Estimating predation mortality in the Georges Bank fish community

2001 ◽  
Vol 58 (5) ◽  
pp. 908-922 ◽  
Author(s):  
Tien-Shui Tsou ◽  
Jeremy S Collie
Keyword(s):  
Input Data ◽  
Population Analysis ◽  
Fractional Factorial ◽  
Total Biomass ◽  
Georges Bank ◽  
Chi Square ◽  
Gamma Distributions ◽  
Virtual Population ◽  
Predation Mortality ◽  
Consumption Rates

Multispecies virtual population analysis (MSVPA) is one of the most successful methods of including predation in fishery models. By applying MSVPA to nine important fish species on Georges Bank, we estimated predation mortality of prey species, fishing mortality, and population abundance from 1978 to 1992. One of the inputs to the MSVPA, relative stomach content, was estimated by fitting gamma distributions to the logarithmic predator-to-prey size ratios. Chi-square tests indicated that the gamma distributions fit the observed ratios well. Predation mortality was highest at ages 0 and 1. Total biomass of all species remained relatively constant with decreasing predator biomass and increasing prey biomass. MSVPA requires extensive input data, and the uncertainty in the inputs will propagate into the model output. The sensitivity of MSVPA to perturbations in the inputs was assessed with a two-level fractional factorial design. Results of the sensitivity test indicated that MSVPA outputs were most sensitive to predator consumption rates and terminal fishing mortalities. With ±25% perturbations to the input parameters, MSVPA outputs varied within ±10% of the levels from the base run. Therefore, MSVPA appears to be relatively robust to uncertainty in the input data.

scholarly journals Evaluating the effect of predation mortality on forage species population dynamics in the Northeast US continental shelf ecosystem using multispecies virtual population analysis

2008 ◽  
Vol 65 (9) ◽  
pp. 1689-1700 ◽  
Author(s):  
Megan C. Tyrrell ◽  
Jason S. Link ◽  
Hassan Moustahfid ◽  
William J. Overholtz
Keyword(s):  
Population Dynamics ◽  
Continental Shelf ◽  
Population Analysis ◽  
Northwest Atlantic ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Predation Mortality ◽  
Forage Species ◽  
Species Population ◽  
Northeast Us

AbstractTyrrell, M. C., Link, J. S., Moustahfid, H., and Overholtz, W. J. 2008. Evaluating the effect of predation mortality on forage species population dynamics in the Northeast US continental shelf ecosystem using multispecies virtual population analysis. – ICES Journal of Marine Science, 65: 1689–1700. An expanded version of multispecies virtual population analysis (MSVPA) is used to analyse the effects of predation by 14 key predators on Atlantic herring and Atlantic mackerel in the Northwest Atlantic ecosystem for the period 1982–2002. For herring, MSVPA produced greater abundance estimates than single-species assessments, especially for the youngest age classes. The average rate of predation mortality for herring aged 0 and 1 was also higher than the standard total natural mortality rate (0.2) for the 21-year time frame (0.84–3.2). The same was true for mackerel in this MSVPA (0.37–1.6). Consumptive removals of herring and mackerel generally increased over time. From 1999 to 2001, the biomass removed by predators exceeded each species' commercial landings. The sum of consumption and landings notably exceeded the multispecies maximum sustainable yield for herring for the years 1995–2002 and for mackerel for the period 1999–2002. We highlight the importance of accounting for predation on forage species in the context of changes to the fish community that have taken place in the Northwest Atlantic over the past few decades.

Significance of the Functional Response of Predators to Changes in Prey Abundance in Multispecies Virtual Population Analysis

1988 ◽  
Vol 45 (1) ◽  
pp. 89-96 ◽  
Author(s):  
Mskael Hisdén
Keyword(s):  
Population Analysis ◽  
Single Species ◽  
Assessment Methods ◽  
Cohort Size ◽  
Fish Stocks ◽  
Virtual Population ◽  
Predation Mortality ◽  
The Relationship ◽  
Sea Fish ◽  
Increasing Function

Recent applications of multispecies assessment methods (MSVPA) to North Sea Fish stocks indicate that MSVPA and single-species assessments give highly corrected recruitment estimates. This may be an artifact due to the choice of the relationship between predation mortality and prey cohort size. If the predation mortality is an increasing function of prey cohort size over a certain range of cohort sizes, even a constant predator biomass may cause fluctuations in the number of fish recruiting to the fishable part of the population. Thus the correlation between single-species and multispecies recruitment estimates may be lower than earlier analyses have suggested, and changes in predation mortality may have caused fluctuations in year class strengths which previously have been attributed to unspecified environmental conditions. Because a relatively minor alteration of the predation function can cause such a drastic change in the perceived dynamics of the fish stocks, I suggest that more studies of the predation processes in fish communities are needed before one can hope to gain deeper insights into the recruitment of fish stocks by applying multispecies assessment methods.

Virtual Population Analysis (VPA) Equations for Nonhomogeneous Populations, and a Family of Approximations Including Improvements on Pope's Cohort Analysis

1986 ◽  
Vol 43 (12) ◽  
pp. 2406-2409 ◽  
Author(s):  
Alec D. MacCall
Keyword(s):  
Mortality Rate ◽  
Population Analysis ◽  
Seasonal Pattern ◽  
Cohort Analysis ◽  
Natural Mortality ◽  
Close Approximation ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Special Case

A set of "backward" virtual population analysis (VPA) equations relates catch (Ct) from continuous fishing between times t and t + 1 to population n size (Nt, Nt+1) when a portion of the stock is unavailable to fishing. The usual VPA equations become a special case where the entire stock is available (i.e. the stock is homogeneous). A close approximation to the VPA equations is Nt = Nt+1 exp(M) + CtM/(1 − exp(−M)), which has properties similar to Pope's "cohort analysis" and is somewhat more accurate in the case of a continuous fishery, especially if the natural mortality rate (M) is large. Much closer simple approximations are possible if the seasonal pattern of catches is known.

Virtual population analysis of the big eye Priacanthus macracanthus in the waters off northeastern Taiwan

1999 ◽  
Vol 41 (3) ◽  
pp. 243-254 ◽  
Author(s):  
Kwang-Ming Liu ◽  
Yeu-Long Cheng
Keyword(s):  
Population Analysis ◽  
Virtual Population Analysis ◽  
Virtual Population

scholarly journals A Theoretical Study of Equations Used in Virtual Population Analysis

1995 ◽  
Vol 61 (5) ◽  
pp. 752-754 ◽  
Author(s):  
Kazuhiko Hiramatsu
Keyword(s):  
Theoretical Study ◽  
Population Analysis ◽  
Virtual Population Analysis ◽  
Virtual Population

A hybrid stock synthesis—Virtual population analysis model of Pacific bluefin tuna

2013 ◽  
Vol 142 ◽  
pp. 22-26 ◽  
Author(s):  
Alec D. MacCall ◽  
Steven L.H. Teo
Keyword(s):  
Population Analysis ◽  
Bluefin Tuna ◽  
Pacific Bluefin Tuna ◽  
Analysis Model ◽  
Virtual Population Analysis ◽  
Virtual Population

scholarly journals An expansion of the MSVPA approach for quantifying predator–prey interactions in exploited fish communities

2010 ◽  
Vol 67 (5) ◽  
pp. 856-870 ◽  
Author(s):  
Lance P. Garrison ◽  
Jason S. Link ◽  
D. Patrick Kilduff ◽  
Matthew D. Cieri ◽  
Brandon Muffley ◽  
...  
Keyword(s):  
Sensitivity Analysis ◽  
Population Analysis ◽  
Fish Communities ◽  
Atlantic Menhaden ◽  
Fish Stock ◽  
Forage Fish ◽  
Model Parameters ◽  
Western Atlantic ◽  
Predator Prey ◽  
Predation Mortality

Abstract Garrison, L. P., Link, J. S., Kilduff, D. P., Cieri, M. D., Muffley, B., Vaughan, D. S., Sharov, A., Mahmoudi, B., and Latour, R. J. 2010. An expansion of the MSVPA approach for quantifying predator–prey interactions in exploited fish communities. – ICES Journal of Marine Science, 67: 856–870. Ecosystem-based fisheries management requires tools to place fish-stock dynamics in the broader context of fishery, predator, and competitive removals. Multispecies virtual population analysis (MSVPA) is an approach to quantifying predator–prey interactions and estimating the rates of predation mortality for exploited fish populations. Here, an extended MSVPA (MSVPA-X) is presented as an alternative to existing MSVPA approaches. Notably, MSVPA-X uses index-tuned VPA methods, applies a more flexible feeding model, and includes an alternative functional feeding response. The MSVPA-X model is applied to a western Atlantic fish community, focusing on Atlantic menhaden and its major fish predators, and a sensitivity analysis of major model parameters is presented. The sensitivity analysis highlights the need for adequate diet sampling. The MSVPA-X represents an improvement over previous approaches by increasing the flexibility to model seasonal and interannual dynamics in the strength of predator–prey interactions. Model results demonstrate that, for menhaden in particular, and forage fish in general, quantifying predation mortality is an important part of effective assessments of forage fish, their predators, and the fisheries of both.

scholarly journals Testing the stability of the suitability coefficients from an eastern Bering Sea multispecies virtual population analysis

2005 ◽  
Vol 62 (5) ◽  
pp. 915-924 ◽  
Author(s):  
Jesús Jurado-Molina ◽  
Patricia A. Livingston ◽  
Vincent F. Gallucci
Keyword(s):  
Stomach Content ◽  
Bering Sea ◽  
Population Analysis ◽  
Data Set ◽  
Predator Species ◽  
Eastern Bering Sea ◽  
Virtual Population Analysis ◽  
Virtual Population ◽  
Total Data ◽  
The Stability

Abstract Suitability coefficients are important for the estimation of predation mortality in a multispecies virtual population analysis (MSVPA) and subsequent use in the multispecies forecasting model (MSFOR). Testing the assumption of the stability of the suitability coefficients is important in assessing the robustness of the predictions made with MSFOR. We used different statistical methods to partially test this assumption for the eastern Bering Sea MSVPA model with eight species, using stomach content data for the years 1985–1989. Comparison of the estimates from two different sets of stomach content data (set one with all data and set two mainly with data from 1985) suggested that the differences between the two types of estimates were much reduced when the number of predator stomachs sampled increased. In a second approach, we contrasted the residual variances of partial data sets with the results from the fit of the total data set. Results suggested a small increase (∼10.8%) in the variation of the suitability coefficients. Comparison of the means of the suitability coefficients associated with each predator species suggests that only 13 of the 50 possible pairwise contrasts were significantly different (α = 0.05). In general, results suggested that the predator preferences and prey vulnerabilities remained stable over the time period studied. Therefore, MSFOR could be considered as a tool to advise fisheries managers within a multispecies context.

Comparison of the performance of age-structured models with few survey indices

2018 ◽  
Vol 75 (6) ◽  
pp. 2016-2024
Author(s):  
Hiroshi Okamura ◽  
Yuuho Yamashita ◽  
Momoko Ichinokawa ◽  
Shota Nishijima
Keyword(s):  
Stock Assessment ◽  
Population Analysis ◽  
Assessment Model ◽  
Sufficient Information ◽  
Abundance Estimates ◽  
Virtual Population ◽  
Stock Biomass ◽  
Abundance Indices ◽  
Spawning Stock ◽  
Age Structured

Abstract Age-structured models have played an important role in fisheries stock assessment. Although virtual population analysis (VPA) was once the most widely used stock assessment model for when catch-at-age information is available, (hierarchical) statistical catch-at-age analysis (SCAA) is about to take that position. However, the estimation performance of different age-structured models has not been evaluated sufficiently, especially in cases where there are few available abundance indices. We examined the performance of VPA and SCAA using simulation data in which only the abundance indices of spawning stock biomass and recruitment were available. The simulation demonstrated that VPA with the ridge penalty selected by minimizing retrospective bias provided near-unbiased abundance estimates without catch-at-age error and moderately biased estimates with catch-at-age error, whereas SCAA with random-walk selectivity suffered from problems in estimating parameters and population states. Without sufficient information on abundance trends, naïvely using SCAA with many random effects should be done cautiously, and comparing results from various age-structured models via simulation tests will be informative in selecting an appropriate stock assessment model.

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