This article was downloaded by: [Department Of Fisheries] On: 27 October 2013, At: 21:34 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK Transactions of the American Fisheries Society Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/utaf20 Impacts of Diet on Thiamine Status of Lake Ontario American Eels John D. Fitzsimons a , Scott B. Brown b g , Lisa R. Brown b , Guy Verreault c , Rémi Tardif c , Ken G. Drouillard d , Scott A. Rush e & Jana R. Lantry f a Fisheries and Oceans Canada , Great Lakes Laboratory of Fisheries and Aquatic Sciences , 867 Lakeshore Road, Burlington , Ontario , L7R 4A6 , Canada b Environment Canada, Science and Technology Branch , National Water Research Institute , 867 Lakeshore Road, Burlington , Ontario , L7R 4A6 , Canada c Ministère des Ressources Naturelles et de la Faune , 186 rue Fraser, Riviére-du-Loup , Québec , G5R 1C8 , Canada d Great Lakes Institute for Environmental Research, Department of Biological Sciences , University of Windsor , 401 Sunset Avenue, Windsor , Ontario , N9B 3P4 , Canada e Department of Wildlife, Fisheries, and Aquaculture , Mississippi State University , Box 9690, Mississippi State, Mississippi , 39762 , USA f New York State Department of Environmental Conservation , Cape Vincent Fisheries Research Station , 541 East Broadway, Cape Vincent , New York 13618 , USA g Deceased Published online: 02 Sep 2013. To cite this article: John D. Fitzsimons , Scott B. Brown , Lisa R. Brown , Guy Verreault , Rémi Tardif , Ken G. Drouillard , Scott A. Rush & Jana R. Lantry (2013) Impacts of Diet on Thiamine Status of Lake Ontario American Eels, Transactions of the American Fisheries Society, 142:5, 1358-1369, DOI: 10.1080/00028487.2013.811100 To link to this article: http://dx.doi.org/10.1080/00028487.2013.811100 PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions Transactions of the American Fisheries Society 142:1358–1369, 2013 C American Fisheries Society 2013 ISSN: 0002-8487 print / 1548-8659 online DOI: 10.1080/00028487.2013.811100 ARTICLE Impacts of Diet on Thiamine Status of Lake Ontario American Eels John D. Fitzsimons* Fisheries and Oceans Canada, Great Lakes Laboratory of Fisheries and Aquatic Sciences, 867 Lakeshore Road, Burlington, Ontario L7R 4A6, Canada Scott B. Brown1 and Lisa R. Brown Environment Canada, Science and Technology Branch, National Water Research Institute, 867 Lakeshore Road, Burlington, Ontario L7R 4A6, Canada Guy Verreault and Remi´ Tardif Ministere` des Ressources Naturelles et de la Faune, 186 rue Fraser, Riviere-du-Loup,´ Quebec´ G5R 1C8, Canada Ken G. Drouillard Great Lakes Institute for Environmental Research, Department of Biological Sciences, University of Windsor, 401 Sunset Avenue, Windsor, Ontario N9B 3P4, Canada Scott A. Rush Department of Wildlife, Fisheries, and Aquaculture, Mississippi State University, Box 9690, Mississippi State, Mississippi 39762, USA Jana R. Lantry New York State Department of Environmental Conservation, Cape Vincent Fisheries Research Station, 541 East Broadway, Cape Vincent, New York 13618, USA Abstract The Lake Ontario–upper St. Lawrence River (LOUSL) population of American Eels Anguilla rostrata (hereafter, “eels”) was once one of the most important groups of the species but is now in a state of serious decline. Given that thiamine deficiency has been observed in almost all of the top predators in Lake Ontario, we assessed the Downloaded by [Department Of Fisheries] at 21:34 27 October 2013 potential that a diet-induced thiamine deficiency associated with consumption of Alewives Alosa pseudoharengus could be involved. Muscle thiamine was measured in eels from throughout the LOUSL corridor and was compared with putative threshold effect levels established from the literature. Mirex concentrations were used to separate Lake Ontario-resident eels from non-Lake Ontario-resident eels. Stable isotope analyses of eel muscle samples and potential prey, including Alewives, were combined with mixing model software to infer the diets consumed by Lake Ontario eels. Although residence in Lake Ontario was associated with a significant decline in muscle thiamine concentration, estimated Alewife consumption by eels was unexpectedly low. Instead, mixing model results indicated that crayfish and Round Goby Neogobius melanostomus were the major prey. Both taxa are known to contain thiaminase and have the potential to cause thiamine deficiency, but there are no reports of thiamine deficiency associated with Round Goby consumption, thus implicating crayfish. There was no recovery in thiamine levels prior to the initiation of oceanic migration. As a result, thiamine levels of Lake Ontario-resident eels prior to migration were only slightly above putative threshold effect levels for pathological and behavioral effects in Japanese Eels Anguilla japonica,but *Corresponding author: fi[email protected] 1Deceased. Received August 24, 2012; accepted May 28, 2013 Published online September 2, 2013 1358 THIAMINE STATUS OF AMERICAN EELS 1359 this would require confirmation with American Eels. Since thiamine levels are expected to decline further during migration, additional effects on eel behavior, reproduction, and survival seem probable. Because of panmixia, such effects—when combined with the relatively high reproductive potential of Lake Ontario-resident eels—may have consequences for the entire species. The Lake Ontario–upper St. Lawrence River (LOUSL) pop- mercial landings (COSEWIC 2006) indicate that this region ulation of American Eels Anguilla rostrata (hereafter, “eels”) contributed a substantial portion (27–67%) of the total North has experienced dramatic declines in abundance in recent years American spawning output of American Eels. (Castonguay et al. 1994; Axelsen 1997; Casselman et al. 1997); Hydropower dams and overfishing are considered to be the because of panmixia, these declines have the potential to im- two largest sources of mortality for LOUSL eels. The Moses– pact the entire American Eel species (Velez-Espino´ and Koops Saunders and Beauharnois–Les Cedres hydropower dams lo- 2010). The declines are reflected in both CPUE of adults in the cated on the St. Lawrence River (completed in 1958 and 1961, river (de Lafontaine et al. 2010) and reductions in the numbers respectively) represent a major impediment to both upstream of juvenile eels ascending the eel ladder at the Moses–Saunders and downstream migrations of eels in the LOUSL corridor Hydroelectric Dam (Casselman et al. 1997). Casselman et al. (Verreault and Dumont 2003; COSEWIC 2006; Cairns et al. (1997) reported that after 1982, the number of juvenile eels 2007; de Lafontaine et al. 2009, 2010). However, these two ascending the ladder (used as a recruitment index) reached a hydropower facilities alone cannot account for the dramatic record low. The recruitment index fell to its lowest value in decline in abundance of the LOUSL eel population. It was es- 1999 (MacGregor et al. 2008), representing a thousand-fold de- timated that eel mortality due to passage through the turbines crease in abundance relative to that observed in 1982. at the Moses–Saunders and Beauharnois–Les Cedres dams av- The large population of eels that historically resided in the eraged 22% per dam (Verreault and Dumont 2003). Although LOUSL corridor (Figure 1; Casselman 2003) appeared to com- collectively a large source of mortality at approximately 40% plete the entire portion of the adult phase of their life cycle overall, turbine-related mortality alone would have been insuffi- in freshwater up until the point of their spawning migration, cient to completely block access either upstream to Lake Ontario as indicated by otolith Sr:Ca ratios (Goodwin 1999; Thibault or downstream to the ocean. et al. 2007; J. D. Fitzsimons, unpublished data). There is still In the past, fishing mortality of eels was high: eel landings uncertainty as to the habitat occupied within the corridor and in Ontario increased rapidly from 1,435 metric tons in 1950 to the relative dietary contributions from freshwater and marine re- 13,240 metric tons in 1960 and 195,000 metric tons in 1975 sources. Otolith Sr:Ca ratios can confirm