Structural characteristics of towed fishing gears used in the Samsun Coast (Black Sea)

Abstract

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...

A new grid-net design to eliminate by-catch for the veined rapa whelk beam trawl fisheries in the south-eastern Black Sea

“…The gear weighed around 90 kg excluding the weight of the mesh. Steel wires of 5 mm in width present on the frames of the beam trawls provided ground contact to reveal the whelks and to facilitate dragging of the net (Kaykaç et al, 2014). Both ends of the steel wires were http://epublishing.ekt.gr | e-Publisher: EKT | Downloaded at 10/07/2020 23:17:02 | mounted tightly to the feet of the frame (5 cm in depth and 5 mm thickness, Fig.…”

“…Traditional beam trawls (locally known as algarna) are the preferred capture device for this species due to comparatively higher catch efficiency (Altınağaç et al, 2004). Referred to as dredge by some authors (Çelik and Samsun, 1996;Altınağaç et al, 2004;Sağlam et al, 2008) and as beam trawl by others (Kaykaç et al, 2014;Zengin et al, 2014), the algarna better resembles a beam trawl in terms of net design, technical specifications, and operational functions, albeit shorter than conventional beam trawls (Valdermarsen and Suuronen, 2003). The studies in the south-eastern Black Sea have shown that this gear causes damage to small benthic organisms since the diamond mesh openings are clogged by veined rapa whelks during the tow (Sağlam et al, 2008;Eryaşar et al, 2016).…”

Effects of square-mesh codend on the benthic by-catch for the beam trawl fisheries of veined rapa whelk, Rapana venosa

“…In the veined rapa whelk fishery, traditional beam trawl method (locally known as algarna) is preferred because of its high efficiency (Altınağaç et al 2004). Algarna is operated with beam trawl technique (Kaykaç et al 2014) but it is smaller than beam trawl that is normally used. For this fishery, target species is only the veined rapa whelk and other species like fish and crab are thrown back into the sea as dead or alive and small ones like bivalves are packed with the target species without any elimination (Eryaşar et al 2018).…”

Effect of steel wire and claw size on the sea snail ( Rapana venosa ) catch in a Black Sea beam trawl fishery

“…These are more environmentally friendly fishing gears with low ecosystem impact index because they are aimed at the target species and cause minimum damage to the ground (16,17). There are limited studies on beam trawls, the most effective means of fishing for the species (10,18,19). There is an urgent need to make structural changes to the beam trawls and to reduce the benthic effect when it is considered that the average annual production in the last 10 years was about 10,000 t and 90% of the production was provided by this fishing gear.…”