Fitness consequences of early life conditions and maternal size effects in a freshwater top predator

Vindenes, Yngvild; Langangen, Øystein; Winfield, Ian J.; Vøllestad, Leif Asbjørn

doi:10.1111/1365-2656.12489

Cited by 16 publications

(18 citation statements)

References 63 publications

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“…However, under such conditions size‐dependent maternal contributions to egg quality and size‐dependent fecundity effects are confounded, which does not allow to unambiguously identify evidence for size‐dependent offspring quality effects. It has also been shown in field studies (Pagel et al, ) as well as models (Vindenes, Langangen, Winfield, & Vøllestad, ) that stochastic environmental conditions (e.g. temperature fluctuations during spawning and early larval development) have stronger effects on offspring fitness than size‐dependent quality effects.…”

Section: Discussionmentioning

confidence: 87%

Saving large fish through harvest slots outperforms the classical minimum‐length limit when the aim is to achieve multiple harvest and catch‐related fisheries objectives

et al. 2020

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We address the problem of optimal size-selective exploitation in an age-structured fish population model by systematically examining how density and size dependency in growth, mortality and fecundity affect optimal harvesting patterns when judged against a set of fisheries objectives. The study offers five key insights. First, while minimum-length limits often maximize the biomass yield, exploitation using harvest slots (i.e. regulations that protect both immature and very large individuals) can generate within 95% of maximum yield; harvest slots also generally maximize the number of fish that are harvested. Second, density dependence in growth and sizedependent mortality predict more liberal optimal size limits than those derived under assumptions of no density and size dependence. Third, strong density dependence in growth maximizes the catch of trophy fish only when modest harvest is introduced; the same holds for numbers harvested, when the stock-recruitment function follows the Ricker type. Fourth, the inclusion of size-dependent maternal effects on fecundity or egg viability has only limited effects on optimal size limits, unless the increase in fecundity with mass ("hyperallometry") is very large. However, large hyperallometry in fecundity shifts the optimal size limit for biomass yield from the traditional minimum-length limit to a harvest slot. Fifth, harvest slots generally provide the best compromises among multiple objectives. We conclude that harvest slots, or more generally dome-shaped selectivity to harvest, can outperform the standard minimum-length selectivity. The exact configuration of optimal size limits crucially depends on objectives, local fishing pressure, the stock-recruitment function, and the density and size dependency of growth, mortality and fecundity.

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Section: Discussionmentioning

confidence: 87%

Saving large fish through harvest slots outperforms the classical minimum‐length limit when the aim is to achieve multiple harvest and catch‐related fisheries objectives

et al. 2020

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“…This effect is trivial compared with other influences on recruitment (44), and suggests that the spatial extent of the eggs per se is on average of little importance for year-class strength. Similarly, population modeling suggests that maternal size effects on recruit production likely have a much smaller impact on population growth than environmental conditions during early life in long-lived and highly fecund (45) and harvested (46) fish stocks such as the Barents Sea cod.…”

Section: Q3: How Does the Distributional Extent Of Eggs Affect Survivmentioning

confidence: 99%

Effect of a fish stock's demographic structure on offspring survival and sensitivity to climate

Stige

Langangen

Bogstad

et al. 2017

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

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Commercial fishing generally removes large and old individuals from fish stocks, reducing mean age and age diversity among spawners. It is feared that these demographic changes lead to lower and more variable recruitment to the stocks. A key proposed pathway is that juvenation and reduced size distribution causes reduced ranges in spawning period, spawning location, and egg buoyancy; this is proposed to lead to reduced spatial distribution of fish eggs and larvae, more homogeneous ambient environmental conditions within each year-class, and reduced buffering against negative environmental influences. However, few, if any, studies have confirmed a causal link from spawning stock demographic structure through egg and larval distribution to year class strength at recruitment. We here show that high mean age and size in the spawning stock of Barents Sea cod (Gadus morhua) is positively associated with high abundance and wide spatiotemporal distribution of cod eggs. We find, however, no support for the hypothesis that a wide egg distribution leads to higher recruitment or a weaker recruitment-temperature correlation. These results are based on statistical analyses of a spatially resolved data set on cod eggs covering a period (1959−1993) with large changes in biomass and demographic structure of spawners. The analyses also account for significant effects of spawning stock biomass and a liver condition index on egg abundance and distribution. Our results suggest that the buffering effect of a geographically wide distribution of eggs and larvae on fish recruitment may be insignificant compared with other impacts.fisheries | age and size truncation | population dynamics | climate effects | Gadus morhua M any exploited fish stocks have shown large changes in their demographic structure over the past decades, toward a reduced age range of the spawners with fewer old and large fish (1-4). It is feared that these changes impair the reproductive potential of the stocks and make them more susceptible to effects of climate variability and change; hence, a goal of the common fisheries policy of the European Union is to reverse these changes to obtain "a population age and size distribution that is indicative of a healthy stock" (5). In some harvested stocks, age and size truncation has indeed been associated with lower recruitment (i.e., population renewal, often measured as the abundance of the youngest year-class captured in the fisheries) per biomass of spawners (6-8), larger interannual variability in recruitment (9), and higher sensitivity of recruitment to environmental fluctuations (10, 11). In other stocks, however, no such links between age or size structure and recruitment have been found (9, 12, 13). There is therefore disagreement whether the value of maintaining a wide age and size distribution in managed fisheries is overemphasized (14) or underappreciated (15).A causal basis for lower recruitment in age-truncated stocks is supported by field and experimental studies on Atlantic cod (Gadus morhua), a broadcast mu...

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“…Population growth rate is a reasonable measure of fitness for populations with weak density regulation, which seems to be the case for the adult pike population (>age 3) in Windermere. The pike population has fluctuated but steadily increased for decades, indicating that it has not yet reached a carrying capacity where density‐dependent factors would impair further population growth (Langangen et al, ; Vindenes, Langangen, Winfield, & Vøllestad, ). Density dependence is likely more important in the earlier life stages (Skov & Nilsson, ).…”

Section: Discussionmentioning

confidence: 99%

“…The pike population has fluctuated but steadily increased for decades, indicating that it has not yet reached a carrying capacity where density-dependent factors would impair further population growth (Langangen et al, 2011;Vindenes, Langangen, Winfield, & Vøllestad, 2016). Density dependence is likely more important in the earlier life stages (Skov & Nilsson, 2018).…”

Section: Re Sultsmentioning

confidence: 99%

Effects of size‐ and sex‐selective harvesting: An integral projection model approach

Stubberud

Vindenes

Vøllestad

et al. 2019

Ecology and Evolution

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Harvesting is often size‐selective, and in species with sexual size dimorphism, it may also be sex‐selective. A powerful approach to investigate potential consequences of size‐ and/or sex‐selective harvesting is to simulate it in a demographic population model. We developed a population‐based integral projection model for a size‐ and sex‐structured species, the commonly exploited pike (Esox lucius). The model allows reproductive success to be proportional to body size and potentially limited by both sexes. We ran all harvest simulations with both lower size limits and slot limits, and to quantify the effects of selective harvesting, we calculated sex ratios and the long‐term population growth rate (λ). In addition, we quantified to what degree purely size‐selective harvesting was sex‐selective, and determined when λ shifted from being female to male limited under size‐ and sex‐selective harvesting. We found that purely size‐selective harvest can be sex‐selective, and that it depends on the harvest limits and the size distributions of the sexes. For the size‐ and sex‐selective harvest simulations, λ increased with harvest intensity up to a threshold as females limited reproduction. Beyond this threshold, males became the limiting sex, and λ decreased as more males were harvested. The peak in λ, and the corresponding sex ratio in harvest, varied with both the selectivity and the intensity of the harvest simulation. Our model represents a useful extension of size‐structured population models as it includes both sexes, relaxes the assumption of female dominance, and accounts for size‐dependent fecundity. The consequences of selective harvesting presented here are especially relevant for size‐ and sex‐structured exploited species, such as commercial fisheries. Thus, our model provides a useful contribution toward the development of more sustainable harvesting regimes.

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Fitness consequences of early life conditions and maternal size effects in a freshwater top predator

Cited by 16 publications

References 63 publications

Saving large fish through harvest slots outperforms the classical minimum‐length limit when the aim is to achieve multiple harvest and catch‐related fisheries objectives

Saving large fish through harvest slots outperforms the classical minimum‐length limit when the aim is to achieve multiple harvest and catch‐related fisheries objectives

Effect of a fish stock's demographic structure on offspring survival and sensitivity to climate

Effects of size‐ and sex‐selective harvesting: An integral projection model approach

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