Evaluation of Fabrea Salina and Other Ciliates as Alternative Live Foods for First-Feeding Red Snapper, Lutjanus Campechanus, Larvae

Abstract

One of the major challenges with the culture of red snapper Lutjanus campechanus is providing an appropriate food source at the onset of feeding. At first-feeding the larvae has limited endogenous reserves and within hours must find an appropriate size food organism to survive. Protozoans are important trophic links from bacteria and phytoplankton to metazoans. Ciliated protozoans may be more important for first-feeding fish larvae than other similar sized traditional live feeds because they naturally occur in higher densities and without lorica they can be more easily digested. Behavioral observations of first feeding snapper larvae were conducted with three different ciliates as a food source. The three ciliates, Fabrea salina, Strombidium sp. and Strombidinopsis sp. are various sizes and have unique swimming speeds and patterns. Observing the foraging behavior of fish larvae when exposed to different prey allowed for the selection of a diet for the production of fish. There was a reduction in protozoan densities suggesting the protozoans were consumed by the fish larvae. Experiments were conducted to determine the optimum culturing conditions of one of the naked ciliates, Fabrea salina to be used as a food source. Growth conditions evaluated included ciliate stocking density, algae food species and density and photoperiod. The trials optimum results, 12 hours light/day, initially stocking 3 F. salina/mL and feeding 9.0 x 104 Rhodomonas lens cells/mL/day were then applied to 40 and 200 L mass culture conditions. Average densities of 66 to 91 ciliates/mL were common in 6 to 8 days. The mass cultures of F. salina provided approximately 16 million ciliates in 7 days. The F. salina was compared to copepod nauplii as well as a combination of F. salina and copepod nauplii as first-foods for larval red snapper in a large-scale experiment. The treatment provided with the combination of F. salina and copepod nauplii resulted in 2.39 ± 2.75% survival which was much higher than the 0.28 ± 0.15% survival when fed copepod nauplii alone. There was no fish survival in the treatment fed F. salina alone for first-feeding. The growth was significantly higher in the treatment fed F. salina and copepod nauplii than the treatment fed copepod nauplii alone. The results of the snapper rearing trial imply that F. salina and possibly other protozoans can be used to supplement the diet for first-feeding fish larvae to increase growth and survival.