Duck (Hapodon nehereus) which is commercially important along many parts of the west coast is often dumped overboard as bycatch along the coast of Orissa. Besides the small, low priced and unwanted species mentioned above; larger more charismatic species such as dolphins, porpoises and sea turtles also sometimes constitute bycatch of shrimp trawlers in India and very often die due to drowning. The species in India which has gained the maximum amount of public attention during the recent time is the Olive Ridley sea turtle (Lepidochelys olivacea), a species that occurs along the entire Indian coastline. This species is known to congregate in especially large numbers along the coast of Orissa, where the females come ashore to lay their eggs, a phenomenon commonly termed as Arribada or mass nesting. The areas in the sea off the Gahirmata coast where the sea turtles emerge, are also excellent fishing grounds and during this period thousands of turtles caught in trawl nets and gill nets die of drowning. This area in the recent past had been declared as a marine sanctuary, however illegal fishing in this area still continues, leading to a large number of turtles getting caught in trawl and gill nets and dying every year. 62 RESONANCE May 2007
GENERAL ARTICLE 3 4 5 6 7 8 Figure 3. Trawler fleet at Pamban (Gulf of Mannar). Figure 4. Trawl bycatch in the Gulf of Mannar often results in several coral reef fish (trigger fish, damselfish, butterfly fish, etc). Figure 5. Turtles are common bycatch in commercial fishing operations such as this dead Green turtle (Chelonia mydas). Figure 6. Dolphins are occasionally caught and drown in gill nets. Figure 7. Bycatch dumped overboard on arriving the fish landing site. Figure 8. Bycatch being dried for poultry food (Rameswaram Palk Bay). RESONANCE May 2007 63
Estimates suggest that during the nesting season, trawlers and gill netters in Orissa incidentally catch and kill 5000-10,000 turtles each year. Estimates suggest that during the nesting season, trawlers and gill netters in Orissa incidentally catch and kill 5000-10,000 turtles each year. It is known that over 100,000 turtles have succumbed to the commercial fishing operations in the last 10 years in Orissa alone. Turtles are not the only reptiles that suffer the unfortunate fate resulting from these fishing operations. My research in Goa and in the Gulf of Mannar have documented other less known, though well represented species such as sea snakes being killed in large numbers. A study on the diet of these creatures revealed that some of them fed on certain species of fish that were also commercially exploited. Thus trawlers besides killing a large number of sea snakes, could also have an indirect impact on their populations through prey depletion and habitat destruction. It has been well document that the removal of predators such as these, high in the food chain adversely affects the functioning of the marine ecosystem. This is because many of these species help keep their prey populations in check and play an important role in maintaining an ecological balance. Is Bycatch of Any Use? Trawlers besides killing a large number of sea snakes, could also have an indirect impact on their populations through prey depletion and habitat destruction. Highly unsustainable fishing methods such as shrimp trawling have been responsible for the steady decline of several of the commercially important seafood species. This decline in target catch species has been offset by the increasing use and value of previously discarded, low value bycatch. This trend is becoming increasingly apparent throughout Asia and other countries in the developing world, with most of the developed nations, continuing to discard large quantities of bycatch. In most coastal states of India, a large proportion of bycatch from local prawn trawlers which was previously discarded is now commonly bought at very low rates. The majority of it is dried with or without salt depending on the species and quality of raw material. It is then supplied as feed to the poultry and aquaculture industries and also used as manure. 64 RESONANCE May 2007
Box 1. Reasons for Not Retaining Bycatch 1. Sorting problems onboard: In India the sorting of the catch is done onboard manually. Sorting the shrimp (target catch) from other forms (bycatch) is a cumbersome process. If further sorting of the fish species within the bycatch is to be carried out especially in not so commercially valuable forms, it is pretty much a waste of time and labour. 2. Limited storage space and preservation facilities on board: In case of smaller shrimp trawlers, there is not enough space for storage of species other than shrimp. This is especially true in the case in longer voyages where fish is spoiled if not stored properly (the cost of ice adds to this problem). Moreover if bycatch (fish) and shrimp is stored together it could lead to mixing and possible contamination of the shrimp resulting in a decrease of its market value. 3. Time taken for unloading bycatch in port: In many cases bycatch is usually caught in much greater proportions as compared to the target catch. Unloading this huge amount of load is waste of time, labor and ultimately money especially if the species has a low commercial value. The situation along the east coast of India is more varied probably because of a wide range in the kind and the size of the fishing crafts and the use of bycatch also varies across this range. For example, some of the large shrimp trawlers have facilities for freezing the bycatch, so even if the vessels are off on long voyages some of the more expensive bycatch is stored and then sold to major fish markets such as Howrah in Calcutta. The remaining bycatch is then dried, ground and used as poultry food or manure. Certain large bycatch which include dolphins, sea turtles and certain species of elasmobranches eg. Rhynchobatus djiddensis are protected by the Wildlife Protection Act, and landing of these creatures is strictly prohibited. They are to be discarded either dead/alive while at sea itself. Implications of Bycatch Removal Removal of species, from the marine ecosystem can have varied effects on the function of the ecosystem. Killing apex predators such as dolphins, sharks and sea snakes, which control populations of their prey fish can lead to sudden proliferation of prey species, which has been documented in other parts of the world. Likewise removal of prey species can impact populations of their RESONANCE May 2007 65
Even though the problem of bycatch is a global issue, our knowledge of the potential ramifications of its removal on the marine ecosystem are in their infancy. predators. The removal of certain planktivores (plankton feeding) species such as sardines, mackerel and anchovy which are shoaling fish and caught in large numbers can have drastic implications on their predator populations. Certain prey species caught as bycatch may also constitute the diet of sea birds and marine mammals. It is known that the reproductive success and behavior in many sea birds and marine mammals depends on the availability of their avored prey fish which may be incidentally caught, thus reducing prey populations may in turn lead to a decline in the predator population. This phenomenon has been documented in the Gulf of Alaska where decline of Harbor seal population coincided with over fishing of their prey in that area. Possible Solutions to the Problem Even though the problem of bycatch is a global issue, our knowledge of the potential ramifications of its removal on the marine ecosystem are in their infancy. The following solutions if followed systematically might help decrease the present quantum of this problem. Revamping the Present Monitoring System used to Collect Fisheries Data We have to develop a more robust monitoring technique to establish a good baseline, in order to make informed decisions for the management of our fisheries on which the livelihoods and lives of millions rest. Most of our fisheries statistics data is based on commercial catch that is landed at designated fish landing sites. Present data collection and analysis in India is usually conducted in a haphazard manner, making little or no attempt to segregate seafood catches based on the type of fishing craft/gear, fishing grounds or the effort. There is a paucity of information with respect to actual catches made at sea, considering a large proportion of bycatch is discarded at sea. This makes us uncertain about the status of most marine species, many of them which may be threatened and others may go extinct without us having a clue. We have to develop a more robust monitoring technique to establish a good baseline, in order to make informed decisions for the management of our fisheries on which the livelihoods and lives of millions rest. 66 RESONANCE May 2007
Box.2. Bycatch Reduction Devices used in Different Fishing Methods Pelagic long lines Tori (bird scaring)lines: Keep sea birds from baited hooks. Weighted lines: Sink hooks faster out of reach of seabirds. Side setting: Reduces the scavenging area by half. Line Setting: Places baited hooks immediately underwater. Circle hooks: Reduce frequency of deeply ingested hooks and limit gut perforation. Gill nets Pingers: Acoustic devices that alert marine mammals to the presence of gill nets to prevent entanglement. Purse seines Media panels: Fine mesh net aprons that reduce the probability of dolphin entanglement during net retrieval. Adapted from Lewison et al., 2004. Technical Know-How Deaths in the case certain charismatic species such as the Olive Ridley sea turtles in Orissa have made officials realize how fishing activities can also impact several other species. Sea turtles along the coast of the country were dying in large numbers in trawl nets. This lead officials to enforce the use of a Turtle Excluder Device (TED). The TED is a frame consisting of a grid of bars installed before the codend (the fag end of the trawl net) at an angle leading upward or downward to an escape slit. Small animals such as shrimp which constitute the target catch can slip through the bars and are retained in the codend while large species, such as turtles, dolphins and other large fish species are stopped by the grid bars and can escape through the opening. A scientific study has recently recommended the mandatory use of TED by all mechanized trawlers operating in areas where higher incidental mortalities have been recorded in Indian waters. A study conducted by the Wildlife Institute of India demonstrated that the TED did reduce small quantities of the target catch, but it constituted a negligible proportion of the total catch. Even though there has been progress made on the use of other kinds of bycatch Reduction Devices (BRD s) worldwide (Box 2), bringing about RESONANCE May 2007 67
The development and use of solutions such as TED s and BRD s can only be effective if the present rate of commercial fishing is seriously checked. the use of even TED in India and that too at Orissa has been met with failure. There is no doubt that methods such as BRD s, help reduce bycatch and in a way minimize the impact on the marine ecosystem, but if we think that this is our only solution, then we are far from solving the problem. The development and use of solutions such as TED s and BRD s can only be effective if the present rate of commercial fishing is seriously checked. This is most pertinent in the case of trawling, more so shrimp trawlers, which are perfectly designed to destroy marine ecosystems. Policy Intervention There exist several laws that help regulate fishing in the country. Some of these include the Marine Fishery Regulation Act which stipulates a Fishing Free Zone, 5 km from the shoreline. The Wildlife Protection Act of 1972 prohibits the landing and selling of several species of marine organisms, right from marine mammals such as dolphins and dugongs, several species of elasmobranchs (sharks and rays), a few species of fish and even other smaller marine organisms such as molluscs and the echinoderms. Alternate day fishing is carried out in certain parts of the country, such as the Gulf of Mannar and the Palk Bay and there is also the observance of a closed season in all the coastal states of the country, which hypothetically coincides with the breeding season of several commercial fish species, with a view of replenishing fish stocks. However the present monitoring is so lax, that illegal fishing continues unchecked. These laws are however often violated, in many cases by bribing officials. A serious effort will have to be made before the situation becomes irreversible a prevalent scene in many parts of South East Asia. Marine Protected Areas Another option worth considering, that will actually enhance marine protection could be the creation of Marine Protected Areas (MPA s). There is clear evidence available from research 68 RESONANCE May 2007
in other countries that MPA s have greatly helped in increasing the fish yield while conserving other forms of biodiversity simultaneously. These areas can also serve as sources for replenishing populations of marine species in the surrounding areas a process commonly termed as the Spillover effect [3]. Another role of MPA s and a very important one is to serve as control sites for scientific research and experimentation, something that is lacking presently in India. Marine Protected Areas have greatly helped in increasing the fish yield while conserving other forms of biodiversity simultaneously. India has a few MPA s along its coastline, however none of these are offered the level of protection they deserve and thus suffer from a huge number of threats. Among these, over fishing in areas theoretically closed to these activities is a prevalent one. Other threats, specific to particular areas, include coral reef mining in the Gulf of Mannar and oil pollution in the Gulf of Kutch. Conclusion A group of scientists led by Boris Worm recently analyzed trends in fish catches from all major coastal and marine ecoregions of the world. Their shocking predictions revealed that if we continue to plunder and pollute our marine ecosytem at the present rate, we are likely to face a global collapse of all commercially exploited marine species by the year 2048 [4]. So are we too late after all? Luckily not yet, the paper has an underlying message of hope. Their analysis suggests that if we act fast and mend our unsustainable ways these trends are still reversible and the recovery of local biodiversity is still possible at least on local and regional scales. This can however be achieved only by the proper management and judicious harvesting of marine resources. It is well known that nature has an immense capability of restoring itself. Marine ecosystems, just like forests if left untouched for a while, can recuperate to a state similar to the original. However the damage to some areas due to years of persistent trawling may be irrevocable. At this point in time, we are left with If we continue to plunder and pollute our marine ecosytem at the present rate, we are likely to face a global collapse of all commercially exploited marine species by the year 2048 [4]. RESONANCE May 2007 69
Scientific research should aim at establishing accurate baseline information and developing robust monitoring protocols to understand the present state of affairs and forecast predictions. very little choice. We need to act quickly and efficiently if are to save what remains. Scientific research should aim at establishing accurate baseline information and developing robust monitoring protocols to understand the present state of affairs and forecast predictions. Managers in the Forest and Fisheries Departments with the mandate of protection of marine ecosystems and regulation of fishing should enforce their laws and make sure that offenders are brought to task. Our resources must be utilized judiciously in order to ensure a continual supply for our future generations. Suggested Reading Address for Correspondence Aaron Savio Lobo Nature Conservation Foundation, 3076/5 IV Cross, Gokulam Park Mysore 570 002, India. Email: aaronlobo79@yahoo.co.uk [1] K Kelleher, Discards in the world s marine fisheries, An update, FAO Fisheries Technical Paper, No.470, pp.131, 2005. [2] R L Lewison, L B Crowder, A J Read and S A Freeman, Understanding impacts of fisheries bycatch on marine megafauna, TRENDS in Ecology and Evolution, Vol.19, No.11, pp.598-604, 2004. [3] T Agardy, Effects of fisheries on marine ecosystems: a conservationist s perspective, Journal of Marine Science, Vol. 57, pp.761 765, 2000. [4] B Worm, E Barbier, N Beaumont, E Duffy, C Folke, B S Halpern, J B C Jackson, H K Lotze, F Micheli, S R Palumbi, E Sala, K A Selkoe, J J Stachowicz, R Watson, Impacts of biodiversity loss on ocean ecosystem services, Science, Vol. 314, pp.787 790, 2006. 70 RESONANCE May 2007