Ecological Studies and Mathematical Modeling of Cladophora in Lake Huron: 4. Photosynthesis and Respiration as Functions of Light and Temperature

Laboratory experiments were conducted with Cladophora glomerata isolated from Lake Huron near Harbor Beach, Michigan, to determine gross and net photosynthesis and respiration as functions of temperature and light intensity. Rates of net photosynthesis and respiration were measured in three replicate cultures at all combinations of eight temperatures (1° to 35° C) and eight light levels (12 to 1235 μE/m²?sec) using oxygen electrode techniques. Maximum net photosynthesis occurred between 13 and 17° C and 300 to 600 μE/m²?sec. The data were converted to specific rates of growth and respiration for use in a mathematical model, and three-dimensional response surfaces were generated for gross and net growth and respiration over the entire range of light levels and temperatures examined.     

Effect of Temperature on Feeding and Survival of Mysis relicta

During their diel vertical migration, Mysis relicta can experience temperatures from 4°C to about 15°C. High temperatures may limit the ascent due to direct effects on survival or through decreased feeding rates. Mysis relicta survival (over 8 hours) was high up to 17°C (93%) and decreased with an increase in temperature over 18°C to 0% at 26°C. Feeding rates on newly hatched nauplii of Artemia salina were measured in 4-hour experiments at temperatures between 4 and 20°C. Feeding rates for 13 to 16 mm mysids were highest at 12°C and decreased at both higher and lower temperatures to 40% of peak feeding rates at 18 to 20°C and to 75% of peak feeding rates at 4°C. Smaller mysids (average length 10.5 mm) had peak feeding rates at 14°C. These results are consistent with field observations. Mysids seldom occur in temperatures above 15°C and smaller mysids are often found higher in the water column than larger animals. Consumption rates at both higher and lower temperatures were higher relative to peak consumption than assumed in a published bioenergetics model for Mysis (Rudstam 1989).     

Water temperature as a hindrance,but not limiting factor for the survival of warm water invasive crayfish introduced in cold periods

The success of non-native species establishment depends on various abiotic and biotic factors that determine the outcome of an introduction event. Limiting temperature ranges have been studied for various non-native species; however, such previous assessments of species-specific temperature thresholds may be inadequate. Because several non-native crayfish species prefer warmer water temperatures, introductions were generally assumed to occur during preferable, warmer periods. However, despite the generality, traditionally considered ‘warm-water’ species are gradually appearing in new habitats, which were previously considered too cold for successful establishment. Newly discovered overwintering abilities of these species are likely related to the winter stratification in lentic ecosystems, which maintain tolerable conditions. To understand better the survivability of two such non-native species, red swamp crayfish Procambarus clarkii and marbled crayfish Procambarus virginalis individuals were abruptly subjected to a thermic shock which lowered the water temperature from 20 °C (room temperature) to 6 °C, 4 °C and 2 °C, thus mimicking the release by pet owners during various phases of winter. The survival rate and foraging activity were monitored for up to 98 days. Procambarus clarkii showed a considerable higher survival rate at low temperatures (4 °C, 2 °C) compared to that of P. virginalis with neither sex nor size differences evident. Our findings reveal the ability of warm water invaders to withstand a shock during introduction at low temperature periods without acclimation. Considering these newly discovered shifts in physiological limitations, particularly for the red swamp crayfish, this may indicate a higher threat for areas with colder conditions.     

Initial insights on the thermal ecology of lake whitefish in northwestern Lake Michigan

Lake whitefish Coregonus clupeaformis are a native coldwater species supporting important recreational and commercial fisheries in the Laurentian Great Lakes. Climate-related changes in water temperature may have important implications for the future sustainability of these fisheries. However, projecting future habitat availability is difficult because limited information is available on lake whitefish thermal ecology in the region. In this study, archival temperature loggers were implanted into 400 lake whitefish from northwestern Lake Michigan, including Green Bay, during October–November 2017. Loggers recorded temperature for 11 months at 4-hr intervals. Thirteen recovered temperature loggers were used in analyses. In winter (1 December–31 March), temperatures occupied by lake whitefish ranged from 0 to 8.0 °C, while in spring (1 April–31 May) temperatures ranged from 0 to 20.0 °C. In summer (1 June–15 September) and fall (16 September–7 November), lake whitefish occupied temperatures of 4–21.5 and 4–21.0 °C, respectively. Average temperatures in summer (10.8 °C) were within the previously proposed optimal temperature range (10–14 °C) and broad thermal niche (7–17 °C); however, 58% of observations were outside the optimal temperature range and 11% of observations were outside the broad thermal niche. Our results suggest that lake whitefish from northwestern Lake Michigan inhabit temperatures both above and below previously reported expected temperature ranges. This study provides initial insights on lake whitefish thermal ecology in Lake Michigan and can be used as a baseline for future work aimed at determining how lake whitefish habitat availability may change in the future.     

Movements of Rainbow Steelhead Trout (Salmo Gairdneri) in Lake Ontario and a Hypothesis for the Influence of Spring Thermal Structure

To examine movements of rainbow/steelhead trout (Salmo gairdneri) and associated environmental influences, 28 fish were radiotagged in and near a tributary of Lake Ontario during spring spawning runs in 1981 and 1982. Trout initially entering the lake from the tributary generally exhibited east-west reversals of movement along the southern shore of Lake Ontario before dispersing off shore. Seasonal movement rates averaged 3.2 ± 1.6km/d over periods of 6–94 d; mean short term rates were 0.50 ± 0.46 km/h. Temperatures occupied in the lake were 9.1 ± 1.5°C; temperatures at which fish were last observed were 9.8 ± 3.8° C. Movements offshore and ultimate disappearances occurred from April to July, but were most pronounced when temperatures near shore exceeded 10° C. By linking trout movements to seasonal thermal structure in Lake Ontario, a testable hypothesis was established to explain the distribution of rainbow trout in spring and early summer. Based on tracking data, information provided by south shore anglers, and literature on the physical limnology of Lake Ontario, we hypothesize that rainbow trout disperse off shore in spring with thermal fronts, particularly the 6–8° C zone known as the spring thermocline.     

Low temperature effects on phosphorus release and uptake by microorganisms in ebpr plants

A continuous flow pilot plant with a mixed population of activated sludge was used to investigate the influence of temperatures between 5°C and 20°C on the efficiency of enhanced biological phosphorus removal (EBPR) and on the phosphorus release and uptake mechanisms. Bacterial strains, isolated at different temperatures, were tested for their ability to store polyphosphate. At temperatures of between 15°C and 20°C the uptake of phosphate in the aerobic reactor was correlated directly with the quantity of phosphate released in the anaerobic zone. Mainly aerobic microorganisms were isolated. In batch tests they showed comparatively high polyphosphate storing capacities. There was no indication that Acinetobacter sp. played a dominant role in the processes of EBPR. A drop in temperature to 10°C and then to 5°C had no significant influence on the efficiency of EBPR. In spite of a clearly reduced release of phosphate in the anaerobic zone, the bacterial uptake of phosphate reached unchanged high levels. Because of reduced nitrification at low temperatures, making the anoxic zone into an additional anaerobic zone, facultative anaerobic microorganisms accumulated in the microbial population. They showed the best abilities to store polyphosphate under these conditions, whereas aerobic bacteria lost their polyphosphate storing capacities.     

Effects of Temperature and Density on Sediment Reworking by Stylodrilus Heringianus (Oligochaeta: Lumbriculidae)

A non-destructive, radio-marker system was used to follow sediment burial, or reworking rate, by the particle-feeding oligochaete Stylodrilus heringianus Claparede over a range of worm densities and water temperatures in laboratory microcosms. Marker layer burial rates were monitored for seven densities (30,000 to 134,000 worms m⁻²) while slowly altering the temperature from 10°C down to 4°C, up to 20°C, and then back to 10°C. From 10°C to 4°C, reworking rates decreased approximately 90%. When the temperature was increased above 4°C, reworking rates approached levels shown at the initial 10°C but remained relatively constant through the remainder of the experiment. It is assumed that reproductive activities, stimulated by the 4° C period, affected feeding activity. The reworking rate per worm was shown to be independent of the initial oligochaete density. Time dependent and depth dependent models were tested to examine the decline in observed reworking rates during the latter part of the experiment. There was a weak correlation between time and decreased reworking rates and a strong correlation between density and depth of feeding. Correlations suggested that reworking rates per worm remained similar over time, but the depth to which an organism fed increased with increasing worm density.     

Ecological Studies and Mathematical Modeling of Cladophora in Lake Huron: 3. The Dependence of Growth Rates on Internal Phosphorus Pool Size

The relationship between growth rate and internal phosphorus pool size was examined using field populations of Cladophora glomerata from Lake Huron. Algal samples, representing a range of internal phosphorus concentrations, were harvested from the lake and used for laboratory measurements of growth. Rates of net photosynthesis and respiration were measured under controlled conditions of light and temperature using a dissolved oxygen (light/dark bottle) technique. The net specific growth rate and respiration rate were calculated from photosynthesis and respiration measurements using a fixed stoichiometric relationship and the measured carbon content of the algae. The maximum rates for net specific growth rate, gross specific growth rate, and specific respiration rate were 0.77, 1.08, and 0.44 day^?1, respectively. Management decisions may be importantly influenced by the relationships derived from these data. A non-linear response by growth to reductions in phosphorus loading is suggested from the results of these experiments. The internal nutrient status of algal populations (e.g. Cladophora) must be considered in predictions of the impact of phosphorus management strategies on aquatic systems.     

Seasonal Bathythermal Distribution of Juvenile Lake Trout in Lake Ontario

Bathythermal distributions of hatchery-reared lake trout (Salvelinus namaycush) of three genetic strains (Lake Superior; Clearwater Lake, Manitoba; and Seneca Lake, New York) were described from catches with bottom trawls in Lake Ontario during April-May, June, July-August, and October, 1978–1984. This work was part of a program to evaluate post-stocking performance of hatchery-reared fish and identify strains for continued use in rehabilitation of lake trout in Lake Ontario. All age groups of Lake Superior fish were in deeper water in April-May than in June each year; mean depth of capture was greatest at age II and became progressively shallower at ages III and IV. Mean depth of capture in April-May was positively correlated with severity of the preceding winter as judged by heating degree days and average wind speed. During July-August, the fish were concentrated between the epilimnion and 50 m, with no consistent trend in depth by age; however, 92% were captured at water temperatures of 12°C or lower. Mean temperatures of capture for Lake Superior fish during the four respective sampling periods were 3.9, 7.5, 6.9, and 9.5° C for fish of age II and 3.9, 8.4, 6.9, and 8.7° C for fish of age III. The age-II Clearwater Lake fish were consistently at shallower depths than age-II Lake Superior fish. Mean temperatures of capture were 4.2, 9.7, 9.6, and 10.7° C during the four respective sampling periods; during July-August, 91% were taken in water of 12° C or lower. The distribution of Seneca Lake fish was similar to that of the Lake Superior strain. Mean temperatures at which the three strains were captured were well below published preferred temperatures of yearlings in the laboratory. Annual variations in depth distributions during a given season were probably due to differing thermal regimes resulting from annual variations in the weather.     

SHOVELNOSE STURGEON SPAWNING IN RELATION TO VARYING DISCHARGE TREATMENTS IN A MISSOURI RIVER TRIBUTARY

Many lotic fish species use natural patterns of variation in discharge and temperature as spawning cues, and these natural patterns are often altered by river regulation. The effects of spring discharge and water temperature variation on the spawning of shovelnose sturgeon Scaphirhynchus platorynchus have not been well documented. From 2006 through 2009, we had the opportunity to study the effects of experimental discharge levels on shovelnose sturgeon spawning in the lower Marias River, a regulated tributary to the Missouri River in Montana. In 2006, shovelnose sturgeon spawned in the Marias River in conjunction with the ascending, peak (134 m³/s) and descending portions of the spring hydrograph and water temperatures from 16 °C to 19 °C. In 2008, shovelnose sturgeon spawned in conjunction with the peak (118 m³/s) and descending portions of the spring hydrograph and during a prolonged period of increased discharge (28–39 m³/s), coupled with water temperatures from 11 °C to 23 °C in the lower Marias River. No evidence of shovelnose sturgeon spawning was documented in the lower Marias River in 2007 or 2009 when discharge remained low (14 and 20 m³/s) despite water temperatures suitable and optimal (12 °C?24 °C) for shovelnose sturgeon embryo development. A similar relationship between shovelnose sturgeon spawning and discharge was observed in the Teton River. These data suggest that discharge must reach a threshold level (28 m³/s) and should be coupled with water temperatures suitable (12 °C?24 °C) or optimal (16 °C?20 °C) for shovelnose sturgeon embryo development to provide a spawning cue for shovelnose sturgeon in the lower Marias River. Copyright © 2012 John Wiley & Sons, Ltd.     

Laboratory Estimates of Salmonine Egg Predation by Round Gobies (Neogobius melanostomus), Sculpins (Cottus cognatus and C. bairdi), and Crayfish (Orconectes propinquus)

The continued lack of natural reproduction by lake trout (Salvelinus namaycush) in the Great Lakes has prompted development of models focused on the potential negative effects of interstitial predators. To aid in parameterization of such models we investigated the effect of temperature (1–2°C, 4–5°C, 7–8°C, and 10–11°C), predator group size, interspecific competition, egg density (60–6000 eggs m^–2), and an alternate food source on egg consumption by slimy (Cottus cognatus) and mottled (Cottus bairdii) sculpins, round gobies (Neogobius melanostomus), and the native crayfish (Orconectes propinquus) in the laboratory. Egg consumption by the sculpins and round goby all increased over the range of temperatures investigated (ca 0.5 eggs·day^–1 at 1–2°C to 1.5·eggs day^–1 at 10–11°C). Predator group size affected consumption; fewer eggs were eaten per individual slimy sculpin and round goby at densities of 5 or 10 per tank than 1 individual per tank. There was no effect of interspecific competition on egg consumption by slimy sculpins or round gobies at a density of 10 individuals per tank for various species combinations (10:0, 9:1, 5:5, 1:9, 0:10). A type II functional response to egg density was observed for sculpins, gobies, and crayfish although at extreme densities per capita consumption by crayfish and gobies declined. The presence of zebra mussels (Dreissena polymorpha) did not affect the number of rainbow trout (Oncorhynchus mykiss) eggs eaten by round gobies whose mussel consumption averaged 75% BW·day^–1. Of the four species examined, round gobies appeared to be the most effective egg predator while crayfish were the least.     

Influence of temperature and sludge loading on activated sludge settling,especially on Microthrix parvicella

During recent years modern full scale wastewater treatment plants with biological nitrification, denitrification and phosphorus removal have had increasing problems with foam formation on the surfaces of aerobic tanks and with bulking activated sludge. The results of a survey in 1995 (Kunst and Knoop, 1996) showed that most often the filamentous bacterium Microthrix parvicella is responsible for these problems. Up to today there is only little knowledge about its selection criteria in activated sludge. Therefore several expenments were done in full scale activated sludge plants and in laboratory systems under defined conditions to investigate the influence of low (< 0.1 kg/(kg·d)) and high (≤ 0.2 kg/(kg·d)) BOD₅-sludge loading rates on the growth and morphology of M. parvicella and the settlement of activated sludge. Furthermore the influence of temperatures of 5°C, 12°C and 20°C on the growth of M. parvicella was investigated. It was shown that M. parvicella grows at low BOD₅-sludge loading rate and low temperature and is the main causative organism of bulking and foaming sludge in nutrient removal plants. On the basis of this investigation it was concluded that the growth of M. parvicella and the settling problems of the activated sludge resulting from excessive growth of this filament will always appear in modern municipal wastewater treatment plants with BOD₅-sludge loading rate ≤ 0.1 kg/(kg·d) especially under low temperature conditions.     

Evaluation of Different Phytoplankton for Supporting Development of Zebra Mussel Larvae (Dreissena polymorpha): The Importance of Size and Polyunsaturated Fatty Acid Content

A marine alga and variety of freshwater algae of known polyunsaturated fatty acid (PUFA) composition were evaluated in the laboratory for their ability to promote development of Dreissena polymorpha from egg through settling and metamorphosis. The three species of algae which promoted development—the marine and the freshwater strain of Chlorella minutissima and the cryptophyte Rhodomonas minuta—were all rich in long-chain (≥ 18 C) n-3 PUFAs, including some 20:5 or 22:6 PUFAs. Dreissena's need for long-chain n-3 PUFAs is consistent with the needs of marine bivalves and freshwater zooplankton. Larval growth rate on the freshwater strain of C. minutissima was about the same as that for R. minuta, but much faster than that for the marine strain of C. minutissima. Mean ages at settling for larvae fed the freshwater C. minutissima were 15 d at 26°C, 17 d at 24°C, and 22 d at 22° C Low survival rates reported for the larvae in nature may be related to low concentrations of long-chain n-3 PUFAs in blue-green and some green algae that dominate eutrophic lakes in summer.     

Invader amphipods Gmelinoides fasciatus (Stebbing, 1899) inhabiting distant waterbodies demonstrate differences in tolerance and energy metabolism under elevated temperatures

Gmelinoides fasciatus is a successful invasive amphipod (Amphipoda, Crustacea) that dispersed from Lake Baikal to various waterbodies. Here we studied whether Baikal conditions are optimal for G. fasciatus in terms of thermotolerance and investigated lethal temperatures, 70 kDa heat shock protein level, energy metabolism, and antioxidant defense of animals from three geographically distant waterbodies under changing temperatures. We used acute heat exposure to 28 °C to assess the median lethal times and gradual temperature increase from 6 °C to determine the lethal temperatures. Mortality under heat shock was explainable by the baseline content of Hsp70 that correlated with thermal history. But it was not the case under gradual temperature increase where Hsp70 levels became similar and the mortality pattern changed. The most thermotolerant amphipods from the Gulf of Finland demonstrated a higher amount of free glucose during the temperature increase that may be related to the higher salinity of this waterbody and less energy required for ion regulation. Even though concentrations of major physiological ions in Lake Baikal are lower than in Lake Ladoga, G. fasciatus from Ladoga was slightly more sensitive to the gradual temperature increase. This difference could be explained by the influence of high levels of humic and other potentially toxic substances in Lake Ladoga indicated by increased activities of catalase and glutathione S-transferase. Importantly, all G. fasciatus populations accumulated relatively low levels of lactate during the temperature increase, which may reflect the ability of this invasive species to effectively maintain aerobic metabolism under various conditions.     

Salmonid Spawning Runs and Estimated Ova Production in Normandale Creek of Lake Erie

The Normandale Creek study area (2,531 m²)provides spawning and nursery grounds for lake-run coho salmon (Oncorhynchus kisutch), rainbow trout (Salmo gairdneri), and brown trout (Salmo trutta), In 1973–74, 59 adult salmonids (58% rainbow trout, 39% coho salmon, and 3% brown trout) ascended the stream between 31 October and 12 May. Upstream movements were significantly related to peak stream discharge (r = 0.21) and highly significantly related to discharge occurring on the day following the peak freshet (r = 0.34). Despite a highly significant correlation (r = 0.29) between flow and water temperature, the latter factor is not significantly related with upstream movement of adult fish. Coho salmon spawned at water temperatures of 1 to 10° C between 2 November and 19 December, rainbow trout at 1 to 15° C between 9 November and 14 May, and brown trout at 7° C between 4 and 5 November. Of 86 nests constructed, 60% were disturbed by re-use or sand deposition. From a calculated deposition of 90,403 ova, it is estimated that some 22% survived to emergence.     

First Occurrence of Cercopagis pengoi in Lake Michigan

Adults and juveniles of the predaceous cladoceran Cercopagis pengoi, native to the Ponto- Caspian region, were found in nearshore waters of southern Lake Michigan during August and September 1999. This invasive cladoceran was previously reported from Lake Ontario, but this is the first report of C. pengoi from Lake Michigan. In Lake Michigan, densities of C. pengoi peaked at about 75/m3 on 22 September when water temperature was 16°C, and first and second instars comprised up to 90% of the samples. Of the third and fourth instar reproductive forms, parthenogenetic females were most abundant (up to 33% of all individuals sampled) and were present on all sampling dates. Males and females with resting eggs appeared in low abundance on the last two sampling dates perhaps in response to decreasing temperatures. The impact of this invader on the Lake Michigan food web is yet undetermined, but C. pengoi individuals were found in the stomachs of alewife on 22 September indicating that fishes will feed on C. pengoi.     

Measurement of Diporeia respiration rate for Lake Superior

The freshwater amphipod Diporeia is a dominant macroinvertebrate species in Lake Superior’s benthic community and an important prey item for many fish. A capacity to predict growth and production rates of Diporeia using a bioenergetics model requires information on physiological processes of the species. The objective of this study is to quantify oxygen consumption of Lake Superior Diporeia and to determine if respiration rate changes with body length. Diporeia were collected from Lake Superior and kept over natural sediment maintained at 4 °C. Dissolved oxygen levels for groups of immature (2 mm), juvenile (4 mm), and adult (6 mm) Diporeia in 20 ml microcosms were measured using a polarographic microelectrode. Mass-specific respiration rates for Lake Superior Diporeia ranged from 32.0 to 44.7 mg O₂ g DW^− 1 day ⁻¹. A significant relationship between body length and mass-specific respiration rate (p > 0.1) was not found. The estimate of Diporeia respiration presented here is significantly higher (p < 0.05) than previous findings from populations in Lakes Michigan and Ontario. This study provides new data on respiration rates of Lake Superior Diporeia and compares findings to studies for other connecting Great Lakes.     

Linking the thermal regimes of streams in the Great Lakes Basin,Ontario, to landscape and climate variables

The lack of geographically broad‐scale temperature data has limited our ability to classify stream temperatures and assess the processes affecting them. Continuous data (1 July 2005–30 June 2006) from 90 sites throughout the Great Lakes Basin (GLB) were used to classify and model the thermal regimes of streams in Ontario. Existing and newly developed temperature metrics were used to characterize the data for each site. The 90 sites clustered into three thermal regimes based on maximum weekly maximum temperature (°C) and spring rate of change (°C · d^?1). The centroids of regime 1, 2 and 3 had temperatures of 26.4, 28.4, 23.5°C and warming rates of 0.20, 0.12 and 0.10°C · d^?1, respectively. There was a regional pattern in the thermal regimes; most sites in the north were regime 1 and most sites in the south were regime 2 but neither regime was limited to those areas. Regime 3 sites were found throughout the study area. Discriminant function analysis indicated that per cent riparian forest, mean annual air temperature, per cent surface water and groundwater discharge potential influenced the thermal regimes at the sites, and demonstrated how variables at three spatial scales influence stream temperatures. This study provides a framework for thermal assessments elsewhere and demonstrates how anthropogenic activities such as riparian deforestation, groundwater withdrawal, stream regulation and climate change will all affect the main drivers of thermal regimes in streams. Copyright © 2009 John Wiley & Sons, Ltd.     

Stream Temperature Impacts Because of Changes in Air Temperature,Land Cover and Stream Discharge: Navarro River Watershed,California, USA

Stream temperatures are critically important to aquatic ecology, especially cold‐water fish such as salmonids. Stream temperatures are influenced by multiple factors, including local climate, solar radiation on the stream channel, stream discharge volume and groundwater contributions. The Heat Source hydrodynamic and thermodynamic numerical model was used to evaluate temperatures in three stream reaches in the Navarro River watershed, California, USA. The model was calibrated and validated for summer 2015 conditions and then applied to scenarios that address changes in air temperatures, riparian forest cover and stream discharge. Modelling results indicate that stream temperatures are sensitive to changes in air temperatures and riparian forest cover and that higher discharge volume mitigates those impacts. Modelled stream maximum weekly average temperatures (MWAT) increased by 1.5–2.3°C in response to an air temperature increases of 3.5°C under low flow conditions (drought) but by only 0.9–2.0°C under moderate flow. Complete removal of riparian forest in a large‐scale forest fire would increase MWAT by 2.2–5.9°C in low discharges and by 1.0–4.4°C under moderate discharge. Riparian zone reforestation would decrease MWATs by less than 0.8°C, a modest change reflecting high existing shade on the modelled stream reaches. Comparison of identical climate and land cover change scenarios under low and moderate discharge conditions reveals that efforts to conserve stream discharge volume could be an effective mechanism to mitigate stream temperature increases. Copyright © 2016 John Wiley & Sons, Ltd.     

Temperature response in the physiology and growth of lake trout strains stocked in the Laurentian Great Lakes

Fish stocking programs designed for species rehabilitation aim to match the strains being stocked with the environments the fish will inhabit. The ability of different lake trout Salvelinus namaycush populations to adjust their physiological performance over a broad range of environmental conditions will be advantageous as water temperatures rise with climate warming. This study compares the adaptive physiological potential of 6 strains of lake trout stocked within the Laurentian Great Lakes by comparing growth, metabolic and cardiovascular performance, and organ-system tradeoffs across a temperature gradient. Using a common garden design, lake trout were raised from the embryonic stage until 2 years of age, when they were acclimated to temperatures of 8, 11, 15 and 19 °C before undergoing experiments to test their metabolic performance. For all strains, growth rates showed a dome-shaped response with temperature, peaking at 11 °C and reaching negative rates at 19 °C. For 5 of 6 strains, metabolic rates increased while in all strains cardiovascular performance declined with increasing temperature. Higher metabolic rates at higher temperatures generally came at the cost of slower growth, less investment into gastrointestinal mass, and reduced cardiovascular fitness and investment. Importantly, though, the Seneca strain was unique by showing a reduction of aerobic scope at the highest temperature, possibly indicating increased costs as temperature rises in this smaller-sized, potentially slower pace-of-life strain. However, the overall low interpopulation variability in our study suggests limited diversity in the physiological responses to temperature in strains stocked across the Great Lakes basin.