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Modifying effects of a cobble substrate on thermal environments and implications for embryonic development in lake whitefish (Coregonus clupeaformis).

A laboratory flume was constructed to examine substrate effects on aquatic development. The flume was designed as a once through system with a submerged cobble filled corebox. Lake whitefish (Coregonus clupeaformis) embryos and temperature probes were deployed at multiple sites within the cobble and in the open water channel. Embryos were incubated in the flume for two different experimental periods; one to examine substrate impacts during natural lake cooling (37 d: December 5, 2016 - January 10, 2017) and the second to investigate substrate effects while administering a twice weekly 1 h heat shock (51 d: January 11 - March 2, 2017). During incubation, no significant difference was found in the average temperature between locations; however, temperatures were more stable within the cobble. Following both incubation periods, embryos retrieved from the cobble were significantly smaller in both dry mass and body length by up to 20%. These results demonstrate differences between embryos submerged in a cobble substrate and in the open water column, highlighting the need to consider the physical influences from the incubation environment when assessing development effects as part of any scientific study or environmental assessment. This article is protected by copyright. All rights reserved.