• Effects of Vitamin B1 (Thiamine) Deficiency in Lake Trout (Salvelinus Namaycush) Alevins and Preventive Treatments

      Lee, Bong-Joo; Jaroszewska, Marta; Dabrowski, Konrad; Czesny, Sergiusz; Rinchard, Jacques; Illinois Natural History Survey; Ohio State University; The College at Brockport (2009-01-01)
      The objectives of this study were to examine the effect of thiamine immersion of fish from a population known for compromised survival as a result of early mortality syndrome (EMS) and to investigate the cause–response relationship between thiamine concentration and lesions in tissues in swim-up-stage lake trout Salvelinus namaycush alevins. Lake trout eggs from 14 fish from Lake Michigan were artificially fertilized and the progeny divided into two groups based on the thiamine concentration (low [,0.73 nmol/g] or high [.0.85 nmol/g]) in the unfertilized eggs. Progeny were treated or not with a thiamine solution (2,000 mg/L for 2 h) at hatching or the swim-up stage. The survival of progeny in control groups at the swim-up stage correlated with thiamine concentration. The low thiamine-treated groups had significantly higher survival between the swim-up stage (812.0 degree-days) and 16 d after swim-up (963.3 degree-days) than the control groups; the survival of the high thiamine-treated groups did not differ between treated and control fish, regardless of the treatment at hatching and the swim-up stage. Control alevins that had low thiamine levels showed EMS, which resulted in 94.9–100% mortality 16 d after the swim-up stage. No pathological changes were observed in the brain, olfactory lobe, eye, liver, or muscle in alevins of high thiamine-treated group. Glycogen deposits in the liver of alevins from the low control group were variable, no glycogen being observed in the hepatocytes of 7 of the 24 fish. We demonstrate that thiamine treatment at swim-up enhances the survival of EMS-affected lake trout relative to treatment at hatching.
    • Intrapopulation Variation in Egg Lipid and Fatty Acid Composition and Embryo Viability in a Naturally Spawning Walleye Population from an Inland Reservoir

      Czesny, Sergiusz; Rinchard, Jacques; Dabrowski, Konrad; Ohio State University; The College at Brockport (2005-01-01)
      The objective of the study was to evaluate the variation in embryo viability within a population of walleye Sander vitreus from an inland reservoir throughout the spawning season. Egg size, egg lipid content, and fatty acid composition were used as criteria to evaluate egg quality. Additionally, we sought to verify whether any particular size-class of females produces superiorquality eggs or whether the time of spawning (early, middle, or late) has an effect on egg quality. Seventy-seven ovulating walleye females (total length, 465–885 mm) were captured in Salt ForkReservoir, Ohio, throughout the spawning season. Although egg diameter after water hardening varied among females (1.85–2.38 mm), egg size did not correlate with female length (P > 0.05). Average egg lipid content was 12.0 +/- 1.3% (mean +/- SD) of wet weight and was unrelated to egg diameter (P > 0.05). Neutral and phospholipid classes in eggs comprised 77.5 +/- 4.7% and 22.5 +/- 4.7% of total lipids, respectively. Egg diameter was not significantly related to any of the specific fatty acids from neutral or phospholipid fractions (P > 0.05). Moreover, egg fatty acid compositions from both neutral lipids and phospholipids did not change during the spawning season. High survival of embryos (90.0 +/- 8.7%) from females across the observed size range was recorded regardless of the spawning period. We concluded that the quality of walleye eggs was consistently high and thus that the timing of gamete collection would not compromise hatchery programs.
    • Linking Egg Thiamine and Fatty Acid Concentrations of Lake Michigan Lake Trout with Early Life Stage Mortality

      Czesny, Sergiusz; Dettmers, John M.; Rinchard, Jacques; Dabrowski, Konrad; Ohio State University; The College at Brockport; University of Illinois (2009-01-01)
      The natural reproduction of lake trout Salvelinus namaycush in Lake Michigan is thought to be compromised by nutritional deficiency associated with inadequate levels of thiamine (vitamin B1) in their eggs. However, mortality driven by thiamine deficiency (commonly referred to as early mortality syndrome [EMS]) is not the only significant cause of low lake trout survival at early life stages. In this study, we sought to better understand the combined effects of variable levels of thiamine and fatty acids in lake trout eggs on prehatch, posthatch, and swim-up-stage mortality. We sampled the eggs of 29 lake trout females from southwestern Lake Michigan. The concentrations of free thiamine and its vitamers (e.g., thiamine monophosphate [TMP] and thiamine pyrophosphate [TPP]) as well as fatty acid profiles were determined in sampled eggs. Fertilized eggs and embryos were monitored through the advanced swim-up stage (1,000degree-days). Three distinct periods of mortality were identified: prehatch (0–400 degree-days), immediately posthatch (401–600 degree-days), and swim-up (601–1,000 degree-days). Stepwise multiple regression analysis revealed (1) that cis-7-hexadecenoic acid in both neutral lipids (NL) and phospholipids (PL) correlated with prehatch mortality, (2) that docosapentaenoic acid in PL and docosahexaenoic acid in NL correlated with posthatch mortality, and (3) that total lipids, TPP, and palmitoleic acid in NL, linoleic acid, and palmitic acid in PL correlated with the frequency of EMS. These results indicate the complexity of early life stage mortality in lake trout and suggest that inadequate levels of key fatty acids in eggs, along with variable thiamine content, contribute to the low survival of lake trout progeny in Lake Michigan.
    • Molecular Markers of Yolk Sac Fry Development in Nine Families of Lake Trout

      Vuori, Kristiina A.; Paavilainen, Tiia; Nikinmaa, Mikko; Czesny, Sergiusz; Rinchard, Jacques; Illinois Natural History Survey; The College at Brockport; University of Turku (2009-01-01)
      Salmonids in certain areas of North America and northern Europe suffer from reproductive disturbances manifested through the death of yolk sac fry. These disturbances are referred to as early mortality syndrome (EMS) in the Great Lakes region and M74 in the Baltic Sea. Both of these syndromes have been associated with reduced concentrations of thiamine in affected females and their eggs. However, large variations in signs and mortality, both within and between the individual syndromes, have been reported. Yolk sac fry mortality (M74) in Atlantic salmon Salmo salar has been shown to be associated with reduced DNA binding of the hypoxia-inducible transcription factor 1 (HIF-1), reduced production of vascular endothelial growth factor (VEGF) protein, decreased capillary density, and down-regulation of adult-type globin gene transcription (which is responsible for the protein part of adult hemoglobin). One of the main effects of all of these changes is reduced oxygen transport to the tissues of affected fry. In this study, the developmental patterns of HIF-1 DNA binding, VEGF protein expression, and adult-type globin gene transcription were analyzed in nine family groups of Lake Michigan lake trout Salvelinus namaycush. The results indicate that HIF-1 DNA binding and globin gene transcription increase from hatch to the end of yolk sac stage. Interindividual and between-family biological variations were detected, especially in VEGF protein expression and globin gene transcription. Our results demonstrate the possibility of using these molecular markers in investigating the etiology of EMS and making comparisons between the mechanisms of different salmonid yolk sac fry mortalities.