The Mystery Of The Dead Alewives Of Seneca Lake
Visitors to the largest of the Finger Lakes of Upstate New York this 4th of July weekend are thinking twice before they dip a toe in the water. On the eastern side of Seneca Lake, large numbers of 6-inch long silver fish are washing up on shore, dead.
As the summer heat rises, people would like to go swimming, but they don’t want to end up like those fish. They’re wondering if what killed the fish could kill them. Was it a toxic algae? Deadly pollution? An unknown aquatic microorganism?
The answer to this mystery has some ambiguity to it, going back in time to the dawn or serious ecological science in the area. At the heart of the matter is the question of whether this particular species of fish is native to the Finger Lakes, and to Lake Ontario, the Great Lake into which all the Finger Lakes drain.
The fish that are washing up dead on the eastern shores of Seneca Lake are called alewives. The first recorded capture of an alewife in the area dates back to the late 1800s. The trouble is that no one is certain whether the alewives were present in the lakes of Upstate New York before this time. It may be that the alewives weren’t recorded in the region before the late 1800s because they weren’t there before that time, and were introduced through human activity around this time. It could also be that the presence of alewives in the Finger Lakes was not recorded before the late 1800s because careful records weren’t being made before that time.
Whether or not alewives are native to Lake Ontario and the Finger Lakes, they aren’t best adapted to these aquatic environments. The range that alewives were first known in was along the Atlantic coast of North America – in saltwater. The cellular physiology of saltwater fish is different from that of freshwater fish. Because the inside of a fish has a higher concentration of salt than the water in freshwater, water soaks into the body of fish swimming in rivers and lakes. Fish that are adapted to live in freshwater have mechanisms for ejecting that excess water from their bodies. Saltwater can’t do so very well.
Alewives are, like salmon and trout, adapted to live most of their adult lives in saltwater, temporarily coming into freshwater streams in order to spawn. Alewives that live their entire lives in lakes merely migrate from deep water to shallow water near the shoreline when they spawn.
The change in conditions that comes along with spawning time for freshwater alewives is too much for many of the fish. They can survive in freshwater, but are weakened by it. When they move from the cool water of deep in the middle of the lake to the warmer water near shore, their metabolisms speed up, and many alewives don’t survive the shock. The annual die-off of alewives thus can be regarded as a natural phenomenon, except for the possible artificial introduction of the fish into the Finger Lakes and Lake Ontario in the first place. No manmade pollution or toxic algae is involved.
Alewives spawn at the beginning of the summer, which is why so many of them are washing up dead on the eastern shore of Seneca Lake right now. After they float to the top of the water, the westerly wind pushes them there, where they accumulate until, eventually, they’re eaten by seagulls and racoons.
The remaining mystery is why alewives are called alewives. What do these fish have to do with beer and married women? These fish were named after women who worked in taverns selling ale, who grew large bellies from drinking lots of beer… or for other reasons. Alewives can grow big round bellies as well, and that’s how they got their common name.