Journal of the Southeastern Association of Fish and Wildlife Agencies

The effect of the polychlorinated biphenyl (PCB), Aroclor 1254, in eggs of the sheepshead minnow, Cyprinodon variegatus, on fertilization success and survival of embryos and fry was investigated. Adult fish were exposed for four weeks to 0.1,0.32, 1.0,3.2 or 10.0 ug/l of PCB, then injected twice with 50 lU of human chorionic gonadotrophin to stimulate egg production. The eggs were fertilized, placed in PCB-free flowing seawater and observed for mortality. Fertilization success was unimpaired by concentrations in eggs as high as 201 ug/g but survival of embryos and fry was reduced. Usually, fry from eggs containing 7.0 ug/g or more began dying 24-48 hours after hatching. If this PCB affects other species similarly, then populations of fish that presently have comparable concentrations in their eggs may be endangered.

Tests were conducted to determine (1) the acute toxicity of dieldrin in flowing sea water to American oysters (Crassostrea virginica), pink shrimp (Penaeus duorarum), grass shrimp (Palaemonetes pugio) and sheepshead minnows (Cyprinodon variegatus) and (2) the rate of dieldrin uptake and depuration by spot (Leiostomus xanthurus). Acute (96-hour) EC50's were: oysters, 12.5 ug/1; pink shrimp, 0.9 ug/l; grass shrimp, 11.4 ug/1; and sheepshead minnows 23.6 ug/I. Spot exposed to 0.0135,0.075,0.135,0.75 or 1.35 ug/l for 35 days accumulated the chemical with maximum concentrations attained in II to 18 days. Maximum whole-body residue (wet-weight) was 6,000X the concentration in test water. Spot contained no detectable dieldrin residues at the end of a 13-day depuration period in dieldrin-free water. Tissue alterations, such as subepithelial edema in gill lamellae and severe lysis and sloughing of the small intestine epithelium, occurred in spot exposed to 1.35 ug/1 for four days.

The White Amur, Ctenopharyngodon idella, was found to be able to withstand recommended pond treatment concentrations of potassium permanganate, formalin, copper sulfate, and malachite green. In all instances, 100% of the test fish survived a 96 hour tolerance period at concentrations above the dosages recommended and used by the Arkansas Game and Fish Commission for disease and vegetation control in earthen ponds. Both rotenone and antimycin were bio-assayed for possible use as a toxicant selective toward the White Amur. Both show promise as 100% mortality was recorded for test fish at extremely low concentrations in aquariums.

A comparison of tolerance of fingerling black crappie, white crappie and largemouth bass to Fintrol-5 was conducted in aquaria. White crappie were found to be more susceptible to Fintrol-5 than were black crappie and largemouth bass. Largemouth bass and black crappie showed similar tolerance to the toxicant. The mortality of largemouth bass and black crappie was significantly reduced at a pH of 8.0-8.5. All three species suffered significant mortalities beginning with .04 ppm Fintrol-5 at a pH of 7.0. One ppm KMn04 significantly reduced mortality by detoxifying Fintrol-5.

Six experimental catfish feeds, containing 29, 36, and 42% crude protein at metabolizable energy (ME) levels of 1000 and 1300 kcal per Ib, were fed to fingerling channel catfish in 24, 1/ I0-acre earthen ponds for 165 days. Each dietary treatment was randomly assigned to four ponds which were stocked at a rate of 4,000 fish per acre. Feed allowance was increased biweekly on the basis of fish weight gain until a maximum daily allowance of 40 Ib per acre was reached. The higher energy plane resulted in greater weight gains, more fish protein produced per acre, and slightly fatter fish, at each dietary protein level. At the lower ME level the difference in growth among fish fed the 29, 36, and 42% protein diets was not significant (PV.05). At the higher ME level the fish showed increased gains with each increase in diet protein percentage.

Two experimental fish diets, one consisting of50% roasted soybeans and 50% fresh fish, and another consisting of 30% soybeans, 20% corn meal, and 50% fresh fish, both with vitamin and mineral supplements, were compared to Oregon pellets in a 6 week feeding trial using yearling channel catfish (lctalurus punctatus). The experimental diets were ground, blended and pelletized by passing the ingredients through a food chopper four times. Both mixtures proved highly attractive to the fish. Fish fed either experimental diet grew as well as fish fed the Orgon pellets. The experimental diets are suggested for use in parts of the world where commercially prepared fish feeds are not available. The diets also present the possibility of using non-commercial fishes as feed for more valuable fishes. It was observed that the fish exhibited fighting when the vitamin mix was omitted. A variety of pelleted feeds for fish are now available in the United States.

Investigations have shown that small (less than 10 cm) channel catfish fingerlings, Ictulurus punctatus Rafinesque, gained as much weight in a 10 week period on a diet of 25%-75% oxidation pond algae-commercial feed as did control animals fed 100% commercial feed. Larger fish (20-25 cm) fed the algal-supplemented diet did not gain as much weight in 10 weeks as did control fish on 100% commercial feed. Whole body protein and fat levels did not differ significantly between control and experimental fish.

Chinese waterchestnut was grown in rafts floating on catfish pools to determine effects on production of channel catfish fed daily. This plant may remove nutrients from the water and increase catfish production by improving water quality and, also, produce a second crop, the edible corm ofthe plant. Catfish were stocked in March, Chinese waterchestnuts were planted in April, and both were harvested in October. Survival and production of fish were 56% and 1230 kg/ha, 86% and 1871 kg/ha, and 87% and 1952 kg/ha in pools with fish only, fish and raft, and fish and raft with waterchestnut, respectively.

Channel catfish can be cultured at high densities in carefully managed recirculating raceway systems. Various flow rates, exchange rates, and tank to filter ratios were investigated in ten recirculating systems employing biological filters, settling chambers and foam strippers. Limestone, shells, styrofoam and teflon rings served as effective filter media, but coal slag restricted water flow and was not satisfactory. An equation was developed to evaluate the effects of system design on water quality. Water quality varies directly with fresh water exchange, flow rate per tank, and the filter size. Production was greater in systems with small tanks and large filters (5 Ib/ft3) than in systems with large tanks and small filters (1 lb/ft3). Densities in excess of 7lb/ft3 per tank have been obtained, indicating recirculating systems may become an increasingly important method of fish culture.

Techniques were investigated for growing channel catfish, lctalurus punctatus (Rafinesque), from fingerlings to harvestable size fish during the summer months in a recirculation, flowing water fish culture system in South Georgia. When stocked at a density of 2,000 fingerlings per 100 ft raceway unit, mean production was more than 2,400 Ib per unit with a feed conversion ratio of 1.28 to 1. Survival of the fish was 98.1 %. Successful culture of 2,400 fish in one unit indicated that the carrying capacity of the raceways used in this study was greater than 2,000 fish. There was a gradual deterioration of water quality as it flowed through the raceways but, none of the water quality parameters measured were considered detrimental to the fish. Infestations of Cleidodiscus. Scyphidia and Trichodina were controlled by adding formalin to the water in the raceways at the rate of 30 ppm with the water flow stopped for 1 hr.

A comparison was made with a floating and sinking ration of similar analysis produced by the same manufacturer. This study demonstrated an increase in catfish production when using the sinking ration. Moreover, the sinking feed produced fish of a larger average size, a better food conversion, and a smaller Ktl factor. Use of sinking feed represented a savings of approximately $54 to $72 per acre on the feed bill. Data were compared for the influence of fingerlings size at stocking (4.5, 6.5 and 8 inch) upon catfish production. The larger fingerlings experienced larger S-factors; however, the high percent of harvestable size justified using this size fish for one year's production.

The survival of bass (Micropterus spp.) caught and released during the Rebel Invitational B.A.S.S. Tournament on Ross R. Barnett Reservoir, Mississippi, April 4-6, 1973 was studied. Two different techniques for handling the bass prior to release were evaluated. A total of 1,863 bass were caught by 159 fishermen during the tournament. Of these, 197 (10.57%) were judged to be dead at the weigh-in. The remaining 1,666 bass were randomly divided into two groups for treatment or non-treatment. A total of 830 bass were injected IP with oxytetracycline and marked prior to release into a 0.8 hectare blocked-off area. The 836 non-treated bass were handled in the same manner except they were not injected or marked prior to release into the study area. A significantly higher number of treated bass (96.99%) survived the 19 day study period than did the non-treated bass (91.63%).

Homing behavior of flathead catfish in an Oklahoma reservoir was observed by tracking fish bearing a 74 kHz transmitter which had been implanted in the peritoneal cavity. Homing is described from 1,190 fixes (site locations) obtained on 22 flathead catfish. The average tracking interval was 18.7 days. Homing occurred in 8 of 12 (67%) fish displaced a distance of 1.3-2.7 km from the site of capture. Average accuracy of homing fish was within 182m of the original site of capture. One transmitter tagged fish, displaced 1.82 km, returned to the site of capture within 1.7 days. All 12 displaced fish, regardless of whether or not they homed, moved away from their release site before establishing a home range. Most (70%) of the 10 non-displaced fish remained in a well-defined area near the site of release (i.e., the original site of capture) which also provided evidence that the fish recognized a home area.

Research on the production of advanced fingerling striped bass, Morone saxaliis (Walbaum), was conducted in ponds at Auburn University Fisheries Research Unit in the summer and winter of 1971. Investigations were conducted to determine the effects of two feeding regimes and two sources of small fingerlings on the survival and production of advanced fingerling striped bass. Fingerling striped bass from the Cooper River, South Carolina, and the Savannah River, Georgia, were studied. Higher survival and greater production were obtained from the Cooper River fish. One feeding regime fed hourly, 15 hours per day; the other fed at 3-hour intervals, 15 hours per day. The two feeding regimes were not significantly different.

Research on the production of advanced fingerling striped bass, Morone saxalitis (Walbaum), was conducted in ponds at Auburn University Fisheries Research Unit in the summer and winter of 1971. Investigations were conducted to determine the effects of two feeding regimes and two sources of small fingerlings on the survival and production of advanced fingerling striped bass. Fingerling striped bass from the Cooper River, South Carolina, and the Savannah River, Georgia, were studied. Higher survival and greater production were obtained from the Cooper River fish. One feeding regime fed hourly, 15 hours per day; the other fed at 3-hour intervals, 15 hours per day. The two feeding regimes were not significantly different.

Data on commercial catches of blueback herring and alewife were collected at eight locations in the Albemarle Sound area. Scale samples were taken from 1,214 bluebacks and 787 alewife. Bluebacks ranged in age from three to nine years. Alewife ranged in age from three to eight years. Age groups IV and V dominated catches of both species. Data from all locations combined indicated that virgin fish comprised 50 and 57 percent of the landings of blueback and alewife respectively. Samples from Scuppernong River contained 78 percent virgin bluebacks and 92 percent virgin alewife. Data from Scuppernong River were compared to data from Alligator River in 1973. Blueback samples from Scuppernong River contained 79 percent virgins while samples from Alligator River contained 45 percent virgin bluebacks. A possible problem of over-exploitation exists in Scuppernong River.

A computerized creel census system that is nearly automatic after initial field data recording is described. Partially prepunched computer cards are used to record creel data. Cards are processed directly by computer and a detailed tabulation provided to the fisheries manager. The entire system is designed for ease of use in that no programming knowledge is required of the user.

Two marking techniques, freeze branding and subcutaneous tags, were used to evaluate movement of catchable rainbow trout (Salmo gairdneri) stocked into Rich Creek, West Virginia. These marks proved to be a valuable tool in studies requiring both rapid recognition of marked fish and identification of individuals. In general, there was a marked movement of trout downstream from the point of release, even during periods of low water conditions. Mean distances moved in both directions were 465 meters downstream and 197 meters upstream, respectively.

Food habits of 810 northern largemouth bass, 91-2724 g total weight (age groups 0-7) were determined from collections made June 1968 through November 1969 in an 808-hectare, Oklahoma reservoir. Bass were colIected by traversing the shoreline with an electrofishing apparatus and bass stomach contents observed with a gastroscope. Fifty-five percent of all bass stomachs were empty. Similar observations over a wide geographic area were reviewed and the suggestion was made that 56% occurrence of empty stomachs may be used as a guide to evaluate availability of forage for largemouth bass. Bass stomachs contained mostly crayfish and gizzard shad. Gizzard shad and partially digested fish were found in 31.1% of 810 fish, whole and partially digested crayfish were found in 13.9% of the bass. Bass swallowed crayfish and gizzard shad tail-first 96.8% and 33.5% of the time, respectively. Orientation of the prey in bass stomachs did not vary with size ofthe bass. In 1969.

A detailed comparison of the scales of Trinectes maculatus (Bloch and Schneider) and T. inscriptus (Gosse) has demonstrated species specific differences valid for taxonomic purposes. A complex hinged joint attaching very large cteni to the scale plate characterizes both species. The large cteni are associated with a marked increase in skin surface which, in turn, is combined with an apparent increase in the cutaneous vascular bed suggesting a secondary respiratory and excretory function. The rigid skin flaps produced by the cteni may also be associated with a hydrodynamic "spoiler" mechanism. The lateral-line canal in both species is uniquely composed of tubes lying end to end with no ancillary scale appendages.

Meristic variation was examined among samples of northern largemouth bass, Micropterus salmoides salmoides, from Arkansas and compared with variation found in samples of the Florida largemouth, Mifloridanus. Meristic characters employed in this investigation included five scale counts and number of pyloric caeca. Statistical analyses of the data involved analysis of variance, discriminant function analysis, and Hotelling's T2 test statistic. The primary objective of this study was to establish the best criteria for the practical separation of the two subspecies and, if possible, their intergrades. Number of pyloric caeca, which had not been previously compared for these two subspecies, proved to be the best single character for their separation. Utilizing two scale characters and number of pyloric caeca, discriminant function analyses permit classification of unknown specimens to one or the other subspecies with a high degree of certainty.

White amur effectively controlled dense growths of Mougeotia, Zygnema, and Eleocharis, when introduced into a pond containing a supplementally fed largemouth bass-bluegill-redear population. Analysis of stomach contents showed that white amur preferred plant foods (88% by volume), and probably ingested a few insects and crustaceans while "grazing" on plant materials. Largemouth bass preferred fish and other animals (64%), but also ate some supplemental feed (32%). Bluegill stomachs contained more supplemental feed (44%) than any other item, followed by insects and animal parts (28%), and plant parts (17%). Redears seemed to prefer insect larvae (42%), but also ate plant material (38%). White amur apparently did not compete with the sunfishes for either natural or supplementary food items.

Electrically narcotized and untreated lots of two-year-old channel catfish (Ictalurus punctatus) were held in divided cages in a pond to determine the effects of narcosis on their survival, growth, and feed conversion. Fish were narcotized by exposure to 1.5 votls/ cm for 60 seconds duration with either 60 hertz alternating current, continuous direct current, or pulsed direct current of 15, 20, or 25 pulses/sec. There was no significant difference in survival, growth, or feed conversion between the treated and untreated lots at the 0.01 probability level.

An investigation was conducted to determine the effects of cage culturing channel catfish, lctalurus punctatus (Rafinesque), on the native fish found in proximity to the cages. Monogenetic trematodes and copepods parasitizing fish collected were identified to genus. Nine genera of monogenetic trematodes and one genus ofcopepod were found. Comparisons were made between the number of fish· parasitized at cage sites and control sites during three periods of time relative to catfish culture in cages. There were no significant differences between cage sites and control sites during any of the three periods.

An improved design of a portable drop-net is presented. The drop-net was used to sample estuarine nekton populations whose densities were later determined by the DeLury regression method. The drop-net samples provided mean density estimates that were 4-33% of the DeLury estimate for pelagic fishes, 50-100% for semi-demersal and demersal fishes, and 82-100% for macrocrustaceans (crabs and shrimp). The degree of variation between drop-net samples depended on the species, with the greatest variation seen in samples of pelagic fishes. We concluded that there were no important differences in density estimates from day-night drop-net samples.