In closed recirculating systems, a particulate matter consisting of bacteria, algae, fungi, and detritus develops spontaneously. This microbial floc can serve as a high‐protein food source for finfish and shellfish and has the potential to supplement the protein required in shrimp feed. To advance the use of microbial floc as a feed supplement, it is necessary to manipulate its microbial components, which requires thorough characterization of the bacterial components. Pacific white shrimp, Litopenaeus vannamei, were raised in a closed recirculating system, and water was compared to the contents of shrimp foreguts and hindguts. Water consistently contained less microbial biomass than did shrimp guts, but 16S rDNA sequences indicated that water was more diverse than shrimp guts. Phylogenetic analysis of 16S rDNA sequences retrieved from water and shrimp foregut grouped these sequences into various unrelated generic clusters. Fatty acid analysis demonstrated that shrimp feed was not a major contributor of microbial fatty acids to shrimp tanks, as the feed mostly contained polyunsaturated fatty acids, which are typically found only in eukaryotes. It is hoped that elucidating more details about the various components of microbial floc will help in understanding its development and will lead to its use as a high‐protein feed supplement.
The current state of knowledge relating to the reproduction of the commercially important open thelycum shrimps (Crustacea: Penaeidae) is reviewed with particular reference to Penaeus vannamei. Industry standard procedures for the breeding of shrimps in captivity are reviewed against a background of knowledge concerning the maturation processes in males and females. The factors controlling maturation are not completely understood, and it is not clear whether maturation of females is size-or age-dependent. Although unilateral eyestalk ablation is routinely used to induce maturation, the physiological mechanism of this operation is not properly understood. Further research on environmental conditions for successful maturation is required. Nutrition is an important component in successful artificial breeding programs that still rely on the provision of natural foods (squid and polychaeta). The processes of oocyte formation, mating, spawning and hatching are discussed in relation to observations made at the Gulf Coast Research Laboratory.
Over the past several years, we have developed an experimental‐scale rearing system for larval red snapper Lutjanus campechanus that combines extensive outdoor production of live‐feed zooplankton with intensive larval fish rearing. The salient features of the system are (1) use of size‐graded copepods as live feed; (2) culture in clear water; (3) three‐phase water management consisting of an initial static water phase followed by a volume‐doubling phase in which water is gradually added and, finally, a recirculation‐biofiltration phase; (4) a lowered salinity of 25 g/L water; and (5) an indoor location at constant temperature under artificial light. A total of 19,835 juvenile red snapper were produced from 12 larval rearing tanks in three separate batches with an overall survival of 16.5%. Survival varied from 1% to 31% in individual larval rearing tanks. Water quality variables (oxygen, temperature, salinity, total and un‐ionized ammonia, nitrite, nitrate, pH, and alkalinity) were not significantly correlated with larval fish survival. A mean number of 5.36 copepods/mL was added daily to larval tanks during the culture period, with a range of 0.57–23.48 copepods/mL. There was no correlation between mean feed rates and survival in individual tanks. The mean residual copepods per milliliter averaged 2.24, with a range of from 0 to 15.86. There was a significant negative correlation between residual copepod density and survival.
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