Effects of salinity on survival and plasma osmolarity of Totoaba macdonaldi eggs, larvae, and juveniles

Totoaba macdonaldi, an endemic fish from the Gulf of California, is currently considered an endangered species by the Mexican Federal Government since its bladder is a high-priced item in China's black market. Totoaba is considered the cause of extinction of the marine porpoise vaquita marina (Phocoena sinus) due to Illegal fishing. It inhabits the Colorado Delta River Marine Reserve, an area with very high productivity, biomass, species endemism, and a marine nursery. To explore its osmoregulatory capabilities, totoaba specimens were exposed to different salinity conditions (from 5 to 40 psu) under laboratory trials. Several developmental stages were tested (eggs, larvae, and juveniles), from which blood and water osmotic pressure (OP), survival, water and total ash content were evaluated, confirming the euryhaline behavior of juveniles. However, larval stages were very dependent on external media salinity concentration. The responses to salinity acclimation and shifts in survival recorded were closely related to its migratory strategy, which can have important ecological consequences.