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Distribution and Relative Abundance of Spawning American Shad (Alosa sapidissima) in the St. Johns River, Florida

American shad (top) and blueback herring (bottom).
Credit: Florida Fish and Wildlife Conservation Commission (FWC)

The American shad (Alosa sapidissima) is a member of the herring family. American shad ascend rivers from the ocean in order to spawn. Juveniles spend their first growing season in the river of their birth and emigrate to the ocean in the fall to grow and mature. They remain in the ocean for two to six years before they mature and return to spawn in the river in which they originally hatched. American shad range along the Atlantic coast, from Florida to Canada; the St. Johns River, Florida, harbors the southern-most spawning population. Shad that spawn in rivers south of Cape Hatteras, North Carolina, die after spawning. However, those spawning in rivers north of Cape Hatteras often survive to spawn in subsequent years. Populations from all rivers mix in the ocean and migrate between the coastal Atlantic and adjacent bays of Canada in the summer and the Atlantic off the southeast coast of the U.S. in the winter. As the offshore stock reaches the southern end of its migration, it enters the St. Johns River beginning in December. Spawning activity peaks in February and March in the river between Deland and Cocoa, Florida.

Historically, shad have been an important food source in North America since the colonial era. Shad have been important to recreational anglers in the modern era; however, recreational angling peaked in the St. Johns River, Florida, during the 1950s and 1960s. Atlantic coast commercial landings peaked at the turn of the 20th century but have declined dramatically along most of the shad’s range. Obstruction of spawning runs, pollution, and high harvest rates have all taken a toll on abundance, prompting the Atlantic States Marine Fisheries Commission (ASMFC) to mandate protective measures that include a directive to monitor existing populations and rebuild stocks where necessary. Commercial landings in the St. Johns River, Florida, also peaked in the early 1900s and continued to decline significantly throughout the century. Recreational effort and landings have also decreased markedly in recent years. The net ban in 1995 eliminated most of what remained of Florida’s commercial American shad fishery. Most of the current commercial harvest of St. Johns River shad occurs off the coast of mid-Atlantic States, such as North Carolina, during the American shad oceanic migration. The contribution of this fishery to mortality of fish from Florida is unknown.

Even though commercial harvest in the St. Johns has ceased, resurgence in the recreational fishery has not occurred. Recreational angling continues to decline and consists mostly of “old timers” with few new anglers entering the fishery. Are too few fish making the run to interest anglers? Will increased angling be detrimental to the recovery of American shad on the St. Johns River? This study should provide information to help answer these questions.

During the winter and spring of 2002–2005, researchers continue to sample for American shad at three sites on the St. Johns River to describe reproductive biology, abundance, and distribution of spawning individuals. Scientists from the DeLeon Springs Freshwater Resource Assessment and St. Petersburg Marine Fisheries Biology offices sample adult shad by electrofishing every other week from November to May. Samples are collected between the Lake Jesup outlet and Lemon Bluff in an area known as “Shad Alley.” This area is generally considered the heart of the shad spawning grounds, and most of the recreational fishing effort for this species has historically occurred here. Two additional sites (one upstream, and one downstream of Shad alley) are also being sampled. An angler creel survey is being conducted on this stretch of river. Electrofishing catch rates will be compared to the results of this survey to determine if shad abundance, as measured by electrofishing catch rate, can be related to angler success. The electrofishing catch rate of shad in Shad Alley is compared to the electrofishing catch rate at alternative sites to compare shad abundance in different sections of the river between years and at differing water levels. During the 2004–2005 season, sampling frequency will increase in areas other than Shad Alley. This will help researchers to better describe the distribution and abundance of shad in various areas of the river. Additionally, male shad will be marked with a fin clip unique to the capture location and released in an effort to estimate abundance and describe movement between locations through recaptures. Biologists also microscopically examine the reproductive organs of female American shad to determine if, and when, these fish spawn and to describe other aspects of shad reproductive biology.