共查询到20条相似文献，搜索用时 31 毫秒
1.
实际种群分析法(virtual population analysis,VPA)是开展渔业资源评估最有效的技术之一,一般以世代为基础开展评估.基于实际渔业存在渔汛期、休渔期等特点,本研究运用分期评估的概念对传统实际种群分析进行了扩展,即分期种群分析法,并根据不同时期的捕捞死亡特征,评估与分析了4种不同分期情景对评估结果的影响.模拟研究表明,由于分期不当造成评估结果的误差为6％～33％.文中一并给出了开展分期实际种群分析法对资料收集和参数评估的要求.该方法克服了传统实际种群分析法中没有全面分期产生的误差,使其扩展至适合于评估全年捕捞死亡率不稳定或非连续性渔业种群,评估结果也更接近于评估种群的真实值. 相似文献
2.
ABSTRACT: The stock size of sandfish in the northern Sea of Japan was estimated by a virtual population analysis (VPA) and sensitivity analyses were attempted on the VPA estimate. The stock size estimates were approximately 600–900 million until 1975, but since 1976 they have rapidly decreased. In the sensitivity analyses, the estimates of absolute stock size were not sensitive against the changes in the fishing mortality coefficient for terminal age and the measurement error in catch-at-age. This suggested that the relative stock size remains almost unaffected by the error in the data used in the VPA, if the degree of catch-at-age error and the natural mortality coefficient is correct. The relationships between the biomass estimated by the VPA and the density index from Danish seine fisheries, and between the biomass and the catch per unit effort (CPUE) from the experimental survey using Danish seine nets, were also examined. The density index and the CPUE indicated significant relations with the biomass. Consequently, the CPUE is useful to monitor the relative stock size in a timely manner, and the VPA estimate and the CPUE should be utilized for adjusting the total allowable catch in the multiseasons. 相似文献
3.
ABSTRACT: Effects of sampling errors on abundance estimates from virtual population analysis (VPA) were quantified with the bootstrap method for stock of walleye pollock in the the Sea of Japan. In the bootstrap method, individual fish measurements were resampled. A total of 1000 bootstrap samples were produced for each year from 1991 to 2001. The coefficients of variation (CV) of catch at age in 2001 ranged 6.1–33.1%. The CV of an abundance estimate in 2001 ranged 9.0–35.7%. Abundance estimates of the oldest age and the latest year, which had larger CVs than the other estimates, were sensitive to sampling errors. Effects of sampling errors became smaller when the catch at age had been accumulated over a few years. Although VPA includes various types of errors, only the sampling errors have room for improvement in reality. Quantifying the effect of sampling error on VPA estimates is essential for sound and efficient stock management, and is emphasized in this study. 相似文献
4.
鱼类自然死亡系数评估研究进展 总被引：3，自引：3，他引：0
自然死亡系数是渔业资源评估中不可或缺的重要参数,其准确度直接决定了资源评估结果的可靠性,进而影响渔业管理策略的制定。本文从生活史参数、标志回捕和年龄结构3个方面列举了国内外自然死亡系数的常用评估方法,讨论了相关方法的优缺点及影响因素,并以犬齿牙鲆(Paralichthys dentatus)和中国近海鱼类为例对比分析不同模型的计算结果。在此基础上,着重介绍了Pauly经验公式在中国近海主要经济鱼类自然死亡系数评估中的应用进展及存在问题。根据渔业资源调查和研究数据现状,认为现阶段使用Pauly经验公式评估中国近海经济鱼类自然死亡系数具有积极作用。 相似文献
5.
Informative data in fisheries stock assessment are those that lead to accurate estimates of abundance and reference points. In practice, the accuracy of estimated abundance is unknown and it is often unclear which features of the data make them informative or uninformative. Neither is it obvious which model assumptions will improve estimation performance, given a particular data set. In this simulation study, 10 hypotheses are addressed using multiple scenarios, estimation models, and reference points. The simulated data scenarios all share the same biological and fleet characteristics, but vary in terms of the fishing history. The estimation models are based on a common statistical catch‐at‐age framework, but estimate different parameters and have different parts of the data available to them. Among the findings is that a ‘one‐way trip’ scenario, where harvest rate gradually increases while abundance decreases, proved no less informative than a contrasted catch history. Models that excluded either abundance index or catch at age performed surprisingly well, compared to models that included both data types. Natural mortality rate, M, was estimated with some reliability when age‐composition data were available from before major catches were removed. Stock‐recruitment steepness, h, was estimated with some reliability when abundance‐index or age‐composition data were available from years of very low abundance. Understanding what makes fisheries data informative or uninformative enables scientists to identify fisheries for which stock assessment models are likely to be biased or imprecise. Managers can also benefit from guidelines on how to distribute funding and manpower among different data collection programmes to gather the most information. 相似文献
6.
Reliable stock assessments are essential for successful and sustainable fisheries management. Advanced stock assessment methods are expensive, as they require age- or length-structured catch and detailed fishery-independent data, which prevents their widespread use, especially in developing regions. Furthermore, modern fisheries management increasingly includes socio-economic considerations. Integrated ecological-economic advice can be provided by bio-economic models, but this requires the estimation of economic parameters. To improve accuracy of data-limited stock assessment while jointly estimating biological and economic parameters, we propose to use price data, in addition to catches, in a new bio-economic stock assessment (‘BESA’) approach for de-facto open access stocks. Price data are widely available, also in the Global South. BESA is based on a state-space approach and uncovers biomass dynamics by use of the extended Kalman filter in combination with Bayesian estimation. We show that estimates for biological and economic parameters can be obtained jointly, with reliability gains for the stock assessment from the additional information inherent in price data, compared to alternative assessment methods for data-poor stocks. In a real-world application to Barents Sea shrimp (Pandalus borealis, Pandalidae), we show that BESA benchmarks well also against advanced stock assessment results. BESA can thus be both a stand-alone approach for currently unassessed stocks as well as a complement to other available methods by providing bio-economic information for advanced fisheries management. 相似文献
7.
In the present study we utilize tag recapture data to estimate year class abundance and spawning stock biomass of mackerel (Scomber scombrus L.) in the Northeast Atlantic for the period 1986–2008. On average 20,000 jigged mackerel have been tagged annually with internal steel tags in the spawning area west of Ireland and the British Isles, and the tags have been recaptured in commercial catches screened through metal detectors. The spawning stock biomass estimates derived from two different tag-based models were highly variable but were on average 2 and 2.3 times higher than the ICES official estimate. The official estimate is considered uncertain and most likely an underestimate of the actual biomass, due to unregistered mortality in the fisheries and lack of fishery-independent, age-disaggregated data. Hence, tag-based estimates could potentially improve the current assessment if included in the ICES stock assessment on a regular basis. These estimates also involve some uncertainty that needs consideration, especially related to variable tagging mortality, detector efficiency and migrations of the stock. 相似文献
8.
Common uncertainties in stock assessment relate to parameters or assumptions that strongly determine both the estimates of quantities of management interest (e.g. stock depletion) and related reference points (e.g. biomass at maximum sustainable yield). The risks associated with these uncertainties are often presented to managers in the form of decision tables. However, a formal evaluation of the risks from misspecifying an assessment model over time‐horizons spanning multiple assessment cycles requires closed‐loop simulation. There were two aims of this study: (a) develop an approach to identify and evaluate asymmetries in risk to yields and spawning biomass due to biases in key parameters and data sources in a stock assessment model, (b) quantify the relative importance of correctly specifying the various assessment attributes. A computationally efficient stock reduction analysis was evaluated using closed‐loop simulation to identify risks associated with a stock assessment with persistent positive and negative biases in the key parameters and inaccurate assumptions regarding data sources. Six types of assessment misspecification were examined, namely the assumed natural mortality rate, the assumed recruitment compensation ratio, the assumed age of maturity, a hyper‐stable or hyper‐deplete index of abundance, over‐ or under‐reporting of historical catch, and misspecification of the assumed shape of the selectivity curve. This study reveals large asymmetries in risk associated with common uncertainties in stock assessment processes. We highlight the value of reproducible and computationally efficient stock assessment models that can be investigated by closed‐loop simulation before being used for fisheries management. 相似文献
9.
Time-varying catchability is prevalent in many management regions, and can be modeled using density dependence and time trend parameters. A catchability model can be estimated using single- or multi-species data, and parameter estimates might be of interest as an input for stock assessment models or in their own right (e.g., catchability trends as an index of technology improvements). An operating model was developed to replicate the catch-at-age, fishery-independent survey, and catch-per-unit-effort data from the Gulf of Mexico. Ordinary least squares was used to estimate catchability trends, density dependence, and annual catchability using 10 different estimation procedures. Procedures included an “imputation” strategy, where data from similar species are used to estimate catchability parameters for a focal species. Estimated trend, density dependence, and annual catchability were compared with index-specific operating model values to determine the precision and accuracy of different estimation procedures in a factorial model design. Multi-species procedures increased precision and accuracy of parameter estimates when compared with single-species procedures, and minimized errors in annual catchability estimates when compared with the assumption of constant catchability. Multi-species procedures also did not introduce large errors in functional parameter or annual catchability estimates, even when density dependence and trend were absent or when between-species variability was high. Procedures that imputed catchability functional parameters from similar species were precise and median unbiased given the quantity and quality of data that are available for the Gulf of Mexico. 相似文献
10.
Mark–recapture experiments have the potential to provide direct estimates of fundamental parameters required for fishery stock assessment and provision of subsequent management advice in fisheries. The literature on mark–recapture experiments is enormous, with a variety of different experimental designs and estimation models; thus, it can be difficult to grasp the primary features of different approaches, the inter‐relationship among them and their potential utility in different situations. Here, we present an overview of the tagging experimental designs that are appropriate for use in commercial fishery situations. We suggest that most mark–recapture experiments in a large‐scale fishery context can be classified into one of three basic types – Petersen, tag‐attrition or Brownie – based on the fundamental design employed for releases and recaptures. The release and recapture strategy (e.g. the number of release events, whether the size of the sample examined for recaptured tags is known) determines which parameters can be estimated and from where the information for estimating them arises. We conclude that an integrated Brownie and Petersen approach is the most powerful of the different approaches in terms of the range of parameters that can be estimated without underlying assumptions or constraints on parameters. Such an approach can provide direct estimates of fishing mortality, natural mortality and population size, which are the main population dynamics parameters that traditional fishery stock assessments attempt to estimate. 相似文献
11.
Daniel J. Skerritt R. Colin A. Bannister Nicholas V. C. Polunin Clare Fitzsimmons 《Fisheries Management and Ecology》2020,27(5):445-453
The UK coastal trap fisheries target two key species, European lobster Homarus gammarus (L.) and brown crab Cancer pagurus L. Their stock status is assessed periodically using size‐based, yield‐per‐recruit analysis. Fishery trends are described using landings and, where available, effort data to estimate catch per unit of effort (CPUE), nominally proportional to abundance. Despite being caught together, assessments assume that concurrent capture of these species does not distort their individual CPUE estimates. Here, an in situ experiment tested impacts of inter‐specific and intra‐specific interactions by pre‐loading baited traps with different species and observing subsequent catches. Pre‐loaded European lobster significantly reduced brown crab catches, whereas, other species produced no such effects. The findings highlight the likely inconsistency of using CPUE as an index of abundance if landings data originate from a mixed‐species fishery in which species interactions and targeting behaviour of fishers are unknown or un‐quantified. 相似文献
12.
南极磷虾渔业CPUE及其丰度估算适用性 总被引：3，自引：2，他引：1
作为一种衡量渔业资源丰度变化的指标,CPUE常用于多种渔业资源评估。南极磷虾作为一种集群性的生物资源,其资源存在着较为明显的时空变化特征,加之该物种本身所具有的特殊性以及渔业特点,这也使得采用CPUE作为衡量该资源丰度指标的有效性存在着较大的不确定性。为此,本实验详细介绍了4种南极磷虾渔业CPUE的常用估算方法,并总结了这些方法所具有的特点、优势以及劣势,在此基础上从时空尺度和环境影响因素等方面对南极磷虾渔业CPUE估算的影响进行了分析。最后,实验就CPUE作为评估南极磷虾资源丰度的适用性及可行性进行了探讨。近年来,南极磷虾渔业日益受到全球的关注,但如何将渔业调查数据纳入到南极磷虾资源评估当中,一直未得到统一的结论,从而导致基于生态系统的南极磷虾渔业管理进展缓慢,本研究结果可为更好地开展南极磷虾资源评估和丰度估算提供思路。 相似文献
13.
Yasuhiro Ueno Satoshi Suyama Masayasu Nakagami Miyako Naya Mitsuo Sakai Yutaka Kurita 《Fisheries Science》2017,83(1):23-33
Drifting gill-nets were for a long time the main research gear for investigating the distribution of Pacific saury Cololabis saira. However, it has proven to be difficult to estimate the absolute abundance of saury using drifting gill-nets due to a lack of knowledge on the survey areas swept by these gill-nets. A mid-water trawl stock abundance estimation has the advantage of being able to estimate the absolute stock abundance before the commercial fishing season begins, whereas the conventional stock abundance estimation based on catch per unit efforts of commercial fisheries must be done after the commercial fishing season has ended. To confirm the practicality of a mid-water trawl to estimate the stock abundance of saury, we conducted a comparative survey in the northwestern Pacific Ocean using both a mid-water trawl and drifting gill-nets. We found that the geographic distribution pattern of catch per unit effort for both the mid-water trawl and driftnets was similar. Using the area-swept method and data on the fishing efficiency of the mid-water trawl obtained in a previous study, we were able to estimate the stock abundance plus confidence limits within the research areas. Our results suggest that the size composition of saury sampled by the mid-water trawl can be considered to approximate the actual size composition of saury. 相似文献
14.
Abundance indices (AIs) provide information on population abundance and trends over time, while AI variance (AIV) provides information on reliability or quality of the AI. AIV is an important output from surveys and is commonly used in formal assessments of survey quality, in survey comparison studies, and in stock assessments. However, uncertainty in AIV estimates is poorly understood and studies on the precision and bias in survey AIV estimates are lacking. Typically, AIV estimates are “design based” and are derived from sampling theory under some aspect of randomized samples. Inference on population density in these cases can be confounded by unaccounted process errors such as those due to variable sampling efficiency (q). Here, we simulated fish distribution and surveys to assess the effect of q and variance in q on design‐based estimates of AIV. Simulation results show that the bias and precision of AIV depend on the mean q and variance in q. We conclude that to fully evaluate the reliability of AI, both observation error and variability in q must be accounted for when estimating AIV. A decrease in mean q and an increase in the variance in q results in increased bias and decreased precision in survey AIV estimates. These effects are likely small in surveys with mean q ≥ 1. However, for surveys where q ≤ 0.5, these effects can be large. Regardless of the survey type, AIV estimates can be improved with knowledge of q and variance in q. 相似文献
15.
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. 相似文献
16.
CPUE standardisation and the construction of indices of stock abundance in a spatially varying fishery using general linear models 总被引：4，自引：0，他引：4
Construction of annual indices of stock abundance based on catch and effort data remains central to many fisheries’ assessments. While the use of more advanced statistical methods has helped catch rates to be standardised against many explanatory variables, the changing spatial characteristics of most fisheries data sets provide additional challenges for constructing reliable indices of stock abundance. After reviewing the use of general linear models to construct indices of annual stock abundance, potential biases which can arise due to the unequal and changing nature of the spatial distribution of fishing effort are examined and illustrated through the analysis of simulated data. Finally, some options are suggested for modelling catch rates in unfished strata and for accounting for the uncertainties in the stock and fishery dynamics which arise in the interpretation of spatially varying catch rate data. 相似文献
17.
基于生活史特征的数据有限条件下渔业资源评估方法比较 总被引：2，自引：2，他引：0
渔业资源评估是开展渔业资源管理,维系渔业可持续发展的基础工作。传统的渔业资源评估方法需要统计产量、资源丰度指数甚至年龄结构等大量数据,由于调查经费和数据的缺乏,全球仅1%的鱼种进行过系统性的资源评估。近年来,在数据有限(data-limited)条件下如何开展资源评估已日益成为学术界的关注热点。本文将基于生活史特征的评估方法分为仅需要生活史参数,需要产量数据和生活史参数,需要产量数据、生活史参数及体长或年龄数据等3大类,分别从方法、数据要求、输出结果及局限性进行了系统回顾分析,提供了关于生活史特征参数的常见估算方法,并就其中两种模型对北大西洋大青鲨(Prionace glauca)的可持续渔获量进行了初步评估与比较。最后,对数据缺乏模型的使用及模型在中国近海渔业资源评估中的运用提出了建议。 相似文献
18.
Fishery-dependent catch per unit effort (CPUE) data have been used as an abundance index (AI) in fish stock assessments. However, fishery-dependent CPUE data are influenced not only by changes in fish abundance but also by other factors, such as the choice or restrictions of fishing grounds to operate. Accordingly, bias may arise in AIs due to a lack of data from unfished or rarely fished areas. To improve the accuracy of AI estimates, spatially arranged CPUE datasets from both trawl fisheries and research vessel surveys in the East China Sea were concurrently analyzed in the present study using a multivariate autoregressive state-space (MARSS) model. Survey datasets complemented information on stock status in the fishing areas where fishery-dependent datasets were limited. As a result, the combined use of datasets from both sources effectively improved the accuracy of estimates of AIs and the spatial distribution of the population density of each fish species. 相似文献
19.
Age‐ or length‐structured stock assessments require reliable life history demographic parameters (growth, mortality, reproduction) to model population dynamics, potential yields and stock sustainability. This study synthesized life history information for 84 commercially exploited tropical reef fish species from Florida and the U.S. Caribbean (Puerto Rico and the U.S. Virgin Islands). We attempted to identify a useable set of life history parameters for each species that included lifespan, length at age, weight at length and maturity at length. Key aspects of the life history synthesis were development of: (a) a database that characterized study details including sampling region, biological and statistical methods, length range of sampled individuals, sample size, capture gears and sampling time frame; (b) reproducible procedural criteria for parameter identification for a given species; and (c) a reliability metric for each parameter type. Complete life history parameter sets were available for 46 species analysed. Of these, only 16 species had parameter sets meeting the highest standards for reliability, highlighting future research needs. 相似文献
20.
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。 相似文献