Journal of the Southeastern Association of Fish and Wildlife Agencies

Apparently extensive fish mortalities were reported to have occurred in the North Fork Pound Reservoir during February, 1969 and February, 1970. A study was initiated in September, 1969 and continued through October, 1970, in order to ascertain the causes of these mortalities. Chemical water analyses disclosed that the lake pH varied from 4.0-6.4, with a mean near 5.0. The heavy metals, copper, mercury, zinc, iron and manganese were found in the lake waters at levels reported to have chronic effects on fish. Biological investigations revealed fish populations were at low levels (smallmouth bass, channel catfish, largemouth bass, black crappie, green sunfish, bluegill, redear sunfish and brown and yellow bullheads). Reproduction of largemouth bass, green sunfish and black crappie appeared to be nonexistent. Standing crops of zooplankton and phytoplankton appeared extremely low.

Organochlorine-resistant mosquitofish from an insecticide contaminated environment in the Mississippi Delta showed a 3.4-fold tolerance to pyrethrum when compared to a susceptible strain. The 24-hr LC50 values for pyrethrum in susceptible and resistant mosquitofish were 27 and 93 ppb, respectively. Results of studies with sesamex, an inhibitor of mixed-function oxidase (mf0) enzymes, indicated that the tolerance to pyrethrum is partially, but not solely the result of increased levels of mfo enzymes. Additional studies with allethrin show that increased carboxylesterase enzyme levels cannot explain the pyrethrum tolerance which was not accounted for by mfo enzymes; thus yet another mechanism must be involved. Resistant mosquitofish that had been maintained in an insecticide- free environment for several years also possessed a tolerance to pyrethrum but to a lesser degree than the original parents from the insecticide- contaminated area.

The purpose of this investigation was to determine the effect of continuous exposure of pre-adult Daphnia magna to low, presumably sub-lethal doses of phenol. The experimental data were obtained through use of a standard 24-hour toxicity bioassay and a modified long-term toxicity bioassay. Control and test animals were cultured in a synthetic pond water and fed with dried yeast. Six concentrations of phenol were tested. Data were applied to least squares linear regression analysis, multiple linear regression analysis, crossed covariance analysis, and several related tests in order to quantitatively interpret the total effects of the chronic poisoning. It was found that phenol exhibited strong interaction with temperature of the culture medium and with the age of the individual to retard ecdysis. This results in a prolonged generation time. Mortality was also increased and reproduction was greatly inhibited.

An investigation was conducted concerning the effect of mirex bait on production and survival of red crawfish, Procambarus clarki (Girard), in rice fields of southern Louisiana. Twenty experimental plots were stocked with 2,000 brood crawfish (50 pairs per plot). Each plot was randomly assigned to one of four treatments: (1) conventional rice insecticides, malathion and carbofuran; (2) mirex alone; (3) mirex in conjunction with malathion and carbofuran, and; (4) untreated controls. Mirex bait (0.3 per cent technical material) was applied at the rate of 1.25 pounds per acre in three applications, approximately 90 days apart. Statistical analyses of data revealed no significant differences among treatments in crawfish size, sex ratio, and weight yield, whereas the differences among treatments in number harvested were significant (P .05). Plots treated with mirex alone produced the fewest crawfish (3,642) and control plots the most (5,667).

Striped bass eggs, 24 hours after fertilization, and newly-hatched fry were tested to determine their sensitivity to zinc and copper. This study with those of Hughes will provide information on the most sensitive stage ofthesefish to acute exposure to lethal levels of zinc and copper. Newly-hatched fry were more sensitive to both zinc and copper than were eggs, but copper, at the lowest concentration used, retarded hatching. Eggs and fry were more sensitive to copper than to zinc. In order for acute toxicity studies to have a predictive value, confidence limits need to be placed on the TLm values obtained from toxicity studies. Results obtained from three different methods of providing confidence limits are discussed and the relative merits of each method are compared.

This study provides an evaluation of the benthic faunal characteristics of the cold tailwater of Greer's Ferry Reservoir on Little Red River. This Ozark stream is characterized by cold and non-turbid water, and periodic drastic vacillation of water level, the results of a deep water discharge for hydroelectric generation. For these reasons the benthic macroinvertebrate community is qualitatively limited. Pool and riffle habitats were sampled at six-week intervals at each of three stations established between 500 m-23 km below the dam. Most physicochemical characteristics measured were found not limiting, except water temperature and current velocity. Benthic organisms were limited to 59 taxa. Longitudinal zonation was characterized by an increase in diversity downstream with 15,32, and 41 taxa collected at Stations 1,2, and 3, respectively. Overall dominant organisms numerically were oligochaetes, chironomids and isopods.

Teaching natural resource management is especially difficult because of the importance of experience in making management decisions. Most methods for allowing natural resource students to gain management experience in the classroom have not been entirely satisfactory. Computer implemented simulation of natural resource problems allows educators to provide management experience to students. TROUT, a learning exercise which simulates a coldwater lake fishery, is discussed as an example of the role of these teaching tools.

The level of natural hybridization in Lake Texoma between Dorosoma cepedianum and D. petenense for the years 1962-63 and 1968-69 was determined to be 2.5 and 1.7% respectively. The two species have been sympatric in that reservoir since 1957. Male and female hybrids with well developed gonads were collected. Eggs from a hybrid were fertilized experimentally with milt of D. petenense and produced viable larvae. Hybrid fry were produced in the laboratory by crosses between D. cepedianum males and D. petenense females but not the reciprocal. Spawning of the two species is discussed in relation to the possible means of natural hybridization. Natural hybridization between the clupeid species Dorosoma cepedianum and D. petenense was reported by Minckley and Krumholz (1960). They cited as the probable cause, the less abundant D. petenense joining groups of spawning D. cepedianum. Hybrids were first identified in Lake Texoma in 1960 by C. D. Riggs and G. A.

The possible effect of threadfin shad stocking in Dale Hollow Reservoir on the growth of five predatory species was measured by analysis of scale samples taken before and after threadfin stocking. There was no significant change in growth rate of largemouth bass, Micropterus salmoides; smallmouth bass, Micropterus dolomieui; and spotted bass, Micropterus punctulatus. There was a significant increase in growth rate of walleye, Stizostedion vitreum and white crappie, Pomoxis annularis.

Stomachs from angler-harvested specimens of 259 largemouth bass, Mieropterus salmoides, 263 spotted bass, M. punctulatus, and 256 smallmouth bass, M. dolomieui were collected from the mid-lake region of Bull Shoals Reservoir during March 1971 - February 1972. Stomach contents were compared on the basis of frequency of occurrence, weight, and seasonal distribution of food items. Black basses were piscivorous in feeding habits during the summer and early autumn, with young of the year shad contributing substantially to the diets. Utilization of young shad by adult basses followed shad spawning by six to eight weeks. During late autumn and in the spring, food habits of the three species varied. Largemouth bass stomachs contained primarily crayfish and centrarchids during the late autumn and crayfish, yearling shad and unidentified fish remains during the winter and spring months. Spotted bass fed primarily on crayfish throughout the period.

The growth history of largemouth bass in Lake Carl Blackwell is described. Variation in annual increments in growth of largemouth bass age groups I-III are examined in relationships to mean annual water level 1962 through 1967, when the annual average lake level was declining. Weighted mean average total lengths (mm) to the end of each year of life, i.e., to annulus formation which occurred in May, were: 140 (I); 279 (II); 369 (III); 425 (IV); 462 (V); 485 (VI); 504 (VII); and 53 I (VIII). Growth in the first year was positively correlated (r=0.85, P<.035) to the average annual lake level. In the second year the relationship was negative (r = -0.95, P<.004), that is, annual increments in growth in the second year of life were inversely related to lake level. Growth increments in the third and fourth years also were negatively correlated with lake level but the correlation was non-significant (P>.05).

This paper describes the results of a length and weight at maturity study of channel catfish, Ictalurus punctatus, and blue catfish, Ictalurusfurcatus. Total length-collarbone length and collarbone length-total length conversion factors were determined and are presented for future biological references. Data were collected from the marshes of Southwest Louisiana.

Food, growth and length-weight relationships of young-of-the-year largemouth bass (Micropterus salmoides) and black crappie (Pomoxis nigromaculatus) were studied. Stomachs of 220 bass and 186 crappie were examined. Crappie fed mainly on zooplankton but consumed more aquatic insects as their size increased. Bass fed on zooplankton and aquatic insects, but grew faster when small crappie were available. Crappie grew faster when their numbers were reduced by bass predation. Length-weight relationships were calculated for 601 bass and 496 crappie.

Stomachs of black and white crappies (Pomoxis nigromaculatus and P. annularis) collected during the early impoundment (1964-1967) and the late impoundment (1969-70) periods from Beaver Reservoir were analyzed. Black crappie were dominant in the early impoundment period, whereas white crappie was the dominant crappie species in the late impoundment period. During the early impoundment period, large numbers of earthworms (January to April) and shad (during the remainder of the year) were consumed by both species, although white crappie appeared to concentrate on shad even when earthworms were available. During the late impoundment period O-age fishes, zooplankton, and aquatic insects comprised the diet of both species. However, white crappie adults concentrated on fishes all year round, whereas black crappie adults concentrated on benthic insects in the spring and fishes in other seasons.

Juvenile striped mullet, ranging in size from 25 mm to 150 mm standard length and acclimated to 10% and 50% seawater, were subjected to direct transfer from acclimation salinity to salinity levels varying from distilled water to 200% seawater. Tests were also made using two commercially prepared, osmotically balanced, synthetic seawater mixes; one containing twice the normal calcium level and the other calcium-free. The presence of calcium significantly increased both survival time and survival rate. Acclimation tests also indicated a beneficial effect from increased calcium levels.

Lymphocystis disease is a viral disease of freshwater and marine fish. It was found in three species ofSciaenids along the Georgia coast. It was found in six of the eight estuaries sampled and appeared in three forms: cutaneous, visceral and ocular. The cutaneous and visceral lesions were typical. An ocular site of infection, however, had not been previously described. The lymphocystis cells were found in the choroid coat of the eye near blood vessels and transport of the virus to the infection site via the blood was suspected. The disease appeared in the fall and winter months in Cynoscion regalis and Stellifer lanceolatus. No conclusions could be drawn from the data on the seasonal appearance of the disease in Dynoscion nothus. Water temperature changes appear to be associated with the appearance and disappearance of the disease but additional factors need to be studied before a causal relationship can be established.

Two cyprinid fishes, rlinostomus funduloides and Notropis cornutus were tested with naturally occurring substances including some well-known biogenic amines. Behavioral responses to histamine were similar to those observed in previous tests with natural alarm substance extracts. A response threshold was obtained at 0.01 ppm. Spectrophotofluorometric emission spectra also indicated that the natural alarm substance known to exist in many species of fish may be a ringed or double ringed compound.

In 1969-70 there were 50 active commercial, heated fishing docks on Grand Lake, a 18,818 hectare reservoir in northeastern Oklahoma. During the winterspring of 1969-70, fishermen interviews were made to determine fishermen catch statistics. Docks were sampled Friday through Monday during the period 28 January through 30 April 1970. A total of 1365 interviewed fishermen caught 3963 fish in 4462 hours of fishing (0.89 fish/ man-hour). One carp (Cyprinus carpio) was captured, with the balance of 3962 fish in the sample represented by white crappie (Pomoxis annularis) of 239 mm mean total length and 194 g mean weight. Age composition of 234 fishermen caught fish was 94% age group III and IV, with age IV comprising 67.1% of the catch. The total population of fishermen using 41 of the 50 commercial docks was obtained from records kept by the dock operators.

The catch of commercial and game fish with 4-foot trap nets having minimum mesh sizes of 0.5,2, and 3-inch, square measure, were compared. A small trap net having 0.5-inch webbing in the crib has been used for many years to sample fish from Oklahoma reservoirs. Various investigators have indicated that this gear has potential as a commercial fishing device. However. large catches of game fish, especially white crappie, was a serious detriment to this potential. Two designs of large mesh trap nets were therefore dcveloped to determine if by enlarging the mesh size of the standard design, the catch rate of game fish would decline while the catch rate of commercial fish would remain constant. An investigation was conducted on Keystone Reservoir during 1971 and 1972. The results indicated that the large mesh trap nets did take significantly fewer game fish. The catch of commercial fish was also reduced, but to a lesser extent, as the mesh size increased.

In 1970 the Florida Legislature provided for a table of values for fish killed by water pollution. These data were applied to standing crop estimates to determine the monetary value of the 1970 fishery in 22,700 acre Lake Tohopekaliga. The lim netic portion of the fishery was valued at $4,335,120 or $321.12 per acre. The littoral portion was valued at $12,266,636 or $1 ,333.33 per acre. Although the littoral zone has a considerably higher value and is vital for the renewal of the fishery resource, it is continually subjected to accelerated encroachment and piecemeal destruction by a variety of means. Monetary estimates such as these enable biologists to express biological facts in terms of more conventional market pricing techniques when considering water-use policies.

The mercury concentrations in various tissues of an adult bottlenose dolphin, Tursiops truncatus, were determined by nameless atomic absorption spectrophotometry. Mercury was concentrated in the kidneys and liver at levels in excess of 18 parts per million (dry weight basis). One sample from the right lobe of the liver contained 34.5 ppm mercury. With the exception of skin and subcutaneous tissue, a sample from the medulla oblongata and a bone sample (skull fragment), all samples run exceeded 1.0 ppm mercury. Studies as to the prevalence of high mercury levels in Tursiops truncatus and other marine mammals as well as the effects such levels have on behavior, fecundity and survival are recommended.

Alimentary tract evacuation was stqdied by the serial slaughter method after a single unrestricted feeding on commercial pelletized food. Digestion rate was measured at 6, 12, 18, 24, and 30 C. At the lower temperatures there was a "latent" period immediately following ingestion during which the content of the stomach or alimentary tract did not decline. After adjustment for the "latent" period and logarithmic conversion of the amount of food present, evacuation rates were described by double logarithmic regressions which showed time for complete evacuation as a function of temperature and amount of food. Evacuation rates were also measured at25 C for natural food consumed by each species and were similar to the rates using artificial food.

A model power plant, constructed to simulate the time-temperature exposure histories experienced by organisms entrained in the intake of an actual plant, was used to study the thermal effects of an operating power plant on the hatching success of American shad, Alosa sapidissima, eggs. Eggs from a single female were divided into 5 sub-samples; two controls, and three experimental batches. One control was stocked immediately in a constant temperature bath. The second control was passed through the unheated plant to assess the mechanical effects of passage through the model plant on hatching success. The experimental batches of eggs were passed through the operating plant set to produce a Δ T of about 6°C, and were cooled at different rates to the intake temperature of 18.5° C. Exposure times to a Δ T of at least 6° C ranged from 5 to approximately 15 minutes, and the cooling period from I hour to nearly 3 hours.

Techniques used to quantify circulating levels or stcroid hormones in teleostean fishes may help solve problems in fisheries research. Competitive protein binding assay used to determine levels of androgens. corticoids. and radioimmunoassay for estrogens allow analysis of relatively large numbers of samples within a short period of time. Results obtained by these methods indicate that rainbow trout (Salmo gairdlleri) have endocrine responses to various stressors. Repeated bleeding causes a marked lowering of plasma androgens in the male while cortlcoids arc increased in both sexes. Gonadectomy reduces androgens in the male more rapidly than in the female; estrogen levels are not appreciably altered. Carbon dioxide anesthesia greatly elevates plasma corticoids while tricaine methanesulfonate has no apparent effect on corticoids or androgens.