Skip to main content

Science of Shad Winterkill

Science of Shad Winterkill

Mortality caused by cold stress has been identified as a factor regulating the abundance of gizzard shad populations, particularly in waters near the northern edge of the species' distribution where prolonged cold winters might almost eliminate them. Sudden cold spells causing water temperatures to drop several degrees in already cold water can cause massive kills.

In a study by Cornell University researchers, young-of-the-year gizzard shad were held in cages in Oneida Lake, New York, during the winter prior to ice-up.* Shad had low mortality in water above 46°F and mortality was high in water less than 39°F. Researchers also tested survival in cold rooms under controlled temperature treatments of 34°F, 36°F, and 39°F to simulate mid-winter conditions. First, shad were allowed to acclimate to 46°F, then the tank temperatures were reduced by about a half of a degree per day until the final test temperatures were reached.

Mortality was low during the acclimation period. A larger proportion of shad survived for longer periods in the 39°F tanks and mortality was highest in the coldest tanks.


Within each temperature treatment, small fish died faster. The researchers also observed that the average size of shad in field collections increased through winter, indicating higher cold tolerance of larger individuals. They conclude that cold stress and the inability to acclimate to decreasing temperatures, rather than starvation, are key factors in winter mortality.

These findings suggest that you can expect large shad winterkills when severe cold-fronts decrease water temperatures quickly in early winter before ice-up. Once lakes are covered in ice and buffered more from sudden changes in air temperatures, the severity of overwinter mortality should coincide with the duration of the ice-cover period.

*Fetzer, W. W., Brooking, T. E., J. R. Jackson, and L. G. Rudstam. 2011. Overwinter mortality of gizzard shad: Evaluation of starvation and cold temperature stress. Trans. Am. Fish. Soc. 140:1460-1471.


GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

Recent Videos

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

In-Fisherman TV Springtime Smallmouth SlamFest

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

Choose the Right Hooks for Your Harness Rigs and CATCH MORE FISH

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

Andy Montgomery's Strike King Skipping Buzzbait

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

Lew's Signature Series Bladed Jig Rod with Andy Montgomery

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

Hide Your Line--Camo Trick for Fishing Line with Bryant Smith

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

Pick the RIGHT Buzzbait Trailers with Andy Montgomery

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

The Strike King KVD Popping Perch is AWESOME with Bryant Smith

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

When to Fish a BIG JIG for Bass with Greg Hackney

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

The BEST Way to Trim A Jig Skirt with Greg Hackney

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

Prespawn Buzzbaits for BIG Largemouth Bass with Keith Combs

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Learn

Keith Combs talks about the Strike King Rage Cut-R Worm

The swim jig should be a staple in every serious bass angler's arsenal. Legendary professional bass angler Mark Davis ex...
Gear

Swim Jig Secrets for Shallow Water Largemouth Bass with Mark Davis

In-Fisherman Magazine Covers Print and Tablet Versions

GET THE MAGAZINE Subscribe & Save

Digital Now Included!

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE

Buy Digital Single Issues

Magazine App Logo

Don't miss an issue.
Buy single digital issue for your phone or tablet.

Buy Single Digital Issue on the In-Fisherman App

Other Magazines

See All Other Magazines

Special Interest Magazines

See All Special Interest Magazines

Phone Icon

Get Digital Access.

All In-Fisherman subscribers now have digital access to their magazine content. This means you have the option to read your magazine on most popular phones and tablets.

To get started, click the link below to visit mymagnow.com and learn how to access your digital magazine.

Get Digital Access

Not a Subscriber?
Subscribe Now

Enjoying What You're Reading?

Get a Full Year
of Guns & Ammo
& Digital Access.

Offer only for new subscribers.

Subscribe Now