Is Opportunistic Sampling Methodology Effective Enough To Collect Biological Information On Elasmobranch Species: A Case Study From Eastern Mediterranean

Bu makalenin Türkçe yayınlanmamıştır.

Elizabeth Grace Tunka Bengil1,2

1Girne American University, Marine School, Girne, TRNC via Turkey

2 Akdeniz Koruma Derneği, Urla, Izmir, TURKEY

There are questions going around, rather scientific sampling should be questioned, or all stopped due to status of a shark and ray species populations and suggest on a hands-off approach, on the other hand some votes lethal sampling is important for obtaining information on life history for more effective management or conservation strategies. Producing science base biological information on endangered species is crucial for species conservation. In case of sharks and rays, this need increases since these species are the species that have are unpopular and marked as monsters by public, feared trough out most part of the history. Though it is important to obtain biological information, it is also as important to do little damage as possible to the populations since most of elasmobranch species are in a declining trend in the world seas as well as the Mediterranean Sea. Growing concern for shark and ray populations increases the pressure not to kill these animals. This raises concern about how research on sharks should be conducted. Regarding this, aim of this study is to determine if opportunistic sampling methodology is enough to obtain or produce biological information on eight endangerred elasmobranch species (3 sharks and 5 rays) without adding more pressure on their populations. As part of two “The Rufford Foundation Small Grant Program” projects, individuals of Mustelus asterias, Scyliorhinus canicula, Torpedo marmorata, Gymnura altavela, Dasyatis pastinaca, Myliobatis aquilla, and Raja radula were collected from coasts of Izmir Bay to Fethiye Bay, eastern Mediterranean, between May 2015-June 2017. Individuals either were obtained frozen or fresh from fishermen, and only bycatch individuals which died due to fishing activities were collected or bought from local fish mongers. Each individual was examined and morphological measurements, stomach contents and maturity stages were recorded. Among these individuals M. asterias was a near-term pregnant individual carrying 4 embryos and rest were either neonates or fully mature. In conclusion, present study demonstrates that though opportunistic sampling methodology for population dynamic studies on elasmobranch species is not enough in certain cases (such as for length and weigh relationship), it is still a useful tool to obtain biological data on species.

Keywords: Elasmobranch, opportunistic sampling, reproduction biology, Eastern Mediterranean