Effects of salinity on survival, growth, metabolism, and behavior in juvenile hogchokers, Trinectes maculatus fasciatus (Achiridae)
To understand the biological significance of the southern hogchoker's seasonal migration pattern, the effects of salinity (0, 7 and 15 ppt) on survival, growth, metabolism, and behavior were examined. Survival averaged 96% and salinity did not affect (p = 0.25) the growth rates of juvenile hogchokers during the 60 day experimental growth period. However, oxygen consumption rates suggest that juvenile metabolism is influenced by salinity. Circadian patterns of metabolic rates were present in the 7 and 15 ppt treatments, but absent in the freshwater group. The juveniles in the 7 ppt treatment exhibited significantly (p < 0.05) lower overall rates than the freshwater fish, while the fish in the 15 ppt condition had intermediate metabolic rates. Juvenile hogchokers also showed shifts in diel activity and feeding patterns among salinities, with the active time period shortening with increasing salinity. The main conclusion is that juvenile salinity intolerance is not the driving mechanism of their migration pattern, but salinity does affect juvenile metabolism and behavior. The metabolic effects of salinity can explain summer migration in juvenile hogchokers. Additionally, the shifts in their behavioral responses can generally be explained by the summer migration movements.