S.M. Budge, C.C Parrish, C.H. McKenzie, R.J. Thompson
Abstract:
The fatty acid nutritional requirements of marine finfish and shellfish are of utmost importance. The long-chain polyunsaturated fatty acids (PUFA) 20:4w6, 20:5w3 and 22:6w3 are essential for animal growth and survival. Insufficient amounts of these acids in the diet have a variety of deleterious effects, including reduced feeding efficiencies, liver damage and behaviour changes. Studies have suggested that optimum levels of w3/w6 fatty acids in fish diets are in the range of 5:1 to 10:1 while the recommended ratio of the specific fatty acids, 22:6w3/20:5w3, is best at 2:1. Such requirements are often overlooked when establishing bivalve aquaculture sites in the natural environment. Two geographically different locations in Newfoundland have been investigated to determine typical fatty acid compositions of plankton. The quality of plankton-produced fatty acids in the natural environment fluctuates both spatially and temporally and we have found that plankton (>20 micrometer) in these areas often do not have the literature ratios. PUFA levels in plankton in both areas were high, ranging from 31 to 53% of total fatty acids with an average of 42%. Ratios of w3/w6 fatty acids varied from 5 to 21 with an average of 15 while the ratio of 22:6w3/20:5w3 ranged from 0.04 to 1.90 with an average of 0.81. These parameters, along with general fatty acid compositions, will be considered in terms of dietary suitability. In addition, the fatty acid composition of mussels (Mytilus edulis) harvested at one of these sites will be compared to that of the available phytoplankton.
(Chemistry Department, Memorial University of Newfoundland, St. John's, NF A1B 3X7, Canada)