Effects of Canola and Safflower Oil Supplementation in Diets, on Growth Performance and Fatty Acid Composition of Russian Sturgeon (Acipenser gueldenstaedtii Brandt, 1833)

The aim of this study was to determine the impact on growth performance and muscle fatty acid composition, of replacement of 50% fish oil (FO) with canola oil (CO) and safflower oil (SFO) in the diets of Russian sturgeon (Acipenser gueldenstaedtii). Two isoproteic (48%) and isolipidic (12%) diets were formulated combining two oil sources (50% fish oil + 50% canola oil or 50% fish oil + 50% safflower oil). The diets were fed to apparent satiation to triplicate groups for 15 weeks, twice a day. No significant differences were observed between the experimental groups fed CO and SFO diets in terms of weight gain, specific growth rate, feed conversion ratio, and protein efficiency ratio. The experimental groups fed CO and SFO diets did not show significant differences in terms of protein, lipid, ash, and moisture content in their muscle. There were no significant differences in muscle between total n-3 fatty acids but total n-6 fatty acids were significantly higher in SFO group (24.90%) than in CO group (21.30%). Total n-6 fatty acids were also higher than (20.43%) at the start. In conclusion, 50% replacement of FO by CO or SFO in Russian sturgeon diets had no negative effect on growth performance, feed efficiency and fatty acid composition in the muscle of this species

Environmental capacity of receiving water as basis for regulating intensity of milkfish (Chanos chanos Forsskal) culture

This paper presents the results of the assessment of the environmental condition of a receiving water and demonstrates how the environmental capacity of the system can be estimated based on effluent discharge from milkfish ponds and water criteria from scientific literature and other studies. An estuary (average volume, 295 333 m3; average depth, 1.9 m) in Punta Pulao, Dumangas, Iloilo, Philippines served as discharge and irrigation system for commercial milkfish ponds and experimental/verification ponds owned by the Southeast Asian Fisheries Development Center. Total ammonia nitrogen, nitrite, nitrate, phosphate, and chlorophyll a (chl a) were determined monthly (during spring tide) for 4 months. Samples were taken at low and high tides that coincided with the draining and flooding of ponds, respectively. Monthly concentrations of these water quality variables generally increased from the first to fourth month of sampling (April–July 2001) during low tide. Very slight increases were observed during high tide. The magnitude of changes in the diurnal patterns of phosphate, chl a, and dissolved oxygen appeared to be higher at spring tide than at neap tide. This indicates that the inflowing river at low tide (during spring tide) brought effluents containing high amounts of nutrients from ponds located upstream. The water, salt, dissolved inorganic nitrogen (DIN), and phosphate (DIP) budgets of the entire estuary were determined following the one-box model by LOICZ-IGBP (2000, LOICZ biochemical budgeting procedure: a tutorial pamphlet. L. T. David, M. L. San Diego-McGlone, C. J. Crossland and S. V. Smith (Eds). Publ. for LOICZ International Project Office, the Netherlands, 29 pp.). The budgets indicate that the system is net heterotrophic and nitrogen (N) fixing during the dry months, but that there could be no environmental impact during the rainy months because of short water exchange time. Results further suggest that the system is a source of N and phosphorus (P) during the dry and rainy months; the condition is largely influenced by the high amount of nutrient inputs in to the river. Linear regression analysis was performed to determine relationship between nutrient concentrations in the system and total DIN or DIP input to the system at low tide. Environmental capacity in terms of the maximum amount of DIN or DIP input to the system was predicted using regression analysis and following set criteria for nutrients, i.e. nitrite, nitrate, and phosphate. At present, the estuarine water quality has already reached its environmental capacity during the dry months. About 945 ha of commercial milkfish ponds are operating upstream, mostly as extensive systems. If these ponds are converted to semi-intensive or intensive systems, it is recommended that the pond area be reduced to 122 ha if the DIP criterion is to be followed so as not to exceed the environmental capacity. Exceeding this environmental capacity may affect production through reduction of fish growth, occurrence of diseases, and fish mortalities

Genetic Inactivation of European Sea Bass (Dicentrarchus labrax L.) Eggs Using UV-Irradiation: Observations and Perspectives

International audienceAndrogenesis is a form of uniparental reproduction leading to progenies inheriting only the paternal set of chromosomes. Ithas been achieved with variable success in a number of freshwater species and can be attained by artificial fertilization ofgenetically inactivated eggs following exposure to gamma (c), X-ray or UV irradiation (haploid androgenesis) and byrestoration of diploidy by suppression of mitosis using a pressure or thermal shock. The conditions for the geneticinactivation of the maternal genome in the European sea bass (Dicentrarchus labraxL.) were explored using differentcombinations of UV irradiation levels and durations. UV treatments significantly affected embryo survival and generated awide range of developmental abnormalities. Despite the wide range of UV doses tested (from 7.2 to 720 mJ.cm22), only onedose (60 mJ.cm22.min21with 1 min irradiation) resulted in a small percentage (14%) of haploid larvae at hatching in theinitial trials as verified by flow cytometry. Microsatellite marker analyses of three further batches of larvae produced by usingthis UV treatment showed a majority of larvae with variable levels of paternal and maternal contributions and only one larvadisplaying pure paternal inheritance. The results are discussed also in the context of an assessment of the UV-absorbancecharacteristics of egg extracts in this species that revealed the presence of gadusol, a compound structurally related tomycosporine-like amino acids (MAAs) with known UV-screening properties