Report on causes of mortality of sea turtles in Adriatic sea

Transcription

1 Report on causes of mortality of sea turtles in Adriatic sea Introduction In the Adriatic basin the presence of sea turtles appears to be quite large as it is a very important feeding area for these reptiles. The most common species in all of the Adriatic Sea is Caretta caretta; Chelonia mydas is sporadic in the north, while in the south and east the opportunity to encounter it increases; Dermochelys coriacea is extremely occasional. There are several anthropic threats to sea turtles in the waters of the Adriatic Sea: pollution, maritime traffic, fishing effort. In recent years, the collection of reports on strandings and by-catch of these animals has increased in consistency and accuracy, thanks to regional networks and scientific projects. The establishment of regional networks for the conservation of sea turtles has involved different public institutions and no profit associations, while national and European projects have implemented the monitoring effort, so that now we can have a solid view of the problems in the protection of sea turtles. The NETCET project, which has coordinated research groups on both sides of the Adriatic Sea, has allowed the comparison of collected data, the beginning of standardization of monitoring methods, and the creation of a common database. With data sharing, the database enhances knowledge about the extent of incidental catches and subsequent recoveries of these animals along the Adriatic coasts. While recording of data on strandings and by-catch occurs in the different partner countries in a widespread and constant manner, the assessment of the causes of death is not equally widespread. To determine the cause of death of a sea turtle, a necropsy must be performed, so that the scientific data can be collected and statistically analysed and further in depth analyses can be done. Unfortunately, this is not executable on decomposing carcasses, because most of the analyses need fresh samples. For various reasons, the number of necropsy reports is considerably less than the number of reported dead sea turtles. Therefore, the statistical results on such small amounts of data do not totally support the theories neither about the main cause of mortality in sea turtles nor about the environmental occurrences in the Adriatic Sea. Discussion The state partners of the NETCET project are: Italy, Slovenia, Croatia, Montenegro and Albania. In Italy, Emilia Romagna and Marche are the Regions participating in the project, but the data from recoveries also come from the Friuli Venezia Giulia, Veneto, Abruzzo, Molise and Puglia Regions thanks to the local institutions partners. From Croatia and Abruzzo Region (Italy), only the number of performed necropsies is known (no results of diagnostic tests and statistical evaluation of cause of death).

2 From Albania, the 2 investigations done on dead sea turtles found plastic in the digestive tract and a hook. There are no necropsy data for Slovenia, Montenegro, the Region of Marche, Puglia and Molise (Italy). From the Emilia Romagna Region (Italy), a report regarding 04 carcasses analysed at the Institute of Veterinary between July 202 and June 20 was published with the following results: For 37 specimens [it] has not been possible to establish the cause of death (3.6%); 38.% of subjects had clear traumatic injuries (ex. fractures of the skull, limbs and the carapace, deposits in soft tissues.. ). In 9 cases it was detected the presence of fishing nets tangled around the [limbs]. In the same region another necropsies were performed and specifically: in 203, 20 sea turtles were found injuries and in 0 carcasses the cause of death has not been determined; in 204, the necropsies were 2 resulting in 3 causes of death, i.e. trauma (3/2), drowning (/2) and not identified (7/2). In the Veneto Region, 36 necropsies in 203 and 72 necropsies in 204 were performed on sea turtles stranded on regional coasts, while 4 necropsies in 203 and 7 necropsies in 204 were done on sea turtles submitted to the necropsy room of the Department of Comparative Biomedicine and Food Science (University of Padua) from other regions. Unfortunately, most of the carcasses were in bad condition of conservation: the mummified carcasses were 4 in 203 (% total 203) and 7 in 204 (23,6% total 204), and the carcasses in advanced decomposition were 2 in 203 (8,3% total 203) and 2 in 204 (34,7% total 204). Carcasses in moderate decomposition were in 203 (3,9% total 203) and 7 in 204 (23,6% total 204). The most valuable, mildly decomposed and fresh carcasses, were in 203 (3,9% total 203) and 3 in 204 (8,% total 204). The first and only fresh carcass was examined in 203 (2,8% total 203), while none stranded in 204. With so many decomposed samples, nothing could be assessed in 2,8% of necropsies in 203 (9 carcasses, of which 4/4 mummified and /2 in advanced decomposition), and in 47,2% of necropsies in 204 (34 carcasses, of which 7/7 mummified, 4/2 in advanced decomposition and 3/7 in moderate decomposition). No clear causes of death were observed in 8 cases in 204 (3/2 in advanced decomposition, 3/7 in moderate decomposition and 2/3 in mild decomposition). About the results of the performed necropsies, they can be subdivided in two main classes: infectious agents or suspicion of these and anthropic activities. All the following percentages are calculated on the successful necropsies. All together, the anthropic activities cover 29,4% of the subjects examined in 203 and 0,% in 204 and are of two types: impact lesions [ in 203 (,9%) and 3 in 204 (7,9%)] and hook/fishing line [ in 203 (,9%) and in 204 (2,6%)]. Macroplastics were found only in carcass in 203 (,9 % of successful necropsies, 2,8% total). Lesions from infectious disease, or that lead to suspect the presence of an infectious disease, are the main part of the necropsy results. These lesions were all referable to an alteration in the vascular permeability and consisted in haemorrhagic effusion in the coelomic cavity and pericardial cavity, haemorrhagic oedema in the cranial ventral muscles and severe, diffuse, acute/subacute enteritis. Therefore, the results of the necropsies in 203 were 47,% of infectious diseases (8/7 subjects, of which 3/7 confirmed by bacteriological analyses) and in 204 were 42,% (6/38 subjects, of which 6 confirmed by bacteriological analyses). These results have to be added to 47,% (8/7 subjects) in 203 and 3,6% (2/38 subjects) in 204 of cases in which it was only possible to suspect an underlying infectious disease due to the presence of lesions, without the possibility to conduct further

3 deeper analyses. About the bacteria involved, the research was conducted in a more systematic way in 204 than in 203, when for the first time Photobacterium damselae damselae (/8 analysis in proximal intestine), Photobacterium damselae piscicida (/8 analysis in intracardial blood clot) and Enterobacter spp. (/8 analysis in intracardial blood clot) were seen. In 204 the analyses revealed the solid presence of Photobacterium damselae damselae in 8/6 subjects in different tissues (/8 proximal intestine, /8 intracardial bood clot, 3/8 coelomic effusion, /8 cloaca, /8 pharynx, /8 brain), and other bacteria in different but smaller presence, often copresent. They were: Escherichia coli (4/6), Enterobacter spp. (3/6), Enterobacter cloacae (3/6), Klebsiella spp. (2/6), Proteus mirabilis (/6), Proteus spp. (4/6); Enterococcus spp. (3/6); Schewanella putrefaciens (3/6), Schewanella marina (/6); Corynebacterium spp. (/6), Arcanobacterium pyogenes (/6); Pseudomonas spp. (/6); Bacillus spp. (/6). Due to a scarce reference literature and the exiguity of these data, the real implications of bacteria as cause of death in sea turtles are still to be studied. In particular, the role of Photobacterium damselae damselae is considered very controversial: it behaves as a pathogenic bacterium in fish and an opportunistic one in mammals, but its action on reptiles is not know. Regarding the Enterobacteriaceae family, a large-scale research should be done about the effective significance of these bacteria in sea turtles. A wide spread investigation on live animals and fresh carcasses would give a baseline to better understand what the normal resident flora is, at least in Caretta caretta. Histological analyses were conducted on several organs (stomach, intestine, liver, pancreas, spleen, thymus, thyroid, trachea, lungs, kidneys, adrenal, gonads) but not all from the same subject, depending on the conservation status of the organs. Unfortunately, the tissues were severely decomposed and mostly only inflammatory areas were recognizable. Inflammation was seen primarily in intestine slices with various severity and extension and some granulomas were present in lung samples, often with multinucleated giant cells. In the stomach, some severe chronic ulcers were noticed, rarely accompanied with a section of the responsible parasites (Anisakidae, generally Sulcascaris sulcata); other presumable lesions caused from parasites were seen on the great vessel walls, consisting in areas of severe chronic inflammation with moderate fibrotic exophytic response. Finally, on several subjects stranded in 203 chemical analyses were executed to determine the main pollutant levels in muscle, liver, kidney and fat tissue. The reference ranges for heavy metals and POPs present in literature are extremely wide, but the found levels of Hg, Pb, Cd, Cr, Cu, Zn and of PCB28, PCB2, PCB0, PCB3, PCB38, PCB80, ppdde and ppddt in the loggerhead samples from the north Adriatic Sea fall into these ranges. Other analyses are still to be done, like DNA analyses, radioactive isotopes, analyses of the alimentary tracts content, skeletal age. About the necropsies performed by the Department of Comparative Biomedicine and Food Science (University of Padua) from other regions, 44 in 203 and 7 in 204 were from the Emilia Romagna Region and 0 in 203 were from the Friuli Venezia Giulia Region. The carcasses from 203 came from a massive stranding (about 300 dead Caretta caretta) that happened in a very short time (3 months) and on a relatively short stretch of coastline, only in the northeast part of the Adriatic Sea. In that occasion, for the first time, a bacterial cause was suspected, often observing the lesions previously described. However, a

4 certain cause of death for such an unusual occurrence is still not proposed. In 204 the carcasses were severely cachectic and at necropsy nothing specific could be noticed, while the histological exam revealed a very severe and diffuse chronic enteritis (previously frozen tissue). Data Tables The data used for the following tables on the recoveries of sea turtles derive from the archives of the project partners and are in the on-line database of NETCET. The data are not related to the totality of the findings in the Adriatic Sea. TURTLES DEAD NECROPSIES PARTNERS NETCET PROJECT ITALY CROATIA 37 2 ND 2 SLOVENIA 7 4 ND ND MONTENEGRO ND ND ALBANIA 4 ND 2 Tab. - number of collected dead sea turtles and of performed necropsies Dead Alive tot Dead Alive tot Abruzzo Emilia Romagna ITALY Friuli ND ND Marche Molise Puglia ND ND ND 0 Veneto CROATIA SLOVENIA ALBANIA * 4 2* 6 MONTENEGRO * Without the sea turtles caught in the Stavnik Tab.2 - total number of records on dead and live sea turtles in

5 In Drini Bay (Albania), an important foraging area for loggerheads in Adriatic, is used a fishing gear named Stavnik. It is a fishing gear constructed in shallow water in depth -8m. Stavnik is used in sandy seabed, especially in places like bays that are protected from the wind and storms and their purpose is fish. Sea Turtle are frequently found in these nets as a by-catch. During the 3 years of intense study of Sea Turtle in Albania organized by Herpetofauna Albanian Society, stavnik has been the primary provider of the bycatch data and none of the turtles caught (about 00 individuals) had any damage caused by the stavnik. 203 DEAD TOT ALIVE TOT INJURED RELEASE INTO THE SEA AFTER CURE RELEASE INTO THE SEA STRANDED ALIVE STRANDED DEAD BY CATCH ALIVE TRAWL BY CATCH ALIVE GILLNET BY CATCH DEAD GILLNET BY CATCH ALIVE MIDDLE WATER TRAWL BY CATCH ALIVE SEA FARM BY CATCH ALIVE DEAD ADRIFT ALIVE ADRIFT ITALY SLOVENIA CROATIA 7 38 MONTENEGRO 6 *ALBANIA *by-catch in Stavnik alive and released in Albania n 2 Tab.3 - total number of records on dead and live sea turtles in 203.

6 The turtles collected in the collecting chamber of the stavnik can swim and breathe without any problem because the net is straight fixed in the posts. The three stavniks are placed in Drini bay and have been monitored daily for the presence of the turtles. All the individuals found by-caught in stavnik of both species loggerheads and greens, are released back in the sea after the biometric data are taken. There are released back 2 turtles in 203, 28 turtles in ITALY SLOVENIA CROATIA MONTENEGRO *ALBANIA DEAD TOT ALIVE TOT INJURED RELEASE INTO THE SEA AFTER CURE RELEASE INTO THE SEA STRANDED ALIVE 4 STRANDED DEAD BY CATCH ALIVE TRAWL 29 BY CATCH ALIVE GILLNET BY CATCH DEAD GILLNET 6 BY CATCH ALIVE MIDDLE WATER TRAWL BY CATCH ALIVE SEA FARM BY CATCH ALIVE BY CATCH DEAD 2 DEAD ADRIFT ALIVE ADRIFT 0 2 *by catch in Stavnik alive and released in Albania- n 28 Tab.4 - total number of records on dead and live sea turtles in 204.

7 203 Slovenia Croatia Montenegro Albania Italy dead alive dead alive dead alive dead alive dead alive January 8 9 February 2 0 March 2 2 April 4 May 6 9 June July August Septembe r October November December 28 9 Tab. - total number of collected dead and live sea turtles in 203 (monthly) Italy albania montenegro croazia slovenia Graph. - total number of collected dead sea turtles in 203 (monthly) in the project partners Countries.

8 Italy albania montenegro croazia slovenia Graph.2 - total number of collected live sea turtles in 203 (monthly) in project partners Countries.

9 204 Slovenia Croatia Montenegro Albania Italy dead alive dead alive dead alive dead alive dead alive January February March April May June July August Septembe r October November 4 7 December Tab.6 - total number of collected dead and live sea turtles in 204 (monthly) italy albania* montenegro croazia slovenia Graph.3 - total number of collected dead sea turtles in 204 (monthly) in the project partners Countries.

10 italy albania* montenegro croazia slovenia Graph.4 - total number of collected live sea turtles in 204 (monthly) in the project partners Countries.

11 Conclusions Observing the reported data, a similar pattern in 203 and 204 shows a trend about the stranded dead sea turtles: their numbers increase during the autumn, especially for Italy; in the other countries, a relative uniformity is seen during the seasons. About the living sea turtles, there is more discontinuity with peaks in winter, summer and autumn and this is diffuse in the whole Adriatic Sea basin. Since this data collection was done for the first time along almost all the coasts of the Adriatic Sea, its most important aspect is to provide a starting line for all future research. Although the data do not have statistical significance due to the low number of samples analysed, the impact of by-catch together with the bacterial presence in the water seem to be the greater threats for sea turtles in the Adriatic Sea; conversely, and differently from what expected, pollutants like plastic or POP's do not seems to be a problem in the Adriatic basin. However, the different threats observed are not equally distributed in the basin, but vary according to the area of the Adriatic considered.

12 Authors Cetacea Foundation onlus (Italy) Natural History Museum of Venice (Italy) Department of Comparative Biomedicine and Food Science - University of Padua (Italy) WWF Italy City of Pescara with CSC (Centro Studi Cetacei) (Italy) University of Primorska (Slovenia) SINP- State Institute of Nature Protection (Croatia) Marine Educational Center of Pula (Croatia) Institute for Marine Biology IBM (Montenegro) Herpetofauna Albanian Society HAS (Albania)