Survival of by-catch from a beam trawl

Beam trawl fishery is highly important in the Croatian part of the northern Adriatic wherein 116 vessels have a licence for this type of fishing gear. A sharp decrease in the beam trawl catch observed since 2015 has raised concern about not only socio-economic issues but also ecological issues and the effect that beam trawl fisheries have had on exploited stocks. Besides the effect that beam trawl fisheries can have on targeted economically important species, intensive dredging can cause long-term changes in the benthic community. Therefore, this study aimed to detect the effect that this type of fishing gear has on target and by-catch species. Furthermore, survey data were compared with the official beam trawl fishery data gathered through Vessel Monitoring System data together with fishermen’s logbooks. Our research targeted two adjacent areas: an area where beam trawl fishing is allowed and an area where it is forbidden. The results demonstrate that the commercially important catch represented a minor share of the total beam trawl catch in both survey areas, while discard made up more than 93% of the total catch. The main beam trawl commercially important species in the Croatian part of the northern Adriatic Sea was Pecten jacobaeus, followed by Solea solea and Ostrea edulis. Our results suggest that beam trawl fisheries mostly affect target bivalve species and some non-commercial benthic species (e.g. sponges). The differences recorded between areas could suggest that beam trawl fisheries cause changes mostly in the P. jacobaeus population.

Download Full-text

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

Mediterranean Marine Science ◽

10.12681/mms.15351 ◽

2018 ◽

Cited By ~ 2

Author(s):

AHMET RAIF ERYAŞAR

Keyword(s):

Black Sea ◽

The Black Sea ◽

Beam Trawl ◽

The South ◽

South Eastern ◽

Sea Beam ◽

The Mean ◽

By Catch ◽

Trawl Fisheries ◽

Rapa Whelk

The beam trawl fisheries in the Black Sea only target the veined rapa whelk (Rapana venosa) individuals, and other species like fishes and crabs are thrown back into the sea dead or alive. Furthermore, small bivalves and crabs are packed with the target species without any elimination. In this study, a grid-net design (GND) with two different bar spacing was tested to reduce the by-catch. In total 30 hauls (15 hauls for each bar spacing) were carried out in the south-eastern Black Sea between 17 and 26 August 2017. A commercial diamond mesh and one of the grid-net beam trawls were towed simultaneously onboard a commercial vessel to compare the by-catch compositions. Results showed that there were statistically significant (p<0.01) 78% and 83% decreases in the mean weight of the by-catch for 20 and 30 mm grid-nets, respectively. When compared to the conventional gear, a commercial loss of 14% in the 20 mm GND, and 39% in the 30 mm GND in landing values were estimated. In conclusion, use of grid-nets in south-eastern Black Sea beam trawl fisheries can significantly reduce the by-catch of most benthic species. However, it also causes some commercial loss which might be compensated by providing some compensation to fishers such as extension of the fishing season.

Download Full-text