Collapse and recovery of marine fishes

Hutchings, Jeffrey A.

doi:10.1038/35022565

Cited by 720 publications

(518 citation statements)

References 16 publications

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“…It is thus highly probable that commercial harvest, which may deplete 45-99% of the reproductive biomass (26), may cause rapid evolution in commercial fish stocks. Temporal consistency of harvest practices (e.g., systematic removal of the largest individuals) likely magnifies the evolutionary impacts of exploitation.…”

Section: Discussionmentioning

confidence: 99%

Trait changes in a harvested population are driven by a dynamic tug-of-war between natural and harvest selection

Édeline

Carlson

Stige

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

162

203

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Selective harvest of large individuals should alter natural adaptive landscapes and drive evolution toward reduced somatic growth and increased reproductive investment. However, few studies have simultaneously considered the relative importance of artificial and natural selection in driving trait changes in wild populations. Using 50 years of individual-based data on Windermere pike (Esox lucius), we show that trait changes tracked the adaptive peak, which moved in the direction imposed by the dominating selective force. Individual lifetime somatic growth decreased at the start of the time series because harvest selection was strong and natural selection was too weak to override the strength of harvest selection. However, natural selection favoring fast somatic growth strengthened across the time series in parallel with the increase in pike abundance and, presumably, cannibalism. Harvest selection was overridden by natural selection when the fishing effort dwindled, triggering a rapid increase in pike somatic growth. The two selective forces appear to have acted in concert during only one short period of prey collapse that favored slow-growing pike. Moreover, increased somatic growth occurred concurrently with a reduction in reproductive investment in young and small female pike, indicating a tradeoff between growth and reproduction. The age-specific amplitude of this change paralleled the age-specific strength of harvest pressure, suggesting that reduced investment was also a response to increased life expectancy. This is the first study to demonstrate that a consideration of both natural selection and artificial selection is needed to fully explain time-varying trait dynamics in harvested populations.adaptive landscapes ͉ conservation ͉ contemporary evolution ͉ fisheries ͉ top predators

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Section: Discussionmentioning

confidence: 99%

Trait changes in a harvested population are driven by a dynamic tug-of-war between natural and harvest selection

Édeline

Carlson

Stige

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

162

203

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“…Such depensatory growth (also known as Allee effect, positive or inverse densitydependence) will prevent rebound of the population after a crash. Population-level data do not unambiguously support or refute the presence of depensatory mechanisms in natural systems (6)(7)(8)(9). Estimates of spawner abundance and the number of surviving progeny for 128 fish stocks indicated only 3 stocks with significant depensation (7).…”

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confidence: 99%

Size-dependent life-history traits promote catastrophic collapses of top predators

Roos

Persson

2002

Proc. Natl. Acad. Sci. U.S.A.

243

237

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Catastrophic population collapses such as observed in many exploited fish populations have been argued to result from depensatory growth mechanisms (i.e., reduced reproductive success at low population densities, also known as Allee effect). Empirical support for depensation from population-level data is, however, hard to obtain and inconclusive. Using a size-structured, individualbased model we show that catastrophic population collapses may nonetheless be an intrinsic property of many communities, because of two general aspects of individual life history: size-and fooddependent individual growth and individual mortality decreasing with body size. Positive density dependence, characteristic for depensatory growth mechanisms and catastrophic behavior, results as a direct and robust consequence of the interplay between these individual life-history traits, which are commonly found in many species.R ecent studies on lakes, coral reefs, oceans, forests, and arid lands document drastic changes in the composition of the biological community and the functioning of the ecosystem (1, 2). One view is that these abrupt changes represent catastrophic shifts between contrasting states of the system that are both stable equilibria (1, 2). The collapse of several exploited fish stocks, which fail to recover after over-fishing and a closure of fisheries, could be interpreted as such a shift, if the community state without the exploited fish species represents a stable equilibrium (2-4). If the interpretation in terms of alternative stable equilibria is correct, our view of how these ecological systems function and how to manage them is heavily affected (5). Models of biological communities show that the extinct state may be stable if the exploited species exhibits a reduced population growth capacity at low densities (2, 6). Such depensatory growth (also known as Allee effect, positive or inverse densitydependence) will prevent rebound of the population after a crash. Population-level data do not unambiguously support or refute the presence of depensatory mechanisms in natural systems (6-9). Estimates of spawner abundance and the number of surviving progeny for 128 fish stocks indicated only 3 stocks with significant depensation (7). More advanced statistical testing of these stock-recruitment relations showed that the probability of depensation was nonetheless significant (8). Also, 15 years after a collapse of the population most of the exploited fish stocks have yet to recover. Assuming that management strategies have been implemented to reduce fishing mortality after a collapse, such a lack of recovery indicates a reduced capacity to rebound from low densities (9).Community models incorporating depensatory mechanisms do so as an assumption (7), which is justified by verbal arguments. For example, it is argued that depensatory growth may result from adult individuals negatively affecting competitors of their own juveniles (6), from reduced cooperative behavior at low densities (10), or predator swamping at high density (11)...

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“…Coastal marine fisheries and ecosystems are in global decline due to the increasing intensity and diversity of stresses in coastal waters (Hutchings 2000;Jackson et al 2001). Marine protected areas (MPAs) have been advocated as one measure to facilitate continued ecosystem viability (Sale et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Local retention, dispersal and fluctuating connectivity among populations of a coral reef fish

et al. 2011

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The persistence and resilience of marine populations in the face of disturbances is directly affected by connectivity among populations. Thus, understanding the magnitude and pattern of connections among populations and the temporal variation in these patterns is critical for the effective management and conservation of marine species. Despite recent advances in our understanding of marine connectivity, few empirical studies have directly measured the magnitude or pattern of connections among populations of marine fishes, and none have explicitly investigated temporal variation in demographic connectivity. We use genetic assignment tests to track the dispersal of 456 individual larval fishes to quantify the extent of connectivity, dispersal, self-recruitment and local retention within and among seven populations of a coral reef fish (Stegastes partitus) over a three-year period. We found that some larvae do disperse long distances (*200 km); however, self-recruitment was a regular phenomenon. Importantly, we found that dispersal distances, self-recruitment, local retention and the pattern of connectivity varied significantly among years. Our data highlight the unpredictable nature of connectivity, and underscore the need for more, temporally replicated, empirical measures of connectivity to inform management decisions.

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Collapse and recovery of marine fishes

Cited by 720 publications

References 16 publications

Trait changes in a harvested population are driven by a dynamic tug-of-war between natural and harvest selection

Trait changes in a harvested population are driven by a dynamic tug-of-war between natural and harvest selection

Size-dependent life-history traits promote catastrophic collapses of top predators

Local retention, dispersal and fluctuating connectivity among populations of a coral reef fish

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