Effect of depth and Season on Catch Composition and Discard Rate in Gillnet Fishery in the South-eastern Coast of the Black Sea

Yıl 2020, , 82 - 93, 01.03.2020

İsmet Balik

https://doi.org/10.22392/actaquatr.595457

Cited By: 2

Öz

Effects of depth and season on species composition of catch and discard rate in the gillnet fishery on the south-eastern coast of the Black Sea was investigated in this study. for this purpose, fishing trials were carried out in the four different depth strata (0-14 m, 15-29 m, 30-49 m and 50 m≥) using multifilament gilnets with mesh sizes of 32, 34, 36 and 38 mm, from March 2013 to February 2014. In the fishing trials, a total of 2506 individuals (133.729 g) belongs to eight fish species were obtained which were whiting (Merlangius merlangus), red mullet (Mullus barbatus), pontic shad (Alosa immaculata), mediterranean horse mackerel (Trachurus mediterraneus), black scorpionfish (Scorpoena porcus), stargazer (Urascopus scaber), seahorse (Hippocampus sp.) and black-striped pipefish (Syngnathus abaster). Allmost catches for whiting, red mullet, pontic shad and mediterranean horse mackerel were of economic value, while all catches for the other species were were discarded. In the shallow waters varying between 0-14 m depth, red mullet and mediterranean horse mackerel were mostly caught. However, catches of especially mediterranean horse mackerel were decreased gradually with increasing water depth. The most caught fish species in deeper water strata more than 15 m was whiting. In the evaluation of the effect of the season on the species composition of catch, the whiting was the most caught fish species by the trial gillnets in all seasons. These fish species, except autumn season (in autumn, potic shad and Mediterranean horse mackerel) followed by red mullet in all seasons. On the orher hand, the rate of discard was determined as 10.2% in number and 15.9% in biomass. It has been found that the discard rate decreases gradually due to the increase in water depth. Seasonally, the lowest discard rate was calculated in winter, followed by autumn, spring and summer, respectively.

Anahtar Kelimeler

East Black Sea, Gillnet, Catch composition, depth, season

Destekleyen Kurum

Ordu Üniversitesi Bilimsel Araştırma Projeleri Destekleme Birimi

Proje Numarası

TF-1225

Teşekkür

This study was supported by the Scientific Research Fund of Ordu University with the project number TF-1225. I am grateful to Taner Topçu for all of his and help throughout the data collection.

Karadeniz’in Güney-doğu Kıyılarında Yapılan Galsama Ağları ile Avcılıkta Av Kompzisyonu ve Iskarta Oranı Üzerine Mevsim ve Derinliğin Etkisi

Öz

Bu araştırmada, Türkiye’nin Doğu Karadeniz kıyılarında yapılan sade uzatma ağlarıyla avcılıkta avın tür kompozisyonu ve ıskarta oranı üzerine mevsim ve derinliğin etkisi araştırılmıştır. Bu amaçla, Mart 2013-Şubat 2014 tarihleri arasında dört farklı derinlik katmanında (0-14 m, 15-29 m, 30-49 m ve 50 m≥) 32, 34, 36 ve 38 mm göz büyüklüğüne sade uzatma ağları kullanılarak avcılık denemeleri gerçekleştirilmiştir. Denemelerde, mezgit (Merlangius merlangus), barbunya (Mullus barbatus) tirsi (Alosa immaculata), istavrit (Trachurus mediterraneus), iskorpit (Scorpaena porcus), tiryaki (Uranospus scaber), deniz atı (Hippocampus sp.) ve deniz iğnesi (Syngnathus abaster) türlerine mensup toplam 2506 (133.729 g) balık yakalanmıştır. Yakalanan balık türlerinden mezgit, barbunya, tirsi ve istavrit avının tamamına yakını ekonomik değere sahip iken, diğer türlerin avlarının tamamı ıskarta edilmiştir. Derinliği 0-14 m arasında değişen sığ sularda en fazla barbunya ve istavrit yakalanmıştır. Ancak, artan su derinliği ile özellikle istavritin av miktarı hızla azalmıştır. Derinliği 15 m’den daha derin su katmanlarında en fazla yakalanan balık türü ise mezgit olmuştur. Avın tür kompozisyonu üzerine mevsimlerin etkisi bakımından yapılan değerlendirmelerde, tüm mevsimlerde sade uzatma ağlarında en fazla yakalanan balık türünün mezgit olduğu görülmüştür. Bu balık türünü, sonbahar mevsimi hariç (sonbaharda tirsi ve istavrit) barbunya izlemiştir. Diğer taraftan, ıskarta oranı sayıca %10,2, biyokütlece %15,9 olarak belirlenmiştir. Araştırmada, ıskarta oranının su derinliğindeki artışa bağlı olarak tedrici olarak azaldığı tespit edilmiştir. Mevsimsel olarak ise, en düşük ıskarta oranı kış mevsiminde hesaplanırken, bu mevsimi sırasıyla sonbahar, ilkbahar ve yaz mevsimi izlemiştir.

Anahtar Kelimeler

Doğu Karadeniz, sade uzatma ağı, av kompozisyonu, derinlik, mevsim

Proje Numarası

TF-1225

Kaynakça

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