Temporal variations in surf zone fish assemblages from False Bay, South Africa

Abstract

Temporal variations in surf zone fish assemblages and various physical factors at 11 sltes In False Bay, South Africa, were studled over 2 yr from July 1991 to June 1993. Changes in the abundance of fish in the surf and in the relative r a n k ~ n g of the more frequently occurring species were evldent between years and relative to an earlier study. Of the 9 environmental variables monitored, only water temperature and wind direction varied seasonally. Seasonal fluctuations In fish abundance and numbers of species captured were absent, except at 1 site, where numbers of species recorded v a r ~ e d seasonally. Physical factors responsible for these fluctuations varied in response to differences In the physical attributes of the different sites, but water temperature, wave height, wind speed and direction and macrophyte abundance were considered to be the most important. When data from all sites were combined, the overall numbers of flsh captured did not appear to vary seasonally. However, seasonal patterns were evident in the abundance of juvenile fish In the surf, and to a lesser extent in the species richness and total number of species captured. Abundance and species richness were highest from mid-summer up to the beginning of winter, which IS the penod during which most species recruit into the surf zone. We concluded that even when seasonal variations in physical variables such as water temperature are not great, spawning periods of surf zone fish are nevertheless timed to allow most resident and trdnsient O+ juveniles to optimise their use of this habitat K E Y WORDS: Surf zone fish Tcniporal var~ab~l i ty Environnlental influences . Seasonality Sandy beach South Africa