1. Thiamine Variations in Rainbow Smelt from the Great Lakes
ABSTRACT: Eggs from gravid rainbow smelt (Osmerus mordax) captured in each of the Great Lakes and two other water bodies as reference sites (Little Clear Pond, NY and Fore River, MA) were collected during spring for thiamine analysis. Thiamine concentrations (nmol/g ± standard error) were 9.9 ± 0.8 in Lake Huron, 6.4 ± 1.4 in Lake Ontario, 6.4 ± 1.2 in Lake Superior, 3.9 ± 0.7 in Lake Michigan, 3.1 ± 0.4 in Lake Erie, 12.1 ± 1.1 in Fore River, and 8.1 ± 1.1 in Little Clear Pond. Although highly variable within lakes and between years, thiamine concentrations in spawning adults appear to be adequate in the waters sampled except for Lake Erie and Lake Ontario, which may occasionally lead to reduced lake recruitment success.
M. A. CHALUPNICKI, H. G. KETOLA
USGS Great Lakes Science Center,
Tunison Laboratory of Aquatic Science
Cortland, NY
M. H. ZEHFUS, J. R. CROSSWAIT
Department of Chemistry, Black Hills State University
Spearfish, SD 57799
J. RINCHARD
Department of Environmental Science and Biology
The College at Brockport, State University of New York
Brockport, NY 14420
RESULTS: Rainbow smelt significantly differed in size (P<0.001) with the Fore River samples the longest and the Lake Michigan population the shortest. Three significantly different groups were observed in the following order; Fore River (189 ± 12.3mm) > Lake Erie (143 ± 2.3mm), Little Clear Pond (141 ± 4.3mm), Lake Ontario (141 ± 2.3mm), Lake Huron (133 ± 3.1mm) > Lake Superior (128 ± 4.2mm), Lake Michigan (122 ± 0.3mm). Overall mean egg thiamine concentrations in rainbow smelt from the Great Lakes and two additional waters were not similar across (P=0.03) and within (P=0.02) years (Figure 3). Eggs from the Fore River have the highest thiamine concentration, while eggs from lakes Erie and Michigan were the lowest (Fore River > Lake Huron, Little Clear Pond, Lake Superior, Lake Ontario > Lake Michigan, Lake Erie).
INTRODUCTION: Rainbow smelt (Osmerus mordax) is a common forage fish that has been introduced into the Great Lakes as an alternative forage species. Following establishment, rainbow smelt have become prey for many salmonine species including Atlantic salmon (Salmo salar), Chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), and lake trout (Salvelinus namaycush). This species is also an important spring delicacy for many fisherman around the Great Lakes. Rainbow smelt are known to have oscillations in population abundance and distribution; but in the past decade Great Lakes populations have marketly decrease. The cause of this decline is unknown, but it may be related to the introduction of alewife (Alosa pseudoharengus), which is known to be voracious consumers of eggs and newly hatch larvae. Alewife also contains high levels of thiaminase, an enzyme which destroys thiamine (vitamin B1). Mortality related to egg thiamine deficiency, commonly referred to as early mortality syndrome, has been reported in many salmonid species in the Great Lakes. We hypothesize that nutritional deficiencies associated with consumption of young alewives may be responsible for the poor recruitment of rainbow smelt observed in the Great Lakes. Therefore, the objective of this study was to determine the thiamine concentration in the eggs of rainbow smelt from the Great Lakes. We also collected eggs from two bodies of waters which do not contain alewife (Little Clear Pond, NY and Fore River, MA) as reference sites.
FIGURE 2A: Gravid Female Rainbow Smelt
FIGURE 3: Mean total thiamine concentrations in rainbow smelt eggs from the Great Lakes and two control waters.
METHODS: Gravid rainbow smelt were collected during spring trawl surveys conducted by the United States Geological Survey (USGS) in the Great Lakes in (Figure 1). Two locations were selected to represent Lake Superior (Cloud Bay and Kewennaw Penninsula, WI), one location for Lake Michigan (Waukegan, IL), Lake Huron (Carp River, MI), Lake Erie (Fairport Harbor, OH), and three locations for Lake Ontario (Olcott, Rochester, and Oswego, NY). Rainbow smelt were also collected from two additional waters outside the Great Lakes drainage, Little Clear Pond near Saranac Lake, NY and the Fore River, Weymouth, MA, at night using a dip net. Total length was measured and the eggs were collected and immediately frozen (-700C) until biochemical analysis (Figure 2A, 2B). We analyzed 2-10 lots of eggs per lake with each lot representing 1-20 females to better represent lake populations. Total thiamine concentrations in eggs sampled were determined by the method of Brown et al. (1998) as modified by Barnes et al. (2001) using fluorescence measured with a Perkin Elmer model 204 fluorescence spectrophotometer (excitation set at 375 nm and emission monitored at 433 nm).
Because thiamine data were not normally distributed, we used the non-parametric Kruskal-Wallis analyses of variance (Statistix 8.0, Analytical Software, Tallahassee, Florida) to examine differences among locaions. When differences were significant, we used a multiple comparison test to determine which concentrations differed significantly.
FIGURE 1: Sites encompassing the Great Lakes and two additional waters where gravid rainbow smelt were captured and their eggs collected for thiamine analysis.
CONCLUSION: Rainbow smelt populations in the Great Lakes have historically oscillated in abundance and recruitment success since their introduction in the early 1900’s. Current smelt populations are low, especially in Lake Ontario, which has experienced the lowest recorded abundance in the past thirty years. Increased predator-prey interactions and changes in the forage base from native coregonid species to introduced species such as the alewife may have aided in reduced lake populations of smelt. The upper Great Lakes (Superior and Michigan) have healthy salmon and trout populations that have depressed smelt populations where the reproductive year-class has become smaller and younger. Although the lower Great Lakes have healthy salmon populations, lake trout numbers are still recovering while forage pressure has been limited and allowed extra growth in reproductive adult smelt. In Little Clear Pond, smelt are subjected to Atlantic salmon predation and have no alewife to compete with for food. Although smelt have also remained longer in the Atlantic Ocean than in the Great Lakes, spawning runs are recently very low for reasons unknown.
Differences in thiamine content for rainbow smelt within lakes and between years indicate that there may be different forage and/or feeding patterns which produce these variations. Within-lake thiamine variation is a common occurrence among smelt and alewife populations and has been reported in the literature. Despite all-time low abundance records for the Lake Ontario population, minor population increases have been observed with larger year-classes predicted in the future.
The diet of rainbow smelt from the Great Lakes is comprised up to 60% of fish. Certain Notropis species, alewife, and rainbow smelt contain high activities (2,640-32,700 pmol/g/min) of thiaminase, which has been linked to early mortality syndrome in fry of Great Lakes salmonids. Despite thiamine variations in rainbow smelt populations from the Great Lakes, values are still apparently meet their physiological requirements. Although thiamine deficiency has not been reported in smelt populations from the Great Lakes, one avenue of population disruption may be from a thiaminase rich food source which may magnify abundance oscillations through impaired reproduction. Further observations of smelt populations and their trends in the Great Lakes are warranted.
FIGURE 2B: Rainbow Smelt Collection from Great Lakes USGS Trawl
REFERENCES:
Barnes, M. E., M. H. Zehfus, J. A. Schumacher, K. S. Stock, F. Farrokhi, and R. L. Nutter Initial observations on thiamine hydrochloride treatment of eggs of landlocked fall Chinook salmon. North American Journal of Aquaculture. 63:
Brown, S. B., D. H. Honeyfield, and L. VandenByllaardt Pages In: McDonald, G., J. Fitzsimons, and D. C. Honeyfield (eds.). Early life stage mortality syndrome in fishes of the Great Lakes and Baltic Sea. Thiamine analyses in fish tissues. American Fisheries Society Symposium 21, Bethesda, Maryland.
ACKNOWLEDGEMENTS: Special thanks to Ed Rosemund (USGS), Bill Edwards (USGS), Dawn Dittman (USGS), Maureen Walsh (USGS), Gary Cholwek (USGS), Chuck Madenjian (USGS), Edward Grant (New York Department of Environmental Conservation Adirondak Fish Hatchery), and Brad Chase (Massachusetts Marine Fisheries Division) for sample collection.