Browsing by Author "Lazaro-Côté, Analisa"
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- ItemEmbargoThe effect of maternal stress on early life history traits and performance in salmonids(2023-11-23) Lazaro-Côté, Analisa; Vijayan, Mathilakath M.; Harder, Lawrence; Post, John RobertDuring the upstream spawning migration of Pacific salmon, circulating cortisol concentration increases to mobilize energy stores. Pacific salmon contend with a gauntlet of stressors that can further elevate cortisol concentrations in response to stressful stimuli. Consequently, plasma cortisol concentrations measured in maternal fish that have reached their spawning grounds may reflect their recent stress history. Despite studies mimicking the maternal transfer of cortisol to the eggs, how natural variation in maternal cortisol concentrations shapes offspring phenotypes is unclear. Therefore, I assessed whether stress in maternal salmonids alters the growth and stress performance of their offspring via increased cortisol deposition in the eggs. Specifically, I tested whether high concentrations of circulating cortisol in maternal fish reduced embryo survival, and fry growth and stress performance. Eggs from 101 wild coho salmon (Oncorhynchus kisutch) females were collected from three rivers in the interior Fraser River watershed, British Columbia, Canada. The eggs were fertilized and reared until the fry stage at a hatchery. High egg cortisol concentration increased offspring mortality at the eyed stage. Interestingly, the surviving free-swimming fry had enhanced growth, resulting in larger size, and heightened cortisol stress response. The corresponding increase in the transcript abundance of genes related to growth and stress axis functioning in the fry suggest that high maternal cortisol concentrations programmed offspring for faster growth and heightened stress reactivity during early development. To test whether high egg cortisol concentrations specifically causes the phenotypic variation such as that observed in coho salmon, I manipulated steroid concentrations in the eggs of 10 maternal rainbow trout (Oncorhynchus mykiss) by immersion in water-borne cortisol during fertilization. Cortisol treatments increased egg steroid concentrations; however, neither the developmental trajectory nor the stress performance of fry differed statistically among treatments. Therefore, the utility of egg cortisol concentration as a biomarker of offspring developmental performance may be dependent on the life history of the animal. Overall, maternal cortisol concentration seems to act as a cue that prepares the offspring of wild coho salmon for stressful environments.
- ItemOpen AccessThe Effect of Municipal Wastewater Effluent on the Stress Response of Native Fish Species in the Bow River, Calgary, Alberta(2017) Lazaro-Côté, Analisa; Jackson, Leland J.; Vijayan, Mathilakath M.; Hontela, Alice; Ruecker, Norma; Achari, GopalMunicipal wastewater effluent (MWWE) is a point-source of contamination to surface waters, and contains a mixture of nutrients and pharmaceuticals that are not completely eliminated during wastewater treatment processes. There have been many studies using reproductive endpoints to examine sub-lethal effects on fish sampled downstream from MWWE sources; however, few studies have examined effects on the stress performance of fish in the field, particularly in wild populations residing downstream from MWWE sources. The overall objective of this thesis was to determine whether exposure to MWWE in the field compromised the stress performance of native fish species in the Bow River, Calgary, Alberta. The hypothesis was that long-term exposure to MWWE would result in chronic stress and disruption of the hypothalamus-pituitary-interrenal (HPI) axis, leading to a reduced ability to respond to a secondary acute stressor and decreased energy stores due to enhanced energy demands. The results show that feral longnose dace (Rhinichthys cataractae; Chapter 2) and caged fathead minnows (Pimephales promelas; Chapter 3) sampled downstream from municipal wastewater treatment plants (WWTPs) in the Bow River, Calgary, Alberta, did not have elevated basal cortisol levels and were able to mount a cortisol response following exposure to an additional acute stressor. This suggests that there was no disruption in the HPI axis functioning. Furthermore, the energy stores in fish downstream from WWTPs were greater, which could be due to increased feeding, as fish were also greater in size. The effects detected on energy metabolism cannot be fully attributed to MWWE, as fish sampled from an upstream site also showed similar levels of glycogen stores as fish sampled from sites downstream from WWTPs. This suggests that stormwater and urban runoff may contribute to effects on the metabolism of fish.