Abstract
The evolution of life histories over contemporary time scales will almost certainly affect population demography. One important pathway for such eco-evolutionary interactions is the density-dependent regulation of population dynamics. Here, we investigate how fisheries-induced evolution (FIE) might alter density-dependent population–productivity relationships. To this end, we simulate the eco-evolutionary dynamics of an Atlantic cod (Gadus morhua) population under fishing, followed by a period of recovery in the absence of fishing. FIE is associated with increases in juvenile production, the ratio of juveniles to mature population biomass, and the ratio of the mature population biomass relative to the total population biomass. In contrast, net reproductive rate (R0) and per capita population growth rate (r) decline concomitantly with evolution. Our findings suggest that FIE can substantially modify the fundamental population–productivity relationships that underlie density-dependent population regulation and that form the primary population-dynamical basis for fisheries stock-assessment projections. From a conservation and fisheries-rebuilding perspective, we find that FIE reduces R0 and r, the two fundamental correlates of population recovery ability and inversely extinction probability.
Highlights
Life histories can change over contemporary time scales owing to plastic and evolutionary responses to alterations in interspecific interactions (e.g., Reznick et al 1997), environmental shifts (Meril€a and Hendry 2014), as well as human-induced disturbances and anthropogenic selection generated by factors such as harvesting (Hendry et al 2008; Darimont et al 2009)
Inspired by the contrasting findings and arguments surrounding the impacts of fisheries-induced evolution (FIE) on population growth and recovery ability, we investigate how relationships between spawning stock biomass (SSB) and alternative metrics of population productivity might be altered by FIE
Our particular emphasis was on SSB, total population biomass, recruitment and, for each cohort, R0 and r; the latter parameter was estimated through r = log(R0)/T, where T is the generation time approximated by the average age of the spawning population during the lifetime of the cohort
Summary
Life histories can change over contemporary time scales owing to plastic and evolutionary responses to alterations in interspecific interactions (e.g., Reznick et al 1997), environmental shifts (Meril€a and Hendry 2014), as well as human-induced disturbances and anthropogenic selection generated by factors such as harvesting (Hendry et al 2008; Darimont et al 2009). Changes in key fitness-related lifehistory traits such as age and size at maturity, growth rate and adult body size will inevitably feedback to population dynamics, as they will affect rates of natural mortality and reproduction (Hutchings 2005, Saccheri and Hanski 2006; Kinnison and Hairston 2007). In Soay sheep (Ovis aries), it has been shown that a substantial proportion of variation in population growth can be attributed to fluctuations in life-history traits (Coulson et al 2006; Pelletier et al 2007). Density dependence is one of the key mechanisms responsible for regulating population dynamics. From the perspectives of persistence and recovery of declined populations, density dependence offers a pathway through which life-history change can effectively modify population dynamics
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