Abstract:In this study, structural characteristics of towed fishing gears (bottom and beam trawls) used on the coasts of Samsun were investigated as part of EU-FP7 BENTHIS project. Data for bottom and beam trawl (net, otter board, beam etc.) were obtained in situ investigations and survey studies with fishermen face to face. The numbers of total and active trawl vessel in this area were determined after that these vessels were classified according to size categories. Stratified subsampling for representing the main fleet is taken from that worked during 2011/12 and 2012/13 fishing season. General characteristics of the bottom trawl nets are in two configurations and cutting shape, whereas the otter boards are rectangular shaped. In these nets the number of meshes in fishing circle is changed between 450 and 975, 650 and 750 meshes are the most preferred (%38). All of the bottom trawls (40-80 m depths) are towed with a stern trawler, the engine powers of these vessels are changed between 99 and 1067 kW and 57% of these vessels are between 200 and 500 kW. Rapa whelk (Rapana venosa) fishery is also heavily done with beam trawls on the coasts of Samsun (5-30 m). Some technical differences were observed between the functional designs of the beam trawls used in different locations. While 77% of the beam trawls with engine power between 9.6 and 285 kW were used pair gears on deck, the rest was performed with a single gear. The length and weight of the beam trawls changed 2-3.2 m and 22-61 kg, respectively. As a result, a number of modifications for both fishing gears have been made for more catch so far. There is a need to reveal the changes, monitoring and known to the structural characteristics of these gears for ecosystem approach fisheries. Keywords: Black Sea, Samsun, bottom trawl, beam trawl, Rapa whelk.Özet Bu çalışmada Samsun kıyılarında kullanılan sürükleme av araçlarının (dip trolü ve algarna) yapısal özellikleri EU-FP7 BENTHIS adlı proje kapsamında araştırılmıştır. Dip trolü ve algarnaya (ağlar, kapılar, kiriş vs.) ait veriler balıkçılar ile yapılan yüz yüze görüşmelerde ve yerinde incelemelerde elde edilmiştir. Samsun kıyılarında kullanılan toplam ve aktif trol tekne sayısı belirlendikten sonra bu gemiler boy gruplarına göre sınıflandırılmıştır. Ana kitleyi temsil eden tabakalı alt örnekleme 2011/12 ve 2012/2013 balıkçılık sezonu süresince çalışan ana filodan seçilmiştir. Dip trol ağları yapısal olarak iki görünümlü ve kesimli, kapılar ise dikdörtgen şeklindedir. 450 ve 975 göz büyüklüğünde değişen bu ağlardan 650 ve 750 gözler en fazla (%38) tercih edilenlerdir. Dip trollerinin tamamı (40-80 m derinlik) tek tekne ile çekilmekte, tekne motor güçleri 99 ile 1067 kW arasında değişmekte olup %57'si 200 ile 500 kW arasındadır. Samsun kıyılarında (5-30 m) ayrıca algarnalar ile yoğun olarak deniz salyangozu (Rapana venosa) avcılığı da yapılmaktadır. Farklı alanlarda kullanılan algarnaların tasarımları arasında bazı teknik farklılıklar gözlemlenmiştir. 9,6 ve 285 kW arasındaki motor gücüne sahip alagarna tekneleri...

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In this study, the selectivity of commercial and alternative (experimental) codends for the deep-water rose shrimp, Parapenaeus longirostris, in the Aegean Sea demersal trawl fishery was investigated. Tested were the 44-mm diamond mesh codend as used in commercial fisheries (D44), in addition to a 50 mm diamond (D50), a 40 mm square (S40), and a 40 mm 90° turned mesh (T40), respectively. Sea trials were carried out in the eastern Aegean Sea, with a local commercial trawler using a modified trawl net with 620 meshes circular mouth opening. A total of 35 valid daytime hauls (8 with D44, 9 with D50, 8 with S40 and 10 with T40) were carried out. Selectivity data were collected using the covered codend method and analysed by means of a logistic equation with the maximum-likelihood method. Mean selection curves were estimated and compared using the between-haul variations model. The mean 50% retention carapace length values (LC50) were estimated as 21.2 ± 0.1, 23.2 ± 0.3, 20.8 ± 0.2 and 20.5 ± 0.4 mm CL for D44, D50, S40, and T40, respectively. Selection range (SR) values were determined as 4.9 ± 0.1 mm in D44, 8.7 ± 0.3 mm in D50, 4.0 ± 0.3 mm in S40, and 10.1 ± 0.3 mm in T40. While haul duration and total catch among the parameters did not affect the LC50 values for the investigated codends, the value of the parameter describing the weight of P. longirostris caught in that codend showed an effect for the D50 and T40 codends. Consequently, all investigated codends yielded sufficient LC50 results when considering the minimum landing size (MLS) value imposed by the EU (20 mm CL). In conclusion, the legally allowed S40, which gave an LC50 value close to that of D44, and which would be the preferable codend in terms of its releasing characteristics for individuals under the MLS value (89%), can be used as a good alternative for the D44 (preferred by the fishermen) in the deep-water rose shrimp fishery.

A large part of the total whiting (Merlangius merlangus euxinus) fishing in the Black Sea is carried out with the traditional bottom trawl nets along the coast of Turkey. Diamond mesh shape with 40 mm mesh size (40D) has been used in the codends of these trawls. In this study, the traditional trawl codend (40D) and square-mesh codend with different size (36S and 40S) were compared for whiting size selectivity in August 2014. Selectivity data were collected by using a covered codend method and analysed taking between haul variations in to account. The selectivity parameters were estimated by using CC2000 software. Results showed that commercially used 40D trawl codend is not selective enough to release immature of whiting. However, the net change in square mesh (36S and 40S) instead of a diamond-shaped (40D) mesh significantly improved the mesh selectivity for whiting. The 40S trawl codend is even higher than the first maturity size (LM50) with a length at fifty percent retention (L50) of 15.74 cm. In conclusion all square mesh codends with different mesh size tested here supplied appropriate selection considering minimum landing size (MLS) of whiting.

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