Aquatic Plant Management and Importance to Sport Fisheries Presentation to Michigan Inland Lakes Convention May 2014 Mike Maceina Professor Emeritus School of Fisheries, Aquaculture, and Aquatic Sciences Auburn University, Alabama
Background Florida Texas Alabama New York (Hudson River) Lake Houghton, Michigan Ontario (lake homeowner, Board of Directors) Aquatic plants and fish (sport fish and populations) Aquatic plant impacts on water quality Fishing fish about 130-150 days a year
Why Do People Live on Lake Aesthetics serenity, beauty, quiet, peaceful living, life-style, to get away from it all Climate Swimming Boating Fishing Many lakes contain aquatic plants that can be viewed positively or negatively
Fish derived their energy from the bottom of the food chain (got to have some sort of plants)
Four types of larger aquatic plants 1) Floating 2) Submersed 3) Emergent 4) Floating attached
Fish in Michigan that Live/Rely on Aquatic Plants Sunfish (bluegill, pumpkinseeds) Bass (largemouth and smallmouth) Crappie Muskellunge Northern Pike Pickerel Yellow perch Walleye Killifish Minnows
Crappie
The Role of Aquatic Plants and Fish Plants provide: habitat for spawning; a nursery area for young fish; habitat for older fish food Abundant food resources are found in aquatic plants Plants provide cover and a refuge from predators Submersed aquatic plants coverage can be extensive, typically fish diversity (number of species goes up) and the number of small fish increases Aquatic plants can improve fishing success and quality
1000 Abuandance of Age-0 Bass in Guntersville Number per acre 800 600 400 200 Plants No plants 0 1991 1992 1993 1994 Year class
50 40 Abundance of Age-1 Bass from Guntersville Plants No plants Catch-per hour 30 20 10 0 1991 1992 1993 1994 Year class
Percentage of fish 30 25 20 15 10 5 0 20 16 12 October 1992 in Plants 1 2 3 4 5 6 7 8 9 October 1992 in Areas without Plants During the first year, young age-0 bass should reach 4 inches or greater. This increases the probability of making it through the first winter and reaching age 1. 8 4 0 1 2 3 4 5 6 7 8 9 Bass Length in Inches
Age-0 Bass Abundance in Florida Lakes over 150 acres Age-0 Bass Density (Number/acre) 1000 500 100 50 10 5 1 0 20 40 60 80 100 Percent Cover of Submersed Plants
At some point, too many plants will cause a decline; bass growth rates and stunting will occur
Similarly, at some point too many plants will make it hard for bass and other predator fish to obtain food and fish will get skinny Skinny bass
Percent 14 1988 12 Plant Cover 28% 10 8 6 4 2 0 16 14 12 10 8 6 4 2 0 15" Size Limit 5 10 15 20 25 1993 Plant Cover 9% 15" Size Limit 5 10 15 20 25 Size Group (Inches) Biomass remained unchanged between 1988 and 1993 (32-34 lbs/acre)
Number of Species Plants would help the fishery Lake or Reservoir Size (Instability)
100 80 60 40 20 Illinois Model Largemouth Bass Invertebrates and Forage Fish 0 20 40 60 80 Plant Coverage Production
What does this all mean? Best science - general consensus/agreement among fishery managers/researchers 10% to 40% areal coverage of plants is ideal for fisheries Curve ball or caveat to this is the presence of abundant exotic plants (i.e. Eurasian watermilfoil). Exotic or invasive plants can provide good habitat for fish. Homeowners typically want less plants Conflict has occurred and will occur!
Survey of anglers fishing on Lake Seminole, Georgia. Lake has lots of plants. Coverage over the years ranged from 40 to 75%
Aquatic Plant Control Methods Biocontrol Water level manipulations Mechanical Herbicides
ocontrol ass carp banned in Michigan t a good option in larger water bodies; little or no trol or complete elimination of plants.
Another invasive exotic plant that may be coming your way
Advantages of Grass Carp for Plant Control - inexpensive - can result in complete elimination of plants - long lasting effect Disadvantages of Grass Carp for Plant Control - can result in complete elimination of plants - long lasting effect - grass carp can migrate long distances - can cause water to turn green (algal blooms)
Water level manipulation (draw down)
Advantages of Water Level Drawdowns - inexpensive - results in desiccation of submersed aquatic plants - can promote native plant establishment Disadvantages of Water Level Drawdowns - can only be done on lakes with water control structure (s) or dams - navigation issues - water access issues (docks become dry) - aesthetics
Mechanical harvesting
Advantages of Mechanical Harvesting for Plant Control - environmental or ecosystem friendly - cut and control plants where you want Disadvantages of Mechanical Harvesting for Plant Control - short-term - plant fragmentation and spread - not efficient and very costly - dumping plants on land (bad stink) - kills fish and other critters
A study on mechanical harvesting of plants in a Florida lake found - 2,500 fish killed per acre (mostly small fish) - 50 sport fish killed per acre (mostly sunfish) - 75 lbs per acre of fish killed (18% of the biomass) - 120 largemouth bass were killed and these fish weighed 2.2 lbs for every acre of harvested plants These numbers are not a big deal unless the lake is small and constant mechanical harvesting is occurring.
Aquatic herbicides
Advantages of Herbicides for Plant Control - effective control - can promote the establishment of native plants - control plants where you want control (less so than mechanical) Disadvantages of Herbicides for Plant Control -short-term (exceptions) - can be moderately costly - large or whole lake treatment runs the risk of complete elimination of plants (exception: native seed bank present).
Before After Aquatic herbicides can be very effective
Fish Behavior, Movement, and Feeding in Relation to Herbicide Applications (fluridone and endothall) Largemouth bass did not leave areas after being treated with herbicides. With the loss of dense submersed vegetation, home ranges and movement (activity) of fish tended to increase. Depending on cover available, bass either moved deeper (into woody structure) or shallow (into shoreline emergent plants) After reduction in aquatic plants, bass switched from being ambush predators to search predators After reduction in aquatic plants, food consumption increases, and smaller bass consume less small invertebrates (insects, scuds, other invert critters) For adult bass, sometimes switch from sunfish to open-water prey (shad, smelt, alewife, minnows)
What happens when you spray herbicides on fish nests
Nests were sprayed with Aquathol K (endothall) and water After being sprayed (either water or endothall), fish left the nests for about 15-20 minutes Fish remained on the nests at the same rate for those treated with endothall and water for up to 14 days Production and size of young fish were the same in ponds treated with endothall and water.
Spring Creek 2000
4,500 acres of hydrilla removed, Some native plants became reestablished Spring Creek 2002
Apply endothall or fluridone to coves native plants return
Largemouth bass response to exotic plant control with herbicides and establishment of native plants Adult fish utilized these treated areas, density and biomass increased 50-100% compared to areas infested with exotic plant and no control took place. Adult fish were larger in the herbicide treated coves Young fish density was the same or higher in herbicides treated coves compared to untreated coves. Young fish grew faster in herbicide treat coves than in coves completely infested with an exotic plant.
Lake Homeowners and Aquatic Plant Control Get involved early proactive versus reactive Establish a plan with goals For fish issues, contact and establish a point person in your state fishery conservation agency (Michigan Department of Natural Resources) The Michigan Department of Environmental Quality Water Bureau permits and is responsible and regulates the use of herbicides for the control on nuisance aquatic plants Really important that one agency is in charge of aquatic plant control activities Bring in the pros, use professional applicators
Thoughts Assume free benefits from the water we live on. How much does a home owner spend a year per acre on outdoor landscaping/maintenance? For me $60/month = $720/year on ¼ of an acre. Thus, about $3,000 per acre per year What about costs for improving aquatic habitat including aquatic plant management?
Management goal is to keep everyone happy!