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May 27, 2021     Post 125
alewife die off



If you’re old enough to remember the 1960s along the lake shore, the photos will look familiar- stinky dead ‘mooneyes’ rotting on the beach were part of the summer scene then. I recall tons of them. Around May 15 I first noticed a few three inch juvenile fish swimming in circles on their sides and lying stiff and still shiny fresh but stiff on the beach.

A week later a visit to the beach showed many more juveniles plus a few adults. I queried a fisheries researcher at the USGS and learned that this die off was reported from Oak Orchard to Oswego so it was a considerable quantity of young fish.

The researcher confirmed my suspicion this was the old 1960s problem of thermal shock from moving into warm water plus poor condition. Hopefully disease was not the main cause. Last year surveys showed a strong production of young alewife. The little guys presumably competed hard for phytoplankton food ( also being diverted to the bottom by zebra mussels). The young fish went into the winter without the fat reserves and strength needed to get them through the movement into warmer waters this spring.
The die off is nature’s way of balancing the lake’s available food supply with the fish population. If you want to “blame” someone it would probably be the zebra and quagga mussels.


You can read more about the alewife, its Lake Ontario history, and its current status in my forthcoming book “A Natural History of Lake Ontario” being released later this summer by Arcadia Press.



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