Thermal habitat characteristics for warmwater fishes in coastal embayments of Lake Ontario

The effects of cool and variable temperatures on the hatch date, growth and overwinter mortality of a warmwater fish in small coastal embayments of Lake Ontario

“…Because very little is known about the ecology of the warmwater fish in small coastal embayments of the Great Lakes, the designers of these habitats have had to rely largely on our understanding of warmwater fishes in the many studies of small inland lakes and ponds. This paper is the second in a series aimed at evaluating the success of these designs; the first paper describes the thermal regime of these small coastal embayments, uses bioenergetic modeling to predict if thermal differences among embayments are sufficient to have substantial effects on young-ofthe-year (YOY) fish growth and correlates embayment temperature with their bathymetric characteristics (Murphy et al, 2011).…”

“…However, an embayment's connection to the adjacent lake creates a cooler and more variable thermal regime than in inland lakes (Murphy et al, 2011), which might severely compromise an embayment's habitat quality for warmwater fishes (Hennyey, 2006). Whereas the thermal regime of small inland lakes during ice-free months can be reasonably described with a symmetrical sine wave (Shuter et al, 1983), the thermal regimes of coastal embayments are less predictable because their connection to a much larger lake allows the input of cool water.…”

“…Whereas the thermal regime of small inland lakes during ice-free months can be reasonably described with a symmetrical sine wave (Shuter et al, 1983), the thermal regimes of coastal embayments are less predictable because their connection to a much larger lake allows the input of cool water. During the heating part of the year, the shallow embayments warm quickly, so exchange with the much larger (and slower warming) Great Lake cools the embayments (Murphy et al, 2011;Rueda and Cowen, 2005). Conversely, during the cooling period of the year, embayments cool faster than the connected lake, so exchange keeps the embayments warmer than they would otherwise be.…”

“…Conversely, during the cooling period of the year, embayments cool faster than the connected lake, so exchange keeps the embayments warmer than they would otherwise be. However, the overall effect of exchange with the adjacent is cooling (Murphy et al, 2011). In addition, when a Great Lake upwells cold hypolimnetic water, (which occurs especially frequently along the northwest shoreline of Lake Ontario (Rao and Murthy, 2001)), the temperatures in coastal embayments can decrease by over 10°C in just a few hours (Lawrence et al, 2004;Murphy et al, 2011;Rueda and Cowen, 2005).…”

“…Studies of warmwater fish ecology in small inland lakes indicate that, at Great Lakes latitudes, suboptimal temperatures often limit growth and survival of YOY warmwater fish (Sharma et al, 2007;Shuter et al, 1980). Therefore, in the many coastal embayments of the Great Lakes, where exchange of water with the adjacent lake lowers embayment temperatures through the warming period of the year (Murphy et al, 2011), temperature is likely to be an even more important ecological influence. In this paper, we select two embayments with different thermal regimes that represent the warmer half of the thermal range of embayments along the shoreline of Toronto, and quantitatively evaluate the impact of thermal differences between embayments on the hatch date, growth and overwinter survival of YOY pumpkinseed (Lepomis gibbous).…”