Article from Environotes: A publication from the Northeast Ohio Regional Sewer District. For the complete article click here.

As the leaves fall and Lake Erie cools, beachgoers may have seen a surge of dead fish washed up on the shore. Is the die-off of these silvery blue-green fish a sign of environmental turmoil, or a natural occurrence? Studies have concluded it’s the latter.

Shad can’t stand the change: Known as the eastern gizzard shad, this fish species (Dorosoma cepedianum) is not native to Lake Erie or its tributaries, and is very sensitive to rapid temperature changes. Lake Erie’s water temperature, because of the lake’s shallow depth and northerly location, can change very quickly in early winter months, causing die-offs of significant numbers of gizzard shad during October and November, according to study findings.

“It can be unsightly, but it’s important to note that in most cases the die-offs are natural,” said John Rhoades, Northeast Ohio Regional Sewer District Supervisor of Environmental Assessment.

Study source: Four scientists conducted the study in the 1980s, summarizing their findings in the 1986 report, The effects of natural winter stresses on the mortality of the Eastern Gizzard Shad in Lake Erie, which noted several other factors in the annual shad die-offs.

Other causes: Colder temperatures slow the shad’s body’s ability to draw nutrients from surrounding water, which commonly leads to starvation during colder months, causing further die-offs in December, January and February.

In 2006, the Northeast Ohio Regional Sewer District received numerous calls from concerned citizens believing some form of chemical spill may have caused the massive late-fall fish mortality. This was not the case, and shore-bound citizens should anticipate similar occurrences this time of year.

Who to contact: If you see large numbers of dead fish on Lake Erie’s shore during the fall and winter, these may be gizzard shad die-offs. If you are uncertain, or concerned there may be other environmental factors involved, please contact the Ohio Department of Natural Resources, Division of Wildlife (330) 644-2293, the Regional Sewer District’s Water Quality & Industrial Surveillance Department (216) 641-6000, or the Ohio Environmental Protection Agency (800) 686-6330.

Northeast Ohio Regional Sewer District
3900 Euclid Avenue | Cleveland, OH 44115 | www.NEORSD.org