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Cold water temperatures can negatively impact spawn

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outdoors Bemidji, 56619
Bemidji Pioneer
(218) 333-9819 customer support
Bemidji Minnesota P.O. Box 455 56619

Most lakes in the Bemidji area would still be covered with ice if this was a normal spring. Lake Bemidji is usually ice free around April 26.

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Temperatures have been near or below average since the ice went out on the lakes, which has slowed down the progress of the spawn for species like walleyes, northern pike and perch.

Surface water temperatures in most lakes have stalled in the mid 40s, which is just barely warm enough to get some of the fish ready to spawn.

Many walleyes were not ready to spawn when they showed up at the DNR egg stripping stations and needed to be held in nets until they were ready to drop their eggs.

Most fish prefer a consistent warming trend when they spawn. The ideal situation is to have water temperatures continue to rise through the spawn, to give the fish fry the best chance for survival.

Fish eggs usually hatch somewhere between three and 10 days after the adult females lay their eggs. The incubation goes faster when water temperatures are increasing during and slower when water temperatures stay cold.

The worst situation is to have falling water temperatures and a prolonged cold front during the critical period right after the eggs are laid.

Fish fry have an egg sack after they hatch that provides food for their first few days of life. Once the fish fry's built-in food supply is exhausted, they have to find their own food to eat.

The concept of a food chain works well, because everything in the lakes is inter-connected at a fundamental level, like links in a chain.

The beginning of the food chain is plant based, with phytoplankton the fundamental building block in the lakes.

Phytoplankton gets its food from the sun and nutrients in the water. Populations of phytoplankton are at their lowest levels early in the spring, and begin to increase once the water in the lakes begins to warm.

Once phytoplankton populations reach a certain level in the lakes, populations of zooplankton begin to increase proportionally, because zooplankton feed primarily on phytoplankton.

How all this relates to young walleyes and perch is the young fish feed on zooplankton they find swimming in the water until they are large enough to eat other prey.

The more zooplankton there is in the lakes, the easier it is for the young fish to find enough to eat, which increases survival rates.

If the lakes are too cold, it usually means phytoplankton levels are low, so zooplankton levels are also low and the young walleyes and perch struggle to find enough to eat.

When food is scarce at the beginning of the food chain, it can have a negative impact on the whole food chain.

The survival rates of each new age class of fish can depend on what the conditions were like when the adult fish spawned.

An early spring can produce a good age class of fish if the weather cooperates, but it can also produce a poor age class of fish if the weather is too cold.

A poor age class of fish creates a gap in the adult fish populations that may be felt by anglers for years to come, especially if it happens in consecutive years.

The cold temperatures have also had a negative impact on anglers trying to do a little fishing for panfish early in the season.

Perch anglers were able to find some active perch early in the season, with the fish in a holding pattern waiting for the water temperatures to increase. Fishing for perch slowed down once the perch began to spawn.

Crappies and sunfish usually move into the shallows when water temperatures reach the low 50s. Anglers have been finding most crappies and sunfish suspended along the breakline, close to the areas they will move into once the lakes warm-up.

Anglers wanting to give their boats a test run or go fishing for panfish should be prepared to launch without the aid of a dock for at least another week.

Schedules to put in the docks are based on when the lakes are usually ice free, so most docks are not scheduled to be put in until later in April.

PAUL A. NELSON runs the Bemidji Area Lakes Guide Service. He can be contacted at panelson@paulbunyan.net

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