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1.
Gillnets and traps often are considered to have fewer holistic environmental impacts than active fishing gears. However, in addition to the targeted catches, gillnets and traps still cause unwanted mortalities due to (i) discarding, (ii) ghost fishing of derelict gear, (iii) depredation, (iv) escaping or dropping out of gear, (v) habitat damage, and potentially (vi) avoiding gear and predation and (vii) infection of injuries sustained from most of the above. Population‐level concerns associated with such ‘unaccounted fishing mortalities’ from gillnets and traps have been sufficient to warrant numerous attempts at mitigation. In this article, we reviewed relevant research efforts, locating 130 studies in the primary literature that concomitantly quantified mortalities and their resolution through technical modifications, with the division of effort indicating ongoing concerns. Most studies (85) have focused on discard mortality, followed by ghost‐fishing (24), depredation (10) and escape (8) mortalities. The remaining components have been poorly studied (3). All problematic mortality components are affected by key biological (e.g. species), technical (e.g. fishing mechanisms) and/or environmental (e.g. temperature) factors. We propose that these key factors should be considered as part of a strategy to reduce impacts of these gears by first assessing modifications within and then beyond conventional configurations, followed by changes to operational and handling practices. Justification for this three‐tiered approach is based not only on the potential for cumulative reduction benefits, but also on the likely ease of adoption, legislation and compliance. 相似文献
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3.
Effects of intensive fishing on the perch population in a large oligotrophic lake in eastern Finland
The perch population in Lake Höytiäinen was intensively fished to reduce the density of the population and hence also the predation pressure by perch on vendace larvae. A hypothesis suggests that this predation can prevent recovery of commercially important vendace stock from a state of low-density. In the 1990s the density of the perch population in Lake Höytiäinen has increased, while the vendace stock has been sparse. Intensive fishing was conducted by professional fishermen with a paired bottom trawl, seine net, hoop net and small fish traps and by recreational fishermen with small fish traps. The size of perch population during the intensive fishing period was studied by test fishing with multi-mesh gillnets and the Leslie method in which trawl YPUE was regressed on the cumulative yield. The results suggest that the population size clearly diminished in the area where the fishing pressure was strongest. YPUE of test fishing decreased ca. 30% whereas the Leslie method gave almost a decrease twice as large as that of the former. Mean weight of perch increased in the trawl and test fishing catches during the intensive fishing period. The most effective fishing gear was trawl (62% of the total yield), but importance of trap net fishing by recreational fishermen was also high as they caught 22% of the total yield. 相似文献
4.
Trap mesh selectivity and the management of reef fishes 总被引：1，自引：0，他引：1
The regulation of mesh size has frequently been proposed as a management measure for fish traps, the predominant gear used by the reef fish fisheries in the Caribbean. Studies on trap mesh selectivity show that mesh size is a determinant of catch rates and the size at which fish recruit to fish traps. Mesh size also affects the species composition in fish traps, probably through size selectivity. Other factors also affect catch rates, and the fish size and species composition in traps, for example, soak time, trap design, trap size, species body shape. Given the variety of growth rates and maturity schedules of reef fish commonly taken in fish traps in the Caribbean, no single mesh size will optimise the yield or protect against recruitment overfishing for the entire range of exploited species. Preliminary data suggest that the fishing power of traps may decrease with increased mesh size. This would reduce the effective fishing effort and thus mortality on fully recruited size classes. Studies indicate that the mesh sizes currently in use in most Caribbean countries are too small, and that a minimum mesh size of at least 3.8–5.1 cm would be required to optimise yields for local consumption. Comparative fishing experiments indicate that an increase in mesh size in areas of high fishing mortality typically results in a reduction in catch per trap. Thus increasing trap mesh size can be expected to result in short‐term loss in revenue for fishers. However, no studies have examined the times that would be required for catches to return to the levels prevailing before the increase of mesh size, and thereafter, for fishers to recover the losses incurred during the transition period. To provide managers with an estimate of the impacts that mesh‐size regulation could have on fishers, the recovery time of catches and the financial recovery times for fishers should be modelled for a hypothetical assemblage of 10–15 reef fishes using available information. These studies would enable managers to plan for the implementation of mesh‐size increases and to communicate the potential benefits to fishers in quantitative terms. 相似文献
5.
Abstract The factors influencing fish catches on Kenya's coral reefs were studied. Catch data were collected at the species level by counting the number of fish landed at each landing site of each fishing ground. Live coral cover, topographic complexity, fish and sea urchin density, and the number of fishers and gear units used in each fishing ground were compared with catch data. Fishing grounds included one location where only basket traps were allowed, six locations where all gear types were used except beach seines, and three locations where all types of gear, including beach seines, were used. Catch and effort variables were similar across the fishing grounds whereas live coral cover and sea urchin density differed ( P < 0.01). The sites fished by all types of gear including beach seines had the lowest coral cover (8.4 ± 0.9%) and topographic complexity (1.12 ± 0.01). Catch levels were positively correlated with the number of fishers and fish density but not with the number of gear units deployed or sea urchin density. The number of fishers and live coral cover were the strongest factors determining total catch levels. The results suggest that high levels of fishing effort coupled with the use of destructive gear types, exacerbate the effects of overfishing on Kenya's reefs. 相似文献
6.
Blue swimmer crabs (Portunus pelagicus) are an economically important crab caught in baited traps throughout the Indo-west Pacific and Mediterranean. In Australia they are traditionally caught using rigid wire traps (≈pots) but there has been a recent increase in the use of collapsible pots constructed from polyethylene trawl mesh. Two experiments were conducted in Moreton Bay, Queensland, to determine the ghost fishing potential of lost crab pots on both target and bycatch species and to evaluate the differences between traditional and contemporary pot designs. A lost contemporary, collapsible trawl mesh pot will catch between 3 and 223 P. pelagicus per year after the bait has been exhausted, while a traditional wire mesh pot would catch 11–74 crabs per year. As most fishers now use the collapsible trawl mesh pots, ghost fishing mortality could be as high as 111,811–670,866 crabs per year. Bycatch retention was also higher in contemporary designs. Periods of strong winds appeared to increase the ghost fishing potential of lost pots. The use of escape gaps, larger mesh sizes and construction options that allow for the deterioration of entrance funnels to minimise ghost fishing are recommended to reduce environmental impacts. 相似文献
7.
Daniel Bloom Paul A. Butcher Andrew P. Colefax Euan J. Provost Brian R. Cullis Brendan P. Kelaher 《Fisheries Management and Ecology》2019,26(4):311-318
The issues surrounding illegal, unregulated and unreported fishing, and that of abandoned, lost and discarded fishing gears, leading to ghost fishing, are intensifying. Estuarine crab trapping is likely subject to high levels of illegal and potential ghost fishing, because it also has good economic incentives regarding potential catch, low gear acquisition costs and accessible fishing grounds. To improve the efficiency and effectiveness of fisheries monitoring, control and surveillance operations, the efficacy of small consumer‐grade drones for sighting traps in an estuary in NSW, Australia, was tested. Twelve sets of two flights were undertaken at 20 and 30 m altitude over a 600‐m stretch of estuary for 5 days to quantify the detectability of submerged mesh traps of three different mesh colours. The drone was able to detect the majority of traps efficiently, with depth in relation to water clarity being the main factor affecting detection. In shallow water, detection rates were high for all mesh colours, but in the slightly deeper placements, orange traps were more readily detected. This study demonstrates that drones could be an efficient and reliable tool for rapidly assessing areas for illegal and derelict traps and can be supplemented into land or vessel‐based fisheries operations. 相似文献
8.
Eric Gilman Jeff Gearhart Blake Price Scott Eckert Henry Milliken John Wang Yonat Swimmer Daisuke Shiode Osamu Abe S. Hoyt Peckham Milani Chaloupka Martin Hall Jeff Mangel Joanna Alfaro-Shigueto Paul Dalzell & Asuka Ishizaki 《Fish and Fisheries》2010,11(1):57-88
There is growing evidence that small-scale, coastal, passive net fisheries may be the largest single threat to some sea turtle populations. We review assessments of turtle interactions in these fisheries, and experiments on gear-technology approaches (modifying gear designs, materials and fishing methods) to mitigate turtle by-catch, available from a small number of studies and fisheries. Additional assessments are needed to improve the limited understanding of the relative degree of risk coastal net fisheries pose to turtle populations, to prioritize limited conservation resources and identify suitable mitigation opportunities. Whether gear technology provides effective and commercially viable solutions, alone or in combination with other approaches, is not well-understood. Fishery-specific assessments and trials are needed, as differences between fisheries, including in gear designs; turtle and target species, sizes and abundance; socioeconomic context; and practicality affect efficacy and suitability of by-catch mitigation methods. Promising gear-technology approaches for gillnets and trammel nets include: increasing gear visibility to turtles but not target species, through illumination and line materials; reducing net vertical height; increasing tiedown length or eliminating tiedowns; incorporating shark-shaped silhouettes; and modifying float characteristics, the number of floats or eliminating floats. Promising gear-technology approaches for pound nets and other trap gear include: replacing mesh with ropes in the upper portion of leaders; incorporating a turtle releasing device into traps; modifying the shape of the trap roof to direct turtles towards the location of an escapement device; using an open trap; and incorporating a device to prevent sea turtle entrance into traps. 相似文献
9.
废弃渔具(ALDFG)像幽灵一样长期在海洋中飘荡,导致一些海洋生物被网具缠绕而死,对渔业资源造成持续危害,形成“幽灵捕捞”现象。废弃渔具类型主要包括陷阱、刺网、拖网等。通过探讨造成幽灵捕捞的原因,总结了幽灵捕捞的现状和国内外研究进展;针对容易形成幽灵捕捞的渔具种类,介绍了ALDFG的结构与捕捞作业机理,阐述了陷阱、刺网、拖网等的幽灵捕捞过程,并对各种渔具造成的幽灵捕捞的影响进行了评估。最后总结目前对幽灵捕捞渔具的预防和应对措施,提出了减少幽灵捕捞的方法和建议。 相似文献
10.
Lost or abandoned fishing gear made of synthetic fibers or plastics that do not decompose in the sea. These gear result in “ghost fishing”, that retain their function as fishing gear. To solve this problem, we developed fishing gear made of aliphatic polyester (PBS/PBAT), which is biodegraded by microorganisms after a certain period. The marine fishing performance of the biodegradable material of tubular pots for conger eel was compared with that of commercial pots in the southern coastal sea of Korea, where fishing gear loss rates are high. A comparative analysis of the elastic recovery of different types of funnel material was conducted. Two types of fishing gear were tested: (1) a pot with a body and funnel made of biodegradable materials and (2) a commercial pot made of recycled polyethylene (PE). Then, field experiments were conducted on the two pot types, which were arranged alternately. The funnel rips made of biodegradable material showed better elastic recovery than that of the commercial pot. Marine fishing performance of the biodegradable pots was similar to that of the commercial pots (Mann–Whitney test, p > 0.05). There was also no significant difference in the catch per unit effort (CPUE) by the Mann–Whitney test, p > 0.05. Thus, biodegradable materials represent an environmentally friendly alternative to recycled PE for fabricating tubular pots to catch conger eel. 相似文献
11.
ABSTRACT: In this study, we developed a new automatic system, comprised of a radio frequency identification (RFID) system and global positioning system (GPS), for monitoring fishing effort, and effectiveness of effort, in fisheries using many pieces of fishing gear, such as hooks of longlines. The outline of this system is as follows. A single RFID tag with an identification (ID) number is attached to each piece of fishing gear. The RFID tag on the fishing gear passes the antenna of the RFID reader before being shot into the sea and after being hauled up from the sea. Data on the time and geographic location are measured by the GPS and recorded along with the ID number in a personal computer (PC). When a fish is caught, it is brought close to the fish-sorting table. Then, the second antenna of the RFID reader set at the side checks for a catch in the gear. The advantage of this system is that the fishing operation data can be collected without interfering with the fishermen's usual work. The prototype of the system was tested at a conger-eel tube fishery in Tokyo Bay and was able to record data on the time, the location and the catch of individual conger-eel tubes successfully. 相似文献
12.
为掌握影响我国沿海刺网渔船网具遗失率(R_G)的因子及其程度,对中国沿海渔民开展了问卷调查。利用调查数据,结合GAM模型分析了影响我国刺网渔船网具遗失率的因子及其程度。结果显示:(1)影响我国沿海刺网渔船网具遗失率的因子(解释偏差)分别为单航次天数(86.8%)、年作业天数(4.2%)、单航次渔具携带重量(2.8%)、作业水深(2.4%)、渔船吨位(0.9%)和年均渔具采购数量(0.1%);(2)GAM模型能用于研究渔船网具遗失率和影响因子之间的关系;(3)随着单航次天数和年作业天数的增加,R_G呈上升的趋势;(4)随着作业水深的增加、单航次渔具携带重量超过18 000 kg时,R_G呈下降趋势。建议采取以下措施以降低刺网渔船网具遗失率:(1)单航次天数不得超过30 d,减少年作业天数;(2)根据渔船的吨位,确保网具单航次携带重量在18 000 kg以上;(3)根据刺网渔具的高度规定作业水深和作业渔区;(4)渔船总吨位控制在200 t以内。 相似文献
13.
废弃、遗失或以其他方式丢弃的渔具(abandoned, lost or otherwise discarded fishing gear, ALDFG)是海洋生态环境及渔业最为严重的危害之一,世界各国及国际组织对其引发的问题日益关注。本文介绍了ALDFG对海洋生态及渔业的危害、ALDFG产生的主要原因、各国及相关国际组织为减少ALDFG所提出的措施及常用的ALDFG调查和评估方法。发现ALDFG的研究多采用统计模型量化ALDFG,或结合统计检验等评估ALDFG的危害性(幽灵捕捞)和通过经济学层面评估清除ALDFG带来的生态及经济效益等。建议：①通过问卷调查与水下实地调查等评估国家管辖海域ALDFG量和危害程度,并结合海洋动力学模型及渔具水动力性能等分析ALDFG移动轨迹;②开发新材料,改进渔具及属具设计方法,减少ALDFG;③通过水下实地调查,确定ALDFG的物理变化过程、幽灵捕捞能力的变化等;④观察ALDFG清除后对海洋生态系统多样性及渔业资源的积极作用,并结合经济模型分析ALDFG清除后产生的社会及经济效益。 相似文献
14.
Abandoned, lost or otherwise discarded fishing gear (ALDFG) represents a significant, yet ultimately unknown amount of global marine debris, with serious environmental and socioeconomic impacts. This study reviews 68 publications from 1975 to 2017 that contain quantitative information about fishing gear losses. Gear loss estimates reported by the studies ranged widely, with all net studies reviewed reporting annual gear loss rates from 0% to 79.8%, all trap studies reporting gear loss rates from 0% to 88%, and all line studies reporting gear loss rates from 0.1% to 79.2%. Information obtained from this review was used to perform a meta‐analysis that provides the first synthetic, statistically robust estimates of global fishing gear losses. The meta‐analysis estimates global fishing gear losses for different major gear types. We estimate that 5.7% of all fishing nets, 8.6% of all traps, and 29% of all lines are lost around the world each year. Furthermore, we identified key gear characteristics, operational aspects and environmental contexts that influence gear loss. These estimates can be used to support sustainable fisheries development through informing risk assessments for fisheries and monitoring and assessment efforts to reduce gear losses. 相似文献
15.
Yoshiki Matsushita Shusuke Machida Haruyuki Kanehiro Fumio Nakamura Naoto Honda 《Fisheries Science》2008,74(2):230-235
ABSTRACT: A small number of fishers in Chiba Prefecture of eastern Japan use cotton gill nets to catch Japanese spiny lobster Panulirus japonicus. To examine the advantages of cotton gill nets, we analyzed changes in mesh breaking load of a new cotton gill net used in a fishing operation. A new cotton gill net was also soaked in a seawater tank to simulate ghost fishing conditions. The average mesh breaking load of new cotton mesh was 50.3 N. This value decreased to 19.0 N after 38 days (∼912 h), and after 82 days (∼1968 h) the mesh could be easily torn (breaking load 0.07 N). Under fishing conditions, the cumulative soak time was only 744.4 h over 19 months. The average breaking load at the end of this period was 43.1 N, a strength 86% that of the presoaked mesh. The mesh breaking load of a cotton gill net continuously soaked for 744.4 h was 26.1 N, as estimated from tank experiment data. Thus, a cotton gill net maintains reasonable strength under typical use conditions, but will degrade if lost at sea. 相似文献
16.
Respiratory mode and gear type are important determinants of elasmobranch immediate and post‐release mortality 
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下载免费PDF全文 Derek R Dapp Terence I Walker Charlie Huveneers Richard D Reina 《Fish and Fisheries》2016,17(2):507-524
Estimated declines in shark and ray populations worldwide have raised major, widespread concern about the impacts of global fisheries on elasmobranchs. The mechanisms causing elasmobranch mortality during fisheries’ capture are not fully understood, but we must gain greater clarity on this topic for fisheries managers to develop effective conservation plans to mitigate further population declines. To evaluate how two important factors, respiratory mode and fishing gear type, impact elasmobranch survival, we compiled publicly available data sources on the immediate mortality percentages of 83 species and post‐release mortality percentages of 40 species. Using Bayesian models, we found that sharks and rays captured in longlines had significantly lower immediate mortality than those caught in trawls or gillnets. Our models also predicted the mean total discard mortality (combined immediate and post‐release mortality) percentages of obligate ram‐ventilating elasmobranchs caught in longline, gillnet and trawl gear types to be 49.8, 79.0 and 84.2%, respectively. In contrast, total discard mortality percentages of stationary‐respiring species were significantly lower (longline capture mean = 7.2%, gillnet capture mean = 25.3%, trawl capture mean = 41.9%). Our global meta‐analysis provides the first quantified demonstration of how mortality is affected by these two factors across a broad range of species. Our results and approach can be applied to data‐deficient elasmobranchs and fisheries to identify species that are likely to experience high rates of mortality due to respiratory mode and/or fishing methods used, so that appropriate mitigation measures can be prioritized and investigated. 相似文献
17.
幼鱼及非目标种类兼捕已成为许多网具作业共同存在的问题,提高网具选择性能是降低这种兼捕的重要途径。但是选择性能研究主要是基于从网具中逃逸后的鱼类较轻遭受到网具损害并最终存活。如果逃逸死亡率较高,即使选择性提高也是无宜的,因此应当将鱼类逃逸后生存能力作为网具改进效果的评价指标。本文主要由以下三个部分组成:(1)逃逸后死亡的主要影响因素概述,主要包括网具特征、作业时间、作业深度、渔获种类及体长、渔获量及环境因子等;(2)逃逸死亡对资源量和渔业管理决策的影响;(3)总结了近年来通过网具革新措施提高存活率的最新研究概况,如逃逸网片、分离栅及新型材料的应用等。综合分析,认为采取保护幼鱼和非目标种类的一系列措施尽管能够提高鱼类从网具的逃逸几率,但是并不能降低遭遇网具的概率,实施禁渔区、禁渔期制度管理,避免在幼鱼资源高密度区和产卵季节作业是降低这种未报告死亡的最重要的途径。 相似文献
18.
Influences of gear type and analytical methodology on fish assemblage characterisations in temperate lakes 下载免费PDF全文
下载免费PDF全文 C. J. Sullivan D. P. Coulter Z. S. Feiner S. B. Donabauer T. O. Hk 《Fisheries Management and Ecology》2015,22(5):388-399
A variety of gears and analytical methods can be used to characterise lentic fish assemblages; however, the combined influence of gear type and analysis can affect conclusions about assemblage patterns. Fish assemblages sampled with night electric fishing, gillnets and trapnets from 153 lakes were evaluated using summary indices of species composition, pairwise community similarity comparisons and multivariate ordination. For a given amount of effort, electric fishing had the highest species richness, while gillnets had higher diversity and evenness. Pairwise comparisons between gears revealed that (1) richness was positively correlated among all gears, (2) diversity and evenness were generally not correlated across gears and (3) electric fishing and trapnets captured more similar species than all other pairwise comparisons. Gear‐specific multivariate correlation and ordination revealed that gillnet and electric fishing samples more similarly characterised variation in assemblages among lakes, while trapnets characterised assemblages along different gradients of species composition. These results indicate that either electric fishing or trapnetting can be used when assessing shallow‐water assemblages for diversity or evenness, gillnets and either electric fishing or trapnets should be used for whole‐lake assessments, and either gillnets or electric fishing should be used when evaluating regionwide variation in lake assemblages. 相似文献
19.
The rock lobster fishery of Western Australia is one of the largest of its kind; its average catch in the years 1974/75 to 1981/82 was almost 10000 tonnes. The fishery has been stable for many years, largely by virtue of licence limitation and other management measures. Among the regulatory measures is a requirement that all traps used in the fishery must be furnished with escape gaps and another requires fishermen to return to the sea all undersize lobsters that enter the traps, but fail to escape and consequently are brought on board the fishing boat when the trap is lifted.Despite the presence of the escape paps, considerable numbers of undersize lobsters are brought aboard; the number is estimated to be some 16 to 20 million in each season. Moreover, it has been estimated that about a quarter of these retained undersize lobsters remain on board for 10 min or more, and some have been observed to remain on board for more than two hours.Studies were therefore undertaken to ascertain whether this cipture-and-release experience was in fact causative of mortality. Laboratory experiments on animals exposed in direct sunlight resulted in an expected time for 50% mortality of 99, 158 and 233 min with increasing temperature compared with a time of 387 min for animals exposed under shade.Behavioural observations showed that as exposure time increased, returned animals exhibited a decreasing rate of descent through the water column, a decrease in the percentage of active animals and increased loss from predators. In addition, in ten laboratory experiments on octopus predation, octopus predated or injured animals exposed for 15 or 30 min, despite a recovery period of 3.5–5.5 h, but not on unexposed animals.Four tagging operations with over 7000 undersize animals resulted in a significant decrease in recapture rates by commercial fishermen with increasing exposure times. Damage (number of appendages lost) incurred by the rock lobsters and displacement beyond the home range were also generally found to reduce the recapture rates significantly. The combination of all these factors resulted in an estimated reduction in recapture rate of 14.6% in the 1978/79 fishing season and after taking into account natural mortality, this would have resulted in a loss of $A6.4 million to the fishery. 相似文献
20.
J. M. S. GONÇALVES L. BENTES R. COELHO P. MONTEIRO J. RIBEIRO C. CORREIA P. G. LINO & K. ERZINI 《Fisheries Management and Ecology》2008,15(3):199-210
Abstract Non-commercial invertebrate discards in an experimental trammel net fishery were studied in relation to selectivity of the gear, depth, soak time and season. Forty experimental fishing trials were carried out over a 1-year period with six combinations of small mesh (100, 120 and 140 mm) inner and large mesh (600 and 800 mm) outer panels. On average, 43.8 ± 12.2 (SD) (individuals 1000 m−1 of net) of non-commercial invertebrates were discarded, accounting for 48% and 65% of the total catch and total discards by numbers, respectively. Within non-commercial invertebrates discards, the six most abundant species by number were Phallusia mammillata (Cuvier) (27.5%), Cymbium olla (L.) (13.0%), Sphaerechinus granularis (Lamarck) (11.3%), Paracentrotus lividus (Lamarck) (10.9%), Astropartus mediterraneus (Risso) (8.2%) and Astropecten aranciacus (L.) (8.1%); Echinoderms (43.1%) particularly important. The highest and lowest discard ratios were found in autumn and winter, respectively. Discards generally decreased with depth, varied considerably in relation to soak time and were not related to mesh size combinations. Trammel nets seem to be the most important gear in terms of ecological impacts on benthic invertebrates compared with other coastal fishing gears and at the depths studied (15–60 m). 相似文献