Upland Pine, Blackwater River State Forest. Photo by Gary Knight

Tuesday, March 15, 2016

Florida Nature Almanac: An Anadromous Migration

Illustration by Duane Raver.

In February, Alabama Shad (Alosa alabamae) began their migration of over 100 miles, from the Gulf of Mexico up the Apalachicola River to the Chattahoochee area, where they will spawn.  Shad are an anadromous species.  This means that, like northern salmon, spawning occurs in freshwater rivers but adults spend most of their lives in the salt waters of the Gulf.

FNAI scientists monitor research on the status and trends in the Florida population.  Historically, shad spawned in rivers across the northern Gulf Coast from the Mississippi to the Suwannee and were abundant enough to support a commercial fishery for them in Apalachicola.  In recent years, spawning in Florida has been limited to the Apalachicola River system.  The Florida population is ranked S2, meaning that shad are rare and vulnerable to extinction in the state.  Scientists believe declines in shad abundance are mainly due to dams which block the upstream migration of spawning fish.  
Florida Fish and Wildlife Conservation Commission biologists capture, tag, and release adult Alabama Shad to monitor movement and aid in the development of accurate population estimates.  Once a portion of the shad population is tagged and released, biologists can later catch more fish and use the percentage of fish that are caught with tags to estimate the size of the entire shad population.  Photo by Rick Long, FWC.

The Nature Conservancy has a great post on efforts to operate the Jim Woodruff dam on the Apalachicola River in a way that should help to increase spawning success:  Conservation Locking at Jim Woodruff Dam.

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