黄河口渔业资源底拖网调查采样断面数对资源量指数估计的影响

为查明采样强度对多种类渔业调查中资源量指数估计的影响,实验根据2013年8月、10月和2014年2月、5月黄河口渔业资源底拖网调查数据,选取短吻红舌鳎、方氏云鳚、矛尾虾虎鱼、枪乌贼、口虾蛄、日本蟳和小型鳀鲱鱼类为调查目标,利用计算机模拟方法,以相对估计误差(REE)、相对偏差(RB)、变异系数(CV)和准确度变化率(ACR)等为评价指标,研究了调查样本量对不同种类资源量指数估计的影响。结果显示,各种类资源量指数估计的REE、CV和ACR随断面数增加均逐渐降低并趋于稳定;除在断面数3减到1时,日本蟳、口虾蛄和方氏云鳚等个别种类RB绝对值增大外,其他RB不存在一致性的增大或减小趋势。研究表明,由于不同种类的分布存在时空差异,不同种类需要的调查断面数不同;当目标种类数量空间分布变异较小时,减少调查断面数对采样精确度影响较小,反之则需要更多调查断面数。对于多种类渔业资源调查,需要综合权衡各目标种类来确定最适调查断面数。     

采样设计对估计矛尾虾虎鱼体长-体质量关系参数b的影响

鱼类体长-体重关系参数估计的准确与否影响进一步的渔业资源评估和管理。不同采样设计获得的生物学数据,对鱼类体长-体重关系参数b估计可能会有一定的影响。本文基于2013-2014年在黄河口水域调查获得的矛尾虾虎鱼(Chaemrichthys stigmatias)体长、体重数据,采用计算机模拟重抽样方法,选取相对估计误差和相对偏差两个指标,比较了不同采样设计对估计矛尾虾虎鱼体长-体重关系参数b的影响。结果表明,增加样本量可有效提高其体长-体重关系参数b的估计精度。不同季节数据对参数估计精度具有不同影响,应用多季节调查采样数据估计参数精度往往优于单季节采样。夏季数据对矛尾虾虎鱼体长-体重关系参数估计尤为重要。方案9(夏-冬季方案)在样本量达到540尾时,相对估计误差REE为2.08%,相对偏差RB的绝对值为0.71%,在相同样本量下该设计方案表现最好。在估计黄河口矛尾虾虎鱼等鱼类体长-体重关系参数时,应保证获得一定样本量的对参数估计具有较大影响的季节的生物学数据。     

黄河口及其邻近水域矛尾虾虎鱼渔业生物学特征

为了查明黄河口及其邻近水域矛尾虾虎鱼(Chaeturichthys stigmatias)的生物学特征,为其渔业资源评估和管理提供基本参数,本研究根据2013年6月至2014年5月在黄河口及邻近水域进行底拖网调查所得的矛尾虾虎鱼资源生物学数据,对其群体组成、体长-体重关系和性成熟等渔业生物学特性进行了初步分析。结果表明,该海域矛尾虾虎鱼体长分布范围为25~154 mm,平均体长为(87.77±24.18)mm,优势体长为60~120 mm,占总渔获尾数的76.71%。体重范围为0.08~37.83 g,平均体重为(9.1±6.905)g,优势体重为0~10 g,占63.03%。全年矛尾虾虎鱼体长(SL)-体重(W)关系式为W=4.7×10~(-6)SL~(3.183)(R~2=0.962,n=1842)。矛尾虾虎鱼性腺成熟度和性成熟系数均呈现出明显的月变化,其主要繁殖期为4―5月,产卵持续至6月上旬;体长与性腺成熟度之间的关系无显著雌雄差异,瞬时性成熟速率K=0.039,50%性成熟体长L_(50)=117.92 mm。     

基于多目标鱼种资源量指数估计的不同采样设计比较

经济高效的渔业资源调查采样有利于保证调查数据的质量,提高调查效率,从而为渔业科学研究提供可靠数据。根据2016—2017年山东近海渔业资源底拖网季度调查数据,以小黄鱼、矛尾虾虎鱼、方氏云鳚和星康吉鳗作为目标鱼种,使用Kriging插值法模拟了目标鱼种在4个季节的相对资源量分布,设置简单随机抽样(SRS)、常规系统抽样(SYS_r)、等距系统抽样(SYS_h)、按水深分层随机抽样(StRS_depth)、按区域分层随机抽样(StRS_region)和综合水深和区域分层随机抽样(StRS_total)共6种备选采样设计方案,利用计算机模拟方法对Kriging插值数据进行再抽样,估计各目标鱼种资源量指数,以相对估计误差(relative estimation error, REE)和相对偏差(relative bias, RB)衡量估计结果的精准度,以准确度变化率(accuracy change rate,ACR)小于等于10%的标准确定最优调查站位数,比较不同采样设计在估计多目标鱼种资源量指数方面的表现并进行样本量优化。结果发现,3种抽样方法的估计准度不同,简单随机抽样分层随机抽样系统抽样。除系统抽样外,其余采样设计方案均为无偏估计。随调查站位数增加,系统抽样的REE表现出无规律波动趋势。分层随机抽样的REE略低于系统抽样,且随站位数增加而降低。分层随机抽样是最优抽样方法,StRS_total是最优分层方案。不同目标鱼种、季节调查所需站位数不同,StRS_total进行4季度调查的最优站位数可设为80。     

黄河口水域主要鱼种的时空生态位宽度和重叠

生态位在研究群落结构、种间关系和生物多样性等方面具有重要作用。为深入了解黄河口水域鱼类群落结构和种间关系,本研究根据2013—2014年在黄河口水域进行的7个航次的渔业资源底拖网调查数据,应用平均拥挤度、生态位宽度和生态位重叠值等指数研究了该水域12种鱼类的时空生态位宽度和重叠特征。结果表明,黄河口水域主要鱼种时间生态位宽度变化范围为0～1.53,其中矛尾虾虎鱼(Chaemrichthys stigmatias)和方氏云鳚(Enedrias fangi)时间生态位宽度值较高,安氏新银鱼(Neosalanx anderssoni)和鮻(Liza haematocheila)较低。主要鱼种空间生态位宽度具有明显季节变化。所有鱼种间的平均空间生态位重叠值也有着明显的季节差异。生态位宽度和重叠值与各鱼种数量、分布、生态习性和生境状况密切相关,反映了该海域不同鱼种对生境资源的不同利用能力。     

基于鱼类体长频率分布和平均体长的采样站位数优化

鱼类体长数据较易获得，常用于数据有限的渔业资源评估和管理，且基于鱼类体长的指标可以作为渔业生态系统的生态监测指标。本文根据山东半岛南部海域底拖网季度调查收集的方氏云鳚体长数据，应用计算机模拟重采样方法，研究了调查站位数对估计方氏云鳚（Enedrias fangi）体长频率分布和平均体长的影响。结果表明，在各个季节，方氏云鳚体长频率分布离散指数（DI）变化范围为0~0.91，大部分站位的DI值为0.75~0.90，说明调查站位间体长频率分布较为相似，可以对调查站位数进行优化，提高采样效率；调查站位越多，体长频率分布和平均体长估计精确度越高；由于对不同体长数据指标估计的精度不同，用以估计体长频率分布和平均体长的样本量存在差异；20个和30个调查站位分别为估计方氏云鳚体长频率分布和平均体长的可接受样本量。本研究结果可为基于不同体长指标的渔业资源调查设计提供一定的理论支撑，有助于对基于体长指标有效站位数的初步了解，为山东半岛南部海域的鱼类资源科学调查和科学管理提供参考。     

黄河口近岸海域鮻渔业生物学特征研究

为探究黄河口近岸海域鮻(Liza haematocheila)的渔业生物学特征及资源状况,本研究根据2020年4—11月黄河口渔业生产定置网的采样数据,研究了黄河口水域重要渔业种类鮻群体的体长体重分布、体长–体重关系、繁殖、生长和死亡等渔业生物学特征和开发率。结果显示,鮻体长分布范围为45~460 mm,优势体长组为55~185 mm;体重范围为2~1100 g,优势体重组为2~80 g。方差分析表明,鮻的平均体长、体重均存在显著的月间差异;各月及全年鮻的体长–体重关系均呈显著的幂函数关系,生长类型为负异速生长。黄河口近岸海域,鮻在7月肥满度最大,而6月最小;产卵盛期为4—5月。鮻的生长速率为0.31 a?1,总死亡系数为1.42 a?1,自然死亡系数估算结果为0.51 a?1,捕捞死亡系数为0.91 a?1,其开发率为0.64,鮻种群资源被过度利用。定置网渔业生产对于黄河口渔业资源有一定的破坏作用,尤其对幼鱼和补充群体资源影响较大,应对定置网渔业生产采取必要的管理措施。     

采样设计对近岸水域鱼类浮游生物物种丰富度估计的影响

优化调查采样设计, 利用有限的调查成本获取准确可靠的调查数据, 对于开展渔业科学调查十分重要。本研究根据 2014 年 8 月(夏季)和 10 月(秋季)、2015 年 2 月(冬季)和 5 月(春季)在黄海中南部海域调查获得的鱼类浮游生物数据, 以鱼类浮游生物物种丰富度估计为采样优化目标, 利用计算机模拟再抽样方法, 比较了不同采样设计估计鱼类浮游生物物种丰富度的效果。结果表明, 随着采样频次以及采样站位数的增加, 鱼类浮游生物物种丰富度探测率逐渐升高, 相对估计误差(REE)和相对偏差(RB)逐渐减小。分层随机采样优于简单随机采样, 分层随机采样 4 次调查设计效应值(D_e)为 0.766。不同采样频次下最优季节组合分别为春、春夏、春夏秋以及全年, 其对应的 REE 和 RB 值在同频次不同季节组合中最小, 物种丰富度探测率最高; 保持 90%的物种丰富度探测率, 分层随机采样每年调查 3 次和 4 次对应的最佳站位数分别是 80 个和 60 个。在保证精确度的前提下优化采样方法和选择不同调查频次下最佳季节组合, 可为鱼类浮游生物调查采样设计进一步优化提供参考。     

调水调沙前后黄河口渔业资源结构变化

黄河口调水调沙是以人工调控的方式将淤积的泥沙送入大海,增加河床和水库主槽行洪能力的过程。根据2011―2013年调水调沙前(6月)、后(7月)在黄河口海域的渔业资源调查数据,利用相对优势度指数、方差分析以及多元统计分析等方法,研究了该海域夏季渔业资源密度、种类组成、优势种及其年际变化,并探讨调水调沙对黄河口渔业资源结构的影响。结果表明,本次调查共鉴定渔业资源生物92种,其中鱼类52种;黄河口主要优势种为矛尾虾虎鱼(Chaemrichthys stigmatias)、枪乌贼(Loligo spp.)和葛氏长臂虾(Palaemon gravieri)等,各年份优势种有所变动;夏季渔业资源量有明显年际波动,在2011—2013年呈先增加后减少的趋势,各年间差异显著;黄河口渔业资源结构在调水调沙前后有明显变化,调水调沙后渔业资源平均密度增大,且近河口区资源密度较小;CLUSTER聚类分析表明黄河口渔业资源结构年际变化最为明显,其次是调水调沙前后的变化,而断面间的差异性最低。结论认为,黄河调水调沙引起的径流量、营养盐变化可能是引起调水调沙前后渔业资源种类组成、资源量变化的重要原因。     

黄河口及其邻近水域鱼类生物完整性评价

根据2013—2014年在黄河口及其邻近海域进行的鱼类资源底拖网调查数据,并结合20世纪80年代和90年代的历史资料,依照黄河口水域鱼类区域组成特征,从鱼类种类组成、繁殖共位体、鱼类耐受性和营养结构等方面提出了12个评价指标,初步构建了黄河口水域鱼类生物完整性指数评价指标体系,并制定了评价标准,根据不同年代数据之间的差距分3个层次赋值打分,研究了黄河口水域鱼类生物完整性及其年代际变化。结果表明,20世纪80年代初期黄河口水域鱼类生物完整性表现为"极好"水平;90年代处于"差"水平;2013年处于"极差"的水平。与20世纪80年代初期相比,黄河口及其邻近水域的鱼类生物完整性呈下降趋势,人为因素对生态环境干扰较大,过度捕捞等造成黄河口水域鱼类种类减少甚至消失,黄河口水域生态健康状况下降。     

An adaptive sampling method based on optimized sampling design for fishery-independent surveys with comparisons with conventional designs

The adaptive cluster sampling method is widely applied in terrestrial systems; however, it is not suitable for fisheries surveys because of the high cost of unlimited sampling in practice. An adaptive approach is often used in fisheries surveys to allocate sampling effort, usually following a stratified random design. Development of an adaptive sampling method based on optimized sampling design (this design has been suggested by previous study for fishery-independent surveys) has been not yet carried out. An adaptive sampling method based on optimized sampling design using the criterion of minimization of the mean of the shortest distance (MMSD) in the first phase was constructed in this study and compared with five other sampling designs: simple random, stratified random, adaptive based on stratified sampling, systematic, and optimum design based on the MMSD criterion. This design performed neither the best nor the worst among the six sampling designs considered in this study, but its advantages were obvious when the sampling effort saved using this design was considered in the comparison. This method tends to be more flexible and find fish aggregations more precisely. It is based on a more objective sampling design in the first phase compared with other adaptive sampling designs based on stratified sampling designs. We suggest that this design be considered in developing fishery-independent survey programs.     

Value-added sampling for fishery independent surveys: Don’t stop after you’re done counting and measuring

Most fishery independent surveys count, weigh, and measure the majority of species caught. Many surveys also collect selected body structures for in-lab age determinations for selected species. We provide examples from the Northeast Fisheries Science Center's (NEFSC) bottom trawl survey that detail the development of at-sea sampling to elucidate age, growth, maturity, fecundity, spawning season, stomach contents, diet composition, condition, habitat types and prey preferences, basic oceanography (or limnology), and bioenergetics for a suite of diverse species. We show how the development of new methodologies and technologies has decreased both deck-time and time in the lab for processing many of the samples required to provide information on the topics listed above. As new technologies develop to make our trawl catch processing more efficient, we assert that we can notably increase the amount of information collected from trawl surveys with little additional effort. We show that with marginally additional catch processing time on the deck, at-sea sampling can provide a significant return on the knowledge of aquatic and marine resource species, non-resource species, habitats, food webs, and the ecosystems within which they occur. As observing systems continue to expand their remit to provide ecosystem management advice, the need for increased efficiencies on fisheries surveys will remain.     

底拖网资源调查的昼夜误差分析

利用１９８５和１９８６年秋季底拖网资源调查数据，分析了昼夜平均渔获量的差异，采用Ｂｒａｙ－Ｃｕｒｔｉｓ系数测量其不相似性。结果表明，除底层鱼类外，总平均和中上层鱼类平均渔获得昼液差显著，白天平均渔获量远高于晚上，特别是中上层鱼类相差１０余倍，主要种类的差异亦较大。     

Performance comparison of traditional sampling designs and adaptive sampling designs for fishery-independent surveys: A simulation study

We compared the performance of two traditional sampling designs with three adaptive sampling designs using simulated data based on fishery-independent surveys for yellow perch in Lake Erie. Traditionally, the fishery-independent survey has been conducted with a stratified random sampling design based on basin and depth strata; however, adaptive sampling designs are thought to be more suitable for surveying heterogeneous populations. A simulation study was conducted to compare these designs by examining the accuracy and precision of the estimators. Initially in the simulation study, we used bias, variance of the mean, and mean squared error (MSE) of the estimators to compare simple random sampling (SRS), stratified random sampling (StRS), and adaptive two-phase sampling (ATS). ATS was the best design according to these measurements. We then compared ATS, adaptive cluster sampling (ACS), adaptive two-stage sequential sampling (ATSS), and the currently used stratified random sampling design. ATS performed better than the other two approaches and the current stratified random sampling design. We concluded that ATS is preferable for yellow perch fishery-independent surveys in Lake Erie. Simulation study is a preferred approach when we seek an appropriate sampling design or evaluate the current sampling design.     

基于科学调查与渔业生产数据的山东近海口虾蛄生长参数估算

渔业资源评估一般有两种数据来源,即科学调查数据和渔业生产数据;前者需要定期出海采样,耗时长且费用高,后者易于获取但样本代表性存在问题。本研究以山东近海口虾蛄为例,基于电子体长频率方法(ELEFAN)评估了口虾蛄的生长参数,采用bootstrap重抽样方法比较了基于渔业生产数据与科学调查数据分析结果的差异,旨在探讨渔业生产数据在估算生长参数上的准确性。结果表明,科学调查数据估算得到的口虾蛄von Bertalanffy季节性生长方程中的极限体长L_∞=193.16mm,K=0.62,生产数据估算得到的口虾蛄极限体长L_∞=171.70mm,K=0.67;非参数检验表明基于两种采样方法所求得的口虾蛄的极限体长L_∞呈现显著性差异, K和"夏季点"t_s均呈现不显著性差异。本研究表明,渔业生产数据在一定程度上能够反映生物的生长状况,对K和t_s的估算与科学调查数据估算的结果较为接近,但对极限体长的估算误差较大。因此口虾蛄生长研究需要依靠科学调查数据的支持,同时渔业生产数据可以作为辅助信息。     

Proximity of Pacific cod to the sea floor: Using archival tags to estimate fish availability to research bottom trawls

The percentage of Pacific cod available to Alaskan bottom trawl surveys was estimated from the proximity of tagged cod to the seafloor. Archival tags recorded time and depth data at 15- or 30-min intervals. The distance of a cod above the bottom was computed by subtracting tag depth from bottom depth, estimated as the maximum depth recorded during each 24-h day. These estimates of bottom depth are based on the assumption that cod approach the seafloor at least once a day, and do not undergo migrations up or down bottom gradients. To ensure that migrations over variable bottom gradients did not confound our estimates of bottom depth, we narrowed our analysis to 11 tagged cod that were recaptured in areas of flat bathymetry, and only analyzed data recorded within one month prior to recapture (N = 29,462 depth recordings). Pacific cod maintained short distances above the seafloor that often differed between day and night. Over 95% of the daytime tag recordings occurred within 10 m of the seafloor. Average effective headrope heights for survey bottom trawls currently used in the eastern Bering Sea and Alaska Gulf/Aleutian Islands groundfish surveys are approximately 2.5 and 7 m, respectively. In the absence of any behavior responses to an approaching trawl, we would expect 47.3% of the cod within the water column are available to the trawl used on the eastern Bering Sea survey and 91.6% are available to the trawl used on the Gulf/Aleutian Islands surveys. This study demonstrated that Pacific cod are highly demersal, and current values of trawl survey catchability (Q) used in current stock assessments are consistent with estimates of cod availability to the trawl gear.     

Modeled day–night biases in decapod assessment by bottom trawling survey

The activity rhythms of marine species may consistently bias demographic evaluation by bottom trawl survey, depending on the time of day. In this study, we examine occurrence data of selected commercial and non-commercial decapod species at different depths (0–800 m) of the western Mediterranean as produced by the Mediterranean international trawl survey (MEDITS) UE Program by sampling during daytime. In order to show how the activity rhythms and types of displacement (pelagic, nektobenthic and endobenthic) of different species can alter the occurrences determined by bottom trawling, and to quantify relative bias, we modeled potential outcomes of a putative nocturnal MEDITS sampling. MEDITS and published data for studies with 24-h hauls were compared in order to obtain a folding correction factor. We found that the temporal bias of sampling is moderate when trawling is performed on the continental slope and more important when it occurs on the continental shelf. The configuration of daytime and nighttime occurrence data by depth was performed using non-metric multidimensional scaling (nMDS). For the daytime configuration, association with irradiance (PAR) was evaluated by fitting occurrence data with a generalized additive model (GAM). Symmetry in species assemblages was found according to depth (inflection point at 200 m depth) as a significant irradiance-dependence distribution pattern of occurrences that took place on the shelf, above 200 m depth. For the night configuration, the inflection point relaxed due to the active displacements of some species, mixing the assemblages reported in daytime data. Results of the present study indicated that a deep knowledge of the autoecology of decapod species as it relates to activity rhythms (including a precise assessment of displacement typology) is of importance in population distribution and biomass evaluation and also influences locally perceived biodiversity. Accordingly, bottom trawl surveys for population assessment should take into account the timing of sampling as a factor potentially biasing obtained abundances.     

Model of trawlable area using benthic terrain and oceanographic variables—Informing survey design and habitat maps in the Gulf of Alaska

Bottom trawl surveys provide fishery‐independent data on relative abundance and life history parameters for a wide range of marine taxa. Survey data are used to assess species distribution, biological interactions, and ecosystem structure and to manage marine resources. Not all bottom types or oceanographic conditions accommodate this survey method. We applied National Ocean Service hydrographic smooth sheets to evaluate physical attributes associated with habitat available to surveys. Random forests were used to evaluate the relative influence of benthic terrain and oceanographic predictors in determining accessibility to bottom trawl gear. We examined the marginal importance of each predictor, quantified the response gradient, and applied piecewise regression to determine threshold breakpoint values. Thresholds were used to develop predictive maps and distinguish untrawlable habitat at the scale of discrete towpaths and survey stations. Untrawlable habitat was associated with increased complexity in terrain, roughness, slope, surface curvature, substrate coarseness, current, and aspect. Maps of critical thresholds suggest different variables constrain the probability of a successful trawl in the nearshore, shelf, and continental slope. Overlay analysis of the model projection demonstrates the utility of archived smooth sheet data and identifies areas where higher resolution data might improve results. The model and maps produced in this analysis might be used to identify habitats available to and impacted by commercial trawl fisheries, inform the relative availability of various species and habitat types to bottom trawl surveys, evaluate bias in assessment indices and ecosystem metrics derived from survey data, and advance habitat‐specific biomass estimates.