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Aquatic Weed Control FAQsBen Sperry

Research Assistant Scientist

USACE ERDC/UF-IFAS Center for Aquatic and Invasive Plants, Gainesville, FL

Outline

• Do herbicides cause sores on fish?

• Do herbicides build up in lake sediment?

• Is hydrilla good for fishing?

FAQ #1 – Do herbicides cause sores on fish?

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FAQ #1 – Do herbicides cause sores on fish?

What causes these fish sores?

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Sores from spawning

• “During spawning, the fish bite and rub on each other on the bottom during the nest building. That rubs off the slime and creates opportunities for parasites, bacteria and fungus that are always in the water to attack the fish. All the flooding last year brought lots of nutrients into the lake and probably fueled a “bloom” in the parasite and bacteria populations. Now with warmer weather and fishes’ immune systems compromised a bit during the spawn, it sets up a perfect situation for these conditions. The sores will heal; very seldom are they lethal.” - Gene Gilliland, B.A.S.S. conservation director

Confinement Stress

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Diquat?

• Diquat actually controls columnaris infections in channel catfish (Darwish and Mitchell 2009).

FAQ #2 Do herbicides build up in lake sediment?

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FAQ #2 Do herbicides build up in lake sediment?

Lake Istokpoga Sediment Study 2019

Herbicide Usage

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Herbicide Analysis

FAQ #3 Is hydrilla good for fishing?

FAQ #3 Is hydrilla good for fishing?

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Fish can use hydrilla for cover

Sammons et al. 2003

Hydrilla infestation and bass size

Johnson et al. 2014

What about other fish species?

Colle et al. 1987

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Angling effort?

Colle et al. 1987

What do the big data say?

Hoyer et al. 2008

What do the big data say?

Hoyer et al. 2008

“The presence of hydrilla had no statistical effect on fish species richness, diversity, or abundance.”

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Literature Cited• Colle DE, Shireman JV, Haller WT, Joyce JC, Canfield DE (1987) Influence of hydrilla on harvestable sport-fish populations, angler use,

and angler expenditures at Orange Lake, Florida. North American Journal of Fisheries Management 7:410-417

• Darwish AM, Mitchell AJ (2009) Evaluation of diquat against an acute experimental infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus (Rafinesque). Journal of Fish Diseases 32:401-408

• Gilliland G, Schramm H (2009) Keeping Bass Alive: A Guidebook for Tournament Anglers & Organizers. https://www.ncwildlife.org/Portals/0/Fishing/documents/Keeping_Bass_Alive_Handbook.pdf

• Hoyer MV, Haller WT, Ferrell J, Jones D (2020) Legacy herbicides in lake sediments are not preventing the growth of submersedaquatic plants in Lake Istokpoga. J Aquat Plant Manage 58:47-54

• Hoyer MV, Jackson MW, Allen MS, Canfield DE (2008) Lack of exotic hydrilla infestation effects on plant, fish and aquatic bird community measures. Lake and Reservoir Management 24:331-338

• Johnson KG, Dotson JR, Pouder WF, Trippel NA, Eisenhauer RL (2014) Effects of hurricane-induced hydrilla reduction on the largemouth bass fishery at two central Florida lakes. Lake and Reservoir Management 30:217-225

• Noga EJ, Botts S, Yang MS, Avtalion R (1998) Acute stress causes skin ulceration in striped bass and hybrid bass (Morone). Vet Pathol35:102-107

• Reed P, Francis-Floyd R (1993) “Red Sore Disease” in Game Fish. University of Florida Cooperative Extension Service, Institute of Food and Agriculture Sciences, EDIS. http://edis.ifas.ufl.edu/pdffiles/VM/VM05900.pdf

• Sammons SM, Maceina MJ, Partridge DG (2003) Changes in behavior, movement, and home ranges of largemouth bass following large-scale hydrilla removal in Lake Seminole, Georgia. J Aquat Plant Manage 41:31-38

• Suchan M (2016) Sores on bass come from rough spawning. https://www.bassmaster.com/blog/sores-bass-come-rough-spawning

Learn more at plants.ifas.ufl.edu

AcknowledgementsJay Ferrell UF-CAIP

Mark Hoyer UF-LAKEWATCH

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