Characterizing Hogfish salinity tolerance for the development of low-salinity culture protocols

ABSTRACT Objective The Hogfish Lachnolaimus maximus is a popular sport and food fish and has historically experienced overfishing in parts of its range. Hogfish are a new candidate for aquaculture, and culture techniques are in the early stages of development. Understanding the osmoregulatory capacity of aquaculture species is important, as salinity can influence metabolic rates, which can impact somatic growth and production efficiency. Low-salinity culture could lower production costs by reducing the need for artificial salt water and may enhance somatic growth by reducing metabolic energy for osmoregulation. Methods Four experiments were conducted to examine the osmoregulatory capacity of cultured Hogfish across various salinity regimes. Experiment 1 assessed fish survival after an acute transfer to six salinity levels from 0 to 32 g/L. Experiment 2 evaluated the physiological response of Hogfish to reduced salinity in a 96-h challenge at 8 and 16 g/L. The physiological effects of gradual salinity change from 32 to 12 g/L were determined in experiment 3. Lastly, experiment 4 assessed growth over 65 d at a salinity of 16 g/L. Results After acute transfer to lower salinity treatments, Hogfish survived at salinities of at least 8 g/L for 96 h; however, plasma chloride, plasma osmolality, and muscle water content were significantly altered at 8 g/L, and mortalities were noted during long-term retention at 8 g/L. Gradual transfer from 34 to 12 g/L yielded no significant physiological alterations compared with acute transfer to the same salinity for the physiological parameters measured. Growth indices for Hogfish cultured in 16 and 32 g/L were similar, though variance in metrics suggests a need for further exploration. Conclusions Hogfish should be tolerant of rapid transfer to salinities as low as 12 g/L, and growth may be unaffected when the fish are cultured at 16 g/L. Further research on feed types, lowering of feed conversion ratio values, and ontogeny of salinity tolerance is warranted.