Allen Lab

Assessing Effects of Gizzard Shad Removal on Nutrient Cycling and Gizzard Shad Population Dynamics
Reversing the effects of eutrophication can be challenging and requires the reduction of external nutrient sources and internal nutrient loading. Omnivorous gizzard shad Dorosoma cepedianum can facilitate nutrient loading from the sediments as a consequence of their foraging activity at the sediment-water interface and subsequent excretion of nutrients in the water column.  This feeding activity may contribute considerably to the release of nutrients from the sediments in eutrophic Florida lakes.

Biomanipulation via removal of gizzard shad has been proposed as a management strategy for improving water clarity by reducing internal nutrient loading from the sediments.  Preliminary studies at Lake Denham, Florida, suggested that strong biomass reductions of gizzard shad using haul seines may reduce phytoplankton biomass.  Recently, biomanipulations have been attempted on several lakes of the Harris Chain of Lakes, Florida using gill nets, but the results of these efforts have yet to be experimentally evaluated.  Understanding how fish life history metrics respond to density reductions is critical to understanding the potential impact of biomanipulation on lake food webs.  We used a whole-lake gizzard shad reduction experiment (i.e., a biomanipulation) to 1) assess impacts of a commercial gizzard shad removal on their population dynamics (i.e., recruitment, growth, mortality), 2) measure diet contents of gizzard shad to indicate mode of feeding, 3) explore the potential for gizzard shad removal to influence lake water quality, and 4) evaluate the potential for bycatch impacts on black crappie Pomoxis nigromaculatus fisheries. 

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Size Selectivity of an Otter Trawl for Black Crappie at Five Florida Lakes
Otter trawls are a commonly employed assessment gear for black crappie in Florida. However, the selective properties of the gear have yet been defined. Our goal is to estimate the size selective properties of the bottom trawl and evaluate its utility for use as an assessment gear for crappie in Florida lakes. Data included in analysis occurs from five lakes with at least 5 and up to 25 years of fishery independent data. Cooperators include the Florida Fish and Wildlife Conservation Commission. 

Fish Community Composition in Tussock Forming Aquatic Macrophytes at Two South Florida Lakes
Understanding the mechanisms of how and why fish utilize aquatic macrophyte habitats under varying environmental conditions is important for management.  Tussocks negatively influence dissolved oxygen concentrations and influence the suitability of habitat for fish.  The Florida Fish and Wildlife Conservation Commission has provided funding for us to research tussocks and the impact they have on dissolved oxygen concentration and fish community at Lakes Kissimmee and Istokpoga.  The objectives of this project are to: 1) evaluate the temporal patterns in hypoxia with emergent aquatic macrophyte species and biomass levels, and 2) assess how fish community metrics (i.e., density, biomass, richness, and diversity) varies with emergent aquatic macrophyte species and biomass levels. 
Images: Poor Sportfish Tussock Habitat photo1, photo2, and Kissimmee Site Map

Hatching Duration, Growth, and Survival of Age-0 Largemouth Bass along a Latitudinal Gradient of Florida Lakes

Survival of age-0 largemouth bass to age-1 is largely influenced by temperature dependent factors such as: hatching date, growth rate, and over-winter mortality. Florida’s climate changes with latitude from sub-tropical to temperate, thus the influence of temperature driven factors affecting survival may differ across Florida’s latitudinal gradient.  Using hatching dates, growth and survival information, we are investigating the mechanisms that influence age-0 largemouth bass survival across Florida and how those mechanisms relate to conventional recruitment hypotheses for this species.  This study was funded by the Florida Fish and Wildlife Conservation Commission.