Fluctuations in the year classes of important food fishes

Hjort, Johan

doi:10.1093/icesjms/1.1.5

Cited by 355 publications

(188 citation statements)

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“…Our findings provide a new perspective on where and when this mortality occurs. Historically (40), fisheries biologists argued that mortality rates were highest early in the life history (when the fish were smallest), so this was the time period likely to determine the number of adult fish that survived. The median survival of the steelhead and sockeye populations estimated in this study was 16.5% (i.e., one in six juveniles surviving to exit from the Salish Sea), with population-specific marine travel times as long as 28 d depending on the distance traveled.…”

Section: Discussionmentioning

confidence: 99%

In situ measurement of coastal ocean movements and survival of juvenile Pacific salmon

Welch

Melnychuk

Payne

et al. 2011

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

111

120

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Many salmon populations in both the Pacific and Atlantic Oceans have experienced sharply decreasing returns and high ocean mortality in the past two decades, with some populations facing extirpation if current marine survival trends continue. Our inability to monitor the movements of marine fish or to directly measure their survival precludes experimental tests of theories concerning the factors regulating fish populations, and thus limits scientific advance in many aspects of fisheries management and conservation. Here we report a large-scale synthesis of survival and movement rates of free-ranging juvenile salmon across four species, 13 river watersheds, and 44 release groups of salmon smolts (>3,500 fish tagged in total) in rivers and coastal ocean waters, including an assessment of where mortality predominantly occurs during the juvenile migration. Of particular importance, our data indicate that, over the size range of smolts tagged, (i) smolt survival was not strongly related to size at release, (ii) tag burden did not appear to strongly reduce the survival of smaller animals, and (iii) for at least some populations, substantial mortality occurred much later in the migration and more distant from the river of origin than generally expected. Our findings thus have implications for determining where effort should be invested to improve the accuracy of salmon forecasting, to understand the mechanisms driving salmon declines, and to predict the impact of climate change on salmon stocks.

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Section: Discussionmentioning

confidence: 99%

In situ measurement of coastal ocean movements and survival of juvenile Pacific salmon

Welch

Melnychuk

Payne

et al. 2011

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

111

120

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“…Ottestad 1942Ottestad , 1979Ottestad , 1986Cushing & Dickson 1976;Mann & Lazier 1991;Laevastu 1993;Cushing 1995;Kjesbu et al 1996). Temporal £uctuations in the year class strength have been related to abiotic factors (such as changes in temperature, salinity, wind ¢eld, currents and food availability; see Hjort 1914Hjort , 1926May 1974;Koslow & Thompson 1987;Cury & Roy 1988;Ellersten et al 1989;Skreslet 1989;Dickson & Brander 1993;Cushing 1996), biotic factors (such as density-dependent survival due to competition and cannibalism; see Sundby et al 1989;Myers & Cadigan 1993) and human exploitation (see Cook et al 1997). Fromentin et al (1997) analysed the spatio-temporal patterns in the abundance of cod along the Norwegian Skagerrak coast and demonstrated signi¢cant cyclicity with a two to three year period, but also noticed a great deal of irregularity.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of coastal cod populations: intra- and intercohort density dependence and stochastic processes

Stenseth

Bjørnstadf

Falck

et al. 1999

Proc. R. Soc. Lond. B

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Skagerrak populations of Atlantic cod (Gadus morhua L.) have been surveyed at several ¢xed stations since 1919. These coastal populations consist of local stocks with a low age of maturity and a short life span. We investigated 60 time-series of 0-group juveniles (i.e. young of the year) sampled annually from 1945 to 1994. An age-structured model was developed which incorporates asymmetrical interactions between the juvenile cohorts (0-group and 1-group; i.e. one-year-old juveniles) and stochastic reproduction. The model was expressed in delay coordinates in order to estimate model parameters directly from the timeseries and thereby test the model predictions. The autocovariance structure of the time-series was consistent with the delay coordinates model superimposed upon a long-term trend. The model illustrates how both regulatory (density-dependent) and disruptive (stochastic) forces are crucial in shaping the dynamics of the coastal cod populations. The age-structured life cycle acts to resonance the stochasticity inherent in the recruitment process.

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“…In 3 benthic communities, the number of larvae settling and recruiting into the adult population may 4 determine not only changes through time, but also how species interact. Researchers have 5 appreciated the role of new recruits in population processes for a long time (e.g., Hjort, 1926;6 Hatton, 1938;Thorson, 1946;Ayers, 1956;Barnes, 1956;Loosanoff, 1964;Yoshioka, 1982). In 7 the 1980's there was increased attention on the role of larval input on rocky shore community 8 dynamics (Roughgarden et al, 1985), baptized "supply-side ecology" by Lewin, (Lewin, 1986;J.…”

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confidence: 99%

Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

Pineda

Porri

Starczak

et al. 2010

Journal of Experimental Marine Biology and Ecology

185

100

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Marine broadcast spawners have two-phase life cycles, with pelagic larvae and benthic adults. 2 Larval supply and settlement link these two phases and are crucial for the persistence of marine 3 populations. Mainly due to the complexity in sampling larval supply accurately, many 4 researchers use settlement as a proxy for larval supply. Larval supply is a constraining variable 5 for settlement because, without larval supply, there is no settlement. Larval supply and 6 settlement may not be well correlated, however, and settlement may not consistently estimate 7 larval supply. 8This paper explores the argument that larval supply (i.e., larval abundance near settlement sites) 9 may not relate linearly to settlement. We review the relationship between larval supply and 10 settlement, from estimates and biases in larval supply sampling, to non-behavioral and 11 behavioral components, including small-scale hydrodynamics, competency, gregarious behavior, 12 intensification of settlement, lunar periodicity, predation and cannibalism. Physical and structural 13 processes coupled with behavior, such as small-scale hydrodynamics and intensification of 14 settlement, sometimes result in under-or overestimation of larval supply, where it is predicted 15 from a linear relationship with settlement. Although settlement is a function of larval supply, 16 spatial and temporal processes interact with larval behavior to distort the relationship between 17 larval supply and settlement, and when these distortions act consistently in time and space, they 18 cause biased estimates of larval supply from settlement data. 19Most of the examples discussed here suggest that behavior is the main source of the decoupling 20 between larval supply and settlement because larval behavior affects the vertical distribution of 21 3 larvae, the response of larvae to hydrodynamics, intensification of settlement, gregariousness, 1 predation and cannibalism. Thus, larval behavior seems to limit broad generalizations on the 2 regulation of settlement by larval supply. Knowledge of the relationship is further hindered by 3 the lack of a well founded theoretical relationship between the two variables. 4The larval supply-settlement transition may have strong general consequences for population 5 connectivity, since larval supply is a result of larval transport, and settlement constrains 6 recruitment. Thus, measuring larval supply and settlement effectively allows more accurate 7 quantification and understanding of larval transport, recruitment and population connectivity. 8 9 4

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Fluctuations in the year classes of important food fishes

Cited by 355 publications

References 0 publications

In situ measurement of coastal ocean movements and survival of juvenile Pacific salmon

In situ measurement of coastal ocean movements and survival of juvenile Pacific salmon

Dynamics of coastal cod populations: intra- and intercohort density dependence and stochastic processes

Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

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