Recommendations for Stocking Gizzard Shad in a Large Upper Midwest Reservoir

Abstract

Gizzard Shad Dorosoma cepedianum, a pelagic detritivore found throughout the USA, are an important prey fish for many sport fish species and are often stocked in an attempt to bolster sport fish growth and condition. To date, there has been little research on how many or at what density prespawn adult Gizzard Shad should be stocked in order to produce a year-class suitable for sport fish consumption within that year. In Lake Oahe, South Dakota, Gizzard Shad are an important prey resource for Walleyes Sander vitreus and other sport fish when the number of Rainbow Smelt Osmerus mordax is low. However, severe winters in 2009–2011 extirpated the Gizzard Shad population in Lake Oahe (or reduced its abundance to below the detectable limit). Thus, Gizzard Shad were stocked in 2012 and 2013 to improve short-term prey fish production. During this time, we sought to identify how many or at what density prespawn adult Gizzard Shad need to be stocked in select embayments of Lake Oahe to achieve larval Gizzard Shad production similar to that in years when natural reproduction took place. Although the results were quite variable, we found positive linear relationships between the density of larval Gizzard Shad and the number and density of adult stockings, with the number of adults stocked providing a better indication of later larval production than adult stocking density. In general, stocking 150 prespawn adult Gizzard Shad would produce larval densities ≥5.0 fish/100 m³ in select embayments of a large Midwest reservoir.

Received November 8, 2016; accepted February 15, 2017 Published online April 27, 2017