As the weather warms (hopefully soon!) don’t be alarmed if you spot a small number of dead fish along your lake or pond shoreline. Fish die-offs are not at all uncommon in the spring. So-called “spring kills” occur when a small number of fish who survived the winter die as the water warms. These events are almost always related to a combination of natural stresses unique to the spring season. Water temperatures can fluctuate widely as we transition into spring. Fish that have survived the winter are already in a somewhat weakened condition because they’ve been eating at a reduced rate; at the same time, their metabolism rates increase as the water warms and spawning activities begin. Some combination of these stress factors can lead to a few deaths in the population.
Another concern in spring is the natural increased reproduction rates of bacteria and other microorganisms as the water warms. Again, fish that are already in a weakened state coming out of the winter months may be more susceptible to infection.
Keep in mind that fish mortality is high in general and a small-scale die-off event related to unavoidable natural stressors is not a cause for concern; however, if large numbers of dead fish are found, an investigation is warranted to determine if there is a more serious situation in place.
