Dolphins Inhabiting in Black Sea and Effects of Fisheries

Abstract

Dolphins are the most important members of the marine mammals which undergo a decrease in population for many reasons such as overfishing, habitat degradation, maritime / traffic and pollution. Biodiversity in the Black Sea is low mostly due to the geographical isolation and low salinity, high hypoxic amount and anoxic bottom waters of 100-250 m depth as well. Therefore, only the three dolphin species; the harbour porpoise Phocoena phocoena , common dolphin Delphinus delphis and bottlenose dolphin Tursiops truncatus live in the Black Sea region. This study is about harbor porpoise, short-beaked dolphin and bottlenose dolphin living in the Black Sea . The results of the scientific researches and publications focusing on these species are scanned and gathered together. The biological characteristics, ecological requirements and habitats of these species are reviewed, effect on both ecosystem and fisheries are evaluated. Many species of the marine mam- mals are negatively effected by anthropogenic factors and as a result given in the Red List” by the the World Conservation Union IUCN where; Delphinus delphis is stated as least compromised LC , he Mediterranean sub-population is stated as endangered EN , Phocoena phocoena is stated as least compromised LC , Tursiops truncatus is stated as least compromised LC and Mediterranean subpopulation of Tursiops truncatus is stated as sensitive VU . Unintentional catch of dolphins, mostly resulting in death or killing of these species, by turbot nets having 280-360 mm mesh size is one of the leading anthropogenic factors. Besides, dolphins’ stealing fish particularly from the bottom gillnets with 32-44 mm mesh size and destroying these nets have a negative impact on fishing. In many parts of the world, many studies were perfomed to prevent unintentional catch bycatch of the dolphins and to keep away the dolphins from the nets in order to prevent fish stealing depredation and damaging of the nets. Studies have also been carried on focusing on the unintentional catch bycatch of dolphins in the Black Sea region, however researches particularly on acoustic dolphin repellents are very limited.

Keywords

• Black Sea,Fisheries,Dolphin,Delphinus delphis,Tursiops truncatus,Phocoena phocoena

Karadeniz’de Yaşayan Yunus Türleri ve Balıkçılığa Etkileri

Abstract

B aşta coğrafik izolasyon olmak üzere düşük tuzluluk, yüksek hipoksik miktarı ve derinliği 100-250 m’nin altındaki suların anoksik olması nedeniyle Karadeniz’deki biyolojik çeşitlilik düşüktür. Bu nedenle yalnızca mutur Phocoena phocoena , kısa gagalı yunus Delphinus delphis ve afalina Tursiops truncatus olmak üzere üç yunus türü yaşamaktadır. Sunulan bu çalışmada türlerin biyolojik özellikleri, ekolojik istekleri, yaşam alanları üzerinde durulmuş, gerek ekosisteme gerekse balıkçılığa etkileri üzerine değerlendirmeler yapılmıştır. Deniz memelileri gibi birçok türün özellikle antropojenik etmenler sonucunda olumsuz olarak etkilenmesinden dolayı Dünya Koruma Birliği IUCN tarafından “Kırmızı Liste” de Delphinus delphis türü en az tehlikede LC , Akdeniz alt popülasyonu ise soyu tehlike altında EN olarak, Phocoena phocoena türü en az tehlikede LC , Tursiops truncatus türü en az tehlikede LC , Tursiops truncatus türünün Akdeniz alt popülasyonu ise hassas VU şeklinde belirtilmiştir. 280-360 mm ağ göz açıklığına sahip kalkan ağlarıyla gerçekleştirilen balıkçılıkta, yunusların istenmeden avlanması ve büyük olasılıkla ölmesi ya da öldürülmesi bu etkilerin başında gelmektedir. Ayrıca, özellikle 32-44 mm ağ göz açıklığına sahip dip uzatma ağlarıyla yapılan avcılıkta, yunusların ağlara yakalanmış balıkları çalması ve bu sırada ağları parçalaması da balıkçılık üzerinde olumsuz bir etkiye yol açmaktadır

Keywords

• Karadeniz,Balıkçılık,Yunus,Delphinus delphis,Tursiops truncatus,Phocoena phocoena

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