Culture of a Planktonic Cyclopoid, Apocyclops Dengizicus (Lepeshkin, 1900) and Its Suitability as Live Feed for the Postlarvae of Giant Black Tiger Shrimp, Penaeus Monodon Fabricus (1798)

Copepods form an important link between phytoplankton and higher trophic levels such as fish and shrimp. In aquaculture industry, some species of copepods are used as live feed for fish and shrimp larvae. In this study the suitability of a copepod Apocyclops dengizicus as a live food was investigated. For establishment of successful culture protocol, the biology (feeding, reproduction, and growth) and environmental requirements (salinity, temperature, light intensity, and photoperiod) of A. dengizicus were studied Apocyclops dengizicus can reproduce in salinity levels from 5 through 35 ppt. The salinity level of 20 ppt gave maximum production (535.3 ± 30 ind./female). At temperature levels between 20 ºC to 35 ºC, the mean maximum production (386.3 ± 60.3 ind./female) was obtained at 35 ºC. Culture of A. dengizicus at different light intensity levels (from 33.3 to 162.1µmol/m2/s), showed that the mean maximum production (523 ± 37.4 ind./female) was observed at 33.3 µmol/s/m2. In different photoperiods, the mean maximum production (647.5 ± 144 ind./female) was attained at continuous light exposure. Feeding rates of A. dengizicus varied from nauplius to adult (p<0.01). The best feed for all stages of A. dengizicus were Tetraselmis tetrathele, Chaetoceros calcitrans, Isochrysis galbana and Nannochloropsis oculata respectively. The algal species and their densities showed significant effects on the growth rates of A. dengizicus population (p<0.01). Of different algal diets tested, copepod fed with Tetraselmis tetrathele and its combination with other microalgae gave fastest development, maximum offspring production, and maximum production. Nutritional analysis of A. dengizicus revealed that it has 23-60 % protein, 18-20 % lipid, and 4-10 % carbohydrate. Phenylalanine and leucine had the highest concentrations ranging from 12.4 to 26.3 % and 11.3 – 12.2 % respectively. Saturated fatty acids (SFA) constituted the major part of the fatty acids (40.54 ± 5.97 %) followed by mono unsaturated fatty acids (MUFA) (20.67 ± 7.21 %) and highly unsaturated fatty acids (HUFA) (20.69 ± 4.90 %). The major SFA, MUFA, and HUFA for A. dengizicus were C14:0 (30.47 ± 4.61%), C18:1n-7 plus C18:1n-9 (14.23 ± 4.96%) and C22 : 6n-3 (10.54 ± 3.14%) respectively. Considerable increase in n-3/n-6 and DHA/EPA ratios for A. dengizicus compared to newly hatched Artemia nauplii make it as suitable nutritious prey for fish and shrimp larvae. This study showed that the best ingestion rates for Penaeus monodon larvae were 41.5 ind./day for PL3-6 fed on Apocyclops and 101.6 ind./day for PL9-12 for Artemia. The shrimp larvae could also ingest selectively Apocyclops better than Artemia. Experiments on the survival and growth rates of P. monodon larvae fed with different diets showed that survival and growth rates of P. monodon were maximum (56.3%, 14.24 %/day) in mixed diet of A. dengizicus + Artemia nauplii. The n-3/n-6 ratios of larvae increased from 1.88 to 2.56 when fed with Apocyclops, 2.46 with Artemia, and 2.40 with Apocyclops and Artemia. This study illustrated that A. dengizicus has high potential as live feed for P. monodon and could partially replace the imported Artemia cyst.

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