Seagrass habitat utilization by fishes in Christmas Bay, Texas

Abstract

Fishes in Christmas Bay, TX were collected during April 1994 through March 1995 to: 1) assess temporal variability in their density, biomass, and diversity; 2) define the relationship between variability in fish population parameters and hydrographic conditions; and 3) evaluate effect of seagrass biomass on population parameters. ,Cumulative sampling effort yielded 2139 fishes comprised of 29 species in 15 families. Overall density of 17.8 fish/m2 in Christmas Bay was higher than those reported from several Atlantic and Gulf of Mexico seagrass habitats. Individual sample plots yielded between 0 and 8 species while monthly mean species/m2 varied from 2.6 (July) to 5.4 (October), with fall yielding peak seasonal in-plot averages. A total of 5 to 13 species was collected per month while seasonal averages ranged from 6.3 (winter) to 10.3 (fall). Individual sample plots yielded between 0 and 108 fish/m2; monthly mean catch ranged from 3.6 (July) to 31.5 (March) fish/m2. Seasonal means ranged from 73.7 (summer) to 243.3 (spring) fish/month with between 67 and 373 fish collected monthly. Summer fish density was low while species density was high (9.7 species/m2). Distinct seasonal trends in biomass and species diversity were not evident. Water temperature and salinity exerted significant effects on fishes in Christmas Bay, with lowest catches concurrent with highest temperature (> 30 C) and salinity (> 25 ppt) readings during summer. Seagrass biomass, in contrast to hydrographical conditions, exhibited no significant effect on fish population parameters. Darter goby (Gobionellus boleosoma), code goby (Gobiosoma robustum), and pinfish (Lagodon rhomboides) represented 7 1 % of the total catch and appeared to exhibit sequential usage of seagrass habitat. Other fishes, including certain life history stages of commercially and recreationally important species, used seagrass habitat for limited durations. Although any one month may have been characterized by a sparse ichthyofauna, Christmas Bay seagrass beds annually provided vital nursery habitat to a diverse fish assemblage.