Journal of the Southeastern Association of Fish and Wildlife Agencies

Cultural practices which either contribute nutrient materials to the ecosystem or accelerate detrition by induced recirculation of nutrients within the system result in environmental changes which persist after the practices have been discontinued. The effects of environmental modification were found to be reflected in species structure of native fish populations. The percent of centrarchids within the total population was found to occur in direct proportion to the percent of productive bottom. Macroinvertebrate organisms used as food by centrarchids were' found to be restricted to certain bottom types. These studies confirm the conclusion of Eggleton (1933) that forces inherent in the substratum itself bend and shape all other forces and thus condition the reaction of both plants and animals. The role of submersed and floating vegetation as a substrate for invertebrate organisms is discussed.

The use of an aluminum boat as the electrode on streams and rivers is quite simple and is as effective as the electrodes suspended from the side of a boat. This eliminates the need of any electrodes hanging over the side of the boat and allows the operator to work efficiently through trash and submerged obstaeles. It is necessary, if using direct current or pulsed direct current, to connect the negative lead to the aluminum hull of the boat instead of to the electrodes suspended on each side. The individual items required and their use in this operation, e.g., variable voltage pulsating unit, modified negative and positive electrodes and others, are described. The eost of the unit, including boat, motor, trailer, variable voltage pulsator, miscellaneous and safety items, is approximately $2,000.00. Safety items are listed and described to assist in eliminating shock hazards.

The number of largemouth bass (Micropterus salmoides) in a 3.5-acre experimenbal pond located at Auburn University Agricultural Experiment Station was estimated by mark and recovery techniques using both Schnabel and Peterson methods. Sampling was done wirth both electric shocker and angling. Estimates were made during two periods in 1962. Various estimates of the number of bass made in this study were fairly uniform. However, on draining the estimates were found to be in error by approximately 50 percent. Based on number of bass recovered at draining and the computed percentage of survival, the value of N for the first period (May 23, to December 20, 1962), was computed to be 604 bass, whereas the Schnabel and Peterson methods gave N values of 304 bass and 469 bass with percent errors of -49.7 and -22.4, respectively. The theoretical requirements of both methods seemed to be met for the first period.

Plate samplers constructed of VB-inch thick masonite were used in a bioassay study of water quality in the Black Warrior River near Tuscaloosa, Alabama. The samplers were placed in a fertilized pond and allowed to accumulate a dense population of larval chironomids (Chironomidae) for one month. The samplers were then placed into the river at stations above the outfall of the uppermost industry and below each outfall of four industries. Counts of chironomids on each of the samplers were made after one week and comp.arisons were made between the average number of organisms on the samplers at stations above the outfalls and the average number at each of the stations downstream from the outfalls. It appeared that this inexpensive technique of bioassay can be useful in determining the effects of pollution on chironomids. Today there are more people with more leisure time demanding more clean freshwater for recreation than ever before.

One thousand three hundred and forty-six largemouth bass were captured, tagged, and released in nineteen bodies of water throughout the State of Florida. Spaghetti, Petersen disc, and Monel metal strap tags were the principal tags employed. All fish caught by anglers were returned to the Game and Fresh Water Fish Commission for information regarding growth rates of which negative data was obtained. Comparisons were made of the percent returns of each of the three tags represented, plus the Spaghetti tag was compared in two different locations on the fish. The external effects on the recaptured fish showed 258 either slight or heavy infections caused by the initial tag wound or by irritations of mechanical, chemical or biological origin. This study was made in conjunction with the Florida State-wide Fish Tagging Program Sponsored by the Schlitz Brewing Company.

The research function at the Pascagoula Technological Laboratory is described. The staff, the equipment, and the microbiology and chemistry programs are briefly discussed. Biochemical studies of fish and shellfish are a major program at the laboratory. The deterioration of fresh iced shrimp was studied recently by following the increase in pH, analyzing the amino acid, hydroxyproline, and evaluating the variation in the nitrogen values of fractions eluted by different solvents. Microbiological studies accompanied the biochemical studies. Daily total plate counts demonstrated the increase in microorganisms as the shrimp became less acceptable as a food. Fluctuations in the types of organisms present were shown to be related to the changes that took place in the iced environment as the salinity--and the marine bacteria--decreased.

Laboratory experiments were conducted to determine the acute and chronic effects of endrin to estuarine fishes. Short-term bioassays in flowing seawater determined 24-hour LC50's for spot (Leiostomus xanthurus), mullet (Mugil cephalus), menhaden (Brevoortia patronus), longnose killifish (Fundulus similis), and sheepshead minnows (Cyprinodon variegatus). A population of spot was exposed continuously for eight months to a sublethal concentration (0.05 ppb.). No pathology was found in the spot after seven months of exposure, but, a three-week exposure to a near-lethal concentration (approximately 0.075 ppb.) produced pathology characterized by systemic lesions involving the brain and spinal cord, liver, kidneys and stomach. Residue analyses (gas chromatography) of spot exposed to 0.05 ppb. endrin for five months revealed an accumulation of 78 ppb. (micrograms/kilogram). No endrin could be detected in these fish after a 13-day holding period in uncontaminated water.

A description is given of the physical f,acilities in which mass cultures of penaeids have been reared from eggs to postlarvae. The metal chelator EDTA was added to the water in which the shrimp were grown. Larvae of Penaeus aztecus developed more rapidly, at 30° C than at lower temperatures. Salinity varied from 20.5% to 36.0% during rearing trials in which P. aztecus Iarvae were reared to postIarvae. Addition of mixed, algal cultures ,as food g,ave better survival than additions of their individual components. EDTA was used as an additive to filtered sea water to grow a diatom, Skeletonema sp., in mass culture, as food for larval shrimp.

The spotted seatrout, Cynoscion nebulosus, are found throughout the year in the Biloxi Marsh Area in southeastern Louisiana. A total of 368 stomachs were analyzed; 152 were empty. Fish occurred in 74.4 per cent of these stomachs and crustaceans in 25.3 per cent. During the summer months fish and crustaceans were comparable in per cent occurrence as food items. In this same period food availability samples showed that crustaceans had become more prevalent. This suggests a correlation of the food habits of the spotted seatrout to food availability. Fish seem to be the most important food group in the Biloxi Marsh Area utilized by the spotted seatrout.

Age and growth of blue catfish, Ictalurus furcatus (LeSueur), collected on Delta National Wildlife Refuge, Venice, Louisiana were determined by length frequency and the pectoml spine technique. Lengths calculated from p,ectoral spines agree with the length frequency mode for age I fish collected during January, 1965. Three regressions were computed for the data and the cubic equation provided the best fit. This equation indicated that weight increased faster than the cube of the length.

Fish in Pine Creek, in DeKalb County, Tennessee, were eradicated with rotenone and brown trout were stocked in the stream. This management tool, stream reclamation, was evaluated by studying the growth rate of the brown trout, their condition, the rate at which other species of fish re-entered the stream, and the effect of the toxicant, rotenone, on the bottom fauna. Populations of bottom dwelling organisms were reduced from 34 to 100 per cent by the rotenone. All organisms except two, Plecoptera and Isopoda, recovered up to or beyond their original abundance within one year after eradication. The brown trout had an average growth rate per month of 11 millimeters in length and 18.1 grams in weight during the 16-month study period. This growtth rate was exceptional when compared to the growth rate of brown trout reported by other investigators and was equal to the growth r,ate of brown trout ina Tennessee hatchery.

The City of Tulsa, Oklahoma has long heen a proponent of the multiple-use concept of its water resources; including approximately 5,000 surface acres of impounded water. These waters are: Lake Eucha (2,880 surface acres), also known as Upper Spavinaw, DeIaware County, Oklahoma, Spavinaw Lake (1,637 surface acres) , Mayes County, Oklahoma, and Lake Yahola (425 surface acres) Tulsa County, Oklahoma (J.ackson, 1957). The fishery management program on the Spavinaw Lakes was initiated by A. D. "Bob" Aldrich in 1949 and has been expanded and continuous for a period of sixteen years. Although progress may have appeared slow at times during this period, the trend has been toward improved fishing and an improved fishable fish population. The rough fish removal program was initiated in 1949. 436,513 fish weighing 163,265 pounds have been removed from Spavinaw Lake during the past fourteen years (1951-1964).

Scales of largemouth bass taken from two ponds at Baton Rouge, Louisiana over a three-year period agreed closely with the known past stocking history on these fish. Largemouth bass scales from a 50-acre pond at Clinton, Louisiana indicated agreement with the six years fish had been stocked. Total length growth rates of bass were increased by controlled fall drawdown; however, prolonged summer droughts decreased total length growth and condition factors. Spawning and drastic drawdowns resulted in more pronounced growth checks than winter cessation on the scales of bluegill and redeal' sunfish from ponds of known stocking history.

A total of 3,174 native fish of 29 species was tagged and released in Bayou D'Arbonne during the spring and summer of 1963. The distance and direction of movement of captured fish were recorded before inundation and ag,ain ,after the flooding of the 15,000-acre impoundment, D'Arbonne Lake, in January 1964. Of the 57 tagged fish returned before inundation, 54 were recaptured in the same locaJtion. One fish moved upstream for a distance of 3.3 miles and two fish moved downstream for ,an ,average distance of 6.8 miles. After the lake was filled, the fish exhibited extensive movements and only 11 percent of the returns occurred in release areas. Thirty-three of the 84 fish recaptured in the lake moved toward the headwaters while 35 fish moved toward the spillway. A total of 4.4 percent of the n,ative fish tagged were recovered.

Adult striped bass purchased from commercial fishermen on Albemarle Sound, N. C. were transported to the Fayetteville and Weldon Hatcheries, injected with hormones,and spawned. In addition to ripe fish brought into the Weldon Hatchery by fishermen, sexually mature striped bass were obtained from the Roanoke River by electro-fishing gear. These fish, like those from Albemarle Sound, were injected with hormones, held in glass-front plywood aquaria (32" x 24" x 16"), and spawned. Excellent hatches were obtained from these eggs. Laboratory experiments, confirmed by actual practice, indicated that striped bass eggs following six to 28 hours of incubation can be transported up to 12 hours in plastic bags containing water and oxygen with no significant increase in mortality. Attempts to rear fry in aquaria failed although limited success was obtained in outdoor concrete pools. The fry in these pools began baking artificial food 28 days after hatching.

Prolarvae striped bass Roccus saxatilis (Walbaum) were brought to Oklahoma for experimental rearing in culture ponds. Postlarvae were stocked in ponds which were rich in plankton and later fed 246.5 pounds of prepared foods. Samples were taken periodically for detailed examination of growth and food habits. A preliminary examination indicated that prepared foods were utilized by these fish. The ponds were stocked with adult Tilapia and no small individuals of this species were found at the time of draining. The striped bass harvested after two months with a 15 to 60 percent recovery of the number stocked.

Several water filters constructed of Saran cloth of different porosities were tested for efficiency in filtering undesirable firsh from hatchery pond water supplies. A cloth filter bag, attached to pond water supply pipes, gave promising results. Thirteen ponds tested with these filters were free of wild fish (fish not stocked in test ponds by hatchery personnel) af,ter periods ranging from four to 29 weeks. The remaining four test ponds contained a total of 16 wild fish. Control ponds were heavily infested with wild fish species introduced through the water supply.

Single applioations of 0.25 ppm Dylox effectively controlled the tadpole shrimp, Apus longicaudatus, and the fairy shrimp, Streptocephalus texanus, in hatchery ponds without adverse effects on bass or channel catfish fry. Bass survival in treated ponds was boosted from 20 to 80 per cent by the Dylox treatment. Plankton populations in the treated ponds appeared unaffected.