Stability and return times of Leslie matrices with density-dependent survival: applications to fish populations

1980 ◽  
Vol 8 ◽  
pp. 149-163 ◽  
Author(s):  
D.L. Deangelis ◽  
L.J. Svoboda ◽  
S.W. Christensen ◽  
D.S. Vaughan
Keyword(s):  
Fish Populations ◽  
Density Dependent ◽  
Return Times ◽  
Leslie Matrices

Rapid growth and large body size in annual fish populations are compromised by density‐dependent regulation

2019 ◽  
Vol 95 (2) ◽  
pp. 673-678 ◽  
Author(s):  
Milan Vrtílek ◽  
Jakub Žák ◽  
Matej Polačik ◽  
Radim Blažek ◽  
Martin Reichard
Keyword(s):  
Body Size ◽  
Rapid Growth ◽  
Large Body ◽  
Fish Populations ◽  
Large Body Size ◽  
Annual Fish ◽  
Density Dependent ◽  
Density Dependent Regulation

scholarly journals Protection reveals density-dependent dynamics in fish populations: A case study in the central Mediterranean

PLoS ONE ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. e0228604
Author(s):  
Paco Melià ◽  
Renato Casagrandi ◽  
Antonio Di Franco ◽  
Paolo Guidetti ◽  
Marino Gatto
Keyword(s):  
Fish Populations ◽  
Central Mediterranean ◽  
Density Dependent

Recruitment and survival rate variability in fish populations: density-dependent regulation or further evidence of environmental determinants?

2014 ◽  
Vol 71 (2) ◽  
pp. 290-300 ◽  
Author(s):  
Javier Lobón-Cerviá
Keyword(s):  
Environmental Factors ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Survival Rates ◽  
Fish Populations ◽  
Data Set ◽  
Site Specific ◽  
Density Dependent ◽  
Long Term Study ◽  
Brown Trout Salmo Trutta

Recently, Minto et al. (2008) , based on a fishery data set including marine, estuarine, and freshwater fishes, described higher variability in the survival rates of juveniles at low rather than at high parental density in an inversely density-dependent fashion and suggested density-dependent mechanisms underpinning those patterns. This study, based on a long-term study of brown trout (Salmo trutta; a species and habitat not included in the Minto et al. (2008) analysis), documents that survival rates in these stream-living populations exhibit a pattern that matches exactly those reported by Minto et al. (2008) . Nevertheless, hypothesis testing rejected the occurrence of stock–recruitment relationships and the operation of density-dependent recruitment regulation. The patterns elucidated for these brown trout populations can be entirely explained by the operation of two single environmental factors, namely, stream discharge in March determining annual survival rates across streams and sites and site-specific depth determining site-specific survival rates. It is open to question that exactly the same patterns can be generated by two sets of opposing factors, density-dependent (i.e., Minto et al. 2008 ) and environmental factors (i.e., this study). The consistency of this pattern suggests that survival rates and recruitment are probably determined by environmental factors across fish populations and habitats.

Using reproductive values to define optimal harvesting for multisite density-dependent populations: example with a marine reserve

2002 ◽  
Vol 59 (5) ◽  
pp. 875-885 ◽  
Author(s):  
Elizabeth N Brooks
Keyword(s):  
Egg Production ◽  
Marine Reserve ◽  
Structured Populations ◽  
Reproductive Value ◽  
Density Dependent ◽  
Site Model ◽  
Age Class ◽  
Optimal Harvest ◽  
Leslie Matrices ◽  
The One

A new method for determining optimal harvest from age-structured populations with a density-dependent stock-recruit relationship is presented. The theoretical optimal harvest comes from removing the age-class with the smallest ratio of reproductive value to weight. The method is derived from considering the sensitivity of equilibrium egg production to harvest using results for density-dependent Leslie matrices. The method holds in both single- and multi-site contexts and is derived for both Ricker and Beverton–Holt recruitment functions. I illustrate the method for a one-site model of Arcto-Norwegian cod (Gadus morhua) and obtain the same optimal strategy as previous methods, namely that age-class 6 should be harvested 45%. Including age-specific selectivities, the best constrained yields occur at a harvest rate of 11% on ages 5–12. This yield is 73% of the theoretical optimum. I considered the same model when a reserve is established and found that high transfer rates out of the reserve (where spawners attain a higher fecundity) produced greater yields that were 86% of the one-site (no reserve) yield. Also, if overfishing occurs at 1.5 and 2.0 times the optimal level in the one-site case, then most yields from the reserve model are greater than those from the one-site model.

scholarly journals Power of monitoring surveys to detect abundance trends in depleted populations: the effects of density-dependent habitat use, patchiness, and climate change

2007 ◽  
Vol 65 (1) ◽  
pp. 111-120 ◽  
Author(s):  
Julia L. Blanchard ◽  
David L. Maxwell ◽  
Simon Jennings
Keyword(s):  
Climate Change ◽  
Habitat Use ◽  
Survey Data ◽  
Fish Populations ◽  
Small Scale ◽  
Density Dependent ◽  
Wide Range ◽  
Abundance Trends ◽  
Survey Designs ◽  
Effects Of Density

Abstract Blanchard, J. L., Maxwell, D. L., and Jennings, S. 2008. Power of monitoring surveys to detect abundance trends in depleted fish populations: the effects of density-dependent habitat use, patchiness, and climate change. – ICES Journal of marine Science, 65: 111–120. Traditionally, trawl surveys were designed to collect fishery-independent data for assessing the population dynamics of commercially exploited species. However, trawl survey data are increasingly used to describe the abundance, distribution and ecology of a wide range of species in studies of climate change and fishing effects. These new uses of survey data suggest that improved understanding of the value and limitations of existing survey designs is required. We compared the power of different survey designs (where stations are fixed, fixed stratified, random, or random stratified) to detect known trends in the abundance of depleted populations. Modelled populations were characterized by different temperature preference, density-dependent habitat selection, and patterns of small-scale aggregation (patchiness). Temperature preferences and local patchiness had an influence on the power of different surveys to detect increases in abundance, and in some scenarios, survey-area indices would consistently underestimate or overestimate trends in overall abundance. As the distributions of many fish populations have shifted in response to climate change, exhibit distribution-abundance relationships, and have been depleted by fishing, we conclude that survey indices may provide partial or unreliable information on changes in the true abundance of the wider range of species now of interest. To disentangle the effects of fishing, climate, and biology on the abundance of fish populations, and to monitor the depletion and recovery of species threatened by fishing, there should be greater emphasis on coordinating the timing, areas of coverage, and methods of sampling of surveys of the Northeast Atlantic continental shelf.

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