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Impact of Depth and Season on the Demersal Trawl Discard

Yıl 2012, Cilt: 12 Sayı: 4, - , 01.08.2012

Öz

Given that the discard has crucial impact on the coastal ecosystems, various countries around the world adopted various regulations to reduce the discard of non-commercial and undersized commercial species in the trawl catch, such as trawl exclusion depths and closed season. In this work discarded part of the catch of a trawl has been assessed to evaluate impact of depth and season. Monthly trawl-survey data, collected by the same research vessel operating all year round over the entire depth ranges of the same fishing ground, were used in order to minimize the sources of variation. By this mean, potential rather than absolute composition and quantity discarded by a trawl boat were estimated regardless of fishing regulations applied to the fleet. A generalized additive model was used to model the quantity of discarded catch as a function of depth and time. The model outputs were then used to quantify the impact of fishing regulations on the reduction in discard. The results suggested that the quantity of the catch returned to the sea is reduced 49% by trawl closure and 57% by trawling depth limitations. Overall, season and depth regulations reduce the discard by 77% at the expense of a 73% reduction in marketable catch. Finally, past trawl-survey data collected in the 1980s at the same site with the same research vessel and with the same net were used to evaluate possible impacts of regulations on the modification of fish composition

Impact of Depth and Season on the Demersal Trawl Discard

Yıl 2012, Cilt: 12 Sayı: 4, - , 01.08.2012

Öz

Given that the discard has crucial impact on the coastal ecosystems, various countries around the world adopted various regulations to reduce the discard of non-commercial and undersized commercial species in the trawl catch, such as trawl exclusion depths and closed season. In this work discarded part of the catch of a trawl has been assessed to evaluate impact of depth and season. Monthly trawl-survey data, collected by the same research vessel operating all year round over the entire depth ranges of the same fishing ground, were used in order to minimize the sources of variation. By this mean, potential rather than absolute composition and quantity discarded by a trawl boat were estimated regardless of fishing regulations applied to the fleet. A generalized additive model was used to model the quantity of discarded catch as a function of depth and time. The model outputs were then used to quantify the impact of fishing regulations on the reduction in discard. The results suggested that the quantity of the catch returned to the sea is reduced 49% by trawl closure and 57% by trawling depth limitations. Overall, season and depth regulations reduce the discard by 77% at the expense of a 73% reduction in marketable catch. Finally, past trawl-survey data collected in the 1980s at the same site with the same research vessel and with the same net were used to evaluate possible impacts of regulations on the modification of fish composition

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Ayrıntılar

Birincil Dil Türkçe
Bölüm Makaleler
Yazarlar

Ali Cemal Gücü Bu kişi benim

Yayımlanma Tarihi 1 Ağustos 2012
Yayımlandığı Sayı Yıl 2012 Cilt: 12 Sayı: 4

Kaynak Göster

APA Gücü, A. C. (2012). Impact of Depth and Season on the Demersal Trawl Discard. Turkish Journal of Fisheries and Aquatic Sciences, 12(4).
AMA Gücü AC. Impact of Depth and Season on the Demersal Trawl Discard. Turkish Journal of Fisheries and Aquatic Sciences. Ağustos 2012;12(4).
Chicago Gücü, Ali Cemal. “Impact of Depth and Season on the Demersal Trawl Discard”. Turkish Journal of Fisheries and Aquatic Sciences 12, sy. 4 (Ağustos 2012).
EndNote Gücü AC (01 Ağustos 2012) Impact of Depth and Season on the Demersal Trawl Discard. Turkish Journal of Fisheries and Aquatic Sciences 12 4
IEEE A. C. Gücü, “Impact of Depth and Season on the Demersal Trawl Discard”, Turkish Journal of Fisheries and Aquatic Sciences, c. 12, sy. 4, 2012.
ISNAD Gücü, Ali Cemal. “Impact of Depth and Season on the Demersal Trawl Discard”. Turkish Journal of Fisheries and Aquatic Sciences 12/4 (Ağustos 2012).
JAMA Gücü AC. Impact of Depth and Season on the Demersal Trawl Discard. Turkish Journal of Fisheries and Aquatic Sciences. 2012;12.
MLA Gücü, Ali Cemal. “Impact of Depth and Season on the Demersal Trawl Discard”. Turkish Journal of Fisheries and Aquatic Sciences, c. 12, sy. 4, 2012.
Vancouver Gücü AC. Impact of Depth and Season on the Demersal Trawl Discard. Turkish Journal of Fisheries and Aquatic Sciences. 2012;12(4).