Survey of four essential nutrients and thiaminase activity in five Lake Ontario prey fish species

Abstract

Thiamine deficiency is an impediment to salmonine reproduction in the Great Lakes, but little is known about other measures of dietary quality, such as lipid-soluble vitamins or fatty acids in prey fish. The objective of the present research was to measure selected essential nutrients and thiaminase activity in five Lake Ontario prey fish species (alewife Alosa psuedoharengus, rainbow smelt Osmerus mordax, slimy sculpin Cottus cognatus, threespine stickleback Gasterosteus aculeatus and round goby Neogobius melanostomus). Total thiamine was greater in alewife (13.6nmol/g) than in the other species (6.2–9.0nmol/g). In 2006, thiaminase activity was unexpectedly high in goby (12.49nmol/g/min), sculpin (1.99nmol/g/min) and smelt (9.24nmol/g/min). In 2007, thiaminase activity in goby (0.99nmol/g/min) and smelt (4.94nmol/g/min) was low compared to 2006, whereas sculpin thiaminase activity was greatest (6.01nmol/g/min). The causes for this variability are unknown. Thiaminase activity was within the expected range for alewife (4.31–6.31nmol/g/min) and stickleback (0.06nmol/g/min). Concentrations of retinoids, carotenoids, vitamin E (tocopherol) and fatty acids also differed among prey fish species. Tocopherol concentrations in goby (12.74ng/mg), sculpin (25.29ng/mg), and smelt (22.81ng/mg) were greater than in alewife (1.59ng/mg). Goby had the lowest ∑ ω-3 to ∑ ω-6 fatty acid ratio (1.44) when compared to sculpin (2.97) and smelt (2.85). Thiaminase concentrations in alewife and smelt (and possibly goby) suggest that they have the potential to adversely affect natural reproduction in salmonines. Concentrations of carotenoids, retinoids and tocopherol in prey fish appear to be lower than salmonine dietary requirements.