Aerobic and anaerobic enzyme assays in Southern California Rockfish: Proxies for physiological and ecological data

Rockfish are commercially and recreationally important, yet due to the depths they inhabit (3–500 m), little is known about their ecology. The present study examined 19 different species of Sebastes from the Southern California Bight over four seasons (late summer, fall, early winter, and spring) using metabolic enzyme assays. Enzymes used were lactate dehydrogenase (LDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and citrate synthase (CS). Muscle proximate composition data (protein, water and lipid content) were also used to help interpret the enzyme data. Enzyme activity was lowest in the summer when expressed as activity per gram wet weight but when it was expressed per gram protein the trend was reversed. The rockfish have the highest protein as a percentage of wet mass (P%WM) in the spring, right before the upwelling period begins and the lowest P%WM in late summer after the peak of upwelling. Lipid content also showed a seasonal change with the highest lipid content in the late summer and the lowest in winter. The enzyme profiles have been broken into three groups which fit with their locomotory habit and their prey selection. These findings show that enzymes and muscle proximate composition can be used along with limited observational data on related species to deduce condition, seasonal impacts and ecologically important life habits in species that are difficult to observe and monitor.

Research Highlights
► Lipid and protein content in the muscle correlated with season.
► Enzyme activity profiles correlated with past diet and observational studies.
► Enzyme and composition data can help deduce condition and life habits.