One of the coldest winters the East Coast has seen in years is the culprit in the deaths of thousands of fish along coastal Virginia and North Carolina.
That headline and lead sentence from a WAVY-TV news report sounds like something you might expect from what we've been experiencing this past week. In reality, though, it describes a fish kill that occurred about this same time last year. The date on the report is Feb. 17, 2014. Covering this event was WAVY's Liz Palka, along with her photographer, Chris Omahen
(responsible for all photos used here).
One thing that grabbed my attention about this year-old fish kill, other than for the fact I missed it totally when first published, is what's in some of the accompanying photos. Palka's one interviewee (a resident of Virginia Beach) described the kill as involving "large numbers of speckled trout and puppy drum washing up near docks and canals." However, you don't need a magnifying glass to determine that more species than just those two were found in a belly-up state
(check the accompanying photos for yourselves).
A marine-recreation specialist interviewed by Palka characterized the fish deaths (called a "cold stun kill"), as "natural." They first started being reported by Mid-Atlantic anglers the week of Jan. 19, 2014. The marine-recreation specialist went on to say, "From the limited data we have, in terms of numbers, it just seems to be on a larger scale this year." The 2014 cold-stun kill was serious enough, though, to prompt North Carolina to ban all recreational and commercial fishing of speckled trout in that state until mid-June last year.
According to my Internet research, the majority of winter fish kills are experienced as cold temperatures cause bodies of water to freeze over. Low dissolved-oxygen levels result from a combination of factors. The air/water interface is capped by the formation of ice, limiting the exchange of oxygen at the surface. This icy cover also reduces or completely eliminates sunlight from reaching any aquatic plant life that otherwise would produce oxygen through the process of photosynthesis.
With no light available, aquatic plant life will begin to respire (consume oxygen), along with fish and other aquatic life and further increase the oxygen demand. The bacterial decomposition of organic material and bottom sludge also depletes oxygen levels.
Over time, the dissolved oxygen levels eventually become too low to sustain aquatic life. This can vary widely, depending upon the type of aquatic organisms living in the water. For most warm-water species, like bass, crappie and bluegill, minimum oxygen levels need to be about 2 ppm. Trout species require higher oxygen levels, typically around 4 ppm. Oxygen levels below this for extended periods of time will prove to be lethal.
Given the record-setting cold temperatures we had this past week, I suppose we very well may soon see another fish kill. As a matter of fact, I heard just a couple of days ago about an isolated case that already has turned up.
The good news is this: Winter kills that occur in larger lakes and rivers rarely are serious enough, in the long run, to do lasting harm, because of the sheer number of fish those bodies of water support. There usually are enough survivors to repopulate all the species. And, too, fish kills sometimes can be beneficial for the fish community by reducing over-populated, slow-growing species.
Nevertheless, fish kills always should be reported. Contact the Virginia Marine Commission at 757-247-2200 anytime you see one.
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