Effect of age on weaning success in totoaba (Totoaba macdonaldi) larval culture

Abstract

The totoaba (Totoaba macdonaldi) is an endemic marine fish of the Sciaenidae family that has been overfished to the risk of extinction, and after three decades of protection and preliminary culture results, it is now considered an excellent candidate for commercial aquaculture due to its fast growth and good adaptation to culture conditions. However, as with most marine fish species, larval culture and adequate weaning are still one of the main bottlenecks to successful commercial production. Thus, the objective of this study was to evaluate weaning success of totoaba larvae onto a microdiet at various stages of development utilizing growth, survival and condition factor as response variables. Weaning onto a microdiet was evaluated at 17 (17 W), 22 (22 W) and 27 (27 W) days post-hatch (DPH). At the end of the experiment (35 DPH), growth was significantly higher (i.e., two-fold increase) in the weaned treatments compared to their respective controls (i.e., feed with live prey exclusively), except for the 22 W treatment that resulted in no significant differences. Comparing final weight and final length among the different weaned treatments did not result in any significant differences. However, survival rate was significantly lower in the weaned treatments compared to their control groups. Although the experiment was not design to quantitatively evaluate cannibalism, this behavior was observed towards the end of the weaning trial and may have a significant contribution to the mortality observed in the weaned treatments. Based on these results and despite of the lower survival, it appears that totoaba larvae possess a sufficiently developed digestive system as early as 17 DPH and can be weaned onto commercial diets before the stomach is fully functional. Thus, it is possible to perform an early weaning (17 DPH) in totoaba larvae, as a strategy to reduce juvenile production costs and increase profitability of the production system, by reducing the use of Artemia nauplii without affecting growth.