Crystal River Mariculture Center

A BRIEF HISTORY
Progress Energy Florida, a subsidiary of Progress Energy, provides electricity and related services to more than 1.5 million customers in Florida. The company is headquartered in St. Petersburg, Fla., and serves a territory encompassing over 20,000 square miles including the cities of St. Petersburg, Clearwater, as well as the central Florida area surrounding Orlando. It operates five electric generating units at the Crystal River energy complex. Progress Energy is required to have several environmental permits for the operation of these electric generating units. In response to Environmental Protection Agency (EPA) permit requirements, environmental studies were conducted at the Crystal River Power Station from June 1983 through January 1985. Data collected as part of these studies projected annual impact levels on local fishery populations. The annual impact levels for some species were determined to be unacceptable by EPA.

The concept of a multi-species marine hatchery to mitigate fisheries impacts at Crystal River was developed as an innovative, cost-effective, alternative to conventional engineering solutions. The Crystal River Mariculture Center became part of a negotiated settlement, which included flow reduction at two of the power plants and helper cooling towers to further decrease the discharge water temperature.

The Crystal River Mariculture Center began operation October 1991. The facility will remain operative as long as water from the Gulf of Mexico is utilized for condenser cooling at the power plants. Besides offsetting the impacts of power plant operation, the facility will provide educational opportunities for students, teachers, and the general public. New and innovative aquaculture techniques will be developed as different species are selected for culture. Since the Mariculture Center represents an innovative, cost-effective, solution for the mitigation of environmental impacts, the success of this program is of interest to the utility industry as well as federal and state agencies.

WHAT IS MARICULTURE?
Mariculture is defined as the farming and husbandry of marine plants or animals. Mariculture can be used to replenish natural populations which have been depleted by natural or man-made effects. The Mariculture Center will integrate technology associated with fisheries science, marine ecology, and the aquaculture industry to develop effective production techniques for the cultivation of several marine species.

The Mariculture Center complex includes a two-story, 8100-square-foot, hatchery building and eight one-acre ponds. The hatchery building includes a water-chemistry laboratory, four spawn rooms, an incubation tank room, aglae production room, and administrative spaces. Each spawn room contains two 12-foot-diameter tanks connected to a recirculation system. This system includes a biological filter for the removal of dissolved waste products, a sand filter for removal of particulate matter, and an ultraviolet filter for pathogenic bacteria control. The grow-out ponds are located a short distance from the hatchery building. Each one-acre pond has a synthetic rubber liner to prevent water leakage, will hold approximately one million gallons of seawater when filled to capacity, and is three to five feet deep. At one end of the pond is a specially designed concrete drain structure, complete with adjustable drain valve, two removable screens, and a sump area where fish are collected during harvest.

WHAT SPECIES ARE CULTURED?
This is a multi-species marine hatchery with twelve species targeted for culture. Species were selected based on abundance and the estimated level of impact from the power plant. Since not all species are cultured simultaneously, species are listed by priority based on level of impact, ecological importance, and availability of aquaculture information. The first species selected for culture are redfish, spotted seatrout, and pink shrimp. It is important to note that the selection of species is not restricted to recreationally and commercially important fishes but also includes forage fish such as pinfish and pigfish, unique non-game species such as batfish, and certain crustaceans such as stone crab and blue crab.

Each species requires a unique set of conditions under which it will spawn and the newly hatched larvae will grow. For some of the species, those conditions are well documented; for others, they have yet to be discovered. One of the biggest challenges at the Mariculture Center will be to meet the special conditions required by the individual species.

WHICH FISH FIRST?
Since there is a great deal of information available regarding the successful culture of redfish, it was a logical species to start with at the Mariculture Center. The production of fingerling fish for release basically involves a three step process: (1) egg production by the adult fish; (2) collection and incubation of the fertilized egges, and (3) the grow-out of the hatched larval fish.

HOW IS IT DONE?
Adult redfish, called broodstock, are conditioned by careful manipulation of photoperiod and water temperature to spawn in 12-foot diameter tanks. In the tanks, a one-year natural cycle can be condensed into 120 days and the fish will begin to spawn at the end of this shortened cycle. With four spawn rooms available at the site, it is possible to have fish producing eggs at various times throughout the year. A single redfish can release over 500,000 eggs during a single spawning event. The released eggs float to the surface of the water where they can then be skimmed off and placed in incubation tanks until hatching.

Upon hatching, the fish larvae are ready to feed and must either be stocked in ponds or provided with live food in the incubation tanks. Organic and inorganic fertilizers are used prior to stocking to prepare the ponds. The fertilizers create a thick "soup" of microscopic organisms as food for the pond-stocked larvae. Larvae kept in incubation tanks must also be provided with live food. For redfish, a microscopic animal called a rotifer is an ideal live food organism. Rotifers are relatively easy to grow in large numbers using certain types of algae as their food; they then provide good nutrition for the larval fish.

The larvae stocked in the ponds are grown to what is called fingerling size, about one to three inches in length. That takes approximately 60 days, depending upon water temperature and food availability. At harvest, the ponds are drained and the fingerlings are collected and placed in a fish trailer for transport. A single pond may yield as many as 30,000 three-inch fingerlings at harvest time.

WHERE DO THEY GO?
The harvested fish are released into the Gulf of Mexico in areas determined suitable for their survival. The determination is based upon the numbers of fish released, the size of fish, the time of the year, and the availability of acceptable water conditions. Several release sites are identified so no one area is overloaded and to better ensure the survivability of the released fingerlings. To avoid mixing different fish stocks, broodstock are collected on the west coast of Florida only.

HOW DO WE KNOW?
One of the most difficult tasks for a stock replacement program such as this one is an accurate assessment of success. How do we know that the released fingerlings survive? In order to determine the success of releases, it is necessary to tag as many fish as possible. Returns on these tags can be used to calculate survivability and track movements after release.

Tagging large numbers of small fish is a very difficult task. One of the recommended techniques for tagging one-to-three-inch fingerlings involves the use of coded wire tags. The tag is a tiny piece of wire marked with a binary code. The tag is inserted under the skin of the fish near the head. This efficient tagging process allows large numbers of small fingerlings to be tagged with a minimum of handling and disturbance. The only drawback to this system is that there are no external marks on the fish, making identification after release difficult. The tags can only be detected with the use of a special device, and this requires a labor intensive effort for the capture and identification of marked fish. The Mariculture Center will continue to investigate the latest technologies available for the most effective and efficient tagging of fish to be released.

WHAT IS NEXT?
The Crystal River Mariculture Center integrates marine ecology, the aquaculture industry, and the technology associated with fisheries science to develop effective production techniques for the cultivation of several marine species. The great thing about the Mariculture Center is the many opportunities that will be available. The center will not only be able to offset the impacts of the power plants at Crystal River, but it can go far beyond that goal and enhance local fish populations. Procedures developed at the center can be utilized by the aquaculture industry. There will be many educational opportunities through cooperative programs and working agreements.

The Mariculture Center has a small staff of dedicated biologists, and there will be occasion to seek outside assistance for specific aquaculture needs. The center is in the process of developing cooperative programs with several agencies and institutions throughout the state. These agreements will provide the Mariculture Center access to a network of aquaculture experts, and the center can, in turn, provide culture space for their use. For additional information call (352) 563-4584.