Record high temperatures in two Canadian Great Lakes could have an impact on the future of the fishery, if the trend continues.
Lakes Ontario and Erie had the warmest July surface temperatures on record. Erie was an average of 2.2˚C above average for July, although some days 4 to 5˚C higher than average. Ontario was 3.2˚C above average. Lakes Huron and Superior were above average, respectively at 2.9˚C and 2˚C, but these were not records.
Frank Seglenieks, water resources engineer with Environment and Climate Change Canada, said surface water temperatures measured by satellite, only go back to 1995. The only other measure of Great Lake temperature is 10 meters below surface at the intake for the Buffalo water supply on Lake Erie. This has been collected since 1927 and was also record high this July.
Seglenieks said warm temperatures could lead to increased algal blooms and result in less ice cover as a result of warmer water going into winter.
Long-term trends key
OFAH Fisheries Biologist Adam Weir said, “It’s very important not to focus on a snippet, such as a single season or year, rather, look at the bigger picture, over a larger time series, in order to understand the true implications to our fisheries. So, short term, it’s difficult to come to a definitive conclusion. Fish are pretty resilient, and have evolved and adapted to environmental changes and fluctuations.”
He said that if, over the long term, temperatures increase at unnatural rates, such as in the past several decades, fish may not be able to adapt to these changes quickly enough and there could be serious consequences, however.
Ministry of Natural Resources and Forestry spokesperson Jolanta Kowalski added, “Current observed warmer surface temperatures may result in some redistribution of fish – movement further offshore or deeper – but they are unlikely to have large scale population level effects.”
She also noted that gradual warming could reduce available habitat for cold water species like lake trout, and could affect spawning of some moderate temperature species such as walleye.
“While fish wait for that optimal temperature, considerable research has shown how the rate of temperature change, the duration within a specific range, etc. all contribute to the year-class success. In other words, it is more than just an absolute measure of temperature that will affect the fish’s spawning success,” said Kowalski.
Weir further explained, “Yellow perch and walleye, require extended winter periods for adequate gonad development, and without these conditions, shorter winters can lead to suboptimal environments negatively impacting maturation and reproductive success of these species.”
Conversely, he noted warm water species like largemouth bass would flourish in warmer Great Lakes as they will spawn earlier and have a longer growing season.