海州湾及其邻近海域鱼类群落结构冗余度

过度捕捞、环境污染等人类活动以及气候变化等影响着海洋鱼类群落动态及其稳定性。为深入研究海州湾海域鱼类群落结构及其变化,根据2011年、2013—2016年春、秋两季在该海域进行的渔业资源与环境调查数据,应用多元统计分析和结构冗余度分析方法,研究了海州湾海域春、秋季鱼类群落结构冗余度。结果显示,海州湾及邻近海域春、秋季鱼类均可划分为南北两个群落。春季北部群落的典型种包括方氏云鳚、细纹狮子鱼、黄鮟鱇和大泷六线鱼;南部群落的典型种为小黄鱼、短吻红舌鳎、方氏云鳚和星康吉鳗。秋季北部群落的典型种为棘绿鳍鱼、长蛇鲻和星康吉鳗;南部群落典型种包括短吻红舌鳎、棘头梅童鱼、鮸、矛尾虾虎鱼、小黄鱼和皮氏叫姑鱼。春、秋季鱼类群落响应单元数均为1,群落结构冗余度水平低;响应单元中种类与南、北鱼类群落典型种组成相似,表明海州湾春、秋季鱼类群落空间结构特征主要受方氏云鳚、细纹狮子鱼、小黄鱼、棘绿鳍鱼和长蛇鲻等少数种类决定。决定海州湾及邻近海域鱼类群落结构特征的可替代种类较少,当主要种类受损时,群落结构会发生较大变化,鱼类群落结构稳定性较低。     

大泷六线鱼6个群体遗传多样性的微卫星分析

大泷六线鱼资源捕捞量逐渐加大,捕捞个体体型却逐渐减小,研究大泷六线鱼的遗传多样性,对提高在渔业养殖中种群质量具有重要意义。本研究利用7对微卫星分子标记对大泷六线鱼(Hexagrammos otakii)的6个地区群体(大连、丹东和青岛等地)进行了遗传多样性和遗传变异评估。结果表明,获得的等位基因数1~8,平均等位基因数6.29;有效等位基因数1.00~5.72,平均有效等位基因数4.71;各群体的杂合度观测值(Ho)为0.05~0.27;杂合度期望值(He)为0.44~0.75;多态信息含量(PIC)为0.47~0.69,说明这6个群体属于高度多态,遗传多样性水平较高。群体间遗传分化系数(F_(st))为0.27,表明6个大泷六线鱼群体之间存在明显的遗传分化。采用UPGMA法对6个大泷六线鱼群体进行聚类分析,发现大连和长海县大泷六线鱼群体亲缘关系较近且聚为一个分支,其他4个群体聚为另一分支。结合Hardy-Weinberg平衡检验分析,发现各群体表现出极显著的遗传不平衡,不符合Hardy-Weinberg平衡定律,表明6个群体大泷六线鱼遗传多样性较为丰富。综上说明,6个大泷六线鱼群体发生了较大的遗传分化,遗传多样性较为丰富。     

有限数据渔业种群资源评估与管理——以小黄鱼为例

传统的渔业资源评估方法需以翔实的调查和渔业数据为基础,而现有的大多数种类面临着着渔获量、基础生物学、有效捕捞努力量等数据缺失问题,因此并不适合采用数据需求较高的模型进行评估和管理。面临着渔业资源衰退的严峻形势和渔获量限额管理的迫切要求,基于有限数据的评估方法和渔获量相关的管理方案正被越来越多的国家采用。本研究以东海小黄鱼(Larimichthys polyactis)种群为例,根据渔获量、自然死亡、消减率、生物学参数、开捕体长等数据,采用54种有限数据评估方法,模拟3种捕捞动态,对小黄鱼进行管理策略评价和资源评估。结果显示,以相对产量(relative yield, RY)不低于50%、过度捕捞概率(probability of overfishing, POF)小于50%,生物量低于最大可持续生物量的10%(B0.1B_(MSY))的概率小于20%为风险控制水平,捕捞强度随机波动和增长情景下,分别有6个管理方案(management procedures, MPs)满足既定管理目标;"一般型"和"增长型"捕捞强度情景下, 14个MPs满足管理目标。权衡分析3种捕捞动态下的MPs, 50%FMSY基准法(FMSYref50)可作为小黄鱼渔业最佳的管理方案,POF介于5.46%～6.70%, B0.5B_(MSY)概率介于15.66%～22.73%,长期获得的相对产量介于52%～100%;然而, FMSYref50确定的可接受生物学渔获量(acceptable biological catch, ABC)仅有1.08×10~4 t,与当前产量相差较大。因此,考虑到降低捕捞强度为渔业管控的发展趋势,建议采用动态F比值法(DynF)为小黄鱼渔业管理方案,"下降型"捕捞强度情景下,POF为37.84%, B0.5B_(MSY)概率为38.63%,长期获得的相对产量为84%, ABC为4.03×10~4 t。根据敏感性分析,发现DynF评估的ABC对捕捞产量、资源丰度指数不敏感,而对自然死亡系数、最大可持续捕捞死亡系数与自然死亡系数比值(FMSY_M)和当前资源量均较为敏感,参数值增加会导致ABC增加,表明在开展渔业资源评估时需要着重提高这3种参数的准确性。     

大连海域5种经济鱼类的生长、死亡及资源合理利用研究

根据2017—2018年大连海域渔业资源底拖网调查数据,基于FISATⅡ软件对大连海域小黄鱼、高眼鲽、长绵鳚、大泷六线鱼和许氏平鲉这5种常见经济鱼类的生长、死亡及资源利用现状进行评估。研究结果显示,5种鱼类的渐近体长(L_∞)为222.4～495.5 mm,生长系数(K)介于0.36～0.69间。当前5种经济鱼类的开发率(E)为0.57～0.71,均大于0.5和单位补充渔获量最高时开发率(E_max),表明资源已处于过度开发状态;结合Bverton-Holt动态综合模型结果,当前5种鱼类的捕捞强度偏大、开捕体长较小。综合考虑鱼类的拐点年龄、临界年龄、繁殖及经济利益,建议小黄鱼、高眼鲽、大泷六线鱼、长绵鳚和许氏平鲉的最适开捕体长分别为136、237、207、297 mm和160 mm。本研究结果可作为这5种经济鱼类资源管理的参考,在具体的渔业政策制定中,还需要进一步保证调查数据的时效性和调查方式的全面性、科学性。     

黄海小黄鱼（Pseudosciaena polyactis）生态和种群动态的研究

本文通过１９８５年至１９９０年的大规模黄海调查，对小黄鱼的资源分布、种群结构、生殖和摄食、生长和死亡的变化进行了分析研究，表明八十年代以来小黄鱼种群结构趋于简单、性成熟提前、生长加快。当前捕捞死亡率过高，以至于小黄鱼大部分群体在性成熟之前已被捕获。在八十年代中期，小黄鱼的资源量已降至五十年代的十至十五分之一。渔获量和资源量的下降主要是由于过度捕捞所致。只要黄海周围过高的捕捞力量的存在，小黄鱼资源很难得以恢复并达到最大持续产量。若将目前的捕捞死亡系数至少降低５０％，开捕年龄应不低于２龄，则其资源才有可能恢复。     

基于贝叶斯方法的东、黄海鲐资源评估及管理策略风险分析

运用基于贝叶斯的剩余产量模型,对东、黄海鲐资源进行评估,确定了当前鲐资源开发利用状态,估算了在不同收获率水平下未来5年鲐资源量和年总可捕捞量,分析了管理策略实施后鲐资源崩溃的风险。结果表明,2006年东、黄海鲐正遭受过度捕捞,但其资源量并未处于过度捕捞状态。决策分析表明,收获率为0.3是最适预防性的管理策略,在该策略下,鲐平均资源量将从2006年的451千吨将增加到2011年的871千吨,2011年资源量恢复到BMSY的概率为0.48,而过度捕捞的概率为0。     

利用贝叶斯动态产量模型评估印度洋长鳍金枪鱼资源状态

印度洋长鳍金枪鱼(Thunnus alalunga)的生物学信息相对较少, 渔业数据存在较多问题, 致使其资源评估结果仍存在较大的不确定性, 从而影响了渔业管理的科学性。为此, 本研究基于印度洋长鳍金枪鱼的渔业捕捞、标准化 CPUE (catch per unit effort)数据及相关种群假设, 利用贝叶斯动态产量模型对该种群进行了资源评估研究, 结果显示: (1) 渔获量的观测误差对模型参数估计、资源状态的判断及渔业管理具有重要影响, 渔获量观测误差的增大使模型评估的过度捕捞概率上升, 导致总可捕量(total allowable catch, TAC)减少; (2) 动态产量模型形状参数、r 的先验分布和资源丰度指数的选择均会影响资源评估的质量, 本研究显示, Fox 模型的资源评估结果比 Schaefer 模型的评估结果更合理, r 先验分布范围的增大使模型评估的资源状态变好, 使用西南海域标准化 CPUE 时的评估结果相对较好; (3) 设置某些年份的资源量比例(φ、P₂₀₁₇)范围有助于提高数据缺乏下渔业资源评估的质量; (4) 评估结果表明印度洋长鳍金枪鱼发生资源型与捕捞型过度捕捞的概率分别为 34%、50%, 两种过度捕捞同时发生的概率为 32%, 该种群正面临捕捞型过度捕捞的风险; 投影分析显示, 将 TAC 控制在 32658 t (即最后 5 年平均渔获量的 90%)以下时, 印度洋长鳍金枪鱼 10 年后不发生过度捕捞的概率大于 60%。贝叶斯动态产量模型作为一种数据有限的渔业资源评估模型, 适用于印度洋长鳍金枪鱼, 且该模型能较好地考虑参数输入和不确定性因素对资源评估质量、总可捕量估计的影响, 为深入研究印度洋长鳍金枪鱼的资源状态与管理提供了科学依据。     

东海区小黄鱼种群生物学特性的分析

本研究以 196 3、1983和 2 0 0 1年东海区渔业资源监测调查资料为依据 ,对小黄鱼 (Pseudosciaenapolyactis)的种群结构、生长和死亡等主要种群生物学特征进行了动态分析。结果表明 ,目前东海区小黄鱼种群的个体小型化、低龄化现象相当突出 ,平均年龄仅为 0 .92 3龄 ;生长加快 ,生长参数k值达 0 .5 5 ;体重生长的体重生长的拐点年龄变小 ,仅为 1.6 7龄 ;性成熟提前 ;死亡率提高 ,残存率减小。尽管小黄鱼近年来产量有所恢复 ,但资源利用对象主要以当年生补充群体为主 ,生长型捕捞过度趋势加重     

基于CMSY和BSM的东海区重要渔业种类资源评估

有限数据方法(data-limited method)可结合少量易获得数据和相关生物学信息对渔业资源状况、生物学参考点以及生物量等进行评估,已经成为全球区域性渔业管理组织和资源评估学者的关注热点。本研究采用基于渔获量的最大可持续渔获量(catch-based maximum sustainable yield,CMSY)和基于贝叶斯状态空间的Schaefer产量模型(Bayesian Schaefer production model,BSM)评估了东海区19个重要经济种类的资源状况,并提出了基于最大可持续渔获量(maximum sustainable yield,MSY)的渔业管理建议。结果显示,19个种类中有1个种类衰竭,3个种类严重衰退,5个种类过度捕捞,5个种类轻度过度捕捞,5个种类健康。种群状态长期评估结果表明,处于生物可持续水平的鱼类种群占比已由1980年的95%下降至2019年的26%。同时对CMSY和BSM方法的结果进行了比较,整合单位捕捞努力量渔获量(catch per unit effort,CPUE)数据的BSM方法导致了置信区间较宽,并调节了生物量轨迹的变化形态...     

辽宁海域大泷六线鱼的生物学特征、资源丰度时空分布及与环境因子的关系

为了给大泷六线鱼(Hexagrammos otakii)在辽宁海域增殖放流的开展提供科学依据, 本研究根据春季(2020 年 5 月)、夏季(2019 年 6 月、7 月和 2020 年 8 月)和秋季(2019 年 9 月和 2020 年 10 月)共计 6 个航次的底拖网调查, 研究了辽宁海域大泷六线鱼的资源丰度及生物学特征变化, 并基于广义加性模型(GAM)分析了资源丰度的时空分布与环境因子的关系。结果表明, 大泷六线鱼资源丰度的季节变化表现为夏秋季高于春季, 资源丰度在不同站位的差异较大, 空间异质性较高。大泷六线鱼的体长、体重在 5 月至 10 月均表现为逐月增大, 肥满度也表现为夏季较春、秋季高, 且体长、体重和肥满度均具有月份间的显著差异。资源丰度的时空分布表明大泷六线鱼具有对岩礁底、砂底这两种底质生境类型和较低水温的偏好性, 黄海北部海域的资源丰度高于辽东湾海域。GAM 模型显示水深、盐度、水温、底质类型、月份和年份是影响大泷六线鱼资源丰度分布的因素, 大泷六线鱼的资源丰度与水深在 55 m 内具有显著的正相关性, 资源丰度高值区分布在底层盐度低于 31.5 和底层水温区间为 12~22.5 ℃的环境条件下, GAM 的分析结果与大泷六线鱼的生态习性相符。本研究通过上述分析初步建议具有较多岩礁、砂底质生境类型和较低水温的黄海北部海域可作为辽宁海域大泷六线鱼的适宜放流区域, 水温升高至 12 ℃以上的 5—6 月可作为适宜放流时间, 选择以上放流地点和时间, 可对放流群体的成活率及品质提供较好的保障。     

Using fisheries-independent survey data to reinforce China’s data-limited fisheries management: Management strategy evaluation of survey-based management procedures

Fisheries-independent survey data are vital to stock assessment and management because they provide reliable information on stock status. Although survey data have been increasingly recognised for their contributions to fisheries management, they have often not been adequately used to provide quantitative management recommendations for China's fisheries that are subject to limited data. In the present study, a framework was proposed to integrate two types of survey-based management procedures (MPs) into China's fisheries management: the slope-based MP and the target-based MP. Specifically, the former generates fishing effort limits based on the trend in recent years’ abundance index, while the latter sets effort limits based on a static abundance index target. To test the performance of these MPs, management strategy evaluation was performed using a simulated fishery based on the small yellow croaker, Larimichthys polyactis (Bleeker) in Haizhou Bay, China. The sensitivity of MPs was investigated under different algorithm parameterisations and historical exploitation levels. Additionally, their robustness was evaluated in the face of survey uncertainty and changes in recruitment success. Both MPs could effectively improve the stock status compared with the status quo management when appropriately parameterised regardless of exploitation history. The target-based MP was more robust to survey uncertainty than the slope-based MP. Non-stationary changes in recruitment success strongly impaired the management effects, while using recruitment-specific instead of the age-aggregated abundance index could slightly enhance their performance. This work indicates that survey-based MPs can address the current challenges in China's fisheries management and reinforce the status quo management practice with limited data and highlights the potential risks.     

Profile of a fishery collapse: why mariculture failed to save the large yellow croaker

The large yellow croaker (Larimichthys crocea), endemic to East Asia was once one of the three top commercial marine fishes of China PR. Heavily exploited since the 1950s, wild stocks were so severely depleted by the 1980s that most individuals subsequently sold originated from hatcheries. After peaking at about 200 000 tonnes in the mid‐1970s, catches of the croaker in China PR declined by over 90% within just 2 decades; according to most decline criteria this would categorize the croaker as “threatened” and management measures, including restocking, were developed. The extensive government‐sponsored mariculture program introduced to address food supply and overfishing in the 1980s, particularly of the croaker, was one of the earliest for marine finfish, not only in China PR, a nation with a rich and highly successful history in aquaculture, but globally. In this first, in‐depth, profile of a key fishery and early mariculture development, we integrate ecological and biological information with the fishing, management, mariculture and economic history to trace the collapse of wild stocks and assess why management and mariculture did not result in wild stock recovery. Evidence strongly suggests that a combination of heavy exploitation of spawning and over‐wintering aggregations, poor management and overfishing pressure were major factors in stock declines, with contributions from pollution, habitat degradation and marine ecosystem shift. Although the croaker proved a highly successful mariculture candidate, with approximately 70 000 tonnes produced in 2005, the highest of any marine fish cultured in China PR, mariculture and restocking have failed to restore croaker stocks and may have, inadvertently, led to biodiversity losses. The detailed history of the croaker is a sobering reminder that successful mariculture, albeit important for food production and livelihoods, is not necessarily a solution to overfishing, and moreover, may have compromised fishery recovery by competing for funds, attention, space, and maybe genetic resources.     

Understanding patterns of distribution shifts and range expansion/contraction for small yellow croaker (Larimichthys polyactis) in the Yellow Sea

Detecting and analyzing patterns of distribution shifts and range expansion/contraction is important to understand population dynamics and changes in stock status. Here, we develop a spatio‐temporal model for yellow croaker (Larimichthys polyactis), which was fitted to bottom trawl survey biomass data collected in the Yellow Sea in the winter of 2001–2017. The model accounts for both spatial and spatio‐temporal structure and can potentially include the effects of surface temperature and of an annual index, the Pacific Decadal Oscillation, represented using a recently developed spatially varying coefficient model. We selected a spatio‐temporal model with no covariates based on Akaike's information criterion. The center of gravity for yellow croaker was found to move northwest between 2001 and 2010, and then southwest over the period 2010–2017. These results reflected the predicted progressive disappearance of yellow croaker density hotspots (i.e., highest density areas) in the north and southeast areas of the Yellow Sea, which resulted in the central area of the Yellow Sea becoming the only yellow croaker density hotspot in 2017. This finding has important implications for fisheries management in the context of the China–South Korea fisheries agreement, as it indicates a measurable displacement of yellow croaker biomass toward China. The exclusion of covariates from the spatio‐temporal model was not expected a priori and may be due to the facts that environmental variations are not pronounced in winter in the Yellow Sea and that the representation of spatial and spatio‐temporal structure in spatio‐temporal models accounts for a large proportion of the variability in the data.     

基于多源数据的东海小黄鱼资源评估与管理

为建立稳定环境和波动环境机制下预防性渔业管理生物参考点, 整合调查设计和渔捞日志等多源资源指标构建混合矩阵, 利用logistic和Fox剩余产量模型的两步分析技术, 对东海区小黄鱼(Larimichthys polyactis)渔业资源动态进行评估。模型估算参数和管理参考点显示, Fox模型对渔获量和CPUE拟合的方差贡献率高于logistic模型, 两者分别为68%和57%, 环境承载力和内禀增长率相差较大。logistic模型估算了相对较低的承载力和较高的内秉增长率、初始开发率以及MSY。稳定环境下资源状况评判结果表明: 1999―2008年间多数年份的捕捞强度超过捕捞水平限制参考点, 渔业遭受过度开发, 平均资源量保持在中位水平且未达到过度捕捞状态, 但已超过目标参考点; 波动环境条件下的判别结果显示: logistic和Fox模型拟合的渔业水平均已达到过度捕捞。采用保护性捕捞参考点可增强渔业资源稳定性, 当捕捞死亡从参考点F_MSY降至预防性参考点F_opt, logistic模型估算资源量从8.1 t上升到10.1 t, 而渔获量从13.1 t下降至12.3 t; Fox模型资源量则从11 t增加到15.9 t, 相应的捕捞产量从12.8 t下降到11.6 t。Fox模型评估结果较为保守, 适合预防性渔业管理。

     

Status of white croaker Micropogonias furnieri exploited in southern Brazil according to alternative hypotheses of stock discreetness

The exploitation status of white croaker Micropogonias furnieri in southern Brazil is assessed using a production model constructed according to three hypotheses of stock discreetness: an isolated stock in southern Brazil; a straddling stock shared between Brazil and Uruguay; and a straddling stock shared among Brazil, Uruguay and Argentina. Estimates of virgin stock size and maximum sustainable yield were more sensitive to the hypothesis assumed correct, the posterior means varying respectively from 177,648 to 1,007,256 tonnes and from 7459 to 38,677 tonnes. Estimates of stock status in relation to management reference points were more robust to the uncertainties in stock discreetness and indicate that the species in currently overfished (biomass at 60% of B_msy) and under heavy overfishing (F between approximately 2 and 6 times higher than F_msy). Results suggest that the relative stability of catches in the region occurs at the expense of a steady decline in stock abundance and that concerted management actions by the three countries are needed to bring the stock to safer levels of exploitation.     

The sharks of South East Asia – unknown,unmonitored and unmanaged

Sharks fisheries have declined globally due to over‐ and unregulated fishing. As with many collapsed and unmonitored coastal fisheries, information is difficult to obtain, yet it is important to understand the historical changes determining population trends and evaluate the current status of sharks in order to conserve these vulnerable species. Here, we document for the first time the history and general condition of the shark fisheries of Southern China, specifically Hong Kong, and Guangdong, Fujian and Hainan Provinces. This study shows, through the use of historical literature and anecdotal accounts, including fisher interviews, that all known shark fisheries in the region collapsed between the 1970s and the 1990s. Of the 109 species present historically in the South China Sea, only 18 species were recorded in current market surveys, of which all were landed as bycatch and 65% were below the size of sexual maturity. Markets are dominated by smaller species, including the spadenose shark (Scoliodon laticaudus) and the whitespotted bambooshark (Chiloscyllium plagiosum). Marketed large shark species are almost all below the size of sexual maturation, evidence of growth overfishing and a factor in recruitment overfishing. Some species, like the whale (Rhincodon typus) and basking sharks (Cetorhinus maximus), are clearly vulnerable to local extinction without intervention. Given the inherent vulnerability of sharks and the overfished states of many sharks, there is clearly an urgent need to formulate impacting conservation and management plans for these rapidly declining species in a region that has the highest demand for shark products globally.     

Dynamic angling effort influences the value of minimum‐length limits to prevent recruitment overfishing

Recruitment overfishing occurs when stocks are fished to a level where recruitment declines proportionally with adult abundance. Although typically considered a commercial fishery problem, recruitment overfishing can also occur in freshwater recreational fisheries. This study developed an age‐structured model to determine if minimum‐length limits can prevent recruitment overfishing in black crappie, Pomoxis nigromaculatus (LeSueur), and walleye, Sander vitreus (Mitchill) fisheries considering angling effort response to changes in fish abundance. Simulations showed that minimum‐length limits prevented recruitment overfishing of black crappie and walleye, but larger minimum‐length limits were required if angler effort showed only weak responses to changes in fish abundance. Low angler‐effort responsiveness caused fishing mortality rates to remain high when stock abundance declined. By contrast, at high effort responsiveness, anglers left the fishery in response to stock declines and allowed stocks to recover. Angler effort for black crappie and walleye fisheries suggested that angler effort could be highly responsive for some fisheries and relatively stable for others, thereby increasing the risk of recruitment overfishing in real fisheries. Recruitment overfishing should be considered seriously in freshwater recreational fisheries, and more studies are needed to evaluate the responsiveness of angler effort to changes in fish abundance.     

Generic solutions for data‐limited fishery assessments are not so simple

The majority of the world's fisheries, by number, are data‐poor/limited, and there is a growing body of literature pertaining to approaches to estimate data‐limited stock status. There are at least two drivers for assessing the status of data‐limited fisheries. The first is to try to understand and report on the global or regional status of fisheries across many stocks. The second is to attempt to assess individual data‐limited stocks, for status reporting and/or guiding management decisions. These drivers have led to attempts to find simple, generic, low‐cost solutions, including the broad application of generically parameterised models, and the blanket application of a single, or limited number of possible, analytical approach(es). It is unclear that generic methods function as intended, especially when taken out of their original design context or used without care. If the intention is to resolve individual stock status for the purposes of management, there is concern with the indiscriminate application of a single method to a suite of stocks irrespective of the particular circumstances of each. We examine why caution needs to be exercised, and provide guidance on the appropriate application of data‐limited assessment methods (DLMs). We recommend: (a) obtaining better data, (b) using care in acknowledging and interpreting uncertainties in the results of DLMs, (c) embedding DLMs in harvest strategies that are robust to the higher levels of uncertainty in the output of DLMs by including precautionary management measures or buffers and (d) selecting and applying DLMs appropriate to specific species’ and fisheries’ data and context.