南沙群岛重要珊瑚礁水域鱼类资源数量分布

1998年3—5月和1999年5—6月．采用手钓、延绳钓和流刺网3种作业方式在南沙群岛的渚碧、南薰、东门、美济、赤瓜、永署和华阳等7座珊瑚礁水域进行了2个航次的鱼类资源调查。结果表明,7座珊瑚礁水域不同作业方式的鱼类资源相对丰盛度差别较大,其中刺网以永暑礁最高,手钓以华阳礁最高,延绳钓以南薰礁最高;同时．刺网和手钓不同水深区域鱼类资源的相对丰盛度也不相同．其中刺网以11～30m区域最高．手钓以10m以浅和51～80m区域较高;分析认为,造成礁区之间鱼类相对丰盛度差异的主要原因不是初级生产力．而是生态环境因素,主要是礁盘形态和大型海藻的数量。另外．各礁区水域的优势类群有明显不同．这主要与洞穴的大小和数量、大型海藻及珊瑚的种类和数量等生物和非生物环境有关。     

罩网兼作金枪鱼延绳钓的钓钩深度与渔获水层分析

2015年3-4月及2017年1月在南海外海进行了两次罩网渔船兼作金枪鱼延绳钓的捕捞试验,基于试验数据分析延绳钓钓钩深度及渔获水层分布,以期优化改进试验钓具,有效提高南海金枪鱼延绳钓捕捞效益。研究发现:1)经济渔获以剑鱼(Xiphias gladius)与黄鳍金枪鱼(Thunnus albacares)为主,剑鱼的单位捕捞努力量渔获量(CPUE,kg·千钩-1)为所有渔获中最高; 2)钓钩深度(D)与钩位(n)、风速(SW)、风流合压角(γ)成正相关,与漂移速度(SD)、投绳船速(SV)呈负相关,回归方程为:D=10. 259n-37. 247SD-29. 878SV+6. 940SW+23. 493γ+35. 633; 3)模型的预测结果与实测数据间无显著性差异,相对权重表明各影响因子中钩位具有最大的相对重要性; 4)试验中拟合钩深分布范围为35. 08～110. 80 m,剑鱼上钩率与CPUE最高的水层为60～80 m,黄鳍金枪鱼上钩率与CPUE最高的水层为80～100 m; 5) 60～80 m水层主要经济渔获CPUE最大且钓钩数目最多,认为钓钩水层分布较合理。     

灯光罩网渔船兼作金枪鱼延绳钓捕捞试验

2015年3月~4月利用"粤电渔42212"灯光罩网渔船在南沙北部海域开展了金枪鱼延绳钓捕捞试验。延绳钓试验以不影响灯光罩网的正常作业为前提。试验期间,灯光罩网作业40晚,放网297次,平均渔获率336.4kg·h-1,总渔获质量129.6 t,鸢乌贼(Sthenoteuthis oualaniensis)占85.31%,黄鳍金枪鱼(Thunnus albacaes)占0.21%。延绳钓作业7次,放钩2 700枚,总渔获质量1 281.6 kg,剑鱼(Xiphias gladius)和黄鳍金枪鱼分别占72.88%和11.16%;延绳钓平均上钩率和CPUE分别为25.74尾·千钩-1和427.48 kg·千钩-1,其中黄鳍金枪鱼为1.90尾·千钩-1、52.74 kg·千钩-1,剑鱼为3.76尾·千钩-1、291.86 kg·千钩-1。试验证明,金枪鱼延绳钓和灯光罩网的渔场分布恰好一致,作业时间没有冲突。相比发展专业钓船,罩网渔船兼作延绳钓具有投资金额少、生产成本低的优势。建议通过探捕拓展和延长外海渔期,并研究解决金枪鱼保鲜问题。     

北太平洋金枪鱼延绳钓钓钩垂直分布及浸泡时间对渔获物的影响

根据中国金枪鱼延绳钓渔业观察员于2018年9-12月在北太平洋公海(150°W-164°W,30°N-37°N)采集的金枪鱼延绳钓渔获数据,分析了钓钩的垂直分布及浸泡时间与渔获物之间的关系。结果表明,11种主要渔获物钓获深度差异很大,鲣(Katsuwonus pelamis)的平均钓获深度最浅,大青鲨(Prionace glauca)最深;除大青鲨和帆蜥鱼(Alepisaurus ferox)外,其他兼捕鱼类的钓钩深度分布与大眼金枪鱼(Thunnus obesus,目标鱼种)之间差异显著;随着浸泡时间的增加,总渔获率呈先增加后下降的趋势,10~14 h内渔获率较高,且在第10小时达到峰值[1.44尾·(千钩·h)-1];浸泡时间在10~16 h内大眼金枪鱼的渔获率较高,且在第11小时达到峰值[0.45尾·(千钩·h)-1]。研究结果可为渔业生产和CPUE的标椎化提供参考,为制定有效减少兼捕鱼种的管理措施提供科学依据。     

大西洋中上层鲨鱼资源状况的初步探讨

据1994—2001年4个航次在金枪鱼延绳钓渔船对热带大洋性中上层鲨鱼资源进行调查，并分析国际大西洋金枪鱼资源保护委员会提供的关于中上层鲨鱼的渔业数据。结果表明：延绳钓渔业共兼捕13种鲨鱼，其中，尖吻鲭鲨和大青鲨是优势种类。尖吻鲭鲨在第1、第2和第4航次的CPUE分别为每千钩0．3502、0．1754和0．0642尾，呈下降趋势。大青鲨在第1～3航次的的CPUE达到每千钩5～7尾，而在第4航次下降为每千钩0．8尾。研究报告了中国金枪鱼船队自1993年开始在大西洋兼捕尖吻鲭鲨和大青鲨的渔获量，并根据捕捞死亡系数和大西洋总渔获量数据，初步探讨了尖吻鲭鲨和大青鲨年平均资源量，影响CPUE的因素和大西洋中上层资源状况。     

热带中西太平洋金枪鱼延绳钓渔获物组成及其多样性

利用金枪鱼漂流延绳钓作业方式, 于 2018 年 5 月至 2019 年 3 月期间在热带中西太平洋海域(2°03′~11°17′S, 163°14′~173°35′E)进行渔获取样, 分析渔获组成及物种多样性, 并使用广义线性混合模型(GLMM)和圆形统计方法分析渔获水深、月相等时空要素对物种多样性、目标种类和兼捕 CPUE 等影响。结果表明: (1) 3673 尾渔获隶属于 9 目 21 科 30 属 35 种, 其中目标种类大眼金枪鱼(Thunnus obesus)和黄鳍金枪鱼(Thunnus albacores)为优势种, 蓝枪鱼(Makaira nigricans)、长鳍金枪鱼(Thunnus alalunga)、镰状真鲨(Carcharhinus falciformis)、帆蜥鱼(Alepisaurus ferox) 和紫魟(Pteroplatytrygon violacea)为重要种; (2)大眼金枪鱼、黄鳍金枪鱼以及兼捕种类 CPUE 分别为(1.662± 0.89) ind/千钩、(1.39±1.45) ind/千钩、(2.52±1.27) ind/千钩。渔获多样性指数 Shannon-Wiener 指数(H′)、Margalef 指数(D)、Pielou 指数(J)分别为(1.78±0.28)、(2.53±0.60)、(0.79±0.09); (3) GLMM 结果显示, 月相(余弦)对大眼金枪鱼的 CPUE 的具有极其显著的影响(P=0.001, CPUE 在满月较高, 而在新月较低), 而月相(正弦)对黄鳍金枪鱼 CPUE 具有边际显著影响(P=0.067, CPUE 在上弦月较高, 而在下弦月较低), 月相兼捕 CPUE 则没有显著影响, 水深对 CPUE 具有极显著的影响(P＜0.001); (4)月相对多样性指数均不存在显著影响, 但水深对渔获 Shannon-Weiner 指数 (H′)和 Margalef 指数(D)均有显著影响(P＜0.001)。研究结果反映出热带中西太平洋海域物种丰富、群落的复杂程度较高、稳定性较好, 群落对环境变化、渔业活动等具有较好的耐受性。     

中东太平洋金枪鱼延绳钓渔获量及其分布

根据2000年9月至2002年8月两年的中东太平洋金枪鱼延绳钓探捕调查结果,对延绳钓渔获量及其分布特征进行了初步分析。结果显示,延绳钓渔获物以金枪鱼为主,大眼金枪鱼(Thun-nusobesus)等3种金枪鱼的渔获量占总渔获量75·9%。“海欣”船延绳钓作业的平均日产量为(994·8±19·9)kg/d,上钩率为(12·5±0·3)ind/103钩。主要目标鱼种大眼金枪鱼和黄鳍金枪鱼(Thunnusalbacares)的平均日产量分别为(466·9±13·9)kg/d和(190·6±7·2)kg/d。探捕期间日产量的月间差异显著(P<0·001),6~8月为渔发汛期,日产量较高;2~5月为相对淡季,日产量较低。探捕区南部的平均日产量最高,与中、北部比较差异显著(P<0·001);东部平均日产量与西部比较差异不显著(P>0·05)。     

大西洋中部金枪鱼延绳钓性能评估初步研究

利用2009～2010年我国大西洋中部金枪鱼延绳钓调查数据,对金枪鱼延绳钓钓具性能进行评估。结果表明:金枪鱼延绳钓具有较好的种类选择性,大眼金枪鱼渔获量和尾数分别占总渔获量的73.67%和76.00%;大眼金枪鱼(Thunnus obesus)、黄鳍金枪鱼(Thunnus albacares)和剑鱼(Xiphias gladius)未达到性成熟的渔获尾数比例分别为13.00%、25.97%和48.93%;1～6号钓钩,大眼金枪鱼上钩率随钓钩深度增加呈递增趋势,6～8号钓钩上钩率呈递减趋势,6号钓钩上钩率最大为9.46尾/千钩;3号至8号钓钩上钩率均大于7尾/千钩,表明1号和2号钓钩利用率偏低;根据钓钩理论深度,推测大眼金枪鱼主要分布水层为220m～350m。通过调节缩短率和浮子绳长度对钓具进行优化,使得钓钩分布水层与大眼金枪鱼分布水层更为接近,提高钓钩利用率。     

北部湾二长棘鲷的生态分布

根据1997年12月~1999年6月在北部湾17°53′~21°15′N,106°58′~109°34′E水域进行的4个季节5个航次的调查资料,对北部湾二长棘鲷种群数量分季节、平面和纵深分布进行了分析。结果表明,北部湾二长棘鲷的渔获率呈明显的季节分布特征,冬、春季渔获率密度指数高于夏、秋季,以3~5月的渔获率最高;秋末冬初,亲体向湾北部进行产卵洄游,春季产卵后鱼群分布在湾内,幼鱼在沿岸海区成长;二长棘鲷的水深分布也有明显特征,高渔获率主要出现在30~60m水深,尤以30~40m水深海域最高,生物量渔获率和个体数渔获率分别达10·27kg/h和700·9尾/h。此外,本文对二长棘鲷的洄游、数量分布与水系、水团、水温及盐度等环境因子的关系进行了初步地分析。     

基于渔港抽样调查南海不同捕捞方式CPUE比较分析

本研究基于2016年对南海三省区的14个沿海主要渔港的连续4个季节抽样调查(共计5256航次,抽样总功率达到89.2×10~4 kW),以kg?kW~(-1)?d~(-1)作为CPUE(Catch per unit effort,单位捕捞努力量渔获量)标准化后的单位,对南海9种捕捞作业类型渔船的CPUE进行了比较分析。结果显示,CPUE_(围网)CPUE_(双拖)CPUE_(刺网)CPUE_(罩网)CPUE_(张网)CPUE_(单拖)CPUE_(虾拖)CPUE_(笼壶)CPUE_(钓具)。不同捕捞作业类型CPUE随渔船功率段的变化而不同,CPUE峰值数及其所对应的最优功率段(渔获率最高的功率段)也有差异,单拖和虾拖渔船的CPUE随渔船功率的变化具有1个CPUE峰值点,最优功率段分别为(200～250) kW(CPUE=8.6 kg?kW~(-1)?d~(-1))和(150～200) kW(CPUE=5.0 kg?kW~(-1)?d~(-1));围网、双拖、钓具和刺网渔船的CPUE随渔船功率的变化有2个CPUE峰值点,对应的最优功率段分别为(200～250)kW(CPUE=47.7kg?kW~(-1)?d~(-1))、(350～400)kW(CPUE=16.8kg?kW~(-1)?d~(-1))、(50～100)(CPUE=2.9 kg?kW~(-1)?d~(-1))和(0～50) kW(CPUE=6.9 kg?kW~(-1)?d~(-1))。罩网渔船CPUE随功率段变化有3个峰值点,最优功率段为(0～50) kW(CPUE=7.0 kg?kW~(-1)?d~(-1))。不同捕捞作业类型CPUE季节变化表现:围网CPUE均值在春季最高,单拖、双拖、罩网、钓具和笼壶在夏季最高,张网在秋季最高,刺网和虾拖在冬季最高。     

南海主要珊瑚礁(鱼旨)科鱼类的组成与分布

1998年3~5月和1999年5~6月,采用手钓、延绳钓和刺网3种作业方式在西沙的浪花礁、华光礁、琛航岛、永兴岛、北礁和南沙的渚碧礁、南薰礁、东门礁、美济礁、赤瓜礁、永署礁、华阳礁等12座珊瑚礁水域进行了2个航次的鱼类资源调查,捕获科鱼类6属25种,渔获量计942尾256.4kg;其中在南沙调查区捕获6属22种,共641尾205.5kg,优势种依次为尾纹九棘鲈、蜂巢石斑鱼、六角石斑鱼、黑边石斑鱼;在西沙调查区捕获6属14种,共301尾50.9kg,优势种依次为尾纹九棘鲈、六角石斑鱼、黑边石斑鱼、蜂巢石斑鱼,同时分析了主要种类尾纹九棘鲈、六角石斑鱼和蜂巢石斑鱼的生物学特征。     

Species and size selectivity in a ‘red’ sea bream longline ‘métier’ in the Algarve (southern Portugal)

A longline ‘metier’ using small hooks for ‘red’ sea breams (Pagellus acarne and Pagellus erythrinus) in the Algarve (south of Portugal) was studied. Experimental longlining was carried out with three sizes of “Mustad” round bend, flatted, spade end Quality 2316 DT hooks (numbers 11, 13 and 15) and two types of bait: razor shell (Ensis siliqua) and mud shrimp (Upogebia pusilla). A total of 3 328 fish and at least 36 species were caught with 33 600 hooks fished in 28 longline sets. Five species of sea breams (Sparidae) accounted for 79% of the catch: Pagellus acarne, Pagellus erythrinus, Diplodus vulgaris, Spondyliosoma cantharus, and Boops boops. High catch rates of 20–30 fish per 100 hooks were made in a number of 1 200 hook longline sets, with total catch weights of 40 to more than 60 kg per set. In general, the smallest hook (number 15) had the highest catch rate. Bait type did not significantly affect the catch size distributions. Although more fish were caught with the razor shell bait, higher catch rates of ‘red’ sea breams were obtained with mud shrimp. Catch rates were also affected by the location of the fishing grounds and the time of the set, with the highest catch rates obtained when the longline was set within two hours before sunrise. A wide size range was caught for each species, with highly overlapped catch size frequency distributions for the three hook sizes used. Except for Spondyliosoma cantharus, few illegal-sized fish were caught, even with the smallest hook. The logistic model fitted by maximum likelihood was used to describe hook selectivity for Diplodus vulgaris, Pagellus acarne, Pagellus erythrinus, and Spondyliosoma cantharus.     

Potential bycatch of seabirds and turtles in hook-and-line fisheries of the Itaipava Fleet, Brazil

The decline of populations of certain seabirds and sea turtles around the world is partly related to their incidental capture in large-scale fisheries. However, the impacts of small-scale fisheries on endangered seabirds and sea turtles, being carried out in many places around the world, have been largely neglected by scientists and governments. We monitored 178 fishing days and described a range of poorly known hook-and-line commercial fisheries carried out by the Itaipava fleet, southeastern Brazil, composed by 497 vessels and deploying hooks from 18°S to 35°S. Seven fisheries were defined: fast trolling for tuna and tuna-like species, slow trolling for Bigeye tuna, handlining, surface longline for Dolphinfish, pelagic longline for Swordfish, bottom dropline, and pole-and-line with live bait. We observed bycatch of 47 seabirds of six species and 45 turtles of four species. Capture rates were higher for the surface longline for Dolphinfish (0.15 birds/1000 hooks and 1.08 turtles/1000 hooks), slow trolling for Bigeye tuna (0.41 birds/day) and handlining targeting Yellowfin tuna (0.61 birds/day). Endangered Spectacled petrel (Procellaria conspicillata), Atlantic Yellow-nosed (Thalassarche chlororhynchos), and Black-browed (T. melanophris) albatrosses were the main seabirds caught. Immature Loggerhead turtles (Caretta caretta) and immature or adult Leatherback turtles (Dermochelys coriacea) were the main sea turtles affected by the surface longline for Dolphinfish. Monitoring the fleet and bycatch levels, development of mitigation measures, establishment of educational programs, government control over the fleet, and enforcement, are urgently required for the hook-and-line fisheries described in the present study.     

金枪鱼延绳钓环形钩和圆形钩钓获率比较

根据"华远渔18号"和"华远渔19号"两艘冰鲜金枪鱼延绳钓渔船2005年9月15日~12月12日在印度洋热带公海水域(0°47′~10°16′N,61°40′~70°40′E)作业期间收集的数据,以每千钩钓获尾数和平均净重,对环型钩与圆型钩对大眼金枪鱼和黄鳍金枪鱼的选择性、钓获率差异等进行了比较研究。结果表明:不同钓具漂移速度下环型钩与圆型钩各自对大眼金枪鱼和黄鳍金枪鱼的选择性无显著差异;不同钓具漂移速度下环型钩与圆型钩之间对大眼金枪鱼和黄鳍金枪鱼的钓获率无显著差异;环型钩与圆型钩之间对大眼金枪鱼和黄鳍金枪鱼渔获物净重无显著差异。     

Elasmobranch captures in the Fijian pelagic longline fishery

1. Pelagic longline fisheries for relatively fecund tuna and tuna‐like species can have large adverse effects on incidentally caught species with low‐fecundity, including elasmobranchs.
2. Analyses of observer programme data from the Fiji longline fishery from 2011 to 2014 were conducted to characterize the shark and ray catch composition and identify factors that significantly explained standardized catch rates. Catch data were fitted to generalized linear models to identify potentially significant explanatory variables.
3. With a nominal catch rate of 0.610 elasmobranchs per 1000 hooks, a total of 27 species of elasmobranchs were captured, 48% of which are categorized as Threatened under the IUCN Red List. Sharks and rays made up 2.4% and 1.4%, respectively, of total fish catch. Blue sharks and pelagic stingrays accounted for 51% and 99% of caught sharks and rays, respectively.
4. There was near elimination of ‘shark lines’, branchlines set at or near the sea surface via attachment directly to floats, after 2011.
5. Of caught elasmobranchs, 35% were finned, 11% had the entire carcass retained, and the remainder was released alive or discarded dead. Finning of elasmobranchs listed in CITES Appendix II was not observed in 2014.
6. There were significantly higher standardized shark and ray catch rates on narrower J‐shaped hooks than on wider circle hooks. Based on findings from previous studies on single factor effects of hook width and shape, the smaller minimum width of the J‐shaped hooks may have caused the higher shark and ray catch rates. For sharks, the effect of hook width may have exceeded the effect of hook shape, where small increases in shark catch rates have been observed on circle vs J‐shaped hooks.
7. Shark and ray standardized catch rates were lowest in the latter half of the year. Focusing effort during the second half of the year could reduce elasmobranch catch rates.

Copyright © 2016 John Wiley & Sons, Ltd.     

Effects of circle versus J-style hooks on target and non-target species in a pelagic longline fishery

The U.S. Atlantic coastal pelagic longline fishery that targets tunas and swordfish also interacts with a wide range of non-target species including billfishes and sea turtles. Preliminary studies indicate that a change in terminal gear from J-style hooks to circle hooks may reduce bycatch mortality, but the effects of this change on catch rates of target species are unclear. To evaluate this, we monitored catch composition, catch rates, hooking location, and number of fish alive at haulback during 85 sets in the fall and spring seasonal fisheries from a commercial vessel operating in the western North Atlantic. Circle (size 16/0, 0° offset) and J-style (size 9/0, 10° offset) hooks were deployed in an alternating fashion. Hook–time recorders were used to assess time at hooking and temperature–depth recorders to measure gear behavior. Catch rates for most species categories were not significantly different between hook types (P < 0.05), although circle hooks generally had higher tuna catch rates in the fall and lower swordfish catch rates in the spring. In the fall, both total catches and catches of pelagic rays were significantly higher on J-style hooks. Yellowfin tuna in the fall and dolphinfish in the spring caught on circle hooks were significantly larger than those caught on J-style hooks. In both seasonal fisheries, circle hooks caught fishes in the mouth more frequently than J-style hooks, which hooked more often in the throat or gut, although these differences between hook types were not statistically significant. Yellowfin tuna in the fall fishery were over four times more likely to be hooked in the mouth with circle hooks than with J-style hooks. Several target and bycatch species showed higher rates of survival at haulback with circle hooks, although only for dolphinfish in the fall fishery was this difference statistically significant. Our results suggest that the use of 0° offset circle hooks in the coastal pelagic longline fishery will increase the survival of bycatch species at haulback with minimal effects on the catches of target species.     

南沙群岛重点岛礁潟湖微型浮游动物的群落结构与摄食

潟湖是岛礁生物多样性演变的重要环境场,在岛礁水生态系统的物质循环和能量流动中发挥重要作用,而微型浮游动物的生态功能研究是解析南沙群岛岛礁水域潟湖生态系统初级生产力组成、流向、能量流动效率的重要研究内容之一。实验通过对南沙群岛重点岛礁渚碧礁、美济礁与永暑礁潟湖表层水域中微型浮游动物与生态环境调查,研究了其群落结构及其与环境因子的关系,并通过稀释培养实验研究了微型浮游动物的摄食压力。结果显示,调查水域共发现微型浮游动物20种,总丰度的范围为320～1 460个/L,以无壳纤毛虫丰度最高。无壳纤毛虫在渚碧礁潟湖西部水域（ZB-1）丰度最高,砂壳纤毛虫峰值则出现在永暑礁潟湖中部水域（YS-3）,桡足类幼体丰度最大值出现在美济礁潟湖北部水域（MJ-2）。聚类分析结果显示,3个岛礁潟湖中部区域的微型浮游动物群落相似度较高,溶解氧是影响群落结构的最重要因素,特别是对MJ-3站位影响最为突出。摄食实验结果显示,3个岛礁潟湖水域浮游植物生长率为0.22～1.36 d^-1;微型浮游动物摄食率范围为0.22～0.60 d^-1,微型浮游动物每天约摄食浮游植物现存量的...     

Habitat utilization of juvenile Atlantic salmon (Salmo salar L.), brown trout (Salmo trutta L.) and Arctic charr (Salvelinus alpinus (L.)) in two lakes in northern Norway

Abstract— Habitat utilization of juvenile Atlantic salmon, brown trout and Arctic charr was investigated in two lakes in northern Norway during the icefree season. Both the vertical distribution and the distribution among different habitat types were studied by gillnetting with small mesh sized gillnets (8-15 mm) in different habitats. Salmon and trout were predominantly caught in the littoral and sublittoral zones (0-6 m depth). Access to shelter seemed to be the most important factor determining the horizontal distribution of small salmon and trout. Most of these fish were caught in stony or vegetated habitats, while few salmon and trout were caught on sandy locations or in the pelagic zone. In one of the lakes, there were significantly higher catch rates of salmon than of trout in the stony littoral (0-3 m), while in the other lake there were no significant differences in spatial distribution between these two species. Charr were primarily found in the profundal, sublittoral or pelagic zones of the lakes.