Life history through the eyes of a hogfish: trophic growth and differential juvenile habitat use from stable isotope analysis

Abstract

Understanding ontogenetic linkages among fish habitats is critical for conservation of fish populations and the ecosystems on which they rely. Natural tags such as stable isotopes are effective for investigating ecological questions regarding fish movement and habitat use. We analyzed stable isotopes from sequentially deposited laminae of hogfish Lachnolaimus maximus eye lenses from the eastern Gulf of Mexico (eGOM) to investigate trophic and geographic changes across individual life histories. We documented evidence of 1 to 2 step trophic level increases through δ15N increases. We also observed depth separation at the juvenile stage, evidenced by δ13C variation early in life. These results suggest that adult hogfish in deeper habitats likely inhabited deeper juvenile habitats (i.e. nearshore reefs), while adult hogfish inhabiting shallower adult habitats likely used shallower juvenile habitats (i.e. estuaries). This novel finding for eGOM hogfish contradicts prior literature that solely discusses seagrass as juvenile habitat. We used muscle tissue isotopes to characterize juvenile hogfish habitats and linear discriminant function analysis (LDA) to determine the habitats previously inhabited by adults in this study. The LDA revealed Cedar Key as the most used juvenile hogfish habitat in this study, but more evidence is needed to determine its status as a nursery. This study provides the first evidence for ontogenetic migration of individual hogfish using natural tags as tracers and demonstrates a mechanism for identifying juvenile habitats based on eye lens stable isotope analysis. Identifying ontogenetic patterns and habitat use can help to better conserve stocks and essential fish habitats.