Habitat fragmentation decreases fish secondary production in Bahamian tidal creeks

We provide an example of how fish secondary production can be used to assess effects of anthropogenic stress on ecosystem function. Specifically, we demonstrate that fragmentation of hydrologic connectivity in small tidal creeks on Andros Island, Bahamas, decreases secondary production by as much as an order of magnitude for five economically important fish species: gray snapper (Lutjanus griseus Linnaeus, 1758), schoolmaster snapper (Lutjanus apodus (Walbaum, 1792)), cubera snapper (Lutjanus apodus cyanopterus (Cuvier, 1828)), blue striped grunt (Haemulon sciurus (Shaw, 1803)), and sailor's choice (Haemulon parra (desmarest, 1823)). We conducted more than 800 individual quadrat surveys, in eight creeks that varied in degree of habitat fragmentation, to estimate total biomass for the focal species. Biomass values were multiplied by in situ or published growth rates to calculate annual secondary production. Differences in estimates of secondary production among creeks were attributable to fewer species, fewer individuals, and smaller individuals in fragmented creeks. Secondary production estimates are a useful way to measure responses of ecosystem function to anthropogenic stress because they are a composite value that incorporates many important aspects of ecosystem function.