1 NOVEMBER 1998
BIOLOGICAL AND TECHNICAL ASPECTS OF TURBOT SCOPHTHALMUS MAXIMUS L., 1758 CULTURE (in Spanish)
C.A.F. Pato-1998
Microfichas, Instituto Espanol de Oceanografia, No. 12: 1-185
Abstract: The present paper describes different aquaculture techniques, for turbot S. maximus L., 1758 and other species, as well as optimal production installations. The general parameters of such aquaculture are also described.
L-carnitine was used as a nutritional supplement for larvae; a dose of 300 mg/kg of live weight of larvae, favouring growth and survival, produced an increase in weight almost double that of an untreated control group (0.05 g compared with 0.08 g), and 6 % higher survival rate, at a cost of 0.08 pesetas per larva.
Three diets, with fat contents of 21 %, 14 %, and 7 %, were tested, the latter being considered the standard feed. Each of them was used alone, with vitamin E (alpha tocoferol) in a dose of 400 mg kg of fat and/or L-carnitine in two different doses, one of 150 mg/kg of live fish weight and the other of 300 mg/kg of live fish weight. All groups showed significant differences in growth (p < 0.001; MANOVA). The groups presenting the highest growth were those with the lowest fat content. L-carnitine in standard diets (7 % fat) did not favour growth, but did favour a fall in body-fat content. In the case of the diets with a higher fat content, growth was enhanced in relation to the quantity of L-carnitine that was added, while reducing the fat content of muscle. Its use accounted for 3.19 % of the final price per kilogram, and an improvement of 14 % in growth. Used in combination with vitamin E, the effect was the same.
Vitamin E used alone did not favour growth in any of the fat doses, but it did reduce muscular content in lipids in all cases.
With respect to the body content of protein, the groups which showed the highest values were those which fed on the smallest quantity of fat.
These findings indicate that the substitution of protein for lipids in the diet does not improve growth, but nevertheless, with the addition of L-carnitine and vitamin E, growth can be activated by increasing the fat content in the diet and producing animals with a higher fat content in the body.
With respect to survival, significant differences among groups were not found (p > 0.005; Lee-Desu test); a bacterial incidence was detected in the different groups, except for those receiving vitamin E.
The effect of temperature with the same doses of fat were assessed without using any other additives, with the aim of checking the incorporation of fat into the animals' bodies. Temperatures of 12, 18 and 21 C are used. With diets having a 7 % fat content, the content in
the muscle is very similar at the three levels, although it increases progressively with temperature. However, with lipid contents of 14 % and 21 % in the diet, fat accumulation in the muscle increases up to 18 C, and diminishes from 20 C.
The effect of vitamin C is tested against hyperoxidized diets, 45/65 milliequivalents of O2 per kilogram of fat against 7/9 of standard meal. Significant differences in growth were not found in any case, with or without the addition of vitamin C (p > 0.005; MANOVA). A positive effect on survival (p = 0.0000; Lee-Desu test) was found in favour of those groups treated with ascorbic acid.
The protein content in the muscle was greater in all cases in which fish ingested ascorbic acid.
An x-ray sampling showed vertebral synarthrosis among vertebras 11 and 12 (sometimes 11, 12 and 13), in all specimens whose diet lacked vitamin C. This phenomenon was completely absent in those which ingest it.
In hyperthyrosinic diets (the addition of 6 % of L-thyrosine per kilogram of dry diet), the groups which did not ingest vitamin C reached LC 50 (lethal curve) after 19 days of treatment and lordosis in 3 % of specimens. Groups which received ascorbic acid had a survival rate of 81.4 %, against 53.5 % of the group not receiving it, a significant difference (p = 0.0000).
With a dose of 3 % of L-thyrosine, survival at six months was 6.38 % in those which did not receive vitamin C, against 88.6 % in those which received it (p = 0.0000). Its use in a dose of 1 g/kg of live fish weight prevented thyrosinemias, and acted as a corrector in altered diets, reducing the appearance of signs of the so-called granulomatous syndrome by 97 %. Its cost was 24.1 pesetas per kilogram produced.
Folic acid (1 mg/kg of meal) administered alone in experiments lasting for 10 months duration did not show any positive effect on growth in weight in the different groups of specimens on which the experiment was carried out. Vitamin E, administered in doses of 120 mg/kg, which may be considered high, had a slightly positive effect on growth. The use of both together had a very positive effect on growth in weight, compared with the control groups. Significant differences were not detected in body content nor in survival with the use of both substances. The use of both substances at the doses considered the most effective led to a 1.46 % increase in the cost per kilogram of live weight of turbot produced.
According to the reasoning based on the data summarised above, the cost of producing 1 million larvae, fingerlings and kilogram of fish are estimated for growing modules of 50 t per year.
(Centro Oceanografico de Santander, Instituto Espanol de Oceanografia, Apdo. 240, 28080 Santander, Espana)