DAILY VARIABILITY IN ABUNDANCE OF LARVAL FISHES INSIDE BEAUFORT INLET

We measured the daily abundance of larvae of eight species of ocean-sp awned, estuarine-dependent fishes to determine the effect of sampling frequency on the mean and variance estimates during larval immigration past a permanent sampling station inside Beaufort Inlet, North Caroli na, mid-November 1991 to mid-april 1992. Species of interest were Brev oortia tyrannus, Lagodon rhomboides, Leiostomus xanthurus, Micropogoni as undulatus, Mugil cephalus, Paralichthys albigutta, P. dentatus, and P. lethostigma. Our data suggest that sampling at intervals >7 days c an lead to excessive variance in abundance estimates. For all species, abundance varied as much as an order of magnitude from night to night . Proportional residuals from polynomial models of the seasonal recrui tment pattern for a given species were used to assess the potential in fluence of nine environmental variables on daily densities. Twenty-sev en of 72 correlations of proportional residuals with environmental var iables were significant (P<0.05). Proportional residuals were positive ly correlated with time after dusk for six of eight species and were n egatively correlated with turbidity for five of eight species. However , interpretation of correlations must be done cautiously because a spe cies' recruitment pattern may coincide with normal seasonal change in one or more environmental variables. Variability in transport of larva e, from offshore to near the inlet and then through the inlet to the s tation, probably influences species abundance at the sampling station more than locally acting environmental variables. Daily collections of B. tyrannus larvae provided otoliths (n=1,341) showing that a large n umber of younger larvae, averaging 55 days posthatch, arrived at the s tation in mid-March on the date of maximum observed daily density (160 larvae per 100 m(3)).