Marine species are being listed under the Endangered Species Act with increasing frequency and this trend can be expected to continue (Armsworth et al. 2006). The taxonomie focus of marine listings is also diversifying (Armsworth et al. 2006). Despite long-held assumptions that life his tory characteristics of so me marine species render them less vulnerable to extinction, anthropogenie impacts to marine ecosystems have imperiled a growing number of species. In this chapter, we review both the threats endangering marine species and some of the strategies being employed to mitigate those threats.
Listing decisions reveal the relative importance of different threats across taxonomie groups and ecosystems (Kappel 2005). Although many threats facing marine organisms are not unique to the seas, their relative importance differs from those faced by terrestrial species. For listed marine, estuarine, and diadromous species the most commonly identified threat is overexploitation (including targeted harvest, bycatch, and indirect effects), which threatens 81 percent of marine, estuarine, and diadromous listed species (Kappel 2005). Habitat degradation ranks second and is listed as a threat to 76 percent of vulnerable marine species, followed by pollution at 61 percent (Kappel 2005). In contrast, Wilcove et al. (2000) found that habitat impacts topped the list of threats to terrestrial and freshwater species, while invasive species and pollution ranked second and third. As for terrestrial species, habitat degradation is the most frequent threat to many estuarine and diadromous species (Kappel 2005).
Two other efforts to list marine species at risk of extinction, the IUCN Red List ofThreatened Species (IUCN 2003) and the American Fisheries Society list of fish stocks at risk from extinction (Musick et al. 2000), provide interesting comparisons to the set of species listed as endangered, threatened, or as species of concern under the Endangered Species Act (see Armsworth et al. 2006; NMFS 2002d). Where they intersect in their taxonomic and spatial coverage, the three lists generally agree on the species and subspecies that are most vulnerable. However, each list was created for a distinct purpose and each used different criteria to assess extinction risk. Disparities between lists may therefore reflect gaps in coverage of candidate species, differences in assessment criteria, or different assessment outcomes for particular species
