Nature’s Way of Leveling the Playing Field

by · July 5, 2016

From the Reader’s Write section of the Stouffville Free Press

These periodic die-offs may be nature’s way of leveling the playing field.

In the last couple of weeks Musselman’s Lake has experienced a fish die-off similar, but less severe in numbers, to what occurred in the spring of 2009.

There are a number of similarities between this fish die-off and that of 2009. As in 2009 the dying fish are almost exclusively black crappie, as well, both incidences occurred in the early spring when the Crappie are breeding.

Sunfish nesting in Musselman's Lake.

Sunfish nesting in Musselman’s Lake. Photo Dr. Brian Laing

Sunfish, a close relative, are seen mating and nesting as I write this. A water quality issue would affect more than one species of fish.

All of this leads us to believe that the crappie die-off that we have just experienced is caused by the same thing that caused it in 2009, namely, the unusually warm weather followed by a drop in temperature timed just when the crappie are breeding. This theory is further supported by the fact that almost all of the fish are of breeding size, the young fry are not affected.

If the Crappie were not spawning they would have stayed in the deeper cooler water and not been subjected to the water temperature fluctuations. As it is, the breeding fish stay in the shallow water and are stressed becoming prone to a bacterial infection by Columnaris flexibacter.

Columnaris is always present in fish, but typically becomes an issue only in stressed fish.

Postmortems in 2009 confirmed this as the cause at that time. Due to the similarities of the two die-offs, we have not performed postmortems this year, but are confident that the cause of the two incidents is the same.

There is potential ‘silver lining’ to this crappie die-off. Crappie are an aggressive species recently introduced to the lake (likely through release of baitfish). I have seen their young surround a sunfish nest and slowly eat all the eggs. As the male sunfish chases off one juvenile crappie another moves in and eats some eggs. The sunfish returns to the nest and chases off the new interloper while a third rushes in to eat some more eggs. In very little time the sunfish nest is empty.

Because of survival instincts like this, the crappie population has dramatically increased since they were introduced to the lake and is putting pressure on other species.

These periodic die-offs may be nature’s way of leveling the playing field.

Dr Brian Laing

MLRA

Town and Country Animal Hospital

905-640-4107

 

 

Related Links

Natural Occurrence and No Cause For Alarm

Update of the Crappie Die-Off

Phil Bannon Mounts A Cleanup

Crappie Update

It’s Crappie!