Spot Pattern of Girella nigricans, the California Opaleye: Variation among Cohorts and Climate Periods

Abstract

Girella nigricans (California opaleye) exhibits variability in dorsolateral spot pattern. Southern California opaleye usually have one pair of white spots; however, fish with additional spots are frequently observed. Additional spots are thought to result from gene flow with the six- spotted Gulf of California Girella simplicidens. In the present study, the proportion of fish with extra spots was compared among and within nine G. nigricans cohorts settling from 1997 to 1999. This proportion was variable among the nine cohorts. When analyzed by climate regime, cohorts settling during the 1997-98 El Nino event had significantly higher proportions of multi-spotted fish than "normal" and La Nina cohorts. Within five of nine cohorts, the proportion of fish with additional spots significantly increased through time during the study, suggesting that survivorship of multi-spotted fish was greater than that of two-spotted fish during the juvenile stage. The easily identifiable spot polymorphism of Girella nigricans provides a useful tool by which to study hybridization between two marine fishes and track changes in gene flow and gene expression over time.