Jessica Smith
April 19, 2010
Springtime is about a month ahead of schedule, and rapidly warming temperatures may have repercussions on spring spawning and the food supply for animals that have wakened or returned north unseasonably early.
With this spring seeing the warmest water temperatures and earliest ice melt since Atikokan MNR biologist Brian Jackson began monitoring temperatures in the Atikokan River in 1993, the walleye are preparing to spawn before ice would typically be off the lakes. While it may mean good news for opening weekend fishing, because the walleye will have completed spawning and be more active, it may not be as good for this year’s crop of young fry.
“It’s so early, it’s so warm out there, and it’s so unusual, that we’re wondering, ‘How is this going to affect the spawn? Are the males and females going to be ripe at the same time and on the spawning beds at the same time?” said Jackson. The Sportsmen’s Conservation Club has already caught some ripe female Walleye and discovered some eggs late last week, he said.
This year, the ice was off the river March 22 and would typically be gone about April 15 (early to even mid-May on the lakes), and although the ice left only a few days later than this year in 2000, Jackson said the water is warming much more quickly this year, where water temperatures are already averaging about 7°-8°C, compared to the more typical 3°C.
The northern pike, which also spawn in the spring, may have difficulty if the lake levels are low. While walleye and suckers spawn in rocky areas, the pike head to the flooded spring wetland areas to lay eggs, usually on top of the previous year’s vegetation, such as cat tails or flooded grass.
“In years like this where you don’t end up with wetland areas being flooded, they’re having trouble finding places to lay their eggs so they lay them in habitat that is not as good. If they can’t get up [to the wetlands] they lay it in more muddy areas and the eggs tend to suffocate and not nearly as many hatch,” he said.
However, typically a long, warm summer is good for fish health because the younger fish put on more weight and are more robust heading into the winter, he added. If the spawn is successful, there could be a bumper crop like occurred after the early spring of 1998. “We saw a really good, strong year with lots of fish in future years that came from it,” said Jackson.
Bass typically spawn in June when water temperatures are about 15°C, so may also spawn early, while lake trout and white fish spawn in the fall so those eggs will likely hatch early, provided there is enough there is enough moisture in the spawning areas.
The opening of walleye fishing season this year (mid-May) should be a marked difference from recent springs where the lake ice melted quite close to the open of the season and the fish were either in the midst of, or just finished, spawning and were sluggish and close to the spawning areas because temperatures were still cool.
Wildlife
And fish aren’t the only ones a little confused this spring. Some wildlife, vegetation and insects are governed by daylight hours and others by temperature, “so some things are reacting to the temperature, and others are not reacting as fast as the temperature change, for instance, the food supply.” So while some birds have returned early to nest because it is so warm, “the insects they need to feed their young aren’t responding as fast,” said Jackson. “The two things that drive annual events are temperature and partly daylight.” (Swallows for example, are “keyed into” daylight and show up on pretty much the same day each spring, regardless of temperature.)
Black bears are governed by temperatures, so while they emerged from hibernation last month they are now suffering from a time lag while their food supply (grasses and other vegetation) hasn’t greened up as fast.
Warm temperatures are also likely to cause heat stress on gestating moose and could affect calf mortality, a problem that has already been a concern in this area, said Jackson. “The cow has to carry the calf for a certain gestation period, but all of a sudden it warms up and they don’t want to walk around as much or feed because it’s hotter, yet they still have their winter coats on.”
MNR studies in recent years have shown declining moose populations in this part of the province including Quetico Park, he said.
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