John M. Heinen

A culture system for nutritional studies of crustaceans

Abstract A design for a culture system for nutritional experiments with crustaceans is described and evaluated. The design is directed toward eliminating any non-nutritional factors that can undesirably influence weight gain and survival. Experiments indicate that locational effects within each system or between systems do not exist. The system design appears to succeed in reducing the high variance that is characteristic of the weight distributions of communally cultured populations of some species of crustaceans. This is the first reported system with a controlled water supply to individual crustaceans and represents a step toward the standardization of methodology associated with nutritional experiments.

Polyculture of the freshwater prawn (Macrobrachium rosenbergii) with a mixed-size population of channel catfish (Ictalurus punctatus)

Abstract Channel catfish of sizes ranging from 0.03 to 0.57 kg and juvenile freshwater prawns (mean wet weight = 0.52±0.40 g) were stocked into four 0.06-ha ponds at densities of 11 120/ha and 4942/ha respectively. The growout period was 132–133 days. At harvest the mean wet weight of the catfish and prawns ranged from 0.63 to 0.72 kg and 33.8 to 42.3 g, respectively. Survival of prawns and catfish was >87% except in one pond where a disease outbreak reduced catfish survival to 70%. Prawn production averaged 172 kg/ha. Approximately 75% of all the harvested prawns had a wet weight that exceeded 30 g. Male prawn populations, composed of three morphotyes (blue claw, orange claw, small), evidenced less variation in wet weight than that previously observed in monoculture populations. Harvesting techniques which permit selective harvest of the prawns appear to be required for practical polyculture.

A starvation test to determine optimal salinities for larval freshwater prawns, Macrobrachium rosenbergii

Abstract 1. 1. A starvation test was conducted in small beakers with stage 1 (S1) and stage 2 (S2) Macrobrachium rosenbergii larvae to determine optimal salinities. 2. 2. Experiments were first performed with S2 larvae at 13 ppt to identify a suitable medium made with artificial sea salts. 3. 3. A broad-range (0–35 ppt) and a subsequent narrow-range (9–16 ppt) salinity experiment with S2 larvae were used to identify 13 ppt as the optimal salinity, with 12 ppt as the next best; this agrees well with most previous estimates of optimal salinities for rearing larvae. 4. 4. S1 larvae were also tested in a narrow-range salinity experiment but were not used further because, unlike starved S2 larvae, they molted during the experiment. 5. 5. Identification of the optimal salinity was not affected by 50% daily water exchange or by bright light. 6. 6. Exposure of larvae to three different salinities—7, 13 and 19 ppt—during S1 influenced the width of the optimal salinity range for S2 larvae.

Culture System for Evaluating Live and Formulated Diets for Larval Fish

Abstract An inexpensive culture system for evaluating diets of larval fishes is described. The system is self-contained and features biofiltration with six individual rearing units. Major advantages include simple construction and lack of moving parts, portability, ability to keep diets and larval fish suspended and in continuous contact, and promotion of rapid fish growth apparently without significant cannibalism. The system does require intensive cleaning when formulated diets are fed in excess.

Removal of Floating Filamentous Algae from Ponds with a Shallow Seine

Abstract Floating mats of filamentous pond algae can be skimmed effectively from the water surface with a 2-ft-deep seine.

Lay-Flat Plastic Tubing to Prevent Soil Erosion during Pond Filling

Abstract Lay-flat plastic tubing can be used to fill ponds and avoid bank erosion. The lightweight plastic is tear-resistant and can be folded for transport or storage.