The main objective of this study was to investigate small-bodied fish caging as an approach to evaluate selenium (Se) bioaccumulation and speciation in native fish species inhabiting lakes influenced by uranium (U) milling effluent in northern Saskatchewan, Canada. In contaminated environments freshwater fish show a high propensity to accumulate Se beyond levels needed for normal physiological function. Maternal transfer of elevated Se concentrations to offspring can cause deformities and reduced survival in fry, and in certain cases negatively impact the sustainability of native fish populations. This research included a caging validation study using wild, naïve (i.e., collected from a reference lake) lake chub (Couesius plumbeus) and spottail shiner (Notropis hudsonius), and three field based 21-day caging studies to investigate the dominance of the feeding pathway with respect to Se uptake and speciation in wild populations of northern small-bodied fish exposed to a gradient of Se. Three feeding regimes were used: an in situ benthic diet, a basal Se diet of Chironomus dilutus (1.5 µg Se/g dry weight) and a Se-spiked diet of C. dilutus (5.5 µg Se/g dry weight). Lake chub were identified as more suitable candidates for caging due to higher survival and condition factor at the completion of the in situ 21-day trial. The resulting Se bioaccumulation was compared among treatments as well as to wild small-bodied fish populations from the study area. Results from the caging experiments showed that caged lake chub exposed to natural and controlled diets with elevated Se had significantly greater whole-body Se concentrations after 21 days compared to fish caged in the reference lake. The results also showed that whole-body Se concentrations exceeded conservative Se thresholds, and approached the currently proposed USEPA regulatory threshold (7.91 µg/g dry weight) designed to protect fish species in only three weeks. The use of stable carbon (C), nitrogen (N), and sulphur (S) isotope ratios indicated that alternate benthic food sources native to the exposure lake were consumed in conjunction with the controlled diets. Stable isotope analysis of both wild and caged lake chub indicated that the N and S isotopic signatures decreased with increasing Se exposure, representing differences in isotopic signatures of the food sources. Speciation results from caged lake chub indicated that Se substituted for S in methionine (i.e. selenomethionine) was the dominant Se species found in caged lake chub exposed to dietary sources of elevated Se. Overall, this research demonstrates that using caged native lake chub represents a useful biomonitoring approach to investigate patterns of Se bioaccumulation and speciation in fish.

The main objective of this study was to investigate small-bodied fish caging as an approach to evaluate selenium (Se) bioaccumulation and speciation in native fish species inhabiting lakes influenced by uranium (U) milling effluent in northern Saskatchewan, Canada. In contaminated environments freshwater fish show a high propensity to accumulate Se beyond levels needed for normal physiological function. Maternal transfer of elevated Se concentrations to offspring can cause deformities and reduced survival in fry, and in certain cases negatively impact the sustainability of native fish populations. This research included a caging validation study using wild, naïve (i.e., collected from a reference lake) lake chub (Couesius plumbeus) and spottail shiner (Notropis hudsonius), and three field based 21-day caging studies to investigate the dominance of the feeding pathway with respect to Se uptake and speciation in wild populations of northern small-bodied fish exposed to a gradient of Se. Three feeding regimes were used: an in situ benthic diet, a basal Se diet of Chironomus dilutus (1.5 µg Se/g dry weight) and a Se-spiked diet of C. dilutus (5.5 µg Se/g dry weight). Lake chub were identified as more suitable candidates for caging due to higher survival and condition factor at the completion of the in situ 21-day trial. The resulting Se bioaccumulation was compared among treatments as well as to wild small-bodied fish populations from the study area. Results from the caging experiments showed that caged lake chub exposed to natural and controlled diets with elevated Se had significantly greater whole-body Se concentrations after 21 days compared to fish caged in the reference lake. The results also showed that whole-body Se concentrations exceeded conservative Se thresholds, and approached the currently proposed USEPA regulatory threshold (7.91 µg/g dry weight) designed to protect fish species in only three weeks. The use of stable carbon (C), nitrogen (N), and sulphur (S) isotope ratios indicated that alternate benthic food sources native to the exposure lake were consumed in conjunction with the controlled diets. Stable isotope analysis of both wild and caged lake chub indicated that the N and S isotopic signatures decreased with increasing Se exposure, representing differences in isotopic signatures of the food sources. Speciation results from caged lake chub indicated that Se substituted for S in methionine (i.e. selenomethionine) was the dominant Se species found in caged lake chub exposed to dietary sources of elevated Se. Overall, this research demonstrates that using caged native lake chub represents a useful biomonitoring approach to investigate patterns of Se bioaccumulation and speciation in fish.

Previous studies at the Key Lake uranium mill (Saskatchewan, Canada) suggested the complex effluent discharged alters energetic stores of resident fish species. A second study at the same site demonstrated certain fish from lakes downstream of the mill produce larvae with elevated incidence of developmental deformities. The mechanisms by which energy homeostasis is affected in fish downstream of the Key Lake uranium mill are unknown, and the effects of deformities and altered metabolism on swimming ability have not been explored. Therefore, the overall objective of this thesis was to investigate whether effluent exposed fish exhibited differences in swimming performance and energy homeostasis. To achieve this objective two experiments were conducted. In the first experiment juvenile spottail shiner (Notropis hudsonius) were collected from a lake downstream of the Key Lake uranium mill, and compared to fish collected from a nearby reference lake. In the second experiment larvae were collected from laboratory raised fathead minnow (Pimephales promelas) exposed to 5% diluted uranium mill effluent or control (dechlorinated municipal) water, and reared in the same treatments to 60 days post hatch (dph). No gross deformities were observed in any fish, and only shiner collected from the exposure lake in the field experiment had enlarged heart ventricles relative to body size compared to fish from the reference lake. Swimming performance was similar between shiner from the exposure and reference lakes in the field study, but effluent exposure impaired swimming ability in 60 dph fathead minnow in the laboratory experiment compared to fish from the control water treatment. After swimming performance tests fish were considered fatigued and metabolic endpoints were compared to non-fatigued fish. In both non-fatigued and fatigued shiner, liver glycogen was significantly greater in fish collected from the exposure lake compared to the reference lake. There was no difference in liver triglycerides in non-fatigued shiner between lakes, but liver triglycerides decreased after swimming in the field study reference fish. Muscle energy stores were unaffected by site or swimming in the field experiment. Conversely, whole body triglycerides and glycogen were similar between treatments in non-fatigued fathead minnow in the laboratory experiment. Swimming significantly decreased whole body triglycerides in fathead minnow from both treatments, but whole body glycogen was unaffected. In the field experiment blood endpoints (hematocrit, plasma glucose, lactate) in fatigued and non-fatigued shiner from both lakes further supported the possibility of altered intermediary metabolism or blunted stress response in fish downstream of the Key Lake uranium mill. In the field study, shiner muscle citrate synthase activity (an indicator of tissue aerobic capacity) was similar between lakes, but muscle âhydroxyacyl coenzyme A dehydrogenase activity (an indicator of tissue lipolytic capacity) was elevated. In contrast, laboratory fathead minnow whole body âhydroxyacyl coenzyme A dehydrogenase activity was similar between treatments, but citrate synthase activity was significantly lower in fathead minnow from the 5% effluent treatment. In summary, shiner from the exposure lake in the field experiment had similar swimming endurance and greater energy stores compared to fish from the reference lake, despite metabolic alterations. Fathead minnow from the 5% effluent treatment in the laboratory experiment had reduced swimming endurance that was matched by reduced whole body citrate synthase activity, but no other metabolic alterations were observed. Therefore, effluent exposure caused metabolic alterations in both fathead minnow and shiner, but specific effects between experiments were inconsistent. Overall, the physiological significance of the metabolic and swimming effects of effluent exposure is unclear, but suggests discharged effluent has the potential to negatively affect wild fish survivability.

Previous studies at the Key Lake uranium mill (Saskatchewan, Canada) suggested the complex effluent discharged alters energetic stores of resident fish species. A second study at the same site demonstrated certain fish from lakes downstream of the mill produce larvae with elevated incidence of developmental deformities. The mechanisms by which energy homeostasis is affected in fish downstream of the Key Lake uranium mill are unknown, and the effects of deformities and altered metabolism on swimming ability have not been explored. Therefore, the overall objective of this thesis was to investigate whether effluent exposed fish exhibited differences in swimming performance and energy homeostasis. To achieve this objective two experiments were conducted. In the first experiment juvenile spottail shiner (Notropis hudsonius) were collected from a lake downstream of the Key Lake uranium mill, and compared to fish collected from a nearby reference lake. In the second experiment larvae were collected from laboratory raised fathead minnow (Pimephales promelas) exposed to 5% diluted uranium mill effluent or control (dechlorinated municipal) water, and reared in the same treatments to 60 days post hatch (dph). No gross deformities were observed in any fish, and only shiner collected from the exposure lake in the field experiment had enlarged heart ventricles relative to body size compared to fish from the reference lake. Swimming performance was similar between shiner from the exposure and reference lakes in the field study, but effluent exposure impaired swimming ability in 60 dph fathead minnow in the laboratory experiment compared to fish from the control water treatment. After swimming performance tests fish were considered fatigued and metabolic endpoints were compared to non-fatigued fish. In both non-fatigued and fatigued shiner, liver glycogen was significantly greater in fish collected from the exposure lake compared to the reference lake. There was no difference in liver triglycerides in non-fatigued shiner between lakes, but liver triglycerides decreased after swimming in the field study reference fish. Muscle energy stores were unaffected by site or swimming in the field experiment. Conversely, whole body triglycerides and glycogen were similar between treatments in non-fatigued fathead minnow in the laboratory experiment. Swimming significantly decreased whole body triglycerides in fathead minnow from both treatments, but whole body glycogen was unaffected. In the field experiment blood endpoints (hematocrit, plasma glucose, lactate) in fatigued and non-fatigued shiner from both lakes further supported the possibility of altered intermediary metabolism or blunted stress response in fish downstream of the Key Lake uranium mill. In the field study, shiner muscle citrate synthase activity (an indicator of tissue aerobic capacity) was similar between lakes, but muscle âhydroxyacyl coenzyme A dehydrogenase activity (an indicator of tissue lipolytic capacity) was elevated. In contrast, laboratory fathead minnow whole body âhydroxyacyl coenzyme A dehydrogenase activity was similar between treatments, but citrate synthase activity was significantly lower in fathead minnow from the 5% effluent treatment. In summary, shiner from the exposure lake in the field experiment had similar swimming endurance and greater energy stores compared to fish from the reference lake, despite metabolic alterations. Fathead minnow from the 5% effluent treatment in the laboratory experiment had reduced swimming endurance that was matched by reduced whole body citrate synthase activity, but no other metabolic alterations were observed. Therefore, effluent exposure caused metabolic alterations in both fathead minnow and shiner, but specific effects between experiments were inconsistent. Overall, the physiological significance of the metabolic and swimming effects of effluent exposure is unclear, but suggests discharged effluent has the potential to negatively affect wild fish survivability.

Spottail shiner (Notropis hudsonius) and delta smelt (Hypomesus transpacificus) were introduced into Willard Reservoir to improve the forage base for walleye (Stizostedion vitreum vitreum) and black crappie (Pomoxis nigromaculatus). Spottail shiners were stocked in early spring in 1981, 1982, and 1983. Hauling mortality was generally great and an estimated 34,500 live fish were stocked in the 3-year period. Spottail shiner reproduction occurred each year of stocking. Delta smelt were introduced in 1982 with the stocking of 15,000 adult spawning fish. Stocking survival was estimated at 99%. Freshly spawned eggs were also obtained and placed in a tributary to Willard Reservoir. Shoreline seining produced 29 · young-of-the-year delta smelt during June 1982. Growth of the captured young-of-the-year spottail shiner and delta smelt in Willard Reservoir compared favorably with growth found in their respective native waters. Stomach analysis indicated food habits were similar to those in native waters. Food habit analysis of young-of-the-year walleye, black crappie, spottail shiner, and delta smelt indicated very little overlap of food organisms between the four fish species. Spottail shiners occurred in 3 of 56 walleye stomachs containing food items in 1982 and 3 of 41 stomachs containing food items in 1983. Delta smelt were not found in the 132 walleye stomachs examined. However, six adult delta smelt were angler-caught walleye in April 1983. No found in the stomachs of spottail shiners or delta smelt were found in 79 black crappie stomachs examined in 1982 or 62 stomachs examined in 1983. Low utilization of spottail shiner and delta smelt was attributed to the low relative abundance of the two species in Willard Reservoir.