scholarly journals The effect of interannual variation in growth and condition on haddock recruitment

1999 ◽  
Vol 56 (3) ◽  
pp. 347-355 ◽  
Author(s):  
C Tara Marshall ◽  
Kenneth T Frank
Keyword(s):  
Egg Production ◽  
Interannual Variation ◽  
Population Analysis ◽  
Reproductive Potential ◽  
Indirect Approach ◽  
Virtual Population Analysis ◽  
Time Period ◽  
Virtual Population ◽  
Alternative Approach ◽  
The Relationship

The relationship between recruitment and spawner biomass assumes that estimates of spawner biomass are proportional to total egg production by the stock. The validity of this assumption is in question for long-lived gadoid stocks; however, estimating total egg production independently of spawner biomass is seldom feasible. An alternative approach is to examine correlations between recruitment and variables likely to be proxies for total egg production by the stock. This indirect approach was used for haddock on the Scotian Shelf. Indices of growth (mean length at age-4) and condition (weight at 50 cm) were used as proxies for the reproductive potential of individual spawners. Both variables were positively correlated with recruitment over a 3-decade period (1964-1995). During the same time period, there was no relationship between recruitment and spawner biomass estimated by Virtual Population Analysis (VPA). This is further evidence that VPA-based spawner biomass is a poor index of the true reproductive potential of the stock. The results highlight the need to develop more accurate/precise measures of total egg production for use in recruitment research.

scholarly journals Reconstructing the stock-recruit relationship for Northeast Arctic cod using a bioenergetic index of reproductive potential

2000 ◽  
Vol 57 (12) ◽  
pp. 2433-2442 ◽  
Author(s):  
C Tara Marshall ◽  
Nathalia A Yaragina ◽  
Bjørn Ådlandsvik ◽  
Andrey V Dolgov
Keyword(s):  
Egg Production ◽  
Population Analysis ◽  
Reproductive Potential ◽  
Condition Index ◽  
Multiple Regression Model ◽  
Reference Points ◽  
Time Period ◽  
Virtual Population ◽  
Alongshore Wind Stress ◽  
Alongshore Wind

Correlation and simulation analyses suggest that, for the Northeast Arctic (NA) cod stock, the total lipid energy (TLE (kJ)) contained in the livers of mature females is proportional to total egg production, making TLE a potential predictor of recruitment. Accordingly, the TLE of NA cod was estimated for a 51-year time period (1946-1996), using estimates of numbers at length derived from virtual population analysis, modelled values of proportion mature and weight at length, and observed values of the liver-condition index. A significant linear relationship between TLE and recruitment to age 3 was observed. The temporal trend in TLE suggests that the reproductive potential of the NA cod stock has been in decline since the mid-1970s. A multiple-regression model that included TLE, mean temperature, and mean alongshore wind stress as independent variables explained approximately 43% of the variation in recruitment. Reconstructing stock-recruit relationships using more sensitive measures of reproductive potential is the first step in resolving environmental effects on recruitment and in developing biological reference points that are more effective in stock conservation.

Is spawner biomass a sensitive measure of the reproductive and recruitment potential of Northeast Arctic cod?

1998 ◽  
Vol 55 (7) ◽  
pp. 1766-1783 ◽  
Author(s):  
C Tara Marshall ◽  
Olav Sigurd Kjesbu ◽  
Nathalia A Yaragina ◽  
Per Solemdal ◽  
Øyvind Ulltang
Keyword(s):  
Egg Production ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Population Analysis ◽  
Reproductive Potential ◽  
Fish Stocks ◽  
Virtual Population ◽  
Individual Scale ◽  
The Individual ◽  
The Relationship

The assumption that spawner biomass is directly proportional to total egg production by fish stocks underlies most spawner-recruit relationships. Despite its importance, this assumption is largely untested. Data describing the reproductive potential of Northeast Arctic (NEA) Atlantic cod (Gadus morhua) were used to test the proportionality assumption for a period showing strong variation in condition and abundance of spawners. At the individual scale, relative fecundity varied with length and condition. This decreases the likelihood that the proportionality assumption is valid. At the stock level, total egg production was estimated (1985-1996) using acoustic estimates of total abundance and demographic information from trawl sampling in combination with year-specific fecundity-length relationships. For NEA cod, spawner biomass estimated by virtual population analysis (VPA) was not proportional to total egg production. Compared with VPA-based estimates of spawner biomass, total egg production is an improved index of recruitment potential because (i) the magnitude of variation observed in total egg production was closer to that observed in recruitment and (ii) the relationship between recruitment at age 1 and total egg production approaches the origin. The results suggest that further progress in explaining recruitment variation will be achieved using more sensitive measures of the true reproductive potential of the stock.

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 Does increased information about reproductive potential result in better prediction of recruitment?

2011 ◽  
Vol 68 (8) ◽  
pp. 1361-1368 ◽  
Author(s):  
M. Joanne Morgan ◽  
Alfonso Perez-Rodriguez ◽  
Fran Saborido-Rey
Keyword(s):  
Reproductive Biology ◽  
Egg Production ◽  
Gadus Morhua ◽  
Reproductive Potential ◽  
Essential Element ◽  
Greenland Halibut ◽  
Greenland Halibut Reinhardtius Hippoglossoides ◽  
Difficult Challenge ◽  
The Relationship ◽  
Hippoglossoides Platessoides

The relationship between stock size and recruitment is an essential element in the understanding of the productivity of a population. However, predicting the number of recruits produced by a population has proven to be a difficult challenge. This may in part be a result of poor estimation of reproductive potential (RP). We determined if including increased information on reproductive biology in indices of RP results in better predictions of recruitment. We investigated some of the conditions that lead to better (or worse) recruitment prediction when more biologically complex indices of RP are used. Data from four populations in the Northwest Atlantic were examined: southern Grand Bank (NAFO Division 3NO) cod ( Gadus morhua ), Flemish Cap (NAFO Division 3M) cod, Newfoundland (NAFO Division 3LNO) American plaice ( Hippoglossoides platessoides ), and Greenland halibut ( Reinhardtius hippoglossoides ) (NAFO Subarea 2 + Division 3KLMNO). Stock–recruit models paired with complex indices of RP gave a better estimate of recruitment in slightly more than half of the tests conducted. When there were larger trends in the reproductive biology (maturity at age, sex ratio and egg production), more complex indices of RP were more likely to provide a better estimate of recruitment.

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 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.

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.

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