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991.
992.
多种数据源下栖息地模型及预测结果的比较 总被引:3,自引:1,他引:3
由于多来源的海洋环境数据常以不同时间、空间分辨率呈现,并具有不同的误差,因此,有必要分析数据源的差异是否会对研究结果产生显著影响,是否会影响基于不同数据源估计的模型对其他数据的适用性。为此,本研究利用多个网站提供的叶绿素浓度与海表水温数据,采用线性回归与随机检验方法,分析了不同数据源对栖息地模型构建及其预测效果的影响。研究结果表明,不同数据源的数据之间常存在系统性偏差,从而使得模型参数的估计具有显著性差异,该模型不适合于其他数据源的数据;多源环境数据间的离散性反映数据存在随机误差,环境数据的随机误差将使模型结果具有随机性,因此本研究建议定量分析模型结果的不确定性,以使模型结果得到科学应用。 相似文献
993.
994.
M. F. O'Connell 《Fisheries Management and Ecology》2003,10(4):201-208
Conservation spawning requirements (limits) for Atlantic salmon, Salmo salar L., have been developed for a number of rivers in Newfoundland. Status of stocks is evaluated against these limits and scientific advice and recommendations on levels of recreational catch provided to resource managers. A critical factor in this process is the determination of total returns. This has been accomplished for 30–40% of the rivers in question over the years through the use of fish counting fences and traps installed in fishways. In Newfoundland, it is not logistically or financially possible to operate fish counting facilities in all of the approximately 200 Atlantic salmon rivers. Thus angling catch data have been used as an alternative means of estimating total returns to rivers without counting facilities. Estimates of total returns were three to four times higher than the actual values for one of the two rivers studied and deviated from the actual by as much as 60% for the other. Management implications of the approach are discussed. 相似文献
995.
根据Box-Jenkins建模原理,采用ARIMAR(p,d,q)模型,以大菱鲆选育F1优良家系为研究对象,应用时间序列分析方法对在3~27月龄间不同发育阶段体重的生长速度进行动态模拟,建立各家系的预测模型。结果表明,家系E♂1×E♀2和F♂2×E♀4符合ARIMAR(2,0,0)模型(2个家系的模型都不含常数项),家系F♂4×N♀3、E♂2×F♀1和F♂1×F♀4符合ARIMAR(1,0,0)模型(3个家系的模型都不含常数项),且所建模型的残差均为白噪声。由此预测出27~27.5及27.5~28月龄各家系体重生长速度,经与相应实测数据的验证说明,5个家系各自所建模型在一定程度上能够反映大菱鲆体重生长速度的动态变化过程,对各家系体重生长速度的趋势预测有一定的适用性。通过对每一家系后期生长速度的预测,结合前期生长速度的实测值,综合分析体重生长速度的动态变化,为在大菱鲆选择育种过程中确定最佳选择时间提供理论依据。 相似文献
996.
Climatic oscillations and tuna catch rates in the Indian Ocean: a wavelet approach to time series analysis 总被引:3,自引:1,他引:3
We analysed the influence of climatic oscillations [based on the Indian Oscillation Index (IOI)] on monthly catch rates of two tropical tuna species in the equatorial Indian Ocean. We carried out wavelet analysis, an efficient method of time series analysis to study non‐stationary data. Catch per unit of effort (CPUE) of bigeye tuna was computed from Japanese longline statistics from 1955 to 2002 in the equatorial Indian Ocean and CPUE of yellowfin tuna was derived from industrial purse seine statistics from 1984 to 2003 in the Western Indian Ocean. Wavelet analyses allowed us to quantify both the pattern of variability in the time series and non‐stationary associations between tuna and climatic signals. Phase analyses were carried out to investigate dependency between the two signals. We reported strong associations between tuna and climate series for the 4‐ and 5‐yr periodic modes, i.e. the periodic band of the El Niño Southern Oscillation signal propagation in the Indian Ocean. These associations were non‐stationary, evidenced from 1970 to 1990 for bigeye, and from 1984 to 1991 and then from 1993 to 2001 for yellowfin. Warm episodes (low negative IOI values) matched increases of longline catch rates of bigeye during the 1970–1990 time frame, whereas the strong 1997–1998 warm event matched a decrease of purse seine catch rates of yellowfin. We discussed these results in terms of changes in catchability for purse seine and longline. 相似文献
997.
998.
Corbin D. Hilling Yan Jiao Mary C. Fabrizio Paul L. Angermeier Aaron J. Bunch Donald J. Orth 《Fisheries Management and Ecology》2023,30(1):70-88
Stock assessment modeling provides a means to estimate the population dynamics of invasive fishes and may do so despite data limitations. Blue catfish (Ictalurus furcatus) were introduced to the Chesapeake Bay watershed to support recreational fisheries but also consume species of conservation need and economic importance. To assess management tradeoffs, managers need to understand the current status of the population and anticipate future population abundance and trends. A Bayesian size-based stock assessment model was used to estimate blue catfish abundance, fishing mortality, and size structure over time (2001–2016) in the tidal James River. The model estimated population size increases until around 2006, with declines in total abundance after 2011 and large blue catfish (≥80 cm total length) after 2001. These first estimates of blue catfish population dynamics in the Chesapeake Bay region provide inputs for projection models to evaluate prospective management actions and identify monitoring needs. 相似文献
999.
Nineteenth century narratives reveal historic catch rates for Australian snapper (Pagrus auratus) 下载免费PDF全文
Snapper (Pagrus auratus) is widely distributed throughout subtropical and temperate southern oceans and forms a significant recreational and commercial fishery in Queensland, Australia. Using data from government reports, media sources, popular publications and a government fisheries survey carried out in 1910, we compiled information on individual snapper fishing trips that took place prior to the commencement of fisherywide organized data collection, from 1871 to 1939. In addition to extracting all available quantitative data, we translated qualitative information into bounded estimates and used multiple imputation to handle missing values, forming 287 records for which catch rate (snapper fisher?1 h?1) could be derived. Uncertainty was handled through a parametric maximum likelihood framework (a transformed trivariate Gaussian), which facilitated statistical comparisons between data sources. No statistically significant differences in catch rates were found among media sources and the government fisheries survey. Catch rates remained stable throughout the time series, averaging 3.75 snapper fisher?1 h?1 (95% confidence interval, 3.42–4.09) as the fishery expanded into new grounds. In comparison, a contemporary (1993–2002) south‐east Queensland charter fishery produced an average catch rate of 0.4 snapper fisher?1 h?1 (95% confidence interval, 0.31–0.58). These data illustrate the productivity of a fishery during its earliest years of development and represent the earliest catch rate data globally for this species. By adopting a formalized approach to address issues common to many historical records – missing data, a lack of quantitative information and reporting bias – our analysis demonstrates the potential for historical narratives to contribute to contemporary fisheries management. 相似文献
1000.
Is risk consistent across tier‐based harvest control rule management systems? A comparison of four case‐studies 下载免费PDF全文
Catherine M Dichmont André E Punt Natalie Dowling José A A De Oliveira Lorne R Little Miriana Sporcic Elizabeth Fulton Rebecca Gorton Neil Klaer Malcolm Haddon David C Smith 《Fish and Fisheries》2016,17(3):731-747
There can be substantial differences in data quality and quantity among fished species. Consequently, the quality and type of assessments can also vary substantially. However, all species, especially those that are targeted, need to be managed. Several jurisdictions have developed hierarchical tier systems that categorize stocks based on, for example, the data available for assessment purposes and/or the extent to which quantities on which management advice is based can be estimated. Four case‐studies (Australia's Southern and Eastern Scalefish and Shark Fishery, the USA west coast groundfishery, the USA Alaskan crab fishery and EU fisheries) are used to contrast the types of hierarchical tier systems available, and to assess the extent to which each system constrains risk to be equivalent among the tiers (termed risk equivalency). Only the Australian system explicitly aims to achieve risk equivalency. However, this intent has not been fully operationalized. Our review reveals that best practice is not to define tiers simply on data availability, but also on what the assessments based on those data are capable of estimating. In addition, clearly differentiating the quantification of uncertainty from how decision‐makers wish to address that uncertainty would simplify justification of buffers (the gap between the assessment‐produced target catch or effort and the final management decision that accounts for uncertainty and risk). Risk equivalency can be achieved using management strategy evaluation to select the values for control variables, which determine the buffer given the uncertainty associated with the assessment. 相似文献