Catch composition

  • 文章类型: Journal Article
    爆炸捕鱼是非法的,生态破坏性捕鱼方法,对许多大规模鱼类来说是致命的。渔民更喜欢使用炸药进行爆炸捕鱼,尤其是土耳其的小规模渔业,因为它需要最小的努力,但仍然导致更高的渔获量。在目前的研究中,20个受控实时爆破结果的演示涉及物种组成,鱼的大小,渔获率,渔获组成,商业/丢弃率,CPUE对鱼类外部和内部异常症状的估计和临床观察。由于其有害影响,爆破试验是在有限数量的特殊许可下进行的。使用PRIMERv6对收集的数据进行了测试,并分析了多样性指数。对于收集的物种之间的相似性,使用聚类分析来检查结果的稳定性。多维缩放(MDS)也用于评估捕捞中的鱼类物种。总共收集了1014个个体(63.8千克),并检查了属于七个科的18种鱼类。根据实验室检查,研究发现,在研究过程中,爆破在采样的鱼类中引起了不同的外部和内部异常症状。
    Blast fishing is an illegal, ecologically destructive fishing method, fatal for many fish species at large scales. Blast fishing using dynamite is preferred by the fishers, especially small scale fisheries in Turkey, as it requires minimal effort but still results in higher catches. In the current study, demonstration of 20 controlled real-time blasting results involves species composition, size of fish, catch rates, catch composition, commercial/discard ratios, CPUE estimates and clinical observations of external and internal abnormality symptoms of fish species. Blasting trials were carried out with special permission in limited numbers because of its harmful effect. The collected data was tested using PRIMER v6 and diversity indices were also analysed. For the similarity between collected species cluster analysis was used to examine the stability of the results. Multidimensional scaling (MDS) was also applied for the assessment of fish species in the catch. A total of 1014 individuals (63.8 kg) were collected and 18 fish species belonging to seven families were examined. According to laboratory examinations, it was found that blasting caused different external and internal abnormality symptoms in the sampled fish species during the study.
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  • 文章类型: Journal Article
    Gorai River is one of the important rivers in Bangladesh for rich aquatic biodiversity. The river is originated from the Ganges-Padma River system, a trans-boundary river between India and Bangladesh. Once the river was rich in fish biodiversity, but due to man-made and natural causes the availability of fish reduced drastically. A comprehensive analysis of fish diversity indices, gear efficiency, catch composition and decline causes of fish diversity in Gorai River, Bangladesh was accomplished. The data were collected on monthly basis from January to December 2018 from three major fishing sites of the river. A total of 62 fish and 2 prawn species under 12 orders and 24 families were recorded. Cypriniformes was the leading order consisting 27% of the total catch. The mean values of Shannon-Weaver diversity (H\'), Simpson\'s index (1-D), Margalef\'s richness (d) and Pielou\'s evenness (J\') indices were recorded as, 1.478 ± 0.495, 0.57 ± 0.197, 15.115 ± 4.435 and 0.481 ± 0.152, respectively. At the similarity of 58.7%, two groups were attained in the cluster analysis and the Non-metric Multidimensional Scaling (nMDS) showed 40% similarity among the three sites in twelve months based on the Bray-Curtis similarity matrix. The highest and lowest CPUE were recorded from seine net (5.2 ± 1.72 kg gear-1 haul-1) and hook & long lines (0.0135 ± 0.0015 kg gear-1haul-1), respectively whereas, highest and lowest gear efficiency were recorded from lift net (0.321 ± 0.036 kg gear-1person-1hour-1) and fish trap (0.0005 ± 0.0002 kg gear-1person-1hour-1), respectively. Alternatively, the highest fish catch was recorded on April (21228 ± 464.38 kg) and lowest on August (3855 ± 138.21 kg). According to the fishermen fish biodiversity of the Gorai River declined day by day due to overexploitation, destructive fishing practice, pollution, construction of obstacles for fish movement, and natural causes like siltation. Proper implementation of fish acts and regulations, use of authorized fishing gear, community-based fisheries management, sanctuary establishment and management, stocking of fish fingerling, and raising public awareness can play a great role in enhancing and conserving fish biodiversity in the Gorai River of Bangladesh.
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  • 文章类型: Journal Article
    In the Balearic Islands, different trammel net designs have been adopted to promote fisheries sustainability and reduce discards. Here, we compare the catch performance of three trammel net designs targeting the spiny lobster Palinurus elephas in terms of biomass, species composition and revenue from commercial catches and discards. Designs differ in the netting fiber type (standard polyfilament, PMF, or a new polyethylene multi-monofilament, MMF) and the use of a guarding net or greca, a mesh piece intended to reduce discards. Catches were surveyed by an on-board observer from 1,550 netting walls corresponding to 70 nets. The number of marketable species captured indicated that the lobster trammel net fishery has multiple targets, which contribute significantly to the total revenue. The discarded species ranged from habitat-forming species to elasmobranches, but the magnitude of gear-habitat interactions on the long term dynamics of benthos remains unclear. No relevant differences in revenue and weight of discards were detected after Bayesian analyses. However, the species composition of discards was different when using greca. Interestingly, high immediate survival was found for discarded undersized lobsters, while a seven day survival assessment, using captive observation, gave an asymptotic estimate of survival probability as 0.64 (95% CI [0.54-0.76]). Therefore, it is recommended that it would be beneficial for this stock if an exemption from the EU landing obligation regulation was sought for undersized lobsters in the Balearic trammel net fishery.
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