A Study of the Orientation of Selected Embiotocid Fishes to Depth and Shifting Seasonal Vertical Temperature Gradients

Abstract

The effects of seasonal temperature variation on the depth distribution of five species of embiotocids in King Harbor, California were studied. Three types of depth distributions were found: Micromelrus minimus was restricted to the intertidal and subtidal margin: Embiotoca jacksoni was most abundant at middle depths and declined in abundance in both shallower and deeper water; Hypsuris caryi, Rhacochilus vacca, and Phanerodon furcatus formed a deeper water group. The depth distributions of all species except M. minimus shifted into deeper water during late summer and fall and into shallower water during winter and spring. Micrometrus minimus remained in the top 1.5 m throughout the year. Descent into deeper water corresponded to the period of warmest water. Deeper water species selected water colder than I6°C. Embiotoca jacksoni occupied a middle thermal range. The results of this study support an important role for temperature orientation in the spatial organization of this subtidal community.