The offshore Northern shrimp(Pandalus borealis)bottom trawl fishery in eastern Canada currently uses 22 and 28 mm bar spacing Nordmøre grids to limit bycatch from using small mesh codends.However,a recent rebound...The offshore Northern shrimp(Pandalus borealis)bottom trawl fishery in eastern Canada currently uses 22 and 28 mm bar spacing Nordmøre grids to limit bycatch from using small mesh codends.However,a recent rebound of juvenile redfish(Sebastes spp.),that can pass through the grids,has greatly increased bycatch.To address this concern,this study investigated the effectiveness of 17 and 15 mm bar spacing Nordmøre grids in a twin-trawl(paired)configuration against the traditional 22 mm bar spacing grid.Size selectivity analyses showed that the 17 and 15 mm grids resulted in no significant reduction in shrimp catch across all length classes.The 17 mm grid significantly reduced redfish bycatch for all length classes and the 15 mm grid significantly reduced redfish bycatch for individuals larger than 95 mm total length.Less redfish entered the codend with the experimental grids,however,the overlap in width between redfish and Northern shrimp limits the overall sorting efficiency of the grids,leaving some redfish still vulnerable to capture.展开更多
The analysis of cetacean strandings can provide fundamental information about species diversity and composition in a particular region. The present study collected and analyzed cetacean strandings, bycatches and rescu...The analysis of cetacean strandings can provide fundamental information about species diversity and composition in a particular region. The present study collected and analyzed cetacean strandings, bycatches and rescues along the western coast of the Taiwan Strait, China, from 2010 to 2015. In total, 48 records, including 37 strandings, 8 bycatches and 3 rescues, involving 13 known species were collected. Among them, Indo-Pacific humpback dolphins（Sousa chinensis） and finless porpoises（Neophocaena phocaenoides） were the most common species, consisting of 31.3% and 25%, respectively. Notably, 10 out of the 48（20.8%） records were collected from the Pingtan Island and included 3 species of Mysticeti and 4 species of Odontoceti. Finally, we compared the cetacean species composition between the western and eastern coasts of the Taiwan Strait; 31 cetacean species occurred in the Taiwan Strait, indicating a relatively high cetacean diversity in this region. Systematic field surveys are urgently needed to explore the cetacean species composition, population stock and the related habitat status in the Taiwan Strait, which may improve conservation management in the future.展开更多
<span style="font-family:Verdana;">Chimaeras</span><span style="font-family:;" "=""><span style="font-family:Verdana;">, fish in the order Chimaerif...<span style="font-family:Verdana;">Chimaeras</span><span style="font-family:;" "=""><span style="font-family:Verdana;">, fish in the order Chimaeriformes, are among the rarest and least studied fish in the class Chondrichthyes (cartilaginous fish). Previous records have indicated that a species of chimaera known as the elephantfish, or cockfish, </span><i><span style="font-family:Verdana;">Callorhinchus callorynchus</span></i><span style="font-family:Verdana;">, may be found in marine waters off southeastern Brazil, as far north as the state of S<span style="font-size:10.0pt;font-family:"">ã</span>o Paulo. Here we report that </span><i><span style="font-family:Verdana;">C. callorynchus</span></i><span style="font-family:Verdana;">, caught with bottom gillnet, was found in an urban fish market in the city of Rio de Janeiro (~23<span style="white-space:nowrap;">˚</span>S). This and other records from a variety of places call into question the distribution limits of the American elephantfish in the southwestern Atlantic Ocean and whether, at least seasonally, this species may often be found as far north as the state of Rio de Janeiro. Because of scientific and conservation interests in the poorly known Chimaeriformes, we recommend long-term monitoring of the fish catch in ports along the southern Brazilian coast, to better understand the natural history of the intriguing chimeras.</span></span>展开更多
Longline fisheries for tunas and tuna-like species present an existential threat to many populations of albatrosses and petrels worldwide. To prevent this form of mortality we developed a new technology designed to de...Longline fisheries for tunas and tuna-like species present an existential threat to many populations of albatrosses and petrels worldwide. To prevent this form of mortality we developed a new technology designed to deploy baited hooks underwater beyond the dive depths of?seabirds (6 - 10 m for the species most commonly caught). The underwater bait setter is a stern-mounted, hydraulically-operated and computer-controlled?device that catapults?baited hooks underwater in a steel capsule?connected to hydraulic winches by Spectra®rope. Baits are flushed from the capsule by water pressure through a spring-loaded bait release door. The chief engineering challenges in the developmental stageswere ensuring:?1) bait delivery?to target depths with cycle times (time from release to recovery) that were practical for fishing operations;?2) bait retention in the capsule (no drop-outs) on the descent phase of the cycle;?3) baits, upon?release at target depth, were not drawn up the water column on the capsule recovery phase (from possible hook-ups and/or suction);and?4) the retention of baits?on?hooks post-release from the capsule was not affected by the mechanical release underwater. Operational trials with the final version of the capsule yielded?satisfactory cycle times to depths of 6 - 10 m. All baits were retained?in the capsule on the descent and?released as required?at target depths (n = 606 deployments). Bait retention on hooks post release from the capsule and retention on hooks hand-set at the surface (the conventional method) were statistically indistinguishable.?The underwater bait setter is modular in construction and can be fitted to all types of vessel sterns.展开更多
Gillnets are the primary fishing gear used to catch Atlantic cod(Gadus morhua)in coastal areas of Newfoundland and Labrador but are known to catch non-target species and produce lower quality fish than live-catch meth...Gillnets are the primary fishing gear used to catch Atlantic cod(Gadus morhua)in coastal areas of Newfoundland and Labrador but are known to catch non-target species and produce lower quality fish than live-catch methods.The purpose of this study was to compare the catch efficiency of collapsible cod pots against gillnets near the Gilbert Bay Marine Protected Area(MPA),Labrador,where a reduction in by-catch is needed.Results showed that one cod pot caught half as much Atlantic cod as a gillnet,and pots had a relatively stable catch rate throughout the sampling period,whereas gillnets caught relatively few fish later in the sampling season.Moreover,nearly all fish sampled with pots were caught alive undamaged,whereas most gillnet-caught fish experienced damage or mortality.As a conservation measure pot-fishing would enable fishing within close proximity to the Gilbert Bay MPA and the live-release of visually distinguishable Gilbert Bay cod,thereby mitigating against the negative effects of commercial fishing on this protected Atlantic cod population.展开更多
In response to concerns over the mortality of discards and other negative environmental impacts of otter trawling for penaeids,the utility of bottom-set gillnets deployed by artisanal vessels to target Penaeus monodon...In response to concerns over the mortality of discards and other negative environmental impacts of otter trawling for penaeids,the utility of bottom-set gillnets deployed by artisanal vessels to target Penaeus monodon,Metapenaeus affinis and other retained species by-product was assessed in the Sea of Oman.Two gillnets(each comprising several 80-m panels for total lengths of up to 1.3 km)were diurnally fished at two locations(off Beris and Govater,eastern Iran)within established penaeid fishing grounds.During 30 days,the total catch was 2721 kg,comprising penaeids(981 kg),eight retained by-product species(598 kg and mostly Otolithes ruber,Cynoglossus bilinearus and Carangoides talamparoides)and 19 discarded species(1142 kg).The catch-per-unit-of-effort(CPUE,kg/gillnet-panel⋅hour-fished)of targeted penaeids and by-product varied significantly between areas(0.5-1.0 kg),but nevertheless reached economically viable levels.The CPUEs of total bycatch were similar at both sites(<0.5 kg)and no marine turtles were caught.The concomitant ratios of retained-catches-to-bycatch were considerably less than those for regional penaeid-trawl fisheries.Nevertheless,while gillnet selectivity was satisfactory for M.affinis,most of the P.monodon were smaller than their carapace length at maturity at both fished sites.The results support using gillnets to target penaeids and by-product species as an alternative to otter trawling in the Sea of Oman;albeit with ongoing assessments of modifications to maximise selectivity.展开更多
In south-eastern Australia,the same baited,round traps(comprising 50–57-mm mesh netting)are used to target giant mud,Scylla serrata and blue swimmer crabs,Portunus armatus in spatially separated fisheries.Both fisher...In south-eastern Australia,the same baited,round traps(comprising 50–57-mm mesh netting)are used to target giant mud,Scylla serrata and blue swimmer crabs,Portunus armatus in spatially separated fisheries.Both fisheries are characterised by the common,problematic discarding of undersized portunids(<85 and 65 mm carapace length;CL for S.serrata and P.armatus)and fish(yellowfin bream,Acanthopagrus australis).This poor selectivity was addressed here in two experiments assessing the utility of(1)traps partially or completely covered in larger mesh(91 mm to match the minimum legal size of the smaller P.armatus),and then(2)any cumulative benefits of fitting species-specific escape gaps.In experiment 1,there were no differences among catches of legal-sized portunids associated with either partial,or complete trap coverage with larger mesh.Irrespective of mesh coverage,both designs of 91-mm traps also retained significantly fewer(by up to 42%)undersized P.armatus and A.australis.In experiment 2,replicate traps completely covered in 91-mm mesh were tested against conventional traps comprising 56-mm mesh,and traps with the same mesh sizes,but also three escape gaps configured for either S.serrata(46×120 mm)or P.armatus(36×120 mm)(i.e.four treatments in total).All modified traps maintained catches of legal-sized S.serrata,and only the 91-mm traps with escape gaps caught fewer legal-sized P.armatus.Fewer undersized S.serrata,P.armatus and A.australis(mean catches reduced by up to 49%)were retained in all larger-meshed than small-meshed traps,and in all of those traps with escape gaps(by up to 95%)than without.While there were no significant cumulative benefits of escape gaps in largermeshed traps(measured by a statistical interaction),there was a trend of fewer unwanted catches overall.These data support configuring portunid traps with mesh sizes matching the morphology of the smallest legal-sized target species.But,simply retroactively fitting escape gaps in existing,smaller-meshed traps will also realize positive selec展开更多
海龟处于海洋生态结构的顶端,对海洋生态系统的多样性和稳定性起到了重要的调控作用。根据2009—2019年科学观察员对热带大西洋公海海域(15°S~15°N,15°W~45°W)金枪鱼延绳钓渔业的调查数据,分析海龟兼捕现象。结果发...海龟处于海洋生态结构的顶端,对海洋生态系统的多样性和稳定性起到了重要的调控作用。根据2009—2019年科学观察员对热带大西洋公海海域(15°S~15°N,15°W~45°W)金枪鱼延绳钓渔业的调查数据,分析海龟兼捕现象。结果发现:共误捕到蠵龟(Caretta caretta)、大西洋丽龟(Lepidochelys kempii)和棱皮龟(Dermochelys coriacea)等3种累计108只,其中死亡32只。年兼捕率范围为0.0016~0.0693只/千钩,直接咬钩和被支绳缠绕是兼捕的主要方式;兼捕时间上存在一定季节性差异,高兼捕率(bycatch per unit effort,BPUE)发生在10月到翌年5月;赤道以北兼捕率年际间出现波动,但总体变化幅度不大,赤道以南兼捕率年际差异较大,2009—2013年间未发现海龟兼捕,但自2013年后南纬BPUE增长趋势明显,于2015年达到最大值,随后BPUE逐渐降低,2019年到达最小值;海龟兼捕易受到月相强度的影响,往往在满月或接近满月的环境下兼捕现象明显增多;某些特定温度区间会出现不同种类海龟的兼捕,棱皮龟在水温24~26℃时兼捕更易发生,丽龟兼捕则在26~27℃间更为集中。此外,还探究了近年来中国船队海龟兼捕存活率提高的原因,建议今后为有效降低热带大西洋金枪鱼延绳钓渔业中海龟兼捕,应根据作业海域、目标鱼种和环境因子的不同适时调整相关养护对策。展开更多
文摘The offshore Northern shrimp(Pandalus borealis)bottom trawl fishery in eastern Canada currently uses 22 and 28 mm bar spacing Nordmøre grids to limit bycatch from using small mesh codends.However,a recent rebound of juvenile redfish(Sebastes spp.),that can pass through the grids,has greatly increased bycatch.To address this concern,this study investigated the effectiveness of 17 and 15 mm bar spacing Nordmøre grids in a twin-trawl(paired)configuration against the traditional 22 mm bar spacing grid.Size selectivity analyses showed that the 17 and 15 mm grids resulted in no significant reduction in shrimp catch across all length classes.The 17 mm grid significantly reduced redfish bycatch for all length classes and the 15 mm grid significantly reduced redfish bycatch for individuals larger than 95 mm total length.Less redfish entered the codend with the experimental grids,however,the overlap in width between redfish and Northern shrimp limits the overall sorting efficiency of the grids,leaving some redfish still vulnerable to capture.
基金The National Natural Science Foundation for Young Scholars of China under contract No.41506164the foundation of the State Oceanic Administration of China under contract No.201105011+3 种基金the Natural Science Foundation for Young Scholars of Fujian Province under contract No.2017J05062China-ASEAN maritime cooperation fund under contract No.HX150702the foundation of the Ministry of Agriculture of the People’s Republic of China under contract No.1070413701307the Ocean Park Conservation Foundation,Hong Kong(OPCFHK)under contract No.MM03_1617
文摘The analysis of cetacean strandings can provide fundamental information about species diversity and composition in a particular region. The present study collected and analyzed cetacean strandings, bycatches and rescues along the western coast of the Taiwan Strait, China, from 2010 to 2015. In total, 48 records, including 37 strandings, 8 bycatches and 3 rescues, involving 13 known species were collected. Among them, Indo-Pacific humpback dolphins（Sousa chinensis） and finless porpoises（Neophocaena phocaenoides） were the most common species, consisting of 31.3% and 25%, respectively. Notably, 10 out of the 48（20.8%） records were collected from the Pingtan Island and included 3 species of Mysticeti and 4 species of Odontoceti. Finally, we compared the cetacean species composition between the western and eastern coasts of the Taiwan Strait; 31 cetacean species occurred in the Taiwan Strait, indicating a relatively high cetacean diversity in this region. Systematic field surveys are urgently needed to explore the cetacean species composition, population stock and the related habitat status in the Taiwan Strait, which may improve conservation management in the future.
文摘<span style="font-family:Verdana;">Chimaeras</span><span style="font-family:;" "=""><span style="font-family:Verdana;">, fish in the order Chimaeriformes, are among the rarest and least studied fish in the class Chondrichthyes (cartilaginous fish). Previous records have indicated that a species of chimaera known as the elephantfish, or cockfish, </span><i><span style="font-family:Verdana;">Callorhinchus callorynchus</span></i><span style="font-family:Verdana;">, may be found in marine waters off southeastern Brazil, as far north as the state of S<span style="font-size:10.0pt;font-family:"">ã</span>o Paulo. Here we report that </span><i><span style="font-family:Verdana;">C. callorynchus</span></i><span style="font-family:Verdana;">, caught with bottom gillnet, was found in an urban fish market in the city of Rio de Janeiro (~23<span style="white-space:nowrap;">˚</span>S). This and other records from a variety of places call into question the distribution limits of the American elephantfish in the southwestern Atlantic Ocean and whether, at least seasonally, this species may often be found as far north as the state of Rio de Janeiro. Because of scientific and conservation interests in the poorly known Chimaeriformes, we recommend long-term monitoring of the fish catch in ports along the southern Brazilian coast, to better understand the natural history of the intriguing chimeras.</span></span>
文摘Longline fisheries for tunas and tuna-like species present an existential threat to many populations of albatrosses and petrels worldwide. To prevent this form of mortality we developed a new technology designed to deploy baited hooks underwater beyond the dive depths of?seabirds (6 - 10 m for the species most commonly caught). The underwater bait setter is a stern-mounted, hydraulically-operated and computer-controlled?device that catapults?baited hooks underwater in a steel capsule?connected to hydraulic winches by Spectra®rope. Baits are flushed from the capsule by water pressure through a spring-loaded bait release door. The chief engineering challenges in the developmental stageswere ensuring:?1) bait delivery?to target depths with cycle times (time from release to recovery) that were practical for fishing operations;?2) bait retention in the capsule (no drop-outs) on the descent phase of the cycle;?3) baits, upon?release at target depth, were not drawn up the water column on the capsule recovery phase (from possible hook-ups and/or suction);and?4) the retention of baits?on?hooks post-release from the capsule was not affected by the mechanical release underwater. Operational trials with the final version of the capsule yielded?satisfactory cycle times to depths of 6 - 10 m. All baits were retained?in the capsule on the descent and?released as required?at target depths (n = 606 deployments). Bait retention on hooks post release from the capsule and retention on hooks hand-set at the surface (the conventional method) were statistically indistinguishable.?The underwater bait setter is modular in construction and can be fitted to all types of vessel sterns.
基金The study was funded by the Fisheries and Oceans Canada.
文摘Gillnets are the primary fishing gear used to catch Atlantic cod(Gadus morhua)in coastal areas of Newfoundland and Labrador but are known to catch non-target species and produce lower quality fish than live-catch methods.The purpose of this study was to compare the catch efficiency of collapsible cod pots against gillnets near the Gilbert Bay Marine Protected Area(MPA),Labrador,where a reduction in by-catch is needed.Results showed that one cod pot caught half as much Atlantic cod as a gillnet,and pots had a relatively stable catch rate throughout the sampling period,whereas gillnets caught relatively few fish later in the sampling season.Moreover,nearly all fish sampled with pots were caught alive undamaged,whereas most gillnet-caught fish experienced damage or mortality.As a conservation measure pot-fishing would enable fishing within close proximity to the Gilbert Bay MPA and the live-release of visually distinguishable Gilbert Bay cod,thereby mitigating against the negative effects of commercial fishing on this protected Atlantic cod population.
文摘In response to concerns over the mortality of discards and other negative environmental impacts of otter trawling for penaeids,the utility of bottom-set gillnets deployed by artisanal vessels to target Penaeus monodon,Metapenaeus affinis and other retained species by-product was assessed in the Sea of Oman.Two gillnets(each comprising several 80-m panels for total lengths of up to 1.3 km)were diurnally fished at two locations(off Beris and Govater,eastern Iran)within established penaeid fishing grounds.During 30 days,the total catch was 2721 kg,comprising penaeids(981 kg),eight retained by-product species(598 kg and mostly Otolithes ruber,Cynoglossus bilinearus and Carangoides talamparoides)and 19 discarded species(1142 kg).The catch-per-unit-of-effort(CPUE,kg/gillnet-panel⋅hour-fished)of targeted penaeids and by-product varied significantly between areas(0.5-1.0 kg),but nevertheless reached economically viable levels.The CPUEs of total bycatch were similar at both sites(<0.5 kg)and no marine turtles were caught.The concomitant ratios of retained-catches-to-bycatch were considerably less than those for regional penaeid-trawl fisheries.Nevertheless,while gillnet selectivity was satisfactory for M.affinis,most of the P.monodon were smaller than their carapace length at maturity at both fished sites.The results support using gillnets to target penaeids and by-product species as an alternative to otter trawling in the Sea of Oman;albeit with ongoing assessments of modifications to maximise selectivity.
基金This study was funded by Hunter Local Land Services and the NSW Department of Primary Industries,and would not have been possible without the assistance of Wallis Lake commercial fishers,and especially,Malcolm,Adrian and Danny.
文摘In south-eastern Australia,the same baited,round traps(comprising 50–57-mm mesh netting)are used to target giant mud,Scylla serrata and blue swimmer crabs,Portunus armatus in spatially separated fisheries.Both fisheries are characterised by the common,problematic discarding of undersized portunids(<85 and 65 mm carapace length;CL for S.serrata and P.armatus)and fish(yellowfin bream,Acanthopagrus australis).This poor selectivity was addressed here in two experiments assessing the utility of(1)traps partially or completely covered in larger mesh(91 mm to match the minimum legal size of the smaller P.armatus),and then(2)any cumulative benefits of fitting species-specific escape gaps.In experiment 1,there were no differences among catches of legal-sized portunids associated with either partial,or complete trap coverage with larger mesh.Irrespective of mesh coverage,both designs of 91-mm traps also retained significantly fewer(by up to 42%)undersized P.armatus and A.australis.In experiment 2,replicate traps completely covered in 91-mm mesh were tested against conventional traps comprising 56-mm mesh,and traps with the same mesh sizes,but also three escape gaps configured for either S.serrata(46×120 mm)or P.armatus(36×120 mm)(i.e.four treatments in total).All modified traps maintained catches of legal-sized S.serrata,and only the 91-mm traps with escape gaps caught fewer legal-sized P.armatus.Fewer undersized S.serrata,P.armatus and A.australis(mean catches reduced by up to 49%)were retained in all larger-meshed than small-meshed traps,and in all of those traps with escape gaps(by up to 95%)than without.While there were no significant cumulative benefits of escape gaps in largermeshed traps(measured by a statistical interaction),there was a trend of fewer unwanted catches overall.These data support configuring portunid traps with mesh sizes matching the morphology of the smallest legal-sized target species.But,simply retroactively fitting escape gaps in existing,smaller-meshed traps will also realize positive selec
文摘海龟处于海洋生态结构的顶端,对海洋生态系统的多样性和稳定性起到了重要的调控作用。根据2009—2019年科学观察员对热带大西洋公海海域(15°S~15°N,15°W~45°W)金枪鱼延绳钓渔业的调查数据,分析海龟兼捕现象。结果发现:共误捕到蠵龟(Caretta caretta)、大西洋丽龟(Lepidochelys kempii)和棱皮龟(Dermochelys coriacea)等3种累计108只,其中死亡32只。年兼捕率范围为0.0016~0.0693只/千钩,直接咬钩和被支绳缠绕是兼捕的主要方式;兼捕时间上存在一定季节性差异,高兼捕率(bycatch per unit effort,BPUE)发生在10月到翌年5月;赤道以北兼捕率年际间出现波动,但总体变化幅度不大,赤道以南兼捕率年际差异较大,2009—2013年间未发现海龟兼捕,但自2013年后南纬BPUE增长趋势明显,于2015年达到最大值,随后BPUE逐渐降低,2019年到达最小值;海龟兼捕易受到月相强度的影响,往往在满月或接近满月的环境下兼捕现象明显增多;某些特定温度区间会出现不同种类海龟的兼捕,棱皮龟在水温24~26℃时兼捕更易发生,丽龟兼捕则在26~27℃间更为集中。此外,还探究了近年来中国船队海龟兼捕存活率提高的原因,建议今后为有效降低热带大西洋金枪鱼延绳钓渔业中海龟兼捕,应根据作业海域、目标鱼种和环境因子的不同适时调整相关养护对策。
