Seasonal and environmental effects on upper thermal limits of eastern sand darter (Ammocrypta pellucida)

We measured the thermal tolerance, agitation and thermal safety margin of threatened eastern sand darter in multiple seasons and at different turbidity levels. We demonstrate that eastern sand darter has high thermal acclimation capacity and may not be as immediately impacted by warming environments...

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Bibliographic Details
Published in:Conservation physiology 2021-01, Vol.9 (1), p.1-coab057
Main Authors: Firth, Britney L, Drake, D Andrew R, Power, Michael
Format: Article
Language:English
Subjects:
Darters (Fishes)
Environmental aspects
Human beings
Influence on nature
Physiological aspects
Water turbidity
Wildlife conservation
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Summary:We measured the thermal tolerance, agitation and thermal safety margin of threatened eastern sand darter in multiple seasons and at different turbidity levels. We demonstrate that eastern sand darter has high thermal acclimation capacity and may not be as immediately impacted by warming environments as other fishes. Abstract Anthropogenic stressors are predicted to increase water temperature, which can influence physiological, individual, and population processes in fishes. We assessed the critical thermal maximum (CTmax) of eastern sand darter (Ammocrypta pellucida), a small benthic fish listed as threatened under the Species at Risk Act in Canada. Field trials were conducted stream side June–November 2019 in the Grand River, Ontario, to encompass a range of ambient water temperatures (7–25°C) for which agitation temperature (Tag) and CTmax were determined. Additional measures were taken in the comparatively more turbid Thames River to test the effect of turbidity on both measures. In the Grand, Tag and CTmax ranged from 23°C to 33°C and 27°C to 37°C, respectively, and both significantly increased with ambient water temperature, with a high acclimation response ratio (0.49). The thermal safety margin (difference between ambient temperatures and CTmax) was smallest in July and August (~11°C) indicating that eastern sand darter lives closer to its physiological limit in summer. The between-river comparison indicated that turbidity had no significant influence on Tag and CTmax. Comparison of CTmax with in-river temperatures suggested that mean stream temperature 24 hours before the trial was most important for determining CTmax. Fish mass, temperature variance and maximum temperature in the 24-hour period prior to the CTmax trial were also shown to have some effect on determining CTmax. Overall, study results better define the sensitivity of eastern sand darter to temperature changes across the growing season and provide information to assess the availability of suitable thermal habitat for conservation purposes.
ISSN:2051-1434
2051-1434
DOI:10.1093/conphys/coab057