Optimal Thinning of a Year-Class with Density-Dependent Growth

I consider the impact of density-dependent growth on the optimal harvesting of a year-class of fish. In general, density dependence makes "thinning" of the year-class a desirable strategy. Moderate density dependence implies that thinning should be gradual, even in the case of zero harvesting costs where the optimal harvesting strategy would otherwise be instantaneous harvesting. Strong density dependence calls for an immediate thinning at an early date, in the case of zero harvesting costs.

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Density-Dependent Growth of Age 1 English Sole (Parophrys vetuls) in Oregon and Washington Coastal Waters

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f87-006 ◽

1987 ◽

Vol 44 (1) ◽

pp. 48-53 ◽

Cited By ~ 9

Author(s):

Randall M. Peterman ◽

Michael J. Bradford

Keyword(s):

Coastal Waters ◽

Time Trends ◽

Annual Growth Rate ◽

English Sole ◽

Density Dependent ◽

Stock Assessments ◽

Negative Effect ◽

Dependent Growth ◽

Parophrys Vetulus ◽

The Impact

We tested whether English sole (Parophrys vetulus) in Oregon and Washington waters show density-dependent growth. We found that there is a significant negative effect of cohort abundance on annual growth rate of age 1 fish, but not on growth of ages 2–7. Unlike most similar studies of density dependence, this result was not confounded by time trends in abundance and growth. The multiple regression of age 1 growth on cohort abundance and temperature accounted for 91% of the interannual variation in growth, which was a significant increase in r2 over that of the previously published relation with temperature alone. However, stock assessments which take into account only the previously published temperature effect on growth for this stock will probably not seriously overestimate the impact of management regulations which increase cohort abundance.

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Stronger density-dependent growth of Japanese sardine with lower food availability: Comparison of growth and zooplankton biomass between a historical and current stock-increase period in the western North Pacific

10.1101/2021.12.26.474216 ◽

2021 ◽

Author(s):

Yasuhiro Kamimura ◽

Kazuaki Tadokoro ◽

Sho Furuichi ◽

Ryuji Yukami

Keyword(s):

Density Dependence ◽

Food Availability ◽

North Pacific ◽

Western North Pacific ◽

Fish Population ◽

Japanese Sardine ◽

Density Dependent ◽

Mesozooplankton Biomass ◽

Current Period ◽

Dependent Growth

Density dependence is a fundamental concept for fish population dynamics. Although density-dependent growth and maturity among older juveniles and adults is important for regulating fish population size and for fisheries management, the mechanism of density dependence for marine fishes remains unclear. Here, we examined changes in Japanese sardine growth with increasing abundance beginning in the 2010s and how the current pattern of density-dependent growth differs from that of a previous stock-increase period from the 1970s to early 1980s. During the current period of increasing abundance, mean standard length has already dropped to the lowest level yet observed and growth has declined more sharply with increased abundance than in the 1970s and 1980s. Mesozooplankton biomass in July in the summer feeding grounds was also lower during the current period. Therefore, our results suggest that summer food availability in the western North Pacific controls the strength of density-dependent growth. A lower carrying capacity for Japanese sardine could account for the stronger density dependence of growth observed in the 2010s; this indicates that future Japanese sardine abundance might not increase as much as in the 1980s unless food availability improves.

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Roles of density-dependent growth and life history evolution in accounting for fisheries-induced trait changes

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1525749113 ◽

2016 ◽

Vol 113 (52) ◽

pp. 15030-15035 ◽

Cited By ~ 38

Author(s):

Anne Maria Eikeset ◽

Erin S. Dunlop ◽

Mikko Heino ◽

Geir Storvik ◽

Nils C. Stenseth ◽

...

Keyword(s):

Life History ◽

Density Dependence ◽

Time Series Data ◽

Life History Evolution ◽

Series Data ◽

Ecological Processes ◽

Arctic Cod ◽

Density Dependent ◽

History Evolution ◽

Dependent Growth

The relative roles of density dependence and life history evolution in contributing to rapid fisheries-induced trait changes remain debated. In the 1930s, northeast Arctic cod (Gadus morhua), currently the world’s largest cod stock, experienced a shift from a traditional spawning-ground fishery to an industrial trawl fishery with elevated exploitation in the stock’s feeding grounds. Since then, age and length at maturation have declined dramatically, a trend paralleled in other exploited stocks worldwide. These trends can be explained by demographic truncation of the population’s age structure, phenotypic plasticity in maturation arising through density-dependent growth, fisheries-induced evolution favoring faster-growing or earlier-maturing fish, or a combination of these processes. Here, we use a multitrait eco-evolutionary model to assess the capacity of these processes to reproduce 74 y of historical data on age and length at maturation in northeast Arctic cod, while mimicking the stock’s historical harvesting regime. Our results show that model predictions critically depend on the assumed density dependence of growth: when this is weak, life history evolution might be necessary to prevent stock collapse, whereas when a stronger density dependence estimated from recent data is used, the role of evolution in explaining fisheries-induced trait changes is diminished. Our integrative analysis of density-dependent growth, multitrait evolution, and stock-specific time series data underscores the importance of jointly considering evolutionary and ecological processes, enabling a more comprehensive perspective on empirically observed stock dynamics than previous studies could provide.

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Age and growth of redfish (Sebastes marinus, S. mentella, and S. fasciatus) on the Flemish Cap (Northwest Atlantic)

ICES Journal of Marine Science ◽

10.1016/j.icesjms.2003.11.003 ◽

2004 ◽

Vol 61 (2) ◽

pp. 231-242 ◽

Cited By ~ 16

Author(s):

Fran Saborido-Rey ◽

Dolores Garabana ◽

Santiago Cerviño

Keyword(s):

Growth Rate ◽

Density Dependence ◽

Slow Rate ◽

Age Determination ◽

Age And Growth ◽

Northwest Atlantic ◽

Density Dependent ◽

Dependent Growth ◽

Sebastes Mentella

Abstract Age determination of redfish is difficult. In this paper, the ages of Sebastes mentella on the Flemish Cap are validated by following year classes from 1991 to 2000. The criteria used for S. mentella are consistent and coherent. The growth of different year classes is described and compared, and density-dependence is demonstrated to influence the growth rate of the strong 1990 year class, growth of that year class being the slowest of those followed. The slow rate of growth prevented that year class from maturing at the anticipated age. Growth is also compared between sexes, of S. mentella, S. marinus, and S. fasciatus, revealing that females grow faster than males. Finally, growth rate is compared among species. S. marinus grows fastest and S. mentella slowest, although the influence of density-dependent growth in S. mentella needs to be taken into consideration.

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Implications of late-in-life density-dependent growth for fishery size-at-entry leading to maximum sustainable yield

ICES Journal of Marine Science ◽

10.1093/icesjms/fsx236 ◽

2018 ◽

Vol 75 (4) ◽

pp. 1296-1305 ◽

Cited By ~ 8

Author(s):

Rob van Gemert ◽

Ken H Andersen

Keyword(s):

Density Dependence ◽

Maximum Sustainable Yield ◽

Sustainable Yield ◽

Fish Stocks ◽

Density Dependent ◽

Large Size ◽

Adult Growth ◽

Stock Assessments ◽

Stock Recruitment ◽

Dependent Growth

Abstract Currently applied fisheries models and stock assessments rely on the assumption that density-dependent regulation only affects processes early in life, as described by stock–recruitment relationships. However, many fish stocks also experience density-dependent processes late in life, such as density-dependent adult growth. Theoretical studies have found that, for stocks which experience strong late-in-life density dependence, maximum sustainable yield (MSY) is obtained with a small fishery size-at-entry that also targets juveniles. This goes against common fisheries advice, which dictates that primarily adults should be fished. This study aims to examine whether the strength of density-dependent growth in actual fish stocks is sufficiently strong to reduce optimal fishery size-at-entry to below size-at-maturity. A size-structured model is fitted to three stocks that have shown indications of late-in-life density-dependent growth: North Sea plaice (Pleuronectes platessa), Northeast Atlantic (NEA) mackerel (Scomber scombrus), and Baltic sprat (Sprattus sprattus balticus). For all stocks, the model predicts exploitation at MSY with a large size-at-entry into the fishery, indicating that late-in-life density dependence in fish stocks is generally not strong enough to warrant the targeting of juveniles. This result lends credibility to the practise of predominantly targeting adults in spite of the presence of late-in-life density-dependent growth.

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Individual variation in dispersal, and its sources, shape the fate of pushed vs. pulled range expansions

10.1101/2022.01.12.476009 ◽

2022 ◽

Author(s):

Maxime Dahirel ◽

Chloe Guicharnaud ◽

Elodie Vercken

Keyword(s):

Density Dependence ◽

Evolutionary Dynamics ◽

Simulation Models ◽

Dispersal Capacity ◽

Density Dependent ◽

Range Edge ◽

Individual Trait ◽

Edge Populations ◽

The Impact ◽

Density Dependent Dispersal

Ecological and evolutionary dynamics of range expansions are shaped by both dispersal and population growth. Accordingly, density-dependence in either dispersal or growth can determine whether expansions are pulled or pushed, i.e. whether expansion velocities and genetic diversity are mainly driven by recent, low-density edge populations, or by older populations closer to the core. Despite this and despite abundant evidence of dispersal evolution during expansions, the impact of density-dependent dispersal and its evolution on expansion dynamics remains understudied. Here, we used simulation models to examine the influence of individual trait variation in both dispersal capacity and dispersal density-dependence on expansions, and how it impacts the position of expansions on the pulled-pushed continuum. First, we found that knowing about the evolution of density-dependent dispersal at the range edge can greatly improve our ability to predict whether an expansion is (more) pushed or (more) pulled. Second, we found that both dispersal costs and the sources of variation in dispersal (genetic or non-genetic, in dispersal capacity versus in density-dependence) greatly influence how expansion dynamics evolve. Among other scenarios, pushed expansions tended to become more pulled with time only when density-dependence was highly heritable, dispersal costs were low and dispersal capacity could not evolve. When, on the other hand, variation in density-dependence had no genetic basis, but dispersal capacity could evolve, then pushed expansions tended to become more pushed with time, and pulled expansions more pulled. More generally, our results show that trying to predict expansion velocities and dynamics using trait information from non-expanding regions only may be problematic, that both dispersal variation and its sources play a key role in determining whether an expansion is and stays pushed, and that environmental context (here dispersal costs) cannot be neglected. Those simulations suggest new avenues of research to explore, both in terms of theoretical studies and regarding ways to empirically study pushed vs. pulled range expansions.

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Detection of density-dependent growth and fecundity of helminths in natural infections

Parasitology ◽

10.1017/s0031182000076836 ◽

1993 ◽

Vol 106 (5) ◽

pp. 527-539 ◽

Cited By ~ 29

Author(s):

A. W. Shostak ◽

M. E. Scott

Keyword(s):

Monte Carlo Simulation ◽

Monte Carlo ◽

Life Cycle ◽

Density Dependence ◽

Parasite Growth ◽

Parasite Life Cycle ◽

Density Dependent ◽

Monte Carlo Simulation Technique ◽

Life Cycle Interpretation ◽

Dependent Growth

SUMMARYDensity-dependent constraints on parasite growth, survival or reproduction are thought to be important in preventing the unchecked increase in parasite numbers within individual hosts or host populations. While it is important to know where, and with what severity, density dependence is acting within the parasite life-cycle, interpretation of data from natural infections is difficult. In this paper, we present a Monte Carlo simulation technique for examining such data for evidence of density dependence. We also describe how this technique may be used to distinguish among mechanisms hypothesized to generate density-dependent phenomena.

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