The co‐culture of juvenile sea cucumber Holothuria scabra (Jaeger), or ‘sandfish’, with juvenile blue shrimp Litopenaeus stylirostris (Stimpson) was tested by growing groups in co‐culture and monoculture for 3 weeks in tanks with enriched sand substratum. Feed was supplied on trays, accessible only to shrimp. Survival of shrimp and sandfish was high in all treatments (73–100%). Growth of shrimp did not differ between monoculture and co‐culture, but sandfish grew significantly slower in co‐culture (P=0.03), although their sand burying and surface foraging were apparently unaffected by shrimp (P=0.76). However, shrimp increased the levels of total ammonia‐N in tanks, which related inversely with sandfish growth (P=0.04). Conversely, sandfish did not appear to lower the water quality for shrimp culture. While sandfish bioturbate sediments and eat organic deposits, the juveniles did not significantly reduce the organic content of sand in tanks. Co‐culturing juveniles of the two species in earthen ponds appears feasible, with no detriment to shrimp production, presenting a cost‐effective method for growing sandfish to larger sizes for restocking. These findings underpin further studies to test the viability of commercial co‐culture of sandfish with blue shrimp at later stages in the production cycle of shrimp.

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Two populations of the Latin American shrimp Penaeus (Litopenaeus) stylirostris domesticated in Hawaii and in New Caledonia were previously shown to be genetically differentiated and proven highly inbred. In New Caledonia, where different Vibriosis affect shrimp production and antibiotic use is banned in growing ponds, the Hawaiian population was introduced to increase the allelic variability available for local shrimp farmers and start a genetic improvement program. Growth and survival rates of the two pure populations and the two-way F1-hybrids obtained by breeding Hawaiian animals with New Caledonian animals were assessed in several simple experiments (earthen ponds, floating cages and experimental infection challenges) during two years on two successive generations. Results were very consistent: F1-hybrids growth rates in earthen ponds were 37% (± 7% SD) higher than for pure populations. Cage experiments demonstrated no competition between the different populations when reared together or separately in a common environment. The F1-hybrids also showed better survival rates in all experiments. Combining the results on growth and survival rates leads to the conclusion that biomass production is much higher with F1-hybrid populations than with pure populations using the same quantity of juveniles stocked: biomass production in ponds was increased 1.4 and 2.3 times on year 1 and year 2 respectively, and 1.9 times in floating cages. The advantage of growing F1hybrids appeared proportionally higher when environmental and sanitary conditions led to poorer survival (34% in year 2 vs. 56% in year 1). These results are a good example of performance improvement by heterosis effect and/or of performance loss due to inbreeding in the pure populations. This study demonstrates that aquaculture industries which cannot afford large selection programs may benefit from using two different inbred parental stocks to produce F1-hybrids for each commercial growout. This is notably true when only inbred populations are available, or when introduction of genetic variability from the wild or from other genetic resources represents a zoo-sanitary risk. In our case, the expected increase in L. stylirostris production could be around 85% (according to our average results) if producers keep stocking their ponds at their current densities using F1-hybrids. However, for sustainability reasons, it is advisable to stock F1-hybrid animals at lower densities, the gain in performance allowing producing the same amount of biomass with less input.

This study deals with the variation in the lipids of tissues during the molting cycle of prawn, Penaeus japonicus. During the molting cycle, the most notable variation in the lipid concentration (mg/100g fresh tissue) was seen in the hepatopancreas; the lipid concentration reached a maximum at stage D0 (beginning of premolt period). Also, the pre-ecdysial in crease of hepatopancreatic lipids was found to be derived from both polar and niutral lipids, In other tissues such as the muscle, eyestalk, integument, and remains, the lipid concentration varied with the molting stages, but the variation was not as remarkable as observed in the hepatopancreas.

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