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Climate changes threaten fishing

Regional fisheries face negative effects from global warming

Glen Schmitt Times - outdoors writer, St. Cloud Times | WWW.SCTIMES.COM

February 11, 2007

Global warming — or more specifically, global climate change — is occurring.

Scientific studies have determined human influences are causing an increase in the amount of greenhouse gases deposited into the air and it is affecting climate change.

Within this century, scientists believe North America will encounter a 3.5 to 8 degree temperature increase. Most alarming, the majority of studies indicate that Midwestern states are expected to be hit hardest.

Warmer air temperatures and the subsequent climate changes in future years could have an impact on fishing in Minnesota. At the very least, it will have a negative impact on the state’s fisheries and the fish that inhabit them in many regions, according to Don Pereira, DNR fisheries research supervisor.
Pereira was in St. Cloud earlier this week to discuss global climate changes as it pertains to the future of fish and freshwater organisms in Minnesota.

By his assessment, some changes have already begun to be noticed and other negative trends aren’t far down the road if our environment doesn’t start being protected from costly emissions.
“Climate change is very much a habitat issue,” Pereira told the group of about 30 people. “An ecosystem can only handle so many changes before it’s noticeable and we’re chipping away at it.”
Warmer air, warmer water

Over time, a warmer environment will increase water temperatures as well. The amount of cool, oxygen-rich water available to cold and cool water fish species such as lake trout, tullibee, northern pike and walleye could be depleted to the point that some species may disappear all together and others will be much less prominent in certain regions of the state.

According to Pereira, managing lake populations is already challenging in and around the Grand Rapids area. He says it’s not out of the question that the state may stop managing the species in future years throughout this region.

Common fish species such as the tullibee need a cool refuge to survive summer’s heat, under normal conditions. As cold-water habitat is depleted and becomes marginal at best, so will populations of tullibees, which also are a primary food source for many of the state’s more popular gamefish.

Tullibees depleted

The DNR’s large lake assessment program has revealed a trend that more tullibees are dying during the summer months in recent years on lakes such as Cass, Mille Lacs and Winnibigoshish.
The optimum temperature for tullibee during the open water season is 62 degrees. Once it exceeds that level, fish kills become more significant.

“We’ve almost always noted some tullibee kills during the summer months on our larger lakes,” Pereira said. “But we’re seeing more numbers of them dying now and if the trend continues they could be completely gone.”

Northern pike and walleyes, which continue to thrive in water summer water temperatures between 71 and 80 degrees, but can stress when water temperatures reach 82 degrees, may have a more northern population shift in future years.

Threatened species

If current climate trends continue to swing upwards, there’s a good chance some lakes in the southern part of the state could become too warm and eventually too hostile for walleyes and pike to thrive in.
There’s a chance that walleye fishing may only be an option throughout the northern half of the state within this century.

Other species such as the bluegill and bass may actually thrive and increase their abundance and range if warming water characteristics prevail. Noted as warm-water species, most bass and panfish typically don’t see any mortality until water temperatures reach 96 degrees.

“Bass and bluegill will increase their abundance,” Pereira said. “Small populations such as those in the Arrowhead Region could expand and become more prevalent.”

Winter outlook

Winter angling also could be affected by global climate change.

Warm temperatures means less-than-ideal ice making conditions, which in turn means a shorter ice fishing season. Given ice conditions over the past couple years, it’s quite easy to see the potential that exists with this scenario.

Minnesota winters appear to be headed toward the direction of what looks and feels more like a typical Kansas or Nebraska winter season. A later start to the ice making process and earlier ice-out dates in the Midwest in recent years has drawn the attention of scientists and anglers alike.

Winterkill has been less noticeable in many of the state’s shallow lakes. Pereira acknowledges that he knows winterkill is decreasing throughout Minnesota, which has made these shallow bodies of water extremely difficult to manage for waterfowl.

“The lack of winterkill is allowing fish to flourish in our shallow lakes,” he said. “If fish persist, they eat food that’s critical for ducks, especially the survival of young ducks.”

Healthy trout streams, which need cold, clean water for plant life and suitable fish species to thrive in, have deteriorated in recent years and will continue to do so.

Human impact

Human influences such as development have stripped many miles of shoreline streams of their native grasses, which are a necessity to recharge ground water.

It’s estimated that one million acres of farmland and natural land area will be used up for sprawl and development in Minnesota over the next 25 years. In addition, 1.2 million people are expected to move into the state in coming years, putting added pressure on these natural areas and intensifying the need for energy use.

“We have to adapt a need to change how we manage the release of emissions into the environment,” Pereira said. “Even if we limit them very well, we’re still looking at significant increases by the middle of this century.”

Possible solutions

So, the big question remains: What can we do about this problem?

The obvious answer from an environmental standpoint and its future is to not accept the status quo or the business-as-usual approach.

Federal legislation is currently in the works that caps the amount of gases that can be emitted by groups or companies. Most of the bills are intended to limit the amount of greenhouse gases released.
On the state level, this Legislative session has been buzzing with renewable energy and environmentally sound bills. Minnesota is at the forefront in leading this charge and has the opportunity this session to develop precedent-setting legislation that would be the strongest in the nation.

Last Wednesday, the Minnesota Senate approved legislation to ensure that approximately 25 percent of our state’s electricity would come from clean, renewable sources by the year 2020. The bill passed with a 61 to 4 vote, according to a statement released by Steve Morse, executive director of the Minnesota Environmental Partnership (MEP).

“Using Minnesota’s clean, renewable resources to generate power keeps our energy dollars at work right here at home, creates jobs, strengthens our economy and results in a cleaner environment,” Morse said.

“With the Senate’s approval of this vigorous renewable energy standard, we are moving onto a cleaner energy pathway for Minnesota and taking an essential step to reduce the pollution that is causing global warming.”