Development of an optimal microalgal diet for the culture of the calanoid copepod Acartia sinjiensis: Effect of algal species and feed concentration on copepod development

Abstract

Of the calanoid copepods, species of the genus Acartia are most commonly used for larval diets of tropical marine finfish. It is sourced from adventitious harvesting of wild populations or less frequently, cultured specifically as a live feed. However, little work is published on optimising diets for the aquaculture of copepods. In this study, A. sinjiensis was cultured on a range of mono- and binary algal diets and the effect on development assessed. There were significant differences in the rate of copepod development between the mono-algal diets. Rhodomonas was confirmed as an excellent algal diet for Acartia, but it is often unpredictable in mass culture. The cryptophyte, Cryptomonad sp. (CS-412) was shown to support an equally rapid development rate with the advantage of being more stable in mass culture. The algal feed concentration for maximal copepod development rate was dependent on the algal feed species. For the cryptophytes Rhodomonas sp. or Cryptomonad sp., 1.13 μg AFDW ml− 1 was the minimal feed concentration required to support maximal copepod development at 28 °C. Mono-algal diets of the prymnesiophyte Isochrysis sp. (T.ISO) or Pavlova salina supported a lower level of copepod development than an equivalent biomass of either cryptophyte. Also, a higher feed concentration was required to achieve these lower development rates: 2.02 and 1.86 μg AFDW ml− 1 for Isochrysis sp. (T.ISO) and P. salina, respectively. Copepod nauplii fed the prasinophyte Tetraselmis sp., developed as fast as those fed an equal biomass of cryptophyte. However, development did not proceed beyond copepodite stage C1. Although survival was high, almost all of these C1 copepodites exhibited signs of a nutritional irregularity. The eyespot was frequently completely absent, greatly reduced in size or fragmented and setae were twisted. For rapid development, a mono-algal diet of Cryptomonad sp. could be used for the culture of A. sinjiensis. However, inclusion of a lipid-rich prymnesiophyte is likely to be beneficial to maximise egg production, a lipid dependent process.