The variability among populations of coho salmon in the maximum reproductive rate and depensation

摘要

Estimating parameters for population-dynamics models is a critical component in assessing extinction probabilities of populations. For many individual populations, key parameters will be poorly defined, and meta-analysis would provide a basis for estimating the parameters. Here, we introduce meta-analytical techniques to estimate the maximum reproductive rate, carrying capacity, and depensation in coho salmon on the west coast of North America. We used both nonlinear mixed-effects models and Bayesian techniques to estimate several population-dynamics models, including the Beverton-Holt and hockey-stick models, for 14 spawner-recruitment time series. The Beverton-Holt and hockey-stick mixed-effects models yielded equivalent fits to the data but gave very different estimates of alpha (the maximum rate at which female spawners can produce female smolts at low population sizes). The mean alpha for the Beverton-Holt mixed-effect model was 71.5 (1 SE = 1.2) female smolts per spawning female, whereas the hockey-stick estimate was 53.0 (I SE = 1.14). We found little evidence for a general effect of depensation in coho salmon, unless fewer than one female per kilometer of river returned to spawn. [References: 36]