Ontogenetic Dietary Changes and Thiamine Status of Lake Ontario Chinook Salmon, 2005–2006

Abstract

In the Great Lakes, an Alewife Alosa pseudoharengus diet has been reported to cause thiamine deficiency in salmonines as a result of high thiaminase activity. The ontogeny of thiamine deficiency and its relationship to Alewife consumption have not been determined in Chinook Salmon Oncorhynchus tshawytscha within this system. Using stable isotope mixing models along with muscle thiamine, we assessed ontogenetic changes in the diet and corresponding muscle thiamine status of Lake Ontario Chinook Salmon ranging in TL from 100 to 1,000 mm. Thiamine levels were highest in young of the year collected in a tributary of Lake Ontario but declined once Chinook Salmon entered Lake Ontario. In Lake Ontario, the diets of juvenile (200-400 mm; 97-99%) and adult (>400 mm; 97-100%) Chinook Salmon consisted almost entirely of Alewives as estimated using mixing models. This Alewife diet was associated with an ontogenetic decline in muscle thiamine among Chinook Salmon. The asymptotic decline in thiamine concentration with increasing size plateaued at 720-758 pmol/g of muscle. The proportion of individuals below a thiamine threshold of 500 pmol/g (associated with a loss of equilibrium) increased with TL up to 799 mm and then declined between 800 and 1,000 mm. At these muscle concentrations, no outward signs of thiamine deficiency were observed. Calculation of total mass accumulation of body stores of thiamine (muscle concentration times body weight) showed an unexpected and significant increase with size. Although it appears that dietary Alewives affected thiamine status, there were undetermined factors, such as incomplete destruction of thiamine by thiaminase, gut synthesis of thiamine, gill absorption of water thiamine, and/or other factors, that contributed to the overall thiamine status of these Chinook Salmon.Chinook Salmon Oncorhynchus tshawytscha were intentionally stocked in the Great Lakes beginning in the 1960s to control the overabundant populations of nonindigenous Alewives Alosa pseudoharengus and to create a recreational sport fishery (Tanner 1971). Alewives, which have a high thiaminase (enzyme code 2.5.1.2; IUBMB 1992) activity (Tillitt et al. 2005), are found throughout the Great Lakes basin, where they comprise a major proportion of the diet of salmonines, including Chinook Salmon, Coho Salmon Oncorhynchus kisutch, and Lake Trout Salvelinus

Connecting thiamine availability to the microbial community composition in Chinook salmon spawning habitats of the Sacramento River basin

“…While post-embryonic salmonids primarily acquire thiamine through dietary intake, all life stages of salmonids (including eggs and embryos) can acquire thiamine directly from the dissolved pool in the surrounding environment via uptake over the gills and diffusion, respectively ( 1 , 7 , 20 ). The degree to which salmon could be supplemented by environmental dissolved thiamine at each life stage is unknown.…”

Connecting Thiamine Availability to the Microbial Community Composition in Chinook Salmon Spawning Habitats of the Sacramento River Basin

“…While post-embryonic salmonids primarily acquire thiamine through dietary intake, all life stages of salmonids (including eggs and embryos) can acquire thiamine directly from the dissolved pool in the surrounding environment via uptake over the gills and diffusion, respectively (1,7,20). The degree to which salmon could be supplemented by dissolved thiamine at each life stage is unknown.…”