An Evaluation of Nursery Techniques and Feed Management During Culture of Marine Shrimp Litopenaeus vannamei

Abstract

The use of indoor shrimp nurseries is often encouraged, especially prior to intensive and super-intensive shrimp culture. Potential benefits in subsequent grow out include; better control of stock inventory, better management of feed inputs, reduced predation, and the ability to extend the growing season. More recently, nurseries have been recommended for biosecurity reasons. There has been limited research to identify suitable nursery protocols that optimize shrimp performance in indoor nurseries. There is even less information on shrimp performance in the growout phase following various nursery practices. Additionally, feeding is one of the most important activities when considering pond dynamics, management and production economics for pond growout. Despite the importance of feed management there are few studies that have evaluated feeding strategies or feeding programs. These studies were conducted to evaluate various management practices for shrimp nurseries and possible effects on growout following nursing. Objectives of the nursery studies were to evaluate the influence of: 1) nursery stocking rates 2) nursery duration and 3) the use of dried feed, algae and newly hatched artemia; on survival, growth and feed conversion during the nursery phase and on survival, individual shrimp size and total production during the following grow out phase. The evaluation of feed management strategies was conducted with the objective of incorporating general aquaculture considerations into a management and feeding program and evaluating the effects and economic implications of three feeding schedules: 1) Early aggressive feeding schedule with high feed inputs early in the cycle to maximize early growth of the shrimp but then to minimize feed inputs during the end of the production when water quality is most unstable, 2) Late aggressive feeding schedule which minimized early feed inputs when natural productivity is high and maximize feed inputs late in the cycle when natural productivity is more likely to be limiting, and 3) Intermediate feeding (IF) which is intermediate to EAF and LAF. The experiments were conducted at the Claude Peteet Mariculture Center, Gulf Shores, Alabama. The studies included nursery phases and a growout phases. Six fiberglass tanks (3.0 x 1.5 x 0.9 m) located inside a greenhouse and sixteen round plastic tanks of 1 m3, located under a plastic cover, were used for the nursery phase of the experiments. Twelve 0.1-ha plastic lined production ponds were used for the grow out phase. Findings of the studies suggest that nursery densities in the range of 25 to 65 PL/L have no influence on subsequent growth and survival during grow out. However at a higher density (65pl/L), improved feed and culture systems were required. Postlarvae in the best performing nursery treatments also had higher yields and better size distributions during the growout phase. When comparing a nursery period of 14 and 21 days, it was found that a longer nursery period enhanced larger juveniles and improved nursery biomass loading, however under grow out conditions nursed juveniles did not differ significantly in production criteria from direct stocked shrimp. When evaluating type and combination of diets, in terms of final average weight and biomass loading results suggest that there is a clear advantage in supplementing dried feeds with artemia for 3 days. The use of algal paste did not produce better results than algae that grew naturally in nursery tanks. No significant differences were found among treatments in early and late aggressive feeding experiments, but significantly