An Energy Budget for a Rainbow Trout Farm

Abstract

An industrial energy-budget for a Rainbow Trout farm shows that 93% of the energy costs of production are incurred in feeding the fish, seven-tenths of which is due to fishnieal incorporated in the food pellets. Only one-tenth of the input energy is converted into fish, but the energy subsidy of the farming operation compares favourably with conventional fishing and is 423 input megajoules per kg of output fish protein (55 MJ per kg wet-weight of fish landed). However, if the Trout could be fed on a diet composed of suitable vegetable protein, this performance would be improved to an overall conversion efficiency of one-third, and a subsidy of about 160 MJ per kg. A smaller but similar improvement could result if the Peruvian anchovy fishery regained its former production level.As these improved energy-costs are comparable with those of crops of potatoes, and with those of bread and milk production, a 2-men Rainbow Trout farm yielding 25 tonnes per year on one hectare would become an attractive protein-producing enterprise in localities where the necessary water-supply is available.

Energy economy of salmon aquaculture in the Baltic sea

“…In the analysis, cage farm energy return on invested fossil energies (EROI) was found to be 4%, which is somewhat lower than in previous studies (Mathews and others 1976, Pitcher 1977, Adling 1981, depending on differences in estimates of energy requirements in smolt rearing, in dry pellet production, and for recompense to labor. EROI in the sea ranching enterprises ranged from 3% to 26%, being highly dependent on offshore fishery catches which considerably reduce the possibilities for released smolts to return as adults to the site of release.…”

“…In ranching, e.g., investments in fishing; driftnets, buoys, small motorboat or coastal vessel (dependent on the homing accuracy of Atlantic salmon, see Hasler andScholz 1983, Nordeng 1977), cage with equipment during 3 mo in ranching with delayed release, 5-25 years of depreciation (DrummondSedgwick 1982, Cedrins 1985. Quantifications and energy cost: sources (Uhlin and others 1975, Leach 1976, Mathews and others 1976, Hall and others 1979, Pitcher 1977, Jansson and ZuCchetto 1978, Adling 1981, Hannon and others 1985, Limburg 1986, Osthlom 1986, see Folke and Aneer 1988). c Food-to-fish conversion; 2:1 cage farming (Swedish salmon farmers, pers.…”

“…f Pen rearing; electricity (to oil x 3) for running pumps, aerators, automatic feeding; petrol (to oil x 1.1) for boat driving. Ranching; coastal fishing vessels 8 GJ (Jansson and Zucchetto 1978), small fishing boats 2 GJ (Leach 1976, Pitcher 1977 of fuels per t of salmon caught. g Medicals, chemicals, veterinary services, water quality testing, maintenance, transports of smolts and dry pellets on the island of Gotland (Uhlin and others 1975, Leach 1976, Pitcher 1977, Ostblom 1986, Harmon and others 1985.…”

“…As pointed out by Pitcher (1977), the energy cost of cage farming is highly dependent on the input of pellet food (see Table 2). However, the present study indicates that even a 25% reduction in both pellet food .use and energy cost for pellet production would only increase EROI by 1.5-2%.…”

“…Previous energy analyses of salmon rearing have focused on auxiliary energies (e.g., Pitcher 1977, Mathews and others 1976, Adling 1981. This article considers both auxiliary and solar energies.…”