Abundance, diversity and seasonality of fishes in Colorado Lagoon, Alamitos Bay, California

Abstract

A total of 152 169 fishes from 23 species were caught in monthly beach seine hauls during 1973 in Colorado Lagoon, the small, Y-shaped, upper arm of Alamitos Bay in southern California. Four species, northern anchovy, topsmelt, slough anchovy and shiner surfperch, comprised 99% of the catch. Numbers of species and individuals were highest during the summer (May–September) and both were highly correlated with lagoon temperature which ranged from 12·8–25·0 °C. Juveniles of northern anchovy were extremely abundant in August and September. Seven species were collected in only one month and six of these only in one of the warmer months (June–August). Five species, topsmelt, shiner surfperch, California killifish, staghorn sculpin and slough anchovy, occurred in wide size ranges and during most or all of the year and were considered to be residents. Three diversity indices (Shannon-Wiener, evenness and richness) reflected the changes that occur in numbers of species and individuals during the year.