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

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

Role of algae and aquatic plants as primary producers F In most aquatic systems algae (phytoplankton and attached algae) and aquatic plants are the primary source of oxygen and food.

Role of algae and aquatic plants as primary producers F Algae and plants also remove/convert waste from animals and bacteria.

Nitrogen cycle in aquatic systems

Productivity of water can be a measure of fisheries potential F Waters with high productivity are able to support high fish populations and growth

Productivity of water can be a measure of fisheries potential F 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

Secchi disk Indirect measure that estimates algae population from clarity. Inaccurate method.

Light-Dark Reactions in BOD bottles 1. Use one clear exposed bottle to determine photosynthesis rate 2. Use one dark covered bottle to determine respiration rate 3. Do arithmetic to determine gross and net photosynthesis

Fluorometer Systems Old style New styles 1. Water sample is placed inside 2. Sample is excited by light radiation 3. Chlorophyll molecules have excited electrons, which give off fluorescence when they drop to level.

Direct counts and identification of algae 1. Sample on counting slide 2. Focus on counting grid on low magnification 3. Count cells in randomly selected region 4. Identify algae

Fisheries estimate based on productivity F Light – dark bottle results F Plus one or more of the other methods can be used to estimate F About 10% energy or biomass conversion between trophic stages

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

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

Control of problem algae and aquatic weeds F Chemical controls (herbicides, copper, etc) F Mechanical controls (dredges, rakes, backhoes) F Environmental controls (nutrient reduction, shade) F Biological controls (fish, insects) F Integrated Pest Management

Algae - water quality project

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

Salvinia molesta in the Colorado River F Aquatic weed introduced from Brazil F Filling irrigation canals and damaging irrigation pumps F May impact fish and wildlife

Control of Salvinia molesta ??? F Mechanical controls not working F Chemical controls not working and damaging the environment

F Integrated pest management plan F Limited spray, some mechanical, and introduce biological control F Cyrtobagous salvinia, Salvinia weevil from Brazil Best hope for control of Salvinia

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