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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.

10 thoughts on “The Mystery Of The Dead Alewives Of Seneca Lake”

  1. Jon buchwald says:

    I remember 40 years ago there would be a die off for several years in a row. Stink real good

  2. Bertels9 says:

    I don’t know why you wrote Trout and Salmon live in saltwater??? Both are Freshwater fish. Trout have lived in Seneca lake forever – never have they been a saltwater fish

    1. Bill nye says:

      What’s a steelhead… and all the trout native to the west coast then… where the trout were taken from for these fisheries ???? The browns were brought from europe … …. only native salmon to the lakes are land lock atlantics…. correct me if im wrong…???

      1. Deb says:

        I agree that these fish are of the trout family;I am wondering where these fish replacing my smelt.? I so remember in the spring fishing with my family in the parks fishing for smelt thru out Seneca Lake an Ithaca area fishing there falling down with 500 smelt an smelt everywhere going down the creek an a fellow fisherman getting awhole of me as I was swimming to safety gosh those where the days my friends,,,Last time I went fishing for them in the 80’s they were pretty much gone…How sad all because?? Pollution is my answer an exstinsion of another of good natural food source.Here’s to hoping I caught an ate all the last remaining smelt in our area. Knowing that Monterary,Calf. has a fish good supply out there now. Did they all get to the Pacific Ocean ? hmmmm sitting here wanting to eat 100 of them right now.

  3. Michael Black says:

    This article does not explain the die off of the
    Alewives, I have lived on the shore of Seneca Lake for 46 years and I have never seen a die off like this. Something is a miss and it not annual die off. The number of lake trout that I have caught over the last two years is almost zero , and there main diet is sawbellies . Something is very wrong with the lake and the fish in it, I think the high saline count in the lake may be to blame. I don’t believe it’s the algae , but until the DEC has biologist testing these fish we won’t know for sure , and maybe not even than.

  4. Michelle Craven says:

    Could it have anything to do with the raging streams feeding the lake this spring? Maybe more than normal were washed out of Ontario into Seneca by default… just an idea

  5. Bill Cagle says:

    Seneca Lake is not the only Lake with issues. Keuka Lake use to have plenty of sawbellys,now they are none existant , the lake trout have nothing to eat,they are starving or eating perch. Being a charter boat captain i know this for a fact.

  6. David Thomas says:

    The “sawbelly” term comes from the scale pattern on the belly of the alewife. Rub your finger from the tail to the gills along the belly and feel the “sawtooth” pattern. Has nothing to do with the size of the belly…….they are not called fat bellies.

  7. Alex says:

    So why is this the first summer in my 30 years on the lake that I remember this happening?

    I’ve also seen several different species dead in the water and floating up to the shore this season, more than in previous years for sure.

    Why is it only on the Eastern side of the lake?

    I feel like this article raises more questions than it answers, other than the species of fish.

  8. Mark Thomas says:

    Alewives are a huge source of food for both the warm water species of sport fish like bass, pike, perch etc., and cold water sport species like, rainbow trout, brown trout, lakers, and atlantic salmon. This phenomenon of alewives dying off each Spring is extremely alarming to hear about to me as I imagine it is to most sport fisherman. There once was a very large population of smelt in the finger lakes as well, and they also were a huge source of food for the above mentioned warm and cold water sport fish. I am an avid trout fisherman, and over the last 20 years
    I’ve witnessed a large and steady
    decline of trout, and the size of them as well. I’ve asked and spoken with other fisherman over the years, and I can assure you that pretty much all of them have noticed the same decline in both numbers and sizes of the trout species. I’ve heard several speculative reasons for these declining numbers and sizes, but the most common heard are because of the lack of bait fish like smelt, alewives, and certain species of minnows. Most fisherman including me believe that the reduced number of baIt fish is directly related to invasive species like the zebra mussels, gobies, lamprey eels, and certain types of minnows. I’ve read that the main cause for these species to have enterted our lakes is from the ballasts of large ships importing goods from other Countries. The ships are supposed to empty their ballasts in the Atlantic Ocean before entering their fresh water destinations, but it’s more profitable for them to pay a fine than sit out their to empty. I would really like to get a straight answer from a fisheries biologist or someone who’s not just speculating the demise of our sport fish in the finger lakes. I think it’s about time that the speculative answers to our issues are put to rest with the real truths, and what is being done to rectify it?

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