Masters Theses

Date of Award

12-2003

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Dr. J. Larry Wilson

Committee Members

Dr. Thomas K. Hill, Dr. Barry Sims

Abstract

Production of freshwater prawn (Macrobrachium rosenbergii) in temperate regions has gradually increased over the past decade due to advances in research. However, production is limited to one seasonal crop in these regions, increasing the need to intensify production. A nursery phase has been implemented to produce larger juveniles to stock into production ponds.

Three nursery experiments (A, B, C) were performed to evaluate the effects of stocking density, amount of added substrate, feeding frequency, and waste removal on the survival and growth of juvenile prawn. Experiment A involved two concurrent studies. Prawn averaging 0.01 g were stocked at densities of 2.5, 5, 7.5, and 10/L into 24 200-L tanks. The surface area of each tank was 15,485 cm2; horizontal layers of polyester mesh (6 x 6 mm) were added to equal 50 or 100% increase in tank surface area. The first study compared the two amounts of substrate at two densities (5 and 7.5/L). The second study compared four different densities (2.5, 5, 7.5, and 10/L) with the smaller amount of substrate. Each treatment combination of stocking density and substrate amount was replicated four times. After 60 days, the first study revealed that prawn stocked at 5/L had significantly higher survival (73 and 64% for 5 and 7.5/L, respectively), but lower average individual weight (0.13 and 0.14 g for 5 and 7.5/L, respectively) than those stocked at 7.5/L. Substrate equal to 100% of the tank’s surface area did not significantly increase survival over tanks with 50% added substrate, but did produce significantly larger prawn (0.15 vs. 0.12 g). In the second study, the only significant difference in survival was with prawn stocked at 5/L (72%) versus 2.5/L (55%). Prawn stocked at 2.5/L had an average individual weight (0.08 g) that was significantly less than prawn stocked at 5 (0.12 g), 7.5 (0.13 g), or 10/L (0.13 g).

Experiments B and C were initiated with 0.016 g postlarvae stocked at 5/L in circular and rectangular 400-L tanks. In the six circular tanks, polyester mesh (6 x 6 mm) was added in horizontal layers to increase the surface area of the tank by 53% (46.454 cm2). Prawn were fed either a single daily ration or two daily rations that were each equal to half of the single ration, according to a percent body weight regimen. After 60 days, there were no significant differences in survival or average individual weight of prawn fed once daily (66%, 0.13 g) versus twice daily (55%, 0.13 g). In the rectangular tanks, horizontal layers of polyester mesh were added to increase each tank’s surface area by 45% (46,454 cm2). Three tanks were siphoned three times weekly to remove uneaten feed; the three other tanks were never siphoned and uneaten feed and wastes were allowed to accumulate. After 60 days, there were no significant differences in survival or average individual weight of prawn in tanks where waste was removed (57%, 0.11 g) versus tanks where waste was allowed to accumulate (67%, 0.14 g).

One pond experiment was conducted to examine the effects of substrate height on production. In the pond experiment, prawn averaging 0.14 g were stocked at a density of 53,304/ha in six 0.04-ha ponds. Three ponds had 0.61-m high fencing and three had 1.22-m fencing, increasing surface area by 20 and 40%, respectively. After 106 days, no significant differences were found in prawn survival (70 vs. 85%), yield (1296 vs. 1508 kg), mean individual weight (32.2 vs. 29.9 g), or feed conversion (2.14 vs. 1.84) for ponds with 0.61-m high versus 1.22-m high substrate, respectively.

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