Largemouth bass (Micropterus salmoides, LMB) recruitment is limited by a critical developmental period during early life-stages, but this mechanism may be less significant within non-native habitats. We conducted boat electrofishing surveys in four tidal lakes of California’s Sacramento-San Joaquin Delta (SSJD) from 2010-2011 to describe introduced LMB recruitment dynamics. We evaluated growth, proximate composition, and health indices of young-of-the-year (YOY) LMB among tidal lakes and developed an integrated count model to determine how factors known to affect LMB recruitment shape SSJD population structure. Our results show a mismatch between growth, nutrition, and YOY abundance, where the tidal lake with the most abundant and fastest growing LMB had the poorest nutritional status. The warm winter water temperatures and lack of a hatching-cohort growth advantage suggests overwinter starvation plays a less significant role in SSJD LMB recruitment than many native LMB habitats. Collectively, our results suggest that habitat characteristics (submerged aquatic vegetation) and not overwinter mortality shapes SSJD LMB population structure, a mechanism consistent with contemporary hypotheses about the altered fish community structure of the SSJD.
Recruitment dynamics of non-native largemouth bass within the Sacramento-San Joaquin Delta
