Booth, M.A., Pirozzi, I., Allan, G.L. & Fielder, D.S., 2010.  Aquafin CRC Project 1B5: Feed technology for temperate fish species.  Volume 2: Diet development.  Final Report to FRDC Project no. 2004/220.  Industry and Investment NSW. 380 pp.  ISBN 1441 8487.

Summary

World wide, consumption of edible seafood is increasing and by 2025, the world demand for edible seafood is predicted to reach about 140 million tonnes. Capture fisheries are not increasing and already aquaculture production supplies an equal amount of food fish to capture fisheries. In Australia, increasing demand is being met largely through imports and aquaculture.  The largest operating cost for intensive aquaculture is for feeds and feeding. Efficient feeds and feeding systems can significantly affect profitability and are the overall aim for the research described in this report.  The species covered are mulloway (Argyrosomus japonicus) and yellowtail kingfish (Seriola lalandi). Commercial grow-out of these species is occurring in New South Wales and South Australia.  From zero production in 2000/01, production of mulloway increased quickly to over 600 t per annum in 2006/07 (although it was reduced to 309 t in 2007/08) and of yellowtail kingfish to 3,370 t per annum (2007/08).

This report is presented in two volumes.  The first describes research on feeding strategies (Volume 1) and the second describes research on diet development (Volume 2).

Volume 1: Feeding Strategies.
In hatcheries, the global shortage of Artemia and the huge cost of weaning diets has made better and cheaper live feeds, formulated weaning diets and feeding strategies a priority in the quest to improve the quality and reduce the cost of fingerlings. This volume focuses on research to improve the quality of fingerlings.  Initially, research using ozone to disinfect eggs and reduce potential problems with pathogens, including nodaviruses, was undertaken and used to develop practical protocols.  The effects of photoperiod and light intensity for larval and juvenile mulloway (Argyrosomus japonicus) were investigated and improved protocols determined.  Larvae should be kept in a 12L:12D photoperiod until swim bladder inflation occurs followed thereafter by a 18L:6D photoperiod to promote maximum growth.  For yellowtail kingfish, Seriola lalandi, small fish (e.g. 3 g/fish) should be fed four times per day while feeding once per day was adequate for large fish (e.g. 96.0 g/fish).Weaning cost and success were improved by weaning using Artemia in combination with micropellets.  Juvenile mulloway (e.g. >2.7 g) only need to be fed once every 12 h.  The sensory organs (vision, mechanoreception or chemoreception) are used for feeding by larval and juvenile mulloway and their importance was found to change as fish develop and grow. 

Optimum temperature and salinity for juvenile mulloway was also investigated.  Optimum temperature was between 21-26 C (with survival and growth better at the upper end of this range) and intermediate salinities of 15-34 ppt were optimum. Salinity had no effect on survival or growth of juvenile (e.g. 1.3 – 6.2 g/fish ) yellowtail kingfish.

While effective protocols for producing mulloway in extensive larval rearing ponds have been developed, preliminary research suggest that extensive pond culture of early-stage yellowtail kingfish larvae is not a suitable production platform.  However further investigation should be done to determine if stocking advanced larvae into ponds is more appropriate for production of juvenile yellowtail kingfish.

Volume 2: Diet Development
The aquaculture of many species, especially the high value carnivorous species most often cultured in the developed world has historically relied on the use of fish meal and fish oil to provide the protein and energy contained in commercial aqua-feeds. These ingredient resources are and will continue to be under considerable pressure and as such they are becoming increasingly expensive. Now, more than ever, aquaculture nutrition research is focusing on alternatives to fish meal and fish oil and ways to improve the production efficiency of important aquaculture species via a thorough understanding of their nutritional requirements. These advances improve the profitability of farms, ensure that consumers have access to high quality, nutritious seafood and that the potential impacts on the environment are minimised.

Volume 2 provides new information on the digestibility and utilisation of Australian feed ingredients by mulloway and yellowtail kingfish. Species specific digestibility coefficients were determined for fish meal and fish oil as well as rendered animal products (e.g meat and bone meals, poultry offal meal, blood meal), cereals, legumes and oilseeds (e.g. wheat, sorghum, field peas, lupins, soybean meal) and gluten meals (e.g. wheat, maize). As carbohydrates are generally a  poor source of energy for carnivorous species the digestibility of wheat and pre-gelatinised wheat starch is reported at inclusion contents ranging from 10 to 40% diet. These digestibility coefficients together with information on the nutritional composition of ingredients will provide feed companies with valuable data for use in the formulation and manufacture of new commercial feeds for  each species.

This volume also presents new research on the digestible protein and energy requirements of mulloway and yellowtail kingfish. These requirements were determined by applying a factorial approach to nutrient requirements, a powerful tool that combines data on digestibility, growth potential, carcass composition and nutrient utilisation to predict the amount of dietary protein and energy needed to satisfy the total protein and energy demands of rapidly growing fish. This data is invaluable to feed formulators. In addition, the factorial models we present allow prediction of theoretical feed intake and feed conversion efficiency, data that will allow farmers of either species to benchmark production criteria, develop feeding tables and model nutrient flows from their farming operations.

Volume 2 also includes additional research which investigates the utilisation of increasing dietary levels of carbohydrates such as glucose, wheat and pre-gelatinised wheat starch by mulloway and yellowtail kingfish. The outcomes of these investigations have indicated that both species are surprisingly tolerant of simple and more complex carbohydrates and that this area of research provides exciting new opportunities to investigate dietary protein reduction. Finally, this volume presents the results of research which investigates the effects of increasing or decreasing water temperature on the routine metabolism of mulloway and kingfish and experiments that elucidate the effects of stocking density on the performance of mulloway during the important juvenile stage of growth.