Culture of selected marine fish in ponds receiving thermal effluent from a power station and their use as biological monitors of water quality.
Single and mixed cultures of fish were employed to monitor the thermal effluent from the Cedar Bayou Generating Station, Houston Lighting and Power Company. Striped mullet, Mugil cephalus, was cultured with Florida pompano, Trachinotus carolinus; Atlantic croaker, Micropogon undulatus; spotted seatrout, Cynoscion nebulosus; and southern flounder, Paralichthys lethostigma in 0.1 hectare ponds receiving a constant flow of water from the discharge canal. In addition, redfish (red drum), Sciaenops ocellata, was cultured with Atlantic croaker. Striped mullet, Atlantic croaker, Florida pompano, and redfish were also maintained in monoculture. Different age groups were employed in polyculture to produce more fish per hectare. Unstocked and unfiltered ponds were maintained to determine what organisms might enter the ponds from the discharge canal. Relationship of these supplemental organisms to fish productivity was investigated. Survival and growth rates, competition, condition, length-weight and standard length-total length relationships were computed. Heavy metal and pesticide accumulation was measured. Growth for Florida pompano and 1-year-old Atlantic croaker in culture with striped mullet was 56 and 44% better, respectively, than in monoculture. Striped mullet apparently stimulated these fish to more fully utilize the pond resources. Lack of suitable mullet growth was related to high densities (2240 fish/ha) masking any benefits from polyculture. At harvest a sample was taken to determine the abundance of in situ organisms. Striped mullet, in monocultures, did not take full advantage of food sources entering the pond system. Southern flounder cultured with mullet were able to utilize in situ organisms without competing with the mullet for food. Striped mullet, Atlantic croaker, and spotted seatrout were larger, after culture in these ponds, than wild populations of similar age. Southern flounder (193.8 g) were larger than those cultures at higher densities by previous researchers. Flow of heated water into the ponds during winter months was inadequate to maintain temperatures necessary for growth. If more heated water could be supplied cold kills of Florida pompano would be eliminated and overwintering become possible. Selected heavy metals and pesticides concentrations in fishes changed with time in the effluent; they never exceeded harmful levels.