| This dissertation focuses on reef fish utilization of mangrove shorelines in the region of Biscayne and northeastern Florida Bays, Florida, U.S.A. Research was conducted and organized around the four-tiered "essential fish habitat" (EFH) framework defined by the United States National Marine Fisheries Service. A comprehensive review of over 100 empirical mangrove-fish field studies illustrated that these studies have been largely limited in their data treatments and spatial scope. To address these shortcomings, a spatially-expansive, seasonally-resolved fish survey was conducted among five geographically distinct mangrove shoreline types. Fishes were sampled using an underwater visual belt transect (30 x 2 m) method, supplemented by the measurement a suite of biotic and abiotic habitat variables. Sampling locations and effort were determined each season according to an iterative random-stratified survey design. During a 2-year period, fish abundance and size information were collected at 558 locations spanning >500 km of mangrove shoreline. The predominant reef fishes utilizing the mangrove shorelines examined were: Lutjanus griseus, L. apodus, Haemulon sciurus, H. parra, and Sphyraena barracuda . Habitat utilization by each species and size class was quantified in terms of their seasonal frequency of occurrence (presence/absence), concentration (the distribution of non-zero samples), density (both standard and delta-distribution mean estimators), and relative abundance among shorelines. Data were analyzed using a suite of parametric and non-parametric techniques to test the hypothesis that each mangrove shoreline type was utilized in proportion to its relative quantity. Results suggested that density patterns were driven primarily by patterns in frequency of occurrence and not concentration. With the exception of S. barracuda, the species examined exhibited selection among mangrove shorelines, whereby utilization was significantly greater than expected along the Florida Keys, and significantly less than expected along the Florida mainland. These patterns infer that reef fish utilization of mangrove shorelines was a function of habitat isolation (i.e., distance from oceanic sources) rather than habitat quantity. In addition, dramatic seasonal differences in distributions were observed for L. griseus. This species shifted from bays during the winter dry seasons to locations more proximal to oceanic sources during the summer wet seasons. (Abstract shortened by UMI.)... |
