scholarly journals Effect of a lateral square-mesh panel on the catch pattern and catch efficiency in a Mediterranean bottom trawl fishery

2020 ◽  
Vol 21 (1) ◽  
pp. 105
Author(s):  
SARA BONANOMI ◽  
JURE BRČIĆ ◽  
BENT HERRMANN ◽  
EMILIO NOTTI ◽  
ALESSANDRO COLOMBELLI ◽  
...  
Keyword(s):  
Mesh Size ◽  
Lateral Position ◽  
Bottom Trawl ◽  
Important Species ◽  
Commercial Fish ◽  
Trawl Fishery ◽  
Red Mullet ◽  
Commercially Important ◽  
The Mediterranean ◽  
Trawl Fisheries

The current legal codends used in Mediterranean bottom trawl fisheries are at high risk of retaining undersized individuals of several commercial fish species. This entails that codends alone are unable to provide the desired exploitation pattern. A simple technological measure that potentially can provide higher release efficiency of undersized fish are Square-Mesh Panels (SMPs). SMPs are often applied in the upper section of the trawl belly, just ahead the codend. However, recent studies in the Mediterranean have demonstrated that SMPs mounted in this position provided limited release efficiency, because very few fish came into contact with their meshes. In attempt to improve SMPs efficiency in the Mediterranean bottom trawl fisheries, we applied them on the lateral sides of the last tapered section of the trawl belly, just ahead of the codend, and fitted two guiding panels in the trawl belly to enhance fish-SMP contact. We compared the catch performance of a standard commercial trawl with a 52 mm diamond-mesh codend and of a similar trawl fitted with lateral SMPs (70 mm mesh size) in the belly using a twin trawl. The study focused on red mullet (Mullus barbatus), a commercially important species, but data for gurnard (Chelidonichthys lucerna and Chelidonichthys cuculus)  were also obtained and analysed. In contrast to previous research on SMPs mounted in the top panel of the trawl, in this study SMPs induced a significant effect on catch performance for red mullet, demonstrating that their lateral position involved greater fish-SMP contact. However, since the test trawl lost a significant amount of legal-sized red mullet compared with the standard trawl, the effect was not wholly positive, possibly due to an excessively large mesh size. Therefore, future studies should be encouraged to test lateral SMPs with smaller mesh sizes.

scholarly journals Estimating selectivity of experimental diamond (T0) and turned mesh (T90) codends in multi-species Mediterranean bottom trawl

2020 ◽  
Author(s):  
ANDREA PETETTA ◽  
BENT HERRMANN ◽  
MASSIMO VIRGILI ◽  
ROCCO De MARCO ◽  
GIOVANNI CANDUCI ◽  
...  
Keyword(s):  
Mesh Size ◽  
Bottom Trawl ◽  
Size Selectivity ◽  
Important Species ◽  
Trawl Fishery ◽  
The North ◽  
Common Squid ◽  
Commercially Important ◽  
The Mediterranean ◽  
The Difference

The effect of shifting from a diamond mesh codend (T0) to a 90° turned mesh codend (T90) on the size selectivity of seven commercially important species in the Mediterranean bottom trawl fishery was evaluated. During sea trials conducted in the north-western Adriatic, two experimental codends made of 54 mm nominal mesh size netting that differed only in mesh configuration were alternately mounted on the same trawl. Overall, the size selectivity was significantly improved for all the species analysed, shifting from T0 to T90. The difference in the average expected L50values between T90 and T0 was particularly marked in European hake (Merluccius merluccius, 21.26 vs 11.26 cm total length), common squid (Loligo vulgaris, 12.06 vs 7.88 cm mantle length) and mantis shrimp (Squilla mantis, 20.78 vs 13.35 mm carapace length). Both codends had an excessive size selectivity especially for red mullet (Mullus barbatus), Mediterranean horse mackerel (Trachurus mediterraneus) and whiting (Merlangius merlangus), thus involving a commercial loss. These findings demonstrate the efficiency of the T90 codend tested at excluding undersized specimens, especially of hake, whose average L50was above the minimum conservation reference size of 20 cm. The adoption of this practical and inexpensive solution could help improve the management of the demersal resources targeted by the Mediterranean bottom trawl fishery.

scholarly journals Assessment of goatfish fisheries in Turkey based on the microdata set of official landing statistics

2021 ◽  
Vol 38 (3) ◽  
pp. 303-309
Author(s):  
Nuray Çelik Mavruk ◽  
Sinan Mavruk ◽  
Dursun Avşar
Keyword(s):  
Mediterranean Sea ◽  
Black Sea ◽  
Large Scale ◽  
Aegean Sea ◽  
Bottom Trawl ◽  
The Black Sea ◽  
Marmara Sea ◽  
Trawl Fishery ◽  
Red Mullet ◽  
The Mediterranean

Although goatfishes (Mullidae Rafinesque, 1815) are among the most important commercial fishes in Turkey, no research has been found investigating the characteristics and spatial patterns of goatfish fishery. Here, we assessed the goatfish fishery of Turkey based on the microdata set of Turkish National Fishery Statistics gathered by Turkish Statistical Institute (TÜİK) between 2014 and 2017. In this context, we investigated the variation of total goatfish catch by cities. In addition, we compared the contribution of small (boat <10m) and large scale (boat >10m) fishers as well as different fishing techniques to the total goatfish catch in Turkey. Finally, an evaluation was made on the discard rates recorded in the official landing statistics. The results showed that higher red mullet (Mullus barbatus Linnaeus, 1758) catch was reported in the eastern Mediterranean, whereas surmullet (Mullus surmuletus Linnaeus, 1758) catch was significantly higher in the western Black Sea. On the other hand, fishery-independent investigations revealed that the Turkish fishery fleet mostly catches red mullet throughout the coasts of Turkey. Therefore, the separate records of red mullet and surmullet in the landing statistics likely represent the local names of red mullet rather than two different species. Large scale fishers were the main source of fishery pressure in the Mediterranean Sea, the Aegean Sea and the Black Sea. However, the majority of the catch was landed by small scale fishers in the Marmara Sea. The bottom trawl fishery landed 88, 92 and 87% of total goatfish catch in the Black Sea, the Aegean Sea and the Mediterranean Sea, respectively. Purse seiners provided the largest part of total goatfish catch (40%) in the Marmara Sea, where the bottom trawl fishery is prohibited. The overall average for the discard rate was found to be 0.47%. There were no statistically significant differences among the discard rates of two species, marine regions or fishing methods.

scholarly journals Comparison of beam trawl catch, by-catch and discard in fishing and non-fishing areas – a case study from the northern Adriatic Sea

2021 ◽  
Vol 22 (1) ◽  
pp. 108
Author(s):  
DARIA EZGETA -BALIĆ ◽  
NEDO VRGOČ ◽  
IGOR ISAJLOVIĆ ◽  
DAMIR MEDVEŠEK ◽  
ANTE VUJEVIĆ ◽  
...  
Keyword(s):  
Adriatic Sea ◽  
Beam Trawl ◽  
Northern Adriatic Sea ◽  
Important Species ◽  
Northern Adriatic ◽  
Trawl Fishery ◽  
Trawl Catch ◽  
Commercially Important ◽  
By Catch ◽  
Trawl Fisheries

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.

Diets and trophic guilds of demersal fishes of the south-eastern Australian shelf

2001 ◽  
Vol 52 (4) ◽  
pp. 537 ◽  
Author(s):  
C. Bulman ◽  
F. Althaus ◽  
X. He ◽  
N. J. Bax ◽  
A. Williams
Keyword(s):  
Fish Species ◽  
Abundant Species ◽  
Trophic Guilds ◽  
The South ◽  
Important Species ◽  
Trawl Fishery ◽  
South Eastern ◽  
Total Fish ◽  
Wet Weight ◽  
Commercially Important

A total of 8200 stomach samples was collected from 102 fish species caught by trawl or gillnet during research surveys on the south-eastern Australian shelf from 1993 to 1996. Diet compositions were analysed based on percentages of wet weight of prey. Of the total fish examined, 70 species had sufficient stomach samples (i.e. >10) for further analysis. Ten trophic guilds were identified from cluster analysis. Benthic prey dominated the diets. However, analysis on a subset of 28 abundant species that were commercially and ecologically important, showed that pelagic prey was dominant, particularly for 12 quota species. This suggests that pelagic production contributes significantly to the trawl fishery production. Further analysis on the diets of these 28 species found that although fish was more important than invertebrate prey, there was no evidence of significant predation on commercially important species (quota species)by other fish species. A food web diagram was constructed, mostly based on the diet compositions, guild structure and relative abundance of commercially and ecologically important fish species, to show major trophic interactions of the shelf ecosystem.

scholarly journals Mitigating ecosystem impacts of bottom trawl fisheries for North Sea sole Solea solea by replacing mechanical by electrical stimulation

2020 ◽  
Author(s):  
A.D. Rijnsdorp ◽  
J. Depestele ◽  
O.R. Eigaard ◽  
N.T. Hintzen ◽  
A. Ivanovic ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
North Sea ◽  
Bottom Trawl ◽  
Beam Trawl ◽  
Electrode Arrays ◽  
Impact Indicator ◽  
Total Allowable Catch ◽  
Trawl Fishery ◽  
The Impact ◽  
Trawl Fisheries

AbstractEcosystem effects of bottom trawl fisheries are a major concern. We analysed whether the replacement of mechanical stimulation by electrical stimulation may reduce the adverse impacts on the benthic ecosystem in the beam trawl fishery for sole. Although the use of electricity is not allowed to catch fish in European Union waters, a number of beam trawlers got derogation and switched to pulse trawling to explore the potential to reduce impacts. We extended a recently developed assessment framework and showed that the switch to pulse trawling substantially reduced benthic impacts when exploiting the Total Allowable Catch of sole in the North Sea. We applied the framework to Dutch beam trawl logbook data from 2009 to 2017 and estimated that the trawling footprint decreased by 23%; the precautionary impact indicator of the benthic community decreased by 39%; the impact on median longevity decreased by 20%; the impact on benthic biomass decreased by 61%; the amount of sediment mobilised decreased by 39%. The decrease is due to the replacement of tickler chains by electrode arrays, a lower towing speed and higher catch efficiency for sole. The effort and benthic impact of the beam trawl fishery targeting plaice Pleuronectes platessa in the central North Sea increased with the recovery of the plaice stock. This study illustrates the usefulness of a standardized methodological framework to assess the differences in time trends and trawling impact between gears.

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