A Generic Sized-Based Model of the Effect of Habitat Loss on Freshwater Fishes

Habitat loss has been identified as the greatest threat in freshwater environments. Endangered freshwater fishes tend to be smaller-bodied with habitat-related threats, whereas endangered marine fishes are predominantly larger-bodied and threatened by exploitation. Many attributes of fishes are related to body size. Larger fishes tend to grow slower, mature later, be more fecund and live longer. Here we present a generic size-based population matrix model, parameterized using published length-based allometries and relationships among life history traits. Our aim was to examine the sensitivity of fish populations and fisheries productivity to habitat versus exploitation perturbations. Our model predicts that small-bodied fishes (shorter maximum body length) are indeed more sensitive to the loss of habitat. Moreover, distinct stage-based trends show an increased sensitivity of smaller fishes to both habitat loss and changes to vital rates during pre-adult stages. This indicates that the pre-adult period represents a critical stage for the continued production of smaller-bodied fishes and an increased importance to the protection of habitat utilized by young-of-the-year and juvenile fish.