Commercial sponge fishery impacts on the population dynamics of sponges in the Florida Keys, FL (USA)

For more than 100 years, the Florida Keys (USA) have supported a commercial sponge fishery but there is little information about the small artisanal fishery that now exists, which is nonetheless controversial because of concerns about the ecological consequences of sponge harvest. We estimated the harvest of commercial sponges and bycatch (sublegal or non-commercial species), as well as the mortality, growth, and reproduction of commercial sponge species. In heavily fished areas, ∼33% of the legal-sized sponges, ∼3% of the sublegal sponges, and virtually none of the non-commercial species were harvested. Approximately 40% of our study area was never fished during the four month long peak in the fishing season. Self-reporting of harvest by fishers who participated in our study closely matched our fishery-independent estimates. Natural mortality of sublegal-sized sponges was ∼7% of the population/yr, with little difference among species. Discarded “roller” sponges grew at rates comparable to attached sponges and many reattached to the seafloor within 18 mos, although rates of reattachment varied among species. Growth also differed among species and sampling periods (mean = 3 cm dia/yr), and reproductive effort was positively related to sponge size in some species, but not others. Given the careful targeting of commercial sponge species and sizes by fishers and the small fraction of the sponge community that is commercially valuable, harvest is estimated to have minimal impact on the diverse assemblage of sponges in the region.