基于SPiCT模型对数据有限短生命周期阿根廷滑柔鱼的资源评估

以西南大西洋阿根廷滑柔鱼(Illex argentinus)为研究对象,基于连续时间的随机剩余产量模型(a stochastic surplus production model in continuous time,SPiCT),分析了6种方案下参数估计的变化及其对资源评估的影响。对比6种方案中阿根廷滑柔鱼的产量和单位捕捞努力渔获量(catch per unit effort,CPUE)的估计值与观测值间的最小残差平方和,方案3(设置了K、r、q的先验分布)为最适方案。相应的资源评估结果显示,2010年西南大西洋阿根廷滑柔鱼捕捞死亡系数小于最大持续产量时捕捞死亡系数F_(MSY),渔获量小于最大持续产量MSY,预期平衡生物量EEB大于最大持续产量时的生物量B_(MSY),这表明该资源在2010年尚未被过度开发利用。SPiCT模型综合考虑了环境因子、种群间相互作用和网具选择性等因素引起的观测和过程误差,较S、F-EDSP、S-F-EDSP模型及其他离散模型对数据要求低,计算方法简单,更适合数据有限、短生命周期渔业种类的资源评估。另外,可捕系数q值的设置严重影响了SPiCT模型K、B的估计,优化估计可捕系数q将有利于提高其资源评估的准确性。     

渔业数据失真对两种非平衡剩余产量模型评估结果的影响比较

为了研究渔业数据失真对两种非平衡剩余产量模型评估结果的影响,以南大西洋长鳍金枪鱼渔业产量和单位捕捞努力量渔获量(CPUE)数据作为基础数据,加入5种不同程度[变异系数(CV)=1%、5%、10%、20%和30%]的随机误差,模拟了(1)无数据失真,(2)仅产量数据失真,(3)仅CPUE数据失真,(4)产量和CPUE数据均失真等4种情况。利用基于ASPIC的非平衡剩余产量模型(ASM)和基于贝叶斯状态空间建模方法的非平衡剩余产量模型(BSM)分别评估了最大可持续产量(MSY)、B_(MSY)、F_(MSY)、B_(2011)/B_(MSY)、F2011/F_(MSY)等5种生物学参考点和管理指标。结果显示,在无数据失真情况下,ASM和BSM评估的MSY分别为2.866×10~4 t和2.836×10~4 t,B_(2011)/B_(MSY)分别为1.366和1.324,F2011/F_(MSY)分别为0.627和0.667,均相差不大,表明该渔业目前状态良好,ASM得到了较大的B_(MSY)(31.48×10~4 t)和较小的F_(MSY)(0.091);数据失真对ASM评估的B_(MSY)和F_(MSY)分别产生了严重的过低估计和过高估计,且CPUE数据失真产生的影响要比产量数据失真大;随着随机误差的增大,BSM评估的生物学参考点和管理指标的绝对百分比偏差有增大趋势;与ASM相比,BSM能够更好地处理渔业数据中存在的随机误差,除了MSY以外,BSM评估的生物学参考点和管理指标绝对百分比偏差均要比ASM的评估结果低,尤其是B_(MSY)和F_(MSY)。因此,在使用存在较大随机误差的渔业数据进行资源评估时,BSM具有一定的优势。     

秋冬季智利竹鱼栖息地指数模型比较

根据2003—2009年5—9月我国大型拖网渔船捕捞智利竹鱼的生产统计数据,结合海表面温度(SST)和海表面高度(SSH)的海洋环境因子,以作业网次和单位捕捞努力量渔获量(CPUE)作为适应性指数(SI),采用外包络法分别建立SST、SSH的SI,采用算术平均法(AMM)、几何平均法(GMM)、基于权重的AMM分别建立栖息地指数(HSI),并用2010—2011年度生产捕捞数据进行比较与验证。结果显示,以作业网次为基础的SI为最适;AMM优于GMM;考虑到权重的AMM优于没有考虑权重的AMM,5—9月最适HSI模型的SST权重分别为0.4、0.7、0.6、0.7、0.1,2010—2011年渔获量和作业网次的验证预报精度分别为75%~93%、80%~90%,可作为秋冬季智利竹鱼栖息地指数模型。研究表明,不同月份的SST和SSH对秋冬季智利竹鱼渔场分布有着不同的影响。秋冬季是智利竹鱼的主要渔汛期,本研究为准确建立其渔场预报模型奠定了基础。     

应用贝叶斯状态空间剩余产量模型框架评估印度洋大眼金枪鱼的资源状况

根据1950―2016年的渔获量数据及1955―2016年的单位捕捞努力量(Catch Per Unit Effort,CPUE)数据,采用贝叶斯状态空间剩余产量模型框架JABBA(Just Another Bayesian Biomass Assessment)对印度洋大眼金枪鱼(Thunnus obesus)的资源状况进行评估,分析了渔船效应、CPUE数据尺度对评估结果的影响。结果表明,模型拟合效果对于不同时间跨度下CPUE数据的选择比较敏感。当选用时间跨度为1979―2016年的CPUE数据且考虑渔船效应时,模型拟合效果最好。2016年大眼金枪鱼的资源量为812 kt,最大可持续产量(Maximum Sustainable Yield,MSY)为163 kt,远高于同年渔获量86.81 kt,其资源量具有82.50%的概率处于"健康"状态。当总允许可捕量为69.45～104.17 kt时(2016年渔获量的80%～120%),未来10年大眼金枪鱼的资源量仍高于B_(MSY)(达到MSY所需的生物量)。回顾性分析结果表明,该资源评估结果存在一定程度的回顾性问题,捕捞死亡率和资源量分别存在被低估和高估的现象。将来需要在模型结构设定、CPUE数据选择及模型参数的先验分布设置等方面进一步优化。     

异常海洋环境年份智利竹筴鱼捕捞效率的影响因素分析

为了探讨异常海洋环境年份智利竹筴鱼(Trachurus murphyi)捕捞效率及其相关影响因素,利用广义可加模型(GAM),对"开富号"2014年和2015年东南太平洋智利竹筴鱼的渔业生产统计数据进行分析研究。结果表明:(1)智利竹筴鱼的渔场主要位于26°S~28°S、74°W~76°W和37°S~47°S、78°W~93°W的海域内,其中最佳捕捞海域为38°S~47°S、87°W~93°W;最佳捕捞时间为4~6月;(2)放网的持续时间、月份、网口高度、网位、放网位置的经纬度及拖网速度对智利竹筴鱼捕捞效率的影响显著,而曳纲长度、网口水平扩张与智利竹筴鱼捕捞效率间的相关性则较弱;(3)影响智利竹筴鱼捕捞效率的因子按影响程度高低的顺序依次为放网的持续时间、月份、网口高度、放网经度、放网纬度、拖网速度、网位。     

智利:竹荚鱼配额减少影响资源开发

智利渔业公司Corpesca SA和Empresas Copec的负责人Roberto Angelini表示,受2012年智利北部地区竹荚鱼捕捞配额较2011年显著减少的影响,智利渔业今年将面临较多的不确定性和挑战。上层鱼类资源捕捞配额较低也限制了鳀鱼的捕捞,因为捕捞竹鱼将不可避免的附带捕捞到鳀鱼。此外,配额的减少也阻碍了竹鱼资源的开发,抑制了渔业生产和人类消费。Angelini表示,减少北部地区竹荚鱼的捕捞配额引人关注,但这并不能反映该地区的真正需     

应用体重结构的实际种群分析模型估算捕捞死亡系数和资源量的初步研究

实际种群分析(VPA)是渔业评估的经典方法之一,被广泛应用于分析渔业的历史数据、估算渔业种群的资源量及捕捞死亡系数.文章提出了体重结构的VPA(WVPA),蒙特卡罗模拟分析的结果表明,即使在较高的白色噪音水平下(30%),WVPA仍然可以较准确的估算捕捞死亡系数[相对估算误差REE=3.81%(长寿命种群),和2.75%(短寿命种群)].文章应用WVPA与年龄结构的VPA一起评估大西洋赤鲷渔业,结果表明,采用WVPA得到的结论与采用VPA的结果近似一致,但考虑到体重结构产量数据更易获得,该方法更具有优越性.     

运用数据缺乏方法估算印度洋大青鲨可持续渔获量

运用数据缺乏方法,即基于资源衰减的可持续渔获量估算模型(DCAC),结合Monte Carol模拟,对印度洋大青鲨(Prionace glauca)的可持续渔获量进行估计。结果表明,若大青鲨资源衰减比率(Δ)为正值,当自然死亡系数M增大或最大可持续产量对应的捕捞死亡系数(F_(MSY))与M的比值c增大时,可持续渔获量估算值(Y_(sust))增大;若Δ接近零甚至为负值,当M或c增大时,Y_(sust)呈减小趋势。资源丰度指数的选择对DCAC结果有较大影响,基于日本延绳钓渔业1998—2014年和2001—2014年两个时间序列的丰度指数得到的Y_(sust)结果可靠,且与其他模型估算的MSY值接近。2014年印度洋大青鲨的年渔获量正好处在或略高于最大可持续产量(MSY)水平,但该结果仍具有一定的不确定性。本研究表明运用DCAC方法估算印度洋大青鲨可持续渔获量是可行的,但对其他鲨鱼种类的适用性仍需进一步研究,该结果可为数据缺乏方法在大洋和中国近海渔业中的应用提供参考。     

应用体长结构VPA评估东海群系澳洲鲐资源量

为了摸清东海群系澳洲鲐(Scomber australasicus)资源量和渔业状况,以2006年7～11月中国大型围网在东海渔获的澳洲鲐体长测定数据为基础材料,结合渔业产量统计资料,应用体长结构实际种群分析法(VPA)估算2006年东海群系澳洲鲐的资源量,并分析澳洲鲐群体利用结构和资源利用程度.结果表明,中国围网渔业利用澳洲鲐的主体为多数已产过卵的1足龄以上群体,利用结构合理;汛初(7月)可供渔业利用的资源尾数和资源量分别为15×108尾和24×104t,现存年平均资源尾数和资源量分别为7.9×108尾和14.9×104t;最大持续产量(MSY)为10.7×104 t,年渔获量已超过MSY,该渔业的利用程度处于中度偏高开发状态,有捕捞过度迹象,进一步开发利用的潜力不大.通过分析澳洲鲐渔业利用时期、利用结构和繁殖特征,认为即使某些年份产量超过MSY,澳洲鲐资源群体仍能保持相对稳定的状态.     

印度洋长鳍金枪鱼资源评估

本研究运用年龄结构资源评估模型ASAP,利用最新的渔业数据和生物学研究成果,对印度洋长鳍金枪鱼资源进行了评估。结果显示,主要资源变量捕捞死亡系数(F)、产卵亲体生物量(SSB)和生物学参考点受亲体-补充量关系的陡度参数(h)的影响很大。假设陡度参数h=0.7、0.8、0.9时,最大持续产量(MSY)分别为25 268t、27 414t、51 924t,当前(2010年初)F与FMSY之比分别为2.85、2.32、1.11,当前渔获量与MSY之比分别为1.65、1.52、0.80。1984年以来,F总体处于上升趋势,SSB处于下降趋势。基本模型条件下(h=0.8),当前资源状况为"趋向于过度捕捞"(Overfishing),且已接近于"过度捕捞"(Overfished)。若h=0.7、h=0.9,当前资源状况分别为"捕捞过度"、"趋向于过度捕捞"。     

澳洲鲭太平洋群系的资源评估与管理策略

澳洲鲭是西北太平洋重要的经济种类,了解和掌握澳洲鲭太平洋群系资源开发状况对确保其可持续利用具有重要的意义。根据日本中央水产研究所提供的1995—2015年澳洲鲭太平洋群系的生产统计和资源调查资料,利用基于年龄结构的实际种群模型和单位补充量产量模型等进行资源量评估,分析澳洲鲭太平洋群系资源利用情况及其管理策略。结果显示,历年澳洲鲭太平洋群系资源量虽有波动但仍保持在较高水平,2015年资源量最高约为65万t;年平均捕捞死亡系数呈波动下降趋势,2015年捕捞死亡系数只有0.15,近五年平均捕捞死亡系数Fcur=0.33,单位补充量亲体量是未开发时的32.7%,不存在生长型捕捞过度,也不存在补充型捕捞过度,处于可持续开发状态。研究还探讨了水温变化引起自然死亡波动以及不同开捕年龄对澳洲鲭太平洋群系资源状况的影响。研究表明,该渔业目前开发和利用程度合理,建议使用F0.1做为管理参考点进行渔业资源的管理。     

环境因子对东南太平洋智利竹䇲鱼渔场时空分布异质性影响

基于2012—2018 年4—8 月我国东南太平洋智利竹?鱼 (Trachurus murphyi) 渔捞日志数据,应用地理权重回归模型 (GWR) 探究智利竹?鱼渔场资源分布与环境因子的空间异质性关系.结果表明,环境因子海面温度基于GWR 模型回归的拟合优度为0.54,校正的拟合优度为0.34,赤池信息准则 (Aka...     

Identifying spawner biomass per‐recruit reference points from life‐history parameters

Analysis of spawning biomass per‐recruit has been widely adopted in fisheries management. Fishing mortality expressed as spawning potential ratio (SPR) often requires a reference point as an appropriate proxy for the fishing mortality that supports a maximum sustainable yield—F_MSY. To date, a single generic level between F_30% and F_40% is routinely used. Using records from stock assessments in the RAM Legacy Database (RAMLD), we confirm that SPR at MSY (SPR_MSY) is a declining function of stock productivity quantified by F_MSY. We then use general linear models (GLM) and Bayesian errors‐in‐variables models (BEIVM) to show that SPR_MSY can be predicted from life‐history parameters (LHPs, including maximum lifespan, age‐ and length‐at‐maturation, growth parameters, natural mortality, and taxonomic Class) as well as gear selectivity. The calculated SPR_MSY ranges from about 13% to 95% with a mean of 47%. About 64% of the stocks in the RAMLD require SPR_MSY > 40%. Modelling SPR_MSY reveals that LHPs plus Class explain 61% of the deviance in SPR_MSY. Faster‐growing, low‐survival, and short‐lived species generally require a high SPR. With equal LHPs, elasmobranchs require about 20% higher SPR_MSY than teleosts. When F_MSY is estimated from fisheries that harvest older fish, increasing the vulnerable age by one year leads to about an 8% increase in SPR_MSY. The BEIVM yields smaller variance and bias than the GLM. The models developed in this study could be used to predict SPR_MSY reference points for new stocks using the same LHPs for calculating F_x%, but without knowledge of the stock‐recruitment parameters.     

Stock assessment of the blue jack mackerel,Trachurus picturatus,in the North‐eastern Atlantic

A total of 49,151 blue jack mackerel, Trachurus picturatus, (Bowdich) was collected in Madeira Island (North‐eastern Atlantic) between 2002 and 2016 to evaluate possible influence of fishing on landings and reproductive parameters. A decreasing trend in the length composition was observed over the study period and length at first maturity decreased by 2.78 cm TL. Maximum yield per recruit decreased from 2002 to 2016 but the corresponding fishing mortality was constant (F_max = 0.4/year). Considering the fishing mortality level in 2016, it is evident that the stock may be exploited beyond its sustainability limit. Amendments of the purse‐seine fishing regulations and implementation of measures to reduce fishing effort are suggested.     

1999—2011年东、黄海鲐资源丰度年间变化分析

根据1999—2011年我国鲐大型灯光围网渔业数据,使用广义线性模型(generalized linear model,GLM)和广义加性模型(generalized additive model,GAM)估算了影响CPUE的时间(年、月)、空间(经度、纬度)、捕捞性能和环境效应[海表面温度(sea surface temperature,SST)、海表面高度、海表面叶绿素浓度],并以年效应作为资源丰度指数,分析了东、黄海鲐资源丰度的年间变化,东、黄海鲐资源丰度指数的年间变化与产卵场海表面温度以及捕捞强度间的关系。GAM结果表明,时间、空间、捕捞和环境变量对CPUE偏差的解释率为11.69%,其中变量年的解释率最大,占总解释率的38%。结果显示,1999—2011年东、黄海鲐鱼资源丰度指数(abundance index,AI)总体上呈下降趋势,2008年以来更是持续下降,丰度指数由2008年的1.22降至2011年的0.82。东、黄海鲐资源丰度指数年间与产卵场呈正相关,关系式为AI=-3.51+0.23SST(P0.05),这表明较高的产卵场SST对鲐资源量增加有利。过高的渔获量以及我国群众围网渔业渔船数量的快速增长是导致近年来鲐鱼资源下降的重要原因。     

A tale of two seas: a meta‐analysis of crustacean stocks in the NE Atlantic and the Mediterranean Sea

Meta‐analysis of marine biological resources can elucidate general trends and patterns to inform scientists and improve management. Crustacean stocks are indispensable for European and global fisheries; however, studies of their aggregate development have been rare and confined to smaller spatial and temporal scales compared to fish stocks. Here, we study the aggregate development of 63 NE Atlantic and Mediterranean crustacean stocks of six species (Nephrops norvegicus, Pandalus borealis, Parapenaeus longirostris, Aristeus antennatus, Aristaeomorpha foliacea and Squilla mantis) in 1990–2013 using biomass index data from official stock assessments. We implemented a dynamic factor analysis (DFA) to identify common underlying trends in biomass indices and investigate the correlation with the North Atlantic Oscillation (NAO) index. The analysis revealed increasing and decreasing trends in the northern and southern NE Atlantic, respectively, and stable or slowly increasing trends in the Mediterranean, which were not related to NAO. A separate meta‐analysis of the fishing mortality (F) and biomass (B) of 39 analytically assessed crustacean stocks was also carried out to explore their development relative to MSY. NE Atlantic crustacean stocks have been exploited on average close to F_MSY and remained well above B_MSY in 1995–2013, while Mediterranean stocks have been exploited 2–4 times above F_MSY in 2002–2012. Aggregate trends of European crustacean stocks are somewhat opposite to trends of fish stocks, suggesting possible cascading effects. This study highlights the two‐speed fisheries management performance in the northern and southern European seas, despite most stocks being managed in the context of the European Union's Common Fisheries Policy.     

Biomass management targets and the conservation and economic benefits of marine reserves

The establishment of no‐take marine reserves has been increasingly promoted as a key measure to achieve conservation and sustainability goals in fisheries. Regardless of the wide range of benefits cited, the effectiveness of reserve establishment depends critically on fisheries management outside the reserves. We construct a bioeconomic model of a fishery that allows for the establishment of a no‐take marine reserve and evaluate how the choice of the off‐reserve management target influences the effectiveness of reserve establishment. We evaluate two biomass targets: (i) B_MSY or the biomass that produces the maximum sustainable yield (MSY) and (ii) B_MEY or the biomass that maximizes the net present value of the returns to fishing. The parameterized model shows that, for a wide range of scenarios, the fishery will be better off in terms of both conservation and economic objectives when the no‐take reserve is established in conjunction with the B_MEY target rather than with the B_MSY target. Model results further show that the opportunity cost of securing additional fish biomass, in both deterministic and stochastic environments, is lower when the reserve size is increased under the B_MEY target. This finding is important because marine reserves have been established as a key measure to restore depleted fish stocks, and the results suggest that this objective can be achieved with lower economic costs in a B_MEY managed fishery.     

南海北部近海竹荚鱼资源密度的概率分布型特征

竹荚鱼(Trachurusjaponicus)是中国南海北部近海主要渔获物之一,其空间分布具有非均匀性。根据2014—2017年南海北部近海两个周期(2014—2015年为第1周期, 2016—2017年为第2周期)的底拖网调查数据,以单位捕捞努力量(catchperuniteffort,CPUE)表征资源密度,采用柯尔莫可洛夫-斯米洛夫检验(Kolmogorov-Smirnov,K-S test)探索了11种概率分布特征。结果表明,南海北部陆架区竹荚鱼不具明显的概率分布特征,而北部湾海域竹荚鱼资源密度服从对数正态分布型且第二周期较第一周期更为显著。同时,采用基于对数正态理论模型法(对数正态模型与Delta模型)与调查设计法(均值法)对该海域进行资源密度估值比较,发现基于对数正态理论模型更切合竹荚鱼资源密度结构分布特征,而在对数正态理论模型中Delta模型法更适用于该物种资源密度估值。     

Coping with information gaps in stock productivity for rebuilding and achieving maximum sustainable yield for grouper–snapper fisheries

Maintaining fish stocks at optimal levels is a goal of fisheries management worldwide; yet, this goal remains somewhat elusive, even in countries with well‐established fishery data collection, assessment and management systems. Achieving this goal often requires knowledge of stock productivity, which can be challenging to obtain due to both data limitations and the complexities of marine populations. Thus, scientific information can lag behind fishery policy expectations in this regard. Steepness of the stock–recruitment relationship affects delineation of target biomass level reference points, a problem which is often circumvented by using a proxy fishing mortality rate (F) in place of the rate associated with maximum sustainable yield (F_MSY). Because MSY is achieved in the long term only if an F proxy is happenstance with F_MSY, characterizing productivity information probabilistically can support reference point delineation. For demersal stocks of equatorial and tropical regions, we demonstrate how the use of a prior probability distribution for steepness can help identify suitable F proxies. F proxies that reduce spawning biomass per recruit to a target percentage of the unfished quantity (i.e., SPR) of 40% to 50% SPR had the highest probabilities of achieving long‐term MSY. Rebuilding was addressed through closed‐loop simulation of broken‐stick harvest control rules. Similar biomass recovery times were demonstrated for these rules in comparison with more information‐intensive rebuilding plans. Our approach stresses science‐led advancement of policy through a lens of information limitations, which can make the assumptions behind rebuilding plans more transparent and align management expectations with biological outcomes.     

Rebuilding Mediterranean fisheries: a new paradigm for ecological sustainability

In Mediterranean European countries, 85% of the assessed stocks are currently overfished compared to a maximum sustainable yield reference value (MSY) while populations of many commercial species are characterized by truncated size‐ and age‐structures. Rebuilding the size‐ and age‐structure of exploited populations is a management objective that combines single species targets such as MSY with specific goals of the ecosystem approach to fisheries management (EAF), preserving community size‐structure and the ecological role of different species. Here, we show that under the current fishing regime, stock productivity and fleet profitability are generally impaired by a combination of high fishing mortality and inadequate selectivity patterns. For most of the stocks analysed, a simple reduction in the current fishing mortality (F_cur) towards an MSY reference value (F_MSY), without any change in the fishing selectivity, will allow neither stock biomass nor fisheries yield and revenue to be maximized. On the contrary, management targets can be achieved only through a radical change in fisheries selectivity. Shifting the size of first capture towards the size at which fish cohorts achieve their maximum biomass, the so‐called optimal length, would produce on average between two and three times higher economic yields and much higher biomass at sea for the exploited stocks. Moreover, it would contribute to restore marine ecosystem structure and resilience to enhance ecosystem services such as reservoirs of biodiversity and functioning food webs.