Ecology and life history of the clown goby inhabiting the upper Banana River, Cape Canaveral, Florida

Abstract

Monthly collections of clown goby,Microgobius gulosus, were made from March 1984 through February 1985 at two stations located at the head of the Banana River, Brevard County, Florida, as part of the long-term environmental monitoring program at the John F. Kennedy Space Center. A total of 18921 fishes comprising eight families and 12 genera was collected.M. gulosus represented 6.4% of the total catch. Populations ofM. gulosus exhibited aggregation behavior, which varied in intensity depending on densities of individuals m−2 and habitat characteristics. Capture data were best described by the negative binomial distribution. Mean estimates of individuals m−2 ranged from 0.0 to a high of 22.1 during periods of peak recruitment. The total length-weight regression for all individuals measured was log10 weight = −4.65 + 2.72 log10 length.M. gulosus obtained a size of 35–40 mm TL the first year and 50–60 mm TL the second year. Total lengths of all specimens ranged from 11 to 71 mm. Young of the year first appeared in May with smallest individuals collected in June and July. A protracted spawning period was observed. Stomach and gut analyses revealed that crustaceans and annelids combined represented 65% and 66% of the total diet forM. gulosus from stations 1 (open) and 2 (impounded), respectively. However, differences in proportions of the two groups were present between the two stations. Crustaceans represented 47.1% of the diet for gobies collected at station 1 and annelids 40.8% for specimens collected from station 2. Fecundity was low with the mean number of ova being 305 ± 77.5 for females between 35 and 49 mm TL. Estimated mortality rate was approximately 95% annually.