scholarly journals Catch composition of trawl fisheries in Mersin Bay with emphasis on catch biodiversity

2016 ◽  
Vol 40 ◽  
pp. 522-533 ◽  
Author(s):  
Gökhan GÖKÇE ◽  
İsmet SAYGU ◽  
Ahmet Raif ERYAŞAR
Keyword(s):  
Catch Composition ◽  
Trawl Fisheries

scholarly journals Catch and discardfish species of trawl fisheries in the Iskenderun Bay (Northeastern Mediterranean) with emphasis on lessepsian and chondricthyan species

2014 ◽  
Vol 15 (2) ◽  
pp. 380 ◽  
Author(s):  
E. YEMISKEN ◽  
C. DALYAN ◽  
L. ERYILMAZ
Keyword(s):  
Fish Species ◽  
Sparus Aurata ◽  
Depth Range ◽  
Commercial Catch ◽  
Commercial Fish ◽  
Mullus Surmuletus ◽  
Iskenderun Bay ◽  
Fish Catch ◽  
Catch Composition ◽  
Trawl Fisheries

Fish species in catch and discard of trawl fisheries in and around Iskenderun Bay were examined within the fishing closure period and fishingperiod.The sampling was performed from May 2010 to January 2011 by a commercial trawl vessel.Chondricthyan species composed 49 % of discard catch biomass whileGymnura altavela and Dasyatis pastinacawere dominant in hauls. 27 lessepsian fish species were captured during the study,nine of them beingtarget species for trawl fisheries. In total, 14 of the lessepsian fish species were determined as discard species.In both sampling periods, Equulites klunzingeriand Citharus linguatula contributed to discard fish catch dissimilarity among depth ranges (deeper and shallower than 60 m). E. klunzingerishowed high abundance in discard catch.There were no significant differences in the distribution of the discard fish biomass between the sampling periods (ANOVA test, p>0.05). However, depth range pointed out significantdifferences in discard fish catch composition (p<0.05).Among major commercial fish species of trawl fisheries, Mullus surmuletus and Sparus aurata were not separated as discard in anyhaul by fishermen. Any size of these two species  were included in commercial catch (Total length ranged from 61 to 721 mm).

scholarly journals A Deep Learning Approach to Assist Sustainability of Demersal Trawling Operations

2021 ◽  
Vol 13 (22) ◽  
pp. 12362
Author(s):  
Maria Sokolova ◽  
Adrià Mompó Alepuz ◽  
Fletcher Thompson ◽  
Patrizio Mariani ◽  
Roberto Galeazzi ◽  
...  
Keyword(s):  
Absolute Error ◽  
Monitoring Tool ◽  
Video Footage ◽  
Trawl Fishery ◽  
Augmentation Techniques ◽  
Image Acquisition System ◽  
Catch Composition ◽  
First Time ◽  
Trawl Fisheries ◽  
Resolution Dataset

Bycatch in demersal trawl fisheries challenges their sustainability despite the implementation of the various gear technical regulations. A step towards extended control over the catch process can be established through a real-time catch monitoring tool that will allow fishers to react to unwanted catch compositions. In this study, for the first time in the commercial demersal trawl fishery sector, we introduce an automated catch description that leverages state-of-the-art region based convolutional neural network (Mask R-CNN) architecture and builds upon an in-trawl novel image acquisition system. The system is optimized for applications in Nephrops fishery and enables the classification and count of catch items during fishing operation. The detector robustness was improved with augmentation techniques applied during training on a custom high-resolution dataset obtained during extensive demersal trawling. The resulting algorithms were tested on video footage representing both the normal towing process and haul-back conditions. The algorithm obtained an F-score of 0.79. The resulting automated catch description was compared with the manual catch count showing low absolute error during towing. Current practices in demersal trawl fisheries are carried out without any indications of catch composition nor whether the catch enters the fishing gear. Hence, the proposed solution provides a substantial technical contribution to making this type of fishery more targeted, paving the way to further optimization of fishing activities aiming at increasing target catch while reducing unwanted bycatch.

scholarly journals Effect of Cutting Ratio and Catch on Drag Characteristics and Fluttering Motions of Midwater Trawl Codend

2021 ◽  
Vol 9 (3) ◽  
pp. 256
Author(s):  
Wei Liu ◽  
Hao Tang ◽  
Xinxing You ◽  
Shuchuang Dong ◽  
Liuxiong Xu ◽  
...  
Keyword(s):  
Drag Force ◽  
Mesh Size ◽  
Current Speed ◽  
Midwater Trawl ◽  
Minimum Drag ◽  
Fish Catch ◽  
Spatial Geometry ◽  
By Catch ◽  
Trawl Fisheries ◽  
Crucial Part

The codend of a trawl net is the rearmost and crucial part of the net for selective fish catch and juvenile escape. To ensure efficient and sustainable midwater trawl fisheries, it is essential to better understand the drag characteristics and fluttering motions of a midwater trawl codend. These are generally affected by catch, cutting ratio, mesh size, and twine diameter. In this study, six nylon codend models with different cutting ratios (no cutting, 6:1, 5:1, 4:1, 7:2, and 3:1) were designed and tested in a professional flume tank under two conditions (empty codends and codends with catch) and five current speeds to obtain the drag force, spatial geometry, and movement trend. As the cutting ratio of empty codends decreased, the drag force decreased, and the drag coefficient increased. The unfolding degree of codend netting and the height of empty codends were found to be directly proportional to the current speed and inversely proportional to the cutting ratio. The positional amplitude of codend with cutting ratio 4:1 was the smallest for catch. The drag force of codends with catch increased as the current speed increased, and first decreased and then increased as the cutting ratio decreased. To ensure the best stability and minimum drag force of the codend, it is recommended to use the 4:1 cutting ratio codend.

Productive efficiency of the pelagic trawl fisheries in the Southern Black Sea

2021 ◽  
pp. 101853
Author(s):  
Murat Dağtekin ◽  
Osman Uysal ◽  
Serhan Candemir ◽  
Yaşar Genç
Keyword(s):  
Black Sea ◽  
Productive Efficiency ◽  
Trawl Fisheries

Fish and invertebrate by-catch in the crab pot fishery in the Isle of Man, Irish Sea

2017 ◽  
Vol 98 (8) ◽  
pp. 2099-2111
Author(s):  
Fikret Öndes ◽  
Michel J. Kaiser ◽  
Lee G. Murray
Keyword(s):  
Irish Sea ◽  
Target Species ◽  
Catch Per Unit Effort ◽  
Isle Of Man ◽  
Ecosystem Effects ◽  
By Catch ◽  
Catch Rates ◽  
Taxonomic Groups ◽  
Catch Composition ◽  
Autumn And Winter

Baited trap or pot fisheries are considered to have relatively few wider ecosystem effects on the marine environment, particularly when compared with towed mobile fishing gear. However, this assumption is rarely tested in the field. This study aimed to determine the composition of non-target species that occur in crustacean pots and to assess spatial and temporal differences in catches in the waters around the Isle of Man, Irish Sea. The data were collected using fishery independent surveys and a questionnaire study. Based on fishery independent surveys, a total of five taxonomic groups and 43 species occurred as by-catch. The dominant by-catch species was velvet crab Necora puber. The by-catch per unit effort (BPUE) for all of the non-target species was low particularly in comparison to towed bottom gear fisheries around the Isle of Man. BPUE of species composition varied considerably between different locations around the Isle of Man. The results of both the fishery independent and questionnaire data suggested that the by-catch rates varied with season with peak BPUE occurring in spring which then declined into autumn and winter. By-catch composition did not decrease significantly with an increasing target species catch. Overall, by-catch was low relative to target species catch which may be partially attributable to the use of escape panels in pot fisheries in the Isle of Man.

scholarly journals Historical discarding in Mediterranean fisheries: a fishers' perception

2015 ◽  
Vol 72 (9) ◽  
pp. 2600-2608 ◽  
Author(s):  
Dimitrios Damalas ◽  
Christos D. Maravelias ◽  
Giacomo C. Osio ◽  
Francesc Maynou ◽  
Mario Sbrana ◽  
...  
Keyword(s):  
Species Composition ◽  
Market Demand ◽  
Sampling Protocol ◽  
The Past ◽  
Regulatory Constraints ◽  
Fishing Strategies ◽  
Commercially Important ◽  
Trawl Fisheries ◽  
Important Fish

Abstract Discarding of commercially important fish species in the bottom trawl fisheries in the northern Mediterranean Sea was investigated by soliciting the long-term recollections of fishers engaged or formerly engaged in such fisheries. The main aim of our investigation was to describe the prevalence of discarding and its evolution over the past 70 years using information gathered through individual questionnaire-based interviews with fishers from ports in Spain, Italy, and Greece, following a standardized sampling protocol. Although it proved impossible to derive absolute estimates of the volume of discarded catches over the period investigated, we conclude that over the past 70 years, discarding as a practice has gradually increased in the northern Mediterranean trawl fisheries and has been accompanied by a shift in the species composition of the discarded catch. While discarding can occur for a number of reasons, our investigations indicate that discarding in the past was mostly driven by market demand, but recent legal and regulatory constraints have led to changes in fishing strategies and became a significant reason for discards.

scholarly journals Changes in the catch composition of artisanal fisheries attributable to dolphin depredation in a Mediterranean marine reserve

2009 ◽  
Vol 66 (4) ◽  
pp. 699-707 ◽  
Author(s):  
Delphine Rocklin ◽  
Marie-Catherine Santoni ◽  
Jean-Michel Culioli ◽  
Jean-Antoine Tomasini ◽  
Dominique Pelletier ◽  
...  
Keyword(s):  
Marine Reserve ◽  
Bottlenose Dolphins ◽  
Artisanal Fisheries ◽  
Catch Per Unit Effort ◽  
Natural Reserve ◽  
Catch Composition ◽  
The Impact ◽  
High Fish ◽  
Fishing Area ◽  
Fish Avoidance

AbstractRocklin, D., Santoni, M-C., Culioli, J-M., Tomasini, J-A., Pelletier, D., and Mouillot, D. 2009. Changes in the catch composition of artisanal fisheries attributable to dolphin depredation in a Mediterranean marine reserve. – ICES Journal of Marine Science, 66: 699–707. There is increasing evidence from previous studies, and from fishers’ observations, that coastal dolphins use fishing nets as an easily accessible feeding source, damaging or depredating fish caught in the nets. This study investigates the impact of dolphin depredation on artisanal trammelnets by analysing the catch composition of 614 artisanal fishing operations in the Bonifacio Strait Natural Reserve (France). Common bottlenose dolphins (Tursiops truncatus) attacked, on average, 12.4% of the nets and damaged 8.3% of the catch. However, attacked nets were characterized by statistically significantly higher catch per unit effort than unattacked ones. Catch composition also differed significantly after dolphin attacks; bentho-pelagic fish were more represented and reef-associated fish less represented. Our results suggest that (i) dolphins are attracted by high fish densities in the fishing area and/or nets, and (ii) their attacks induce specific fish-avoidance behaviour, according to the fish position in the water column. Although dolphins depredate a small part of the catch, damage to nets, not yet assessed in this area, could weaken the benefits that reserves can provide to artisanal fisheries.

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