You may have noticed dead fish along the shoreline recently. We have seen this before with Sunfish late every spring. But this looks like a different species of fish – Alewife – which we have not seen before in such quantities.

Testing will be done on some of these fish to rule out any unnatural causes for their deaths.

For now we are assuming that it was a combination of factors that led to their deaths:

-The sudden heatwave of Memorial Day weekend,
-The end of the spawning season which leaves fish exhausted and fragile (been there, done that),
-and large flocks of Cormorants hunting these fish which stresses them more.

In short, very likely natural causes.

[ If you are interested in following this topic, you should join the Nextdoor Truesdale neighborhood page and check out your neighbor’s posts and information about these and other current topics! Link to join: https://nextdoor.com/invite/451866249a99d2536836 ]

It is important to note that we have NOT treated the lake to date in 2016 so anything related to Aquathol-K or other treatments can be ruled out as a cause.

We are also interested in learning how Alewife came to be in Truesdale Lake and what impact their population will have on the lake ecosystem. Christian Jenne, who is studying the lake from the SUNY Oneonta Lake Management program, can hopefully offer insight into the impact the fish may have and if it is new to our lake.

It is possible the fish were stocked upstream and escaped down into the lake. Or a lake resident or fisherman may have added them on purpose or inadvertently, perhaps from a baitfish bucket? The long term impact remains to be seen.

Here’s a link to an interesting article Barbara Cohen found online from the University of Wisconsin Sea Grant program with some more detailed explanations noting that Alewife are usually salt water fish and spawn in fresh water unless trapped upstream. Quoting from that article:

“Alewives are not well adapted to the osmotic stress associated with life in fresh water. In freshwater, the salt concentration in a fish’s body is higher than the surrounding water. For this reason water tends to leak into the cells of the fish, a process called osmosis. Freshwater fish must constantly ‘pump’ water out of their bodies; fish that are well adapted to a freshwater environment have larger kidneys than their saltwater counterparts. Because of this physiological stress, alewives are rather sensitive to disturbances in [their] environment… A severe change in water temperature … can cause the fish to die.”

We will update this article if we learn anything new. Continue reading →