Survival, development and growth of the Pacific white shrimp Litopenaeus vannamei protozoea larvae, fed with monoalgal and mixed diets

The larvae of the Pacific white shrimp Litopenaeus vannamei are fed with microalgae from the stage of protozoea I (PZ I), until they change to mysis I (M I). Most hatcheries use monoalgal diets based on the diatom Chaetoceros muelleri, but there is no information on the advantages of this microalga in comparison to other species used for larval feeding, supplied alone or in mixture. In this paper, the survival rate, rate of development, total length and final weight of protozoea larvae (PZ) of L. vannamei fed with the microalga C. muelleri (CHGRA) are compared to those obtained with the Tahitian clone of Isochrysis sp. (TISO) and with Tetraselmis suecica (TETRA), supplied as monoalgal and mixed diets until the stage of mysis I (M I). With TETRA, mortality was 100% before the change to PZ III, the second lowest survival until M I was with the mixture TISO + TETRA and the highest was with CHGRA as the only food source. After 114 h of culture, the best development was with CHGRA supplied alone or in any mixture (90–95% M I), the lowest was with TISO (13%) and the mixture TISO + TETRA gave an intermediate value. The larvae fed with TISO had also the lowest total length (1.8 mm), compared to the 2.5–2.6 mm found with all diets containing CHGRA. The presence of TETRA improved the food value of TISO for growth, but not for survival, whereas TISO affected the performance of CHGRA. After 114 h of culture, the larvae fed with TISO had the lowest organic weight, those fed with TISO + TETRA and TISO + CHGRA had intermediate weights and the best results were with CHGRA alone, or mixed with TETRA or with the other two species. All rations were different in weight because they were used in equal cell concentrations. In a separate experiment, TISO was supplied as a single and double daily ration because of its low individual weight, and this increased the final weight of the larvae by less than 30%, but it did not improve final survival rate, rate of development or final length. In addition, the weight gain was lower than with the CHGRA diet, showing that TISO is not appropriate for L. vannamei PZ larvae, and that a monoalgal diet based on CHGRA is a convenient option for early larval feeding of this species, possibly because of its high content of the PUFAs, EPA and ARA, and because of a low demand of DHA of these larvae. The absence of this PUFA in TETRA is a possible cause of the total mortality observed when this alga was supplied as a monospecific diet.