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Culture of striped trumpeter (Latris lineata) post-larvae
thesisposted on 2023-05-26, 07:07 authored by Bryan ChoaBryan Choa
The striped trumpeter (Latris lineata) has been the subject of research at the Marine Research Laboratories, Taroona since the 1980s as an alternative species for the Tasmanian Atlantic salmon (Salmo salar) farming industry. It is an endemic species with excellent white flesh, high in polyunsaturated fatty acids. Considerable research has been conducted into improving larval survival and quality through better understanding of optimal rearing conditions, nutrition and health. The culture of juvenile striped trumpeter is complicated by a prolonged post-larval or paperfish‚ÄövÑvp stage which can last up to nine months. My study is the first to research the nutrition and optimal rearing conditions of striped trumpeter post-larvae. Prior to this study, post-larvae were weaned from live feeds at three months of age. Research showed post-larvae could be weaned onto formulated diets using a co-feeding strategy at 40 days post-hatch (dph) and could be fully weaned onto microdiets at 50 dph. Feeding larvae with live feeds led to higher survival and growth but the use of live feeds required more financial and human resources and did not have a consistent nutritional profile. The adoption of feeding formulated diets to larvae by 50 dph has greatly increased production of post-larvae. Temperature regime was found to be the most significant factor influencing growth and development of post-larvae. Three-hundred-day-old post hatch post-larvae (12.1 ¬¨¬± 0.2 g, mean ¬¨¬± SE) were reared at 12, 14, 16 and 18 oC, over 84 days. Polynomial models predicted that growth was maximised between 12.9 oC (thermal growth coefficient) and 14.4 oC (specific growth rate). Post-larvae reared at 16 oC exhibited similar growth rates but did not metamorphose into juveniles as quickly as post-larvae reared at 14 oC and 12 oC. Post-larvae reared at 18 oC showed the slowest growth and metamorphosis rates. Post-larvae reared at temperatures outside the optimum required more nutrients to cope with the increased metabolic demand and this was reflected in their whole body chemical composition and productive protein and energy values. The effects of ration were studied by feeding two-hundred-eighty-seven day-old post-larvae (8.1 ¬¨¬± 0.1 g, mean ¬¨¬± SE) at three ration levels, 33 %, 67 % and 100 % satiation, using dietary lipid levels of 18 % and 24 %, over a period of 63 days at 15 oC. Polynomial models predicted a feeding rate of 4 % biomass day-1 to be optimal. Growth, total carcass crude lipid and development into juveniles were influenced by ration level. Dietary lipid levels did not affect growth and development but had a significant effect on carcass total lipid. Minimum thresholds for metamorphosis into juveniles were determined to be 20 g in wet weight and at least 4 % carcass total lipid. Metabolic weight exponents for protein and energy were derived from data collected using starvation trials of ten days in duration on fish of 1 g to 120 g wet weight. Metabolic weight exponents of 0.8 ¬¨¬± 0.2 for energy and 0.6 ¬¨¬± 0.0 for protein were found. A factorial model was used to predict protein and energy requirements of post-larvae via data from the temperature and ration growth trials. Maintenance requirements were 1.8 g body weight-0.7 day-1 of protein and 116.1 kJ body weight-0.8 day-1 of energy. An optimum dietary protein to dietary energy ratio of 21.8 g protein MJ-1 was predicted. My study provides the first empirical data to develop protocols for the rearing of striped trumpeter post-larvae. The results have been successfully used to produce over 5,000 juveniles grown out in pilot sea cage trials in Tasmania. Whole body chemical, mineral and trace elemental composition data from striped trumpeter ranging from 1 g to sexually mature broodstock were collected. The accretion of whole body total lipid was inversely related to moisture while protein and ash content remained constant. Models were developed which predict the whole body chemical, mineral and trace elemental composition of striped trumpeter. My study has important implications for aquaculture and fisheries management of striped trumpeter, in particular the rearing of post-larvae in hatcheries, timing of stocking into sea cages, especially prior to metamorphosis, and for wild stock recruitment models.
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