Assessing essential fish habitat and connectivity using otolith chemistry and growth of temperate and tropical fish.

摘要

Many shallow water habitats are vulnerable to loss or deterioration from a variety of processes, including erosion, pollution, and urbanization. Conservation of these 'nursery' habitats protects an important source of young individuals to offshore adult fish populations. The first part of this dissertation investigates whether young-of-the year (YOY) tautog Tautoga onitis, French grunt Haemulon flavolineatum, and schoolmaster Lutjanus apodus from different nursery habitats can be distinguished by chemical signatures in their otoliths. Concentrations of ten elements, as well as stable oxygen (18O) and carbon (13C) isotopes, were determined in otoliths. Chemical signatures differed significantly among fish from different nurseries (MANOVA p0.001) within each of the two years, although significant interannual differences were observed within nurseries.;Classification success of tautog by their otolith signatures from five nursery areas in Rhode Island ranged from 85-92% in each of the two years, whereas that for nurseries among states (RI, VA, CT, NJ) ranged from 92-96% in each of the two years. Classification success of French grunt and schoolmaster from nursery sites within St. Croix, U.S. Virgin Islands, for 2006 and 2007 ranged from 87-92% and from 76-77%, respectively; whereas in Puerto Rico, it ranged from 80-84% and 84-87%, respectively. When stations were combined among mangrove and seagrass habitats, classification success in Puerto Rico for French grunt ranged from 84-91% and for schoolmaster from 94-99%, whereas in St. Croix, it ranged from 95-96% for French grunt and 86-89% for schoolmaster.;The relative quality of habitats for these species was evaluated by comparing post-settlement growth rates using otolith microstructure (increment widths) as a basis for back-calculation of fish growth. For all species, significant differences in back-calculated growth rates were observed within stations (ANOVA, p0.001) between years, as well as among stations within each year. For both tropical species, average daily growth rates were significantly higher (ANOVA, p0.001) in fish collected from mangrove than seagrass habitats in both St. Croix and Puerto Rico during the two years, indicating that mangroves support faster growth rates than seagrass habitats during the post-settlement period.