Pd/a Crsp Eighteenth Annual Technical Report

Colossoma macropomum growth performance did not significantly differ in trials conducted in ponds at 2,500, 3,250, and 4,000 fish ha-1 in Iquitos, Peru. Fish initially weighing 3.4 g were fed a locally prepared diet (26.7% crude protein; 9.0% crude lipid) in rations ranging from 3 to 5% body weight per day. Fish were harvested after 168 days and had mean weights of 374.7, 307.7, and 287.0 g for the 2,500, 3,250, and 4,000 fish ha-1 stocking rates, respectively. Survival ranged from 67 to 96%, though all but two of nine ponds exceeded 80% survival. Feed conversion efficiency was 40.4, 43.4, and 61.3%, respectively, for the 2,500, 3,250, and 4,000 fish ha-1 treatments. Fish in two of the ponds were reared for an additional five months and attained a mean weight of 1 kg. Water quality parameters remained within acceptable ranges for tropical aquaculture. As with Piaractus brachypomus in a previous study, this study suggests the economic feasibility of rearing Colossoma in the Peruvian Amazon. Generally, the combined cost of fingerlings (US$0.14 each; corrected for 90% survival) and feed (US$1.02 kg-1 to produce 1 kg fresh fish) is under half the price (US$3.00 to $4.00 kg-1) for which the fish are sold in the Iquitos market during flood periods. EIGHTEENTH ANNUAL TECHNICAL REPORT 62 at the Instituto de Investigaciones de la Amazonia Peruana (IIAP) research facilities at Iquitos. Along with this density study, other experiments related to the performance of these fishes are currently in progress. A nutritional study performed by Rebecca Lochmann was set to determine an optimal broodstock diet at low cost, manufactured with locally available ingredients. Konrad Dabrowski is completing an experiment where he studies the fish’s blood plasma steroid concentration during their annual breeding cycle. A study to compare the effects of different inducing hormones on Colossoma and/or Piaractus is also in progress. A second density study with Piaractus is presently under completion at the host country research facility. All together these studies will provide important information to develop an efficient protocol for the spawning and rearing of the Amazon fish species. METHODS AND MATERIALS Nine ponds, ranging in size from 1,015 to 5,320 m2, were stocked with Colossoma macropomum at three densities: three ponds at 2,500 fish ha-1, three at 3,250 fish ha-1, and three ponds at 4,000 fish ha-1. The mean initial weight was 3.4 g. A locally manufactured feed using available ingredients was fed (Table 1). Fish were fed 5% body weight per day (bwd) for the first month and 3% bwd for the remainder of the trial. Rations were divided into three feedings. Fish were sampled (10% minimum population) by seining every two weeks to record lengths and weights. At harvest, biomass, feed conversion efficiency (FCE), specific growth rate (SGR), and condition factor (K) were calculated. The study commenced 17 April 1997 and continued until 20 October 1997. General water quality parameters (dissolved oxygen, temperature, total ammonia nitrogen, and pH) were measured daily or weekly, in the early morning. Harvest data were analyzed using the Statistical Analysis System (SAS Institute 1993) with an alpha of 0.05. Materials and methods, as well as results for the nutrition and blood plasma studies will be presented respectively by Rebecca Lochmann and Konrad Dabrowski in their reports. The remaining density study and reproductive hormone experiment will be reported in the final workplan report.