Abstract
Senescence is often described as an age‐dependent increase in natural mortality (known as actuarial senescence) and an age‐dependent decrease in fecundity (known as reproductive senescence), and its role in nature is still poorly understood. Based on empirical estimates of reproductive and actuarial senescence, we used mathematical simulations to explore how senescence affects the population dynamics of Coregonus albula, a small, schooling salmonid fish. Using an empirically based eco‐evolutionary model, we investigated how the presence or absence of senescence affects the eco‐evolutionary dynamics of a fish population during pristine, intensive harvest, and recovery phases. Our simulation results showed that the presence or absence of senescence affected how the population responded to the selection regime. At an individual level, gillnetting caused a larger decline in asymptotic length when senescence was present, compared to the nonsenescent population, and the opposite occurred when fishing was done by trawling. This change was accompanied by evolution toward younger age at maturity. At the population level, the change in biomass and number of fish in response to different fishery size‐selection patterns depended on the presence or absence of senescence. Since most life‐history and fisheries models ignore senescence, they may be over‐estimating reproductive capacity and under‐estimating natural mortality. Our results highlight the need to understand the combined effects of life‐history characters such as senescence and fisheries selection regime to ensure the successful management of our natural resources.
Highlights
Senescence is considered a fundamentally fitness decreasing trait, and its presence and role in natural populations remains an unsolved problem in biology (Monaghan et al, 2008; Nussey et al, 2013; Selman et al, 2012)
Senescence is often described as age-dependent increase in natural mortality and age-dependent decrease in reproductive function
While much research effort has been put into understanding the links between life-history traits such as body size, growth rate, size and age at maturity, and population dynamics (Ahti et al, 2020), the role of reproductive and actuarial senescence in population dynamics and population recovery remains poorly understood
Summary
Senescence is considered a fundamentally fitness decreasing trait, and its presence and role in natural populations remains an unsolved problem in biology (Monaghan et al, 2008; Nussey et al, 2013; Selman et al, 2012). Given that most fishes express indeterminate growth and high longevity (Carey & Judge, 2000), it has been suggested that fish experience delayed senescence relative to birds and mammals, facilitated in part by the capacity for increasing fecundity with age (Reznick et al, 2002). In fisheries and life-history models, the natural mortality of fish is often assumed to be independent of the age or size of the fish (Gislason et al, 2010). Given that senescence influences the reproductive outcome and natural mortality rate, it would have major consequences to our understanding of fish life-histories and population dynamics. While much research effort has been put into understanding the links between life-history traits such as body size, growth rate, size and age at maturity, and population dynamics (Ahti et al, 2020), the role of reproductive and actuarial senescence in population dynamics and population recovery remains poorly understood. While the empirical data are from Lake Puulavesi in Central Finland, the results can be generalized to any fish with similar life-history properties
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