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1.
Yonat Swimmer Randall Arauz John Wang Jenny Suter Michael Musyl Allan Bolaños Andrés López 《水产资源保护:海洋与淡水生态系统》2010,20(4):445-451
- 1. This study compared the catch rates of targeted dolphinfish or mahimahi (Coryphaena hippurus), and sea turtles and other fish bycatch in a shallow‐set Costa Rican longline fishery using 14/0 circle hooks with and without a 10° offset. The effect of hook offset on hooking location and injury in captured sea turtles, specifically if the hooking was external, in the mouth, or in the esophagus was also evaluated.
- 2. Results were compared from six trips totalling 33 876 hooks with squid (Dosidicus gigas) used as bait. In total, mahimahi catch‐per‐unit‐effort (CPUE, expressed as number caught per 1000 hooks) was similar between hook types (CPUE～52).
- 3. Olive ridley sea turtles (Lepidochelys olivacea) were caught on all 42 sets. In total, 640 olive ridley turtles were caught and released alive. There were no significant differences in the number of sea turtles caught between hooks with and without an offset (CPUE～19) nor between hook type and anatomical hooking location, suggesting similar levels of injury for turtles caught on each hook type.
- 4. These data suggest that a 10° offset on 14/0 circle hooks does not confer any selective advantages over hooks with no offset with respect to capture rates of mahimahi, sea turtles, sharks, or pelagic stingrays in a shallow set pelagic longline fishery. Copyright © 2010 John Wiley & Sons, Ltd.
2.
- Freshwater turtles are susceptible to drowning in commercial fishing nets and this is a major conservation concern. Methods to mitigate turtle bycatch mortality typically involve reducing the capture of bycatch using gear modifications. Another method to reduce mortality is to keep bycatch alive following capture.
- Using physiological measures of anoxia, this study determined whether providing air spaces using floats within fyke nets could prevent turtles from drowning. In a controlled setting, blood lactate and pH of painted turtles (Chrysemys picta) experimentally introduced into submerged nets, nets with floats, and nets that breached the surface were compared. While emulating commercial fishing practices – where turtles and fish voluntarily entered nets – catch rates and compositions as well as blood lactate in turtles captured were compared in submerged nets with and without floats.
- Painted turtles in submerged nets exhibited elevated blood lactate and pronounced acidosis compared with turtles from nets with floats and surfaced nets.
- Catch rates and compositions from emulated fishing were statistically similar in nets with and without floats; however, total fish catches were roughly one‐third less in nets with floats. The same pattern of physiological disturbance was observed with turtles captured in submerged nets with and without floats as in the controlled experiment.
- Overall, blood physiology indicated that anoxia occurred in turtles in submerged nets while nets with floats reduced physiological disturbance. However, variation in blood lactate levels when fishing fyke nets with floats suggests that turtles were experiencing slight anoxia and so the size of air spaces may be important in allowing access to air. Creating air spaces in fyke nets using floats is a simple and cost‐effective method to avoid the drowning of turtles.
3.
- There are few reliable estimates of post‐release mortality for sea turtle species because of the many challenges and costs associated with tracking animals released at sea. In this study, the likelihood of sea turtle mortality as a result of interactions with longline fishing gear was estimated based on satellite telemetry data, such as the number of days an animal was successfully tracked, or days at liberty (DAL) and dive depth data, as well as anatomical hooking locations.
- Pop‐up satellite archival tags were deployed on 29 loggerhead sea turtles (Caretta caretta) caught by the North Pacific US‐based pelagic longline fishery operating from California and Hawaii between 2002 and 2006. Loggerhead turtles were catagorized by observers as shallow‐hooked (55%) if the animal was entangled in the line or the hook was in the flipper, jaw or mouth and could be removed, or deep‐hooked (45%) if the hook was ingested and could not be removed. The vertical movements of turtles were used to infer potential mortalities.
- Of the 25 tags that reported data, the DAL ranged from 3 to 243 days (mean = 68 days). The DAL was shorter (by nearly 50%) for shallow‐hooked (mean = 48 days, range: 3 to 127) compared to deep‐hooked turtles (mean = 94 days, range: 5 to 243), but these changes were not statistically significant (P = 0.0658).
- Although aspects of these analyses may be considered speculative, these data provide empirical evidence to indicate that deep‐hooking is not linked to shorter DAL.
- DAL, anatomical hooking location, and gear removal were evaluated with inferences about the extent of injuries and rates of infection to estimate an overall post‐release mortality rate of 28% (95% bootstrap CI: 16–52%).
- This range of estimates is consistent with those used to shape some US fisheries management plans, suggesting that conservation goals are being achieved at the expected level and ideally striking a balance between the interests of industry and those of protected species.
4.
近年来,霞水母的旺发严重影响了东、黄海秋冬汛张网渔业。为了维持渔业生产的正常进行,利用霞水母和目标渔获物的个体大小以及行为特性的差异,通过在网囊前安装网目长度为45cm的分隔网片和释放口所组成的兼捕减少装置(BRD)来释放霞水母。根据2000年和2001年的海上试验显示,该装置能有效减少霞水母兼捕,平均释放率达91.29%;而目标种类的平均逃逸率为13.35%,其中梭子蟹、鲳鱼的逃逸率较高,分别为52.84%和33.44%,带鱼和小黄鱼的逃逸率较低,分别为5.23%和6.27%,棘头梅童鱼的逃逸率为9.14%;同时由于霞水母的释放,使得作业中的暴网事故明显减少;霞水母BRD自设计开发、试验以后,得到了广泛的运用,自2003年起,已在江苏省启东市所辖350余艘张网渔船上全面推广应用。 相似文献
5.
Wenzhi Liu;Yong Zhou;Nan Jiang;Chen Xu;Qiwang Zhong;Yuding Fan; 《Journal of fish diseases》2024,47(12):e14020
Chinese rice-field eels rhabdovirus (CrERV) causes haemorrhagic disease in Chinese rice-field eels (Monopterus albus), leading to significant mortality and economic losses. Sensitive detection of CrERV nucleic acids is essential to control the spread of this pathogen and to treat infected individuals. Herein, we developed an efficient and sensitive droplet digital PCR (ddPCR) method to rapidly detect and quantify CrERV. The ddPCR assay optimal conditions were an annealing temperature of 53°C, and primer and probe concentrations of 0.5 and 0.25 μM, respectively. The assay had a diagnostic sensitivity of 0.23 copies/μL, and was highly specific, showing no cross reactivity with other viruses (infectious haematopoietic necrosis virus, grass carp reovirus, spring viremia of carp virus, largemouth bass ranavirus, carp edema virus, Chinese giant salamander iridovirus, and white spot syndrome virus). Real-time quantitative PCR testing of 30 Chinese rice-field eels samples detected CrERV in 7 samples (23.3%), whereas ddPCR detected CrERV in 12 samples (40%), demonstrating its higher sensitivity. Thus, ddPCR represents an advanced method to absolutely quantify CrERV in infected fish with low virus concentrations, providing a valuable tool to manage the spread and impact of CrERV. 相似文献
6.
- Bycatch resulting from fishing activities is the main threat for the conservation of sea turtles in the Mediterranean Sea. Fixed nets are a matter of concern for sea turtles mainly in coastal areas during the neritic stage when both juvenile and adult life stages are affected. Mortality caused by entanglement in set nets is related to forced apnoea due to the high soak time of the nets and consequent drowning.
- This study investigated the loggerhead turtle bycatch in set net coastal fisheries in the northern Adriatic Sea (General Fisheries Commission for the Mediterranean Geographical Sub‐Area 17, [GSA 17]) through an interview‐based approach, to understand the potential contribution of these fisheries to the general decline of the sea turtle population. A second goal was to identify a possible hot‐spot turtle bycatch area through on‐board observations.
- The study estimates that more than 5400 turtles are caught in the west GSA 17 each year with the largest number in the summer. A hot‐spot for entanglement was also identified in an area located south of the River Po delta (41.5–69 m depth) during the summer. Sixty‐four turtles were caught over a period of 30 fishing days by either trammel nets and gillnets (0.7 and 0.5 turtle per km of net respectively) and was the greatest number that has been observed anywhere in the Mediterranean.
- Possible management strategies to reduce bycatch include technical modification to gear setting (such as reducing netting slack and using small meshes), bycatch reducer devices (such as LED UV), and area and seasonal gear restrictions to small‐scale fisheries in areas of greatest concern in the northern Adriatic Sea.
7.
Genetic structure of New Zealand eels Anguilla dieffenbachii and A. australis with allozyme markers 总被引：1，自引：0，他引：1
P. J. Smith P. G. Benson C. Stanger B. L. Chisnall D. J. Jellyman 《Ecology of Freshwater Fish》2001,10(3):132-137
Abstract – Glass eels and adults of Anguilla australis and A. dieffenbachii were collected from rivers in the North and South Islands of New Zealand and tested for nine and ten allozyme loci, respectively. There was no heterogeneity among glass eel samples, but there was heterogeneity among adult samples within species. The results indicate that there may be single panmictic populations subject to sweepstake events or different selective pressures in the adult environments. 相似文献
8.
Steven J. Kennelly Valentina Melli Matt K. Broadhurst 《Fisheries Management and Ecology》2019,26(6):630-637
Penaeid trawling is among the world's least selective fishing methods; a characteristic that has evoked spatial closures being implemented in some fisheries if certain bycatch limits are exceeded. For decades, considerable work has been done to develop modifications to penaeid trawls that reduce unwanted bycatches, with most focussed at the posterior section (i.e. codend). More recently, efforts have examined ways to prevent bycatch entry into trawls entirely—via modifications to anterior components. This study assessed the utility of proactively lowering the headlines of Australian penaeid trawls, using clips at the otter boards, to 68% and 54% of their conventional height, and demonstrated mean total bycatch reductions (by weight) of 69% and 79%, respectively, with no effects on the targeted Metapenaeus macleayi (Haswell). The results provide insights into the location and behaviour of various species in the water column preceding capture, and support a simple and easy method for regional fishers to use in situ to avoid excessive bycatch and associated fishing closures. More broadly, the data support ongoing efforts in other penaeid‐trawl fisheries to reduce bycatches via similar, rapid adjustments to anterior components, depending on species‐specific behaviours during capture. 相似文献
9.
The current procedures for slaughtering European eels (Anguilla anguilla) for food are very slow and cause suffering. Although there is little legislation for protecting the welfare of fish at slaughter, the legislation covering farmed mammals and birds at slaughter is well defined, requiring that these animals be rendered insensible immediately or without fear or pain prior to being killed. For many mammals and birds this can be achieved using an electrical stun, which is then followed by a procedure that actually kills them, such as exsanguination. This paper reports the investigation of the possibility of using electricity to stun eels, rendering them insensible to pain. Using 1 s duration alternating currents at 50 Hz applied directly across the head of the fish, it was shown that it was possible to stun the fish with currents of 0.1 A and above. Increasing the applied current increased the length of the period of the stun. When the duration of the application of the current was increased to 30 s it was found that the fish could be killed using currents between 0.50 A and 0.95 A. These results show that it is possible to use electricity to instantly stun eels and also to kill them by using longer duration currents. The use of preslaughter electrical stunning at slaughter could allow the welfare of these fish at slaughter to be improved greatly. 相似文献
10.
To handle large river eels during procedures such as measuring and tagging for field and aquaculture studies, they must be anaesthetized. During our initial biological studies of Anguilla reinhardtii (Steindachner) it was found that the anaesthetic benzocaine was relatively expensive and elicited a variable response, even when used at relatively high concentrations. Human health risks are also a concern when using benzocaine, as some of the eels may later be sold for human consumption. Therefore, experiments were done to evaluate the use of clove oil (a safe, naturally occurring product) for anaesthesia of this species at a range of temperatures (17 and 25 °C) and salinities (0–32 g L?1). It was found that clove oil provided a suitable anaesthetic response through this wide range of temperatures and salinities. Response times were found to be relatively variable for both benzocaine and clove oil. This variability may be related to stress, environmental factors, or the condition of the fish. Clove oil is recommended for anaesthesia of anguillid eels because it is effective, relatively inexpensive, and poses little risk to human health. 相似文献
11.
- 1. Drifting longlines are considered a major threat to endangered sea turtle populations worldwide. However, for a number of reasons, the mortality rate of captured turtles is not known with any certainty.
- 2. Information on 409 loggerhead turtles (Caretta caretta), collected during the day‐to‐day activities of a turtle rescue centre in Lampedusa island, central Mediterranean, in the period 2001–2005 has been analysed.
- 3. Observations indicate that: (i) drifting longlines are a major cause of mortality for sea turtles in the area; (ii) in addition to the hook, the piece of line attached to it (branchline) can easily cause death if it is long enough and well‐anchored; (iii) hooks and branchlines cause death in the short and long term, respectively; (iv) a turtle with a hook in the lower oesophagus/stomach has a very low chance of surviving the combined effect of hook and branchline; (v) the mortality of turtles with a hook in the mouth or higher oesophagus is probably important, though less than that of turtles with a hook in the lower oesophagus/stomach; (vi) in the study fishery, the average mortality of a turtle caught by a drifting longline is probably much higher than 30%.
- 4. Without specific investigations on the mortality of turtles with hooks in the mouth or higher oeasophagus, which are usually removed, the mortality induced by drifting longlines will remain unknown, preventing a full understanding of the effect on population growth and the real effectiveness of conservation measures such as use of different hooks and fishing depths, and proposals for adequate fishery management measures.
- 5. The number of turtles captured by drifting longlines should be drastically reduced, and because of the above uncertainty and the socio‐economic importance of the fishery sector, an ecosystem‐based management scheme should be promoted that is not limited to addressing only the turtle issue.
12.
用肌肉注射HCG的处理方式（剂量为500U/㎏•体重,每周注射1次,注射时间为6周）诱导雄性花鳗鲡性腺发育成熟,成熟率达80.0%。对人工催熟花鳗鲡精子的生物学特性研究结果表明：花鳗鲡精子头部长径为3.81±0.69µm,短径为1.24±0.15µm;尾部长度为24.83±3.05µm;精液pH为7.3~7.5,精子密度为1.02×1010尾/ mL。精子的适宜盐度为15~20,其中盐度为15时,精子激活比率最高,快速运动时间以及精子的寿命最长。精子的pH适宜范围为6.0~8.0,pH值过高或过低都会影响精子的活力与寿命。另外,4 种金属离子(Mg2+、Ca2+、Na+和K+)对花鳗鲡精子活力与寿命的影响趋势基本一致,金属离子浓度过高或过低都会抑制精子的活力、缩短快速运动时间和寿命。而MgCl2、CaCl2、KCl、NaCl溶液浓度为0.4~0.6g/mL时,精子活力最好,最高激活比率为3级（41.0%~60.0%）。 相似文献
13.
Melissa R. Cronin Julia E. Amaral Alexis M. Jackson Jennifer Jacquet Katherine L. Seto Donald A. Croll 《Fish and Fisheries》2023,24(1):56-70
The incidental capture by marine fisheries as bycatch poses a global threat to pelagic sharks and rays. In large, industrialized fisheries that often operate in areas beyond national jurisdiction, at least 22 threatened species of pelagic elasmobranchs are caught as bycatch, representing the majority of megafauna bycatch in tuna fisheries. Here, we investigate (1) the efficacy of the current policies of the five tuna-related Regional Fisheries Management Organizations (tRFMOs) in mitigating elasmobranch bycatch, (2) data needed to better assess the amount and impact of elasmobranch bycatch and (3) the research necessary for the adoption of new policies. We found that tRFMOs have adopted 34 active policies that address pelagic elasmobranch bycatch. However, most policies (~76%, n = 26) are unlikely to avoid or minimize elasmobranch bycatch. Instead, most policies focus on mitigating post-capture mortality via remediation and requiring or encouraging research and data collection. Despite the emphasis on research mandates, we find that the existence of research was not related to policy adoption, suggesting that lack of research has not historically prohibited policymaking. Overall, we suggest that current research and data transparency, though perhaps not necessary for policy adoption, are not sufficient to adequately evaluate the population-level impacts of bycatch on many elasmobranch species in tRFMO-managed fisheries. Given these results, we recommend a precautionary approach that involves reforms in tRFMO voting processes to facilitate the adoption of binding requirements for elasmobranch catch limits, bycatch avoidance, pre- and post-capture handling and release modifications and protection of areas important to threatened pelagic elasmobranchs. 相似文献
14.
In southeastern Australia, some commercial fishers sort their catches of trapped Portunus armatus in ice slurries to pacify and facilitate discarding sub‐legal and ovigerous individuals, but with unknown mortality. To estimate mortality, during 90 trap lifts, 101 and 110 small P. armatus were sorted dry and in ice slurries, respectively (over 0.5–10.0 min). All discards were individually caged and monitored with 32 similar‐sized control animals (caught by benign methods) for 48 hr. Irrespective of handling, only eight discarded P. armatus were physically damaged. None of the controls died, compared with 1 and 13% of the dry‐ and ice‐slurry sorted conspecifics. The probability of mortality was estimated at 0.005 immediately after emptying the traps and remained temporally constant for dry‐sorted individuals, but was positively associated with time in the ice slurries, reaching 50% at 9 min. Minimising sorting in ice slurries to <2 min should cause minimal impact to P. armatus, although other unaccounted mortalities (e.g., predation) and sublethal effects warrant assessment. 相似文献
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16.
Q. DELL D. T. BREWER S. P. GRIFFITHS D. S. HEALES & M. L. TONKS 《Fisheries Management and Ecology》2009,16(3):191-201
Abstract The bycatch in a tropical Australian banana prawn, Penaeus merguiensis (de Man), fishery is described and contrasted with the closely related tiger prawn, Penaeus semisulcatus De Haan and Penaeus esculentus Haswell, fishery. Most of the similarity between banana prawn fishery catches was accounted for by three teleost species constituting 51.4% of the total bycatch weight. The bycatch assemblage structure of this fishery was significantly different ( P < 0.05) from the adjoining tiger prawn fishery. The banana prawn fishery had a higher mean bycatch catch rate from shorter duration trawls, but lower estimated total annual bycatch (1502 t yr−1 ) than the longer duration trawls of the tiger prawn fishery (20 073 t yr−1 ). This study provides new data for quantifying bycatch and improving the accuracy of quantitative risk assessments currently being used to demonstrate sustainability of bycatch populations. The information will be incorporated into collaborative development of a long-term monitoring programme. 相似文献
17.
Rowan Trebilco Rosemary Gales Emma Lawrence Rachael Alderman Graham Robertson G. Barry Baker 《水产资源保护:海洋与淡水生态系统》2010,20(5):531-542
- 1. Seabirds killed incidentally in Australia's eastern tuna and billfish (ETBF) longline fishery between September 2001 and June 2006 were examined to evaluate species composition and to relate, where possible, capture events to operational and environmental factors.
- 2. During this period 2.129 million hooks on 2202 shots were observed, and 369 birds were reported killed. The majority (78%) of these were flesh‐footed shearwaters (Puffinus carniepes), 53% of which were male and 44% female. Smaller numbers of medium to large sized albatrosses (Diomedeidae, predominantly female) and other shearwaters (Puffinus spp.) and petrels (Pterodroma spp.) dominated the remainder of the bycatch.
- 3. Of the 369 birds reported taken as bycatch, 280 were available for necropsy, and species identifications performed in situ by observers were assessed. While observer identifications were generally correct for common species, performance was poor for less common ones.
- 4. The geographical location (latitude) of shots, season, time of day at which shots were set, and bait type and life status (dead or alive) influenced the seabird bycatch rate. The majority of captures (87% overall) occurred between 30 and 35°S, with bycatch being lowest in winter, and remaining at similar levels across the other seasons.
- 5. The use of live fish bait was generally associated with increased captures of both seabirds overall, and flesh‐footed shearwaters in particular. Copyright © 2010 John Wiley & Sons, Ltd.
18.
19.
Abstract The by-catches of fish, mammals and birds from a fyke-net survey of eel, Anguilla angilla (L.), stocks (total effort 1593 end days) at 45 sites in rivers and lakes in the Thames catchment and tidal river were examined. Sizes and compositions of by-catches varied between sites, yielding a total of 21 fish species representative of the types of water body sampled. The largest catches were of shoaling juvenile perch (especially in lakes). Small roach, perch and ruffe were also fairly frequent in running waters (especially the tidal and non-tidal Thames). Carp, tench and pike were less frequently caught (mainly in still waters and upper tributaries). Juvenile flounders and smelt were fairly common in the tidal Thames. Salmonids were rarely caught and fish mortalities overall were very low. Few mammals, wildfowl or crustaceans were trapped, but it is important that nets are set below water level to avoid trapping birds swimming on the surface, and the use of otter guards is recommended. Fouling of fishing tackle was rare. Recommendations are made for practical steps that can be taken to minimize undesirable impacts of commercial fyke-netting, whilst realizing the potential financial and management benefits. The cost-effective uses of fyke-nets for sampling and culling fish for management purposes are discussed. 相似文献
20.
The impact of Anguillicola crassus on European eels 总被引：1，自引：0，他引：1
R. S. Kirk 《Fisheries Management and Ecology》2003,10(6):385-394
The impact of the parasitic swimbladder nematode, Anguillicola crassus Kuwahara, Niimi & Itagaki, on European eel populations is assessed with reference to published research on its origin and rapid dissemination, life cycle and transmission dynamics, and its pathogenic effect. The parasite was originally endemic to East Asia, but has transferred from its native host, the Japanese eel, Anguilla japonica Temminck & Schlegel, to the European eel, Anguilla anguilla (L.) and American eel, Anguilla rostrata (Le Seur). Anguillicola crassus is a very successful colonizer and is now known to occur in four continents (Asia, Europe, Africa and America). The nematode can severely impair swimbladder function and has caused mortalities in both farmed and wild populations in the presence of other stressors. Anguillicola crassus may impair the capacity of European eels to complete the spawning migration, although direct evidence is not available to support this hypothesis. Areas for future research are recommended. 相似文献