Early Life Stage Mortality Syndrome in Fishes of the Great Lakes and Baltic Sea

<em>Abstract</em>.—Lake Michigan Skamania strain steelhead <em>Oncorhynchus mykiss </em>and coho salmon <em>O. kisutch </em>fry exhibit an early mortality syndrome (EMS) in which death is preceded by loss of equilibrium, inability or lack of feeding, and general lethargy. It was hypothesized that decreased egg concentrations of carotenoid pigments, thyroxine, or thiamine contributed to this syndrome. Thiamine analyses of Lake Michigan coho salmon eggs from individual family groups exhibited 16–97% EMS if egg total thiamine concentrations were less than 0.9 nmol/g or egg free thiamine concentrations were less than 0.3 nmol/g. In eggs with total or free thiamine concentrations greater than 0.9 or 0.3 nmol/g, respectively, the range of EMS in fry was 5–12%. Immersion of steelhead and coho salmon eggs in 1.4 mM or greater thiamine hydrochloride significantly decreased EMS compared with controls. Immersion of coho salmon eggs in 2.8 mM thiamine increased the mean concentration of free thiamine in the eggs to 1.0 nmol/g, compared with 0.26 nmol/g in controls. Injection of either β-carotene or astaxanthin (0.86 or 8.6 µg/g, respectively) in steelhead eggs did not significantly reduce the occurrence of EMS. Early mortality syndrome was not decreased in steelhead after immersion of eggs in 2 mg/L thyroxine, but it was significantly decreased in steelhead sac fry immersed in 2 mg/L thyroxine. These results suggest that low egg thiamine is a predisposing factor for EMS; however, other factors that are variable among individual coho salmon females may influence the occurrence of EMS-related mortality. Whether the addition of exogenous thiamine corrects a thiamine deficiency or protects fry from developing EMS through some other mechanism is currently unknown.

<em>Abstract.—</em>Muscle and egg samples from returning adult female Lake Michigan coho salmon <em>Oncorhynchus kisutch </em>were collected for thiamine analysis. Three groups of five females having low (2.5%), medium (42.4%), or high (92.6%) mean fry survival were selected for this study. Egg and muscle samples were collected at spawning and analyzed by high-performance liquid chromatography analysis for free thiamine, thiamine monophosphate (TP), and thiamine pyrophosphate (TPP). Egg concentrations of ascorbic acid, iron, zinc, magnesium, and potassium were measured. Twenty-five contaminants were also measured in muscle tissue of adult females. Total thiamine levels in eggs were similar between the medium and high survival groups but significantly lower in the low survival group. Eggs from the high and medium survival groups had higher levels of free thiamine and TP (<EM>P </EM>< 0.01) than eggs from the low survival group. There were no significant differences among the three groups in egg TPP. Muscle concentrations of TPP, TP, and total thiamine were similar among the three survival groups (<EM>P </EM>> 0.10). Correlations between fry survival and egg free thiamine (<em>r </em>= 0.61) and TP (<em>r </em>= 0.52) were observed. Fry survival was not correlated with adult muscle concentration of any form of thiamine or contaminant measured. Among the three groups, no differences in egg concentration were found for ascorbic acid, dehydroascorbic acid, iron, magnesium, zinc, and potassium. This research supports the hypothesis that low egg thiamine is an important factor in early mortality syndrome.


<em>Abstract</em>.—Dietary amprolium, a thiamine antagonist, was fed to lake trout <em>Salvelinus namaycush </em>broodstock from April to October before spawning to determine its effect on egg and tissue concentrations of thiamine, thiamine monophosphate, and thiamine pyrophosphate. The thiamine concentration of eggs from fish fed no amprolium was 61.8 nmol/g, whereas the concentration of thiamine in fish fed 0.05 and 0.10% amprolium was 4.02 and 1.71 nmol/g (<EM>P </EM>< 0.01), respectively. In lake trout fed 0.10% amprolium beginning in August, egg free thiamine concentration was reduced to 11.6 nmol/g. No sign of early mortality syndrome was observed in sac fry from eggs in this study, which suggests that thiamine concentrations in the egg were not low enough to be below a critical threshold or that factors other than thiamine are involved in early mortality syndrome.


<em>Abstract</em>.—Juvenile and adult lake trout <em>Salvelinus namaycush </em>that were fed semipurified, thiaminedeficient diets or alewives <em>Alosa pseudoharengus </em>containing thiaminase, a thiamine-destroying enzyme, showed no overt symptoms of thiamine deficiency. Growth rates and ovulation rates were similar among all treatments. However, liver thiamine pyrophosphate (TPP), a biochemical indicator of impending thiamine deficiency, in juvenile lake trout fed thiamine-deficient diets was reduced to 35 pmol/ g compared with 59 pmol/g in control groups. Blood TPP in adult female lake trout fed alewives was one-third of that in controls fed a commercial diet. Adult lake trout from Lake Michigan had blood TPP levels similar to those of fish fed the alewife diet in the laboratory. Lake Superior lake trout had TPP levels similar to those of fish fed the control diet in the laboratory. Thiamine synthesis occurred in the intestine of lake trout. At least 81% of thiamine in the posterior intestine was synthesized, presumably by bacteria, when a <sup>14</sup>C-labeled thiamine diet was force-fed to lake trout. Thiamine had a long retention time in the lake trout: at 27 weeks after fish were injected with radioactive thiamine, blood cells retained 11% of the radioactivity that was present at 2 d and liver tissue retained 34% of the 2-d level. Lack of self-sustaining lake trout reproduction by Lake Michigan fish may be related to their lower blood thiamine levels. Thiamine deficiency may cause early mortality syndrome, which is common in Lake Michigan but not Lake Superior fish with higher blood thiamine levels.


<em>Abstract</em>.—Since 1974, feral salmon <em>Salmo salar </em>populations of the Baltic Sea have suffered from a yolk sac fry mortality known as the M74 syndrome. Mortality rates of 40–95% have been recorded during the 1990s in compensatory rearing stations along the east coast of Sweden. The M74 syndrome has been linked to the offspring of specific females and associated with low thiamine (vitamin B<sub>1</sub>) concentrations in both female tissues and their progeny. This study evaluated the effect of thiamine treatments on mortality and thiamine concentrations in progeny with and without M74. Eggs and newly hatched yolk sac fry were immersed in water containing thiamine at concentrations of 100, 500, or 2,000 mg/L. Hardening of eggs in water containing thiamine at 500 or 2,000 mg/L completely eliminated M74-related mortality, whereas treatment with thiamine at 100 mg/L only partially reduced M74 mortality. The mean thiamine concentrations at the yolk sac fry stage (21–23 d after hatching) in untreated normal and M74-affected groups were between 0.70–1.0 and 0.19–0.26 nmol/g, respectively. At the same sampling, the mean thiamine concentrations in groups in which eggs were waterhardened in thiamine at 500 or 2,000 mg/L were between 0.8 and 9.4 times higher than the concentrations in the untreated groups. A thiamine threshold limit interval of 0.34–0.47 nmol/g was estimated for the development of M74 in yolk sac fry.


<em>Abstract</em>.—Reproductive success and vitamin B<sub>1 </sub>(thiamine pyrophosphate, thiamine monophosphate, and free thiamine) concentrations were assessed in feral female lake trout <em>Salvelinus namaycush </em>from Lake Ontario and Lake Manitou. We monitored fertilization success, survival to hatch, incidence of blue-sac disease, other anomalies, and lake trout early mortality syndrome (EMS). Fertilization and hatching success were high, whereas mortality from blue-sac disease and other anomalies was low in egg batches from both lakes. There was no mortality from EMS in families from Lake Manitou. However, EMS occurred after hatching in the offspring of 48% of the females collected from Lake Ontario. We measured thiamine in liver, red blood cells, eggs, and developing embryos. Relative to fish collected in reference lakes, females in Lake Ontario had depressed hepatic, red blood cell, and egg thiamine concentrations. Although more extensive investigation of thiamine balance is required, it may be possible to use red blood cell thiamine pyrophosphate as a predictive index for EMS susceptibility in offspring. Total thiamine concentrations in developing embryos declined by 50% between fertilization and swim-up. Free thiamine reserves declined most rapidly, whereas levels of thiamine pyrophosphate increased between the eyed embryo and hatch stages. A high proportion (67%) of lake trout families in which the initial egg free thiamine reserves or embryonic concentrations of thiamine pyrophosphate levels were <0.8 nmol/g exhibited EMS. Below this threshold (0.8 nmol/g), the occurrence of EMS was variable (0–100%) and only weakly related to free thiamine concentrations (<em>r</em><sup>2</sup> = 0.32, <EM>P</EM> = 0.014). This observation implies the possibility of additional interactions with other factors.


2016 ◽  
Vol 12 (8) ◽  
pp. 20160490 ◽  
Author(s):  
Florian Orgeret ◽  
Henri Weimerskirch ◽  
Charles-André Bost

The early life stage of long-lived species is critical to the viability of population, but is poorly understood. Longitudinal studies are needed to test whether juveniles are less efficient foragers than adults as has been hypothesized. We measured changes in the diving behaviour of 17 one-year-old king penguins Aptenodytes patagonicus at Crozet Islands (subantartic archipelago) during their first months at sea, using miniaturized tags that transmitted diving activity in real time. We also equipped five non-breeder adults with the same tags for comparison. The data on foraging performance revealed two groups of juveniles. The first group made shallower and shorter dives that may be indicative of early mortality while the second group progressively increased their diving depths and durations, and survived the first months at sea. This surviving group of juveniles required the same recovery durations as adults, but typically performed shallower and shorter dives. There is thereby a relationship between improved diving behaviour and survival in young penguins. This long period of improving diving performance in the juvenile life stage is potentially a critical period for the survival of deep avian divers and may have implications for their ability to adapt to environmental change.


2009 ◽  
Vol 21 (4) ◽  
pp. 262-271 ◽  
Author(s):  
Sergiusz Czesny ◽  
John M. Dettmers ◽  
Jacques Rinchard ◽  
Konrad Dabrowski

1974 ◽  
Vol 31 (2) ◽  
pp. 191-199 ◽  
Author(s):  
Robert E. Reinert ◽  
Harold L. Bergman

Concentrations of DDT residues were higher in lake trout (Salvelinus namaycush) from southern Lake Michigan in 1966–70 (average 18.1 ppm in fish 558–684 mm long) than in lake trout of the same size-class from Lake Superior in 1968–69 (4.4 ppm), and higher in adult coho salmon (Oncorhynchus kisutch) from Lake Michigan in 1968–71 (averages for different year-classes, 9.9–14.0 ppm) than in those from Lake Erie in 1969 (2.2 ppm). Residues were significantly higher in lake trout from southern Lake Michigan than in those from the northern part of the lake. In lakes Michigan and Superior, the levels increased with length of fish and percentage oil. In Lake Michigan coho salmon, the residues remained nearly stable (2–4 ppm) from September of the 1st yr of lake residence through May or early June of the 2nd yr, but increased three to four times in the next 3 mo. Residues in Lake Erie coho salmon did not increase during this period, which preceded the spawning season. Although the concentrations of total residues in whole, maturing Lake Michigan coho salmon remained unchanged from August 1968 until near the end of the spawning season in January 1969, the residues were redistributed in the tissues of the spawning-run fish; concentrations in the loin and brain were markedly higher in January than in August. This relocation of DDT residues accompanied a marked decrease in the percentage of oil in the fish, from 13.2 in August to 2.8 in January. Concentrations of residues were relatively high in eggs of both lake trout (4.6 ppm) and coho salmon (7.4–10.2 ppm) from Lake Michigan. The percentage composition of the residues (p,p′DDE, o,p′/DDT, p,p′DDT, and p,p′DDT) did not differ significantly with life stage, size, age, or locality, or date of collection of lake trout or coho salmon.


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