Lake (Coregonus clupeaformis) and round (Prosopium cylindraceum) whitefish are two species of cold-adapted freshwater fish that spawn in shallow (<10m) cobble beds in the Laurentian great lakes. Developing whitefish embryos are potentially exposed to various anthropogenic sources of warming, including climate change and thermal effluents discharged in the nearshore environment. Several studies have investigated the effects of elevated incubation temperatures on whitefish embryos (particularly lake whitefish) but little work has been done to examine post-hatch effects. Thermal preferenda (temperature preference) describe the range of temperatures an organism will occupy when given a choice and are traditionally thought to be species-specific. Temperature preference can be modulated by a variety of abiotic and biotic factors including environmental temperature and is typically correlated with optimal growth temperature for a species. Assays for thermal preferenda require at least 24 hours, which includes a long tank-acclimation period that limits throughput and thus impacts replication in the study. A shuttle box thermal preference assay was optimized from 24-hours to 4-hours; length of acclimation time and trial length had no significant impact on thermal preference. Whitefish were incubated at natural and elevated temperatures until hatching; all groups were moved to common garden conditions (15°C) during the post-hatching stage. Temperature preference was determined at 12 months of age; lake whitefish were also tested at 8 months. Round whitefish displayed a significant decrease in temperature preference when incubated at 2°C and 6°C compared to 0.5°C. Lake whitefish had similar temperature preferences regardless of age and incubation temperature. This suggests that there is a difference in thermal tolerance between these species, as round whitefish were more sensitive to elevated incubation treatments. This thesis identified a persistent effect of elevated incubation treatments on the thermal preference of juvenile round whitefish, lasting up to 12 months post-hatch, which highlights the importance of examining sub-lethal thermal effects and thermal plasticity of cold-adapted species. / Thesis / Master of Science (MSc) / Lake and round whitefish are cold-adapted freshwater species that spawn in shallow coastal water in the Laurentian great lakes. Anthropogenic warming from various sources (e.g. climate change, thermal effluent) has been shown to reduce survival of whitefish embryos, but few studies have investigated the effects of elevated embryonic incubation temperatures on surviving juveniles. Fish typically prefer a small range of temperatures (temperature preference) that they will occupy if given a choice, which can be affected by a variety of factors including early life thermal exposure. This thesis shows round whitefish incubated at elevated temperatures (2°C, 6°C) display decreased temperature preference up to 12 months post-hatch, while lake whitefish had similar temperature preference regardless of incubation temperature. Therefore, this thesis provides more evidence that round whitefish are a more thermally sensitive species.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/25923 |
| Date | January 2020 |
| Creators | Harman, Adam |
| Contributors | Wilson, Joanna, Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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