Factors Influencing the Collection Efficiency of Estuarine Fishes

Abstract

We evaluated the efficiency with which estuarine fishes were collected in a haul seine on 11 dates from 1984 to 1988. Comparisons between the catch in the first haul and the total population in a tidal creek pool demonstrated that species richness, species rank, and size distributions of dominant taxa were represented well in the first haul. However, abundance was not reliably estimated by a single collection. Collection efficiency for the six most common taxa ranged from 7 to 91%. A two-way analysis of variance, used to examine the efficiency of the first haul, indicated significant main effects for species and season. In general, efficiencies were significantly higher in summer and winter than in spring and autumn. Multiple-regression analyses, used to predict the efficiency of the first haul as a function of water temperature, salinity, total numbers, and modal length, only yielded significant relationships for some species. Collection efficiencies of striped mullet Mugil cephalus were related to water temperature and total number of striped mullet present, whereas water temperature and modal length were good predictors for the collection efficiency of spot Leiostomus xanthurus. Seasonal variations in efficiency among species and size-classes were consistent with our observations offish swimming behavior and avoidance responses. The application of rotenone after 15 consecutive seine hauls provided further evidence that differences among species and size-classes within species must be taken into account when seine collection data are interpreted. Because the degree to which a standard sampling effort underestimates estuarine fish abundance varies so greatly in time and space, we recommend that, in future studies, collection efficiency should be measured at least once each season.