Effects of stocking density on performance, proximate composition and pigmentation of cultured arctic charr (Salvelinus alpinus)

Metusalach, 1960- (1995) Effects of stocking density on performance, proximate composition and pigmentation of cultured arctic charr (Salvelinus alpinus). Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (25MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

The effects of stocking density on performance, proximate composition and pigmentation of cultured Arctic charr (Salvelinus alpinus) were studied. Results indicated that specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER) of fish were significantly (p<0.05) influenced by stocking densities, but no significant (p>0.05) effects were evident in the hepatosomatic index (HSI) of fish. These performance parameters of fish correlated inversely with stocking density at 40, 50 and 75 kg/m³ (r = -0.9522 for SGR, -0.9696 for FCR, -0.9886 for PER, and -0.9059 for HSI). Although SGR, FCR and PER of fish from different stocking densities varied significantly (p<0.05), their final weights did not. -- Results also indicated that while the moisture content decreased, protein and lipid content increased as fish grew; the mineral content remained relatively unchanged over this period. Analyses indicated that moisture, protein and lipid content varied significantly (p<0.05) among density groups while ash content did not. Regression analysis showed that moisture and ash content were directly related to stocking density (r = 0.9440 and 0.9994, respectively), whereas protein and lipid content were not (r = -0.5394 and -0.7030, respectively). -- The total amino acid content of fish varied significantly (p<0.05) according to stocking density and sampling dates. Aspartic acid, glutamic acid, leucine and lysine were the most abundant amino acids present, whereas hydroxyproline was the least abundant. The free amino acid content of the fish also varied significantly (p<0.05) and inversely with stocking density (r = -0.9441) and sampling dates. The major free amino acids were anserine, taurine, glycine and alanine. -- Lipid fatty acid composition of charr flesh was relatively unchanged over the course of the experiments. Among density groups, fatty acid contents of fish flesh were also relatively similar. Unsaturated fatty acids were the dominant fatty acids, accounting for up to 75% of the total lipids. Saturated and monounsaturated fatty acids correlated inversely with stocking density (r = -0.9914 and -0.9963, respectively), whereas polyunsaturated fatty acids correlated directly with stocking density (r = 0.9984). -- The Hunter L*. a*, b* values varied significantly (p<0.05) among density groups. For belly skin, these colour parameters decreased with increasing stocking density. No correlation was observed between the total carotenoid contents of fish skin and these colour parameters. On the other hand, the Hunter L* values of fillets and homogenized tissues were inversely correlated with their carotenoid contents (r = -0.9245 to -0.9844, respectively), whereas their Hunter a* and b* values were directly correlated with total carotenoid contents (r = 0.9040 to 0.9824 for a* values and 0.9527 to 0.9924 for b* values, respectively). -- The content of carotenoid pigments in flesh and skin of charr increased with duration of feeding on pigmented diets. After 11 to 16 weeks of feeding on a canthaxanthin-pigmented diet, fish flesh attained the required level of carotenoids (3-4 mg/kg wet tissue) considered sufficient for providing a satisfactory colour impression. However, stocking density did not correlate with flesh carotenoid concentration (r = -0.6034). Canthaxanthin, echinenone, 4'-hydroxyechinenone, lutein and its esters, isocryptoxanthin and β-carotene were identified in different organs of charr. Canthaxanthin was the main carotenoid in charr flesh, whereas β-carotene, lutein esters and 4'-hydroxyechinenone, and echinenone were the dominant carotenoids in charr skin, gonads and liver, respectively. Canthaxanthin was not detected in the liver of fish. Therefore, dietary carotenoids may be deposited in different organs as such or may undergo reductive changes.

Actions (login required)

View Item