Algae and Aquatic Plants for Fisheries

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Algae and Aquatic Plants for Fisheries

• Kevin Fitzsimmons, Ph.D.
• Professor, University of Arizona
• Visiting Fulbright Professor, Thailand
• President, World Aquaculture Society
• Kasetsart University
• August 4, 2004

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Introduction

• Role of algae and aquatic plants as primary
  producers
• Aquaculture of algae and aquatic plants
• Invasive species problems
• Control of problem algae and aquatic weeds

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Role of algae and aquatic plants as primary
producers

• In most aquatic systems algae (phytoplankton and
  attached algae) and aquatic plants are the
  primary source of oxygen and food.

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Role of algae and aquatic plants as primary
producers

• Algae and plants also remove/convert waste from
  animals and bacteria.

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Nitrogen cycle in aquatic systems
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Productivity of water can be a measure of
fisheries potential

• Waters with high productivity are able to support
  high fish populations and growth

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Productivity of water can be a measure of
fisheries potential

• Tools to measure productivity
• Secchi disk measure of water clarity
• Light and dark bottle reactions - measures of
  photosynthesis and respiration
• Fluorometer measures amount of chlorophyll
• Direct algae/plant counts and identification

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Secchi disk
Indirect measure that estimatesalgae population
from clarity.Inaccurate method.
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Light-Dark Reactions in BOD bottles
1. Use one clear exposed bottle to determine
photosynthesis rate2. Use one dark covered
bottle to determine respiration rate 3. Do
arithmetic to determine gross and net
photosynthesis
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Fluorometer Systems
Old style
New styles
1. Water sample is placed inside2. Sample is
excited by light radiation 3. Chlorophyll
molecules have excited electrons, which give
offfluorescence when they drop tolevel.
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Direct counts and identification of algae
3. Count cells in randomly selected region
1. Sample on counting slide
2. Focus on counting grid on low magnification
4. Identify algae
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Fisheries estimate based on productivity

• Light dark bottle results
• Plus one or more of the other methods can be used
  to estimate
• About 10 energy or biomass conversion between
  trophic stages

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Aquaculture of algae and aquatic plants

• Phytoplankton algae used to feed larval fish,
  shrimp, mollusks
• Macroalgae (kelps, red algae) widely used for
  human consumption
• Many aquatic plants used for human and animal food

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Invasive plants and algae

• Invasive weeds damage environment, reduce crop
  yields, and poison livestock
• Aquatic weeds clog irrigation systems, fill
  aquaculture ponds, increase mosquito habitat
• Blue-green algae cause taste and odor problems in
  fish and drinking water supplies

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Control of problem algae and aquatic weeds

• Chemical controls (herbicides, copper, etc)
• Mechanical controls (dredges, rakes, backhoes)
• Environmental controls (nutrient reduction,
  shade)
• Biological controls (fish, insects)
• Integrated Pest Management

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Algae - water quality project
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Algae - water quality project

• Collected data on water chemistry and physical
  parameters
• Counted algae and determined recruitment and
  growth
• Determined nutrient sources and timing
• Changed water removal from dam
• Saved utilities 600,000 per year on water
  treatment costs

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Salvinia molesta in the Colorado River

• Aquatic weed introduced from Brazil
• Filling irrigation canals and damaging irrigation
  pumps
• May impact fish and wildlife

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Control of Salvinia molesta ???

• Mechanical controls not working
• Chemical controls not working and damaging the
  environment

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Best hope for control of Salvinia

• Integrated pest management plan
• Limited spray, some mechanical, and introduce
  biological control
• Cyrtobagous salvinia, Salvinia weevil from
  Brazil

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Quick overview

• Algae and aquatic plants critical to aquatic
  environments
• Many useful aspects for humans
• Can cause problems for humans when out of control
• Many new jobs and opportunities managing aquatic
  systems
• Thank you for opportunity to present our research