Management at a different scale: Marine ornamentals and local processes

In many parts of the world, marine ornamentals, fishes and invertebrates collected and sold in the aquarium trade, comprise an increasingly important fishery. Few management strategies have been devised for these fisheries, yet they may represent the most tractable systems: e.g., the benthic life stages are relatively site attached and easily sampled, and many species are amenable to experimental study. Here, a stochastic population model is developed with which to investigate the efficacy of exploitation strategies designed to manage a marine ornamental fishery. Extensive field studies of the tropical damselfish Dascyllus trimaculatus were used to define functions and estimate associated parameters that govern the dynamics of the unexploited population. Sources of uncertainty in the predictions of the model were then evaluated and the responses to different exploitation-control rules simulated. Effects resulting from uncertainty due to variable larval settlement were comparable in magnitude to effects of uncertainty in parameter estimates. In addition, despite resident-facilitated settlement, yields were not a unimodal function of catch rate. Instead, yield typically increased with catch rate. The absence of a domeshaped yield curve appeared to result from an interaction between facilitated settlement and subsequent density dependence.