Behavior Regulates Larval Dispersal for Nearshore Marine Fish Species in an Upwelling Region

Larval behavior strongly influences dispersal during early life history stages for a variety of marine species. Consequently, understanding larval behavior, particularly horizontal and vertical swimming, is important for predicting population connectivity and recruitment patterns. Unfortunately, larval behaviors are poorly documented for many marine fish species. We present findings from a multi-year study of larval fish distributions off the central coast of California, where seasonal upwelling creates a highly advective environment. In addition, we report distinct behavioral patterns regulating larval dispersal along and across the continental shelf for a diverse group of species. We sampled plankton during the spring from 2017-2019 along two transects, at Bodega Bay (38.3° N) and Stewart’s Point (38.6° N) from 1 to 35 km from shore. All fish larvae were identified to species and developmental stage using visual and genetic methods. Cross-shelf patterns in larval distributions reveal that over 75% of nearshore fish larvae were retained within 10 km of shore. We also found that many species conduct vertical and cross-shelf migrations on daily and ontogenetic time scales, likely altering their net cross- and alongshore transport. Our findings suggest that behavioral regulation of dispersal is common among nearshore fish species in upwelling regions. Furthermore, the behavioral patterns documented in this study may serve to improve biophysical- and individual-based dispersal models used to predict spatial population connectivity and recruitment.