Journal of the Southeastern Association of Fish and Wildlife Agencies

We studied fish populations in four lakes in southwestern Oklahoma before and after stocking striped bass (Morone saxatilis) X white bass (M. chrysops) hybrids to determine if the population structure changed as a result of predation by the hybrids. Two lakes were stocked with hybrid fmgerlings at 45 fish/ha in fall 1979 and again with fry at 120 fishlha in spring 1980. The other two lakes (the controls) were not stocked Although growth of hybrid fmgerlings was good, survival was poor. Mortality was greatest for fingerlings less than 150 mm in total length at the time of stocking. None of the fry stocked was recovered Based on the distribution of hybrids and their food, it appeared that they utilized primarily the limnetic zone and did not feed extensively on centrarchids. Changes in the "apparent" structure of populations of bluegill (Lepomis macrochirus) were not consistent and could not be attributed to predation by hybrids.

Of 80,000 hybrid striped bass (Marone chrysops X Marone saxatilis) stocked in June 1980 in Cherokee Reservoir, Tennessee, only 206 were recaptured. They were stocked at a mean total length of 4.5 cm and averaged 21.5 cm after 7 months of growth. After stocking, hybrids consumed mostly Crustacea, with Chironomidae being the primary food source in fish 5.0 to 12.0 cm in length. Fish first appeared in the diet when hybrids were 5.0 cm and became more abundant as the hybrids grew larger. Condition values (K) for hybrids ranged from 0.9 to 1.2.

In 1980 and 1981, stomach contents were removed from 224 striped bass (Morone saxatilis) X white bass (M. chrysops) hybrids and 149 largemouth bass (Mu:ropterus salmoides) collected from Sooner Lake, Oklahoma. Relative abundances of forage fishes were also estimated and food electivity and overlap of diet were determined seasonally. Gizzard shad (Dorosoma cepedianum) was the most important food of all hybrids except those <301-mm; insects and inland silversides (Menidia beryllina) were seasonally important. Gizzard shad, insects, and sunfishes (Lepomis spp.) and crappies (Pomoxis spp.) were the most important foods of largemouth bass. Insects and inland silversides were the major constituents of the diet of largemouth bass ≤151 mm. Electivity values showed gizzard shad were generally preferred by both hybrids and largemouth bass whereas silversides, sunf18hes, and crappies were consistently underutilized in relation to their abundance.

Otoliths and scales of gray snapper, Lutjanus griseus, sampled from the Florida headboat fishery were examined to see if they could be used to age the species. Scales were not useful, but sectioned otoliths proved to be excellent for determining age and growth. Rings could be identified and counted on 91% of all otoliths examined, and measurements could be made on 86%. The oldest fish encountered was 21 years; 775 mm TL. Back-calculated lengths at annulus formation ranged from 95 mm for age 1 to 772 mm for age 19. The von Bertalanffy equation describing theoretical growth is 1t = 890 (1-e-0.1009(t+0.3161)). Gray snapper were fully recruited to the hook and line fishery as 5 to 7 year olds depending on the area. Total instantaneous mortality estimates for fish landed in North Florida (Mayport and Daytona) and South Florida (Pompano, Boynton and Key West) were significantly different.

Total length-scale radius relationship equations and total length-weight equations were determined for spotted seatrout and red snapper in Alabama. Age was determined from scale readings. Rosa Lee's phenomenon was observed Length frequency curves indicated that age group III+ (425 mm) represented the largest year class examined among spotted seatrout and age II+ (239 mm) represented the largest year class examined among red snapper.

Two hundred fourteen of 218 American eel, AnguiUa rostrata, from brackish portions of Cooper River, South Carolina, were infected with 1 or more of 22 helminth species representing 4 classes: Trematoda, Cestoda, Nematoda and Acanthocephala. Larval nematodes (Contracaecum sp.) predominated, infecting 95% of eels examined. Seasonal, size- and age-related variations in levels of parasitism by trematodes and cestodes are discussed. Six new host and 7 new locality records are established.

Otter trawl data from the Louisiana Department of Wildlife and Fisheries' shrimp monitoring program from 1966 through 1979 were used to determine seasonal and areal abundance of gulf menhaden in five areas along the Louisiana coast. Catches were highest in western Louisiana. Overall peaks in late winter/spring and lows in late summer/fall of catches coincide with the influx of larvae from offshore and emigration of juveniles to the Gulf, respectively.

Fish associated with midwater fish attractors, bottom fish attractors, and open water devoid of cover were sampled by electrofishing at Madison County Public Fishing Lake. Both types of attractors concentrated harvestable-size largemouth bass Micropterus salmoides better than open-water areas devoid of cover. Midwater attractors concentrated harvestable-size largemouth bass as well as bottom attractors.

In September 1976, 1/3 of Lake Orange was treated with rotenone to reduce an overabundant black crappie (Pomoxis nigromaculatus) population. Following the treatment 5,232.4 kg of dead fish were recovered, of which 2,050.0 kg were black crappie. Impact of the treatment on the fishery was monitored by a 2-year pre-treatment and a 2-year post-treatment creel survey. Following the treatment, the number of black crappie harvested decreased but average size increased. Average size of creeled bluegill (Lepomis macrochirus) and pumpkinseed (Lepomis gibbosus) doubled The largemouth bass (Micropterus salmoides) and channel catfish (Ictalurus punctatus) fisheries and total fishing pressure were similar before and after the treatment.

An experimental multiple dewatering plan designed to control Hydrilla verticillata and improve sportftsh habitat was implemented on Fox Lake in 1979 and 1980. Hydrilla above the hydrosoil and turions were eliminated while relative abundance of tubers decreased from 19.44 to 1.79 per m2 by termination of the project. The depth of organic sediments was reduced by 29%, 36%, and 47% for the 30, 60, and 90 cm contour intervals respectively. Expansion of native vegetation was documented by a 40% areal increase in Vallisneria americana and basin-wide germination of Typha latifolia.

A drawdown of Lake Carlton was conducted to evaluate complete dewatering as a method for rehabilitation of a severely eutrophic lake. The water level was lowered 4.1 m exposing 80.7% of the bottom (29.4% sand and 51.3% organic sediments). Substantial germination and growth of terrestrial and aquatic vegetation occurred on the exposed bottom. Following refill a layer of consolidated sediments persisted over most of the area where organic sediments had been exposed. Most new vegetation was established at too great a water depth and died. A net gain in area covered by rooted aquatic vegetation persisted only 2 years after refill.

Incidental game fish capture and mortality in St. Johns River hoop nets is a major source of controversy between sport and commerical interests. The controversy is most severe in that portion of the river from Lake George southward. Project personnel observed 574 hoop nets that had been fished 3,896 hoop net-days over a 12-month period. Four species of catfish comprised 84.8% of the total harvest while the game fish by-catch represented approximately 13%. Harvestable size game fish (that size game fish retained by the sport fisherman) comprised 1.4% of the total harvest. Initial mortality was 2.0% for all game fish caught, but no initi~ mortality for any harvestable size game fish was observed. On the basis of an estimated total fishing pressure of 3,000 hoop nets in the St. Johns River from Lake George southward, 3,171 game fish were caught daily, 346 of which were of harvestable size.

During summer, 1976, fish population data were collected by gillnetting, electrofishing, and seining from 30 flood prevention lakes that maintained coexisting populations of white crappie (Pomoxis annularis), largemouth bass (Micropterus salmoides), and bluegill (Lepomis macrochirus). Abundance and size composition characteristics for white crappie were compared by simple correlation techniques to abundance and size composition characteristics for largemouth bass and bluegill Total numbers of white crappie were not significantly correlated to total numbers of largemouth bass or bluegill Numerous relationships existed between white crappie and largemouth bass/bluegill size structure variables. Flood prevention lakes that maintained balanced largemouth bass/bluegill populations, also maintained populations of white crappie having diverse size distributions.

A 45-cm (18-in) minimum size limit was placed on largemouth bass (Micropterus salmoides) in January 1978 in 4 North Carolina reservoirs. Annual spring electrofishing samples were conducted to obtain size distribution information on each lake, length-weight information on 2 lakes, and largemouth bass population estimates on one of the study lakes. After a 4-year investigation, the proportion of quality size bass in the stock size distribution of 2 lakes increased. On a 3rd lake, a newly developing largemouth bass fishery was successfully protected from a reduction in quality size bass from initial heavy angling exploitation. Concurrently, bass length-weight relationships were unaffected. On a 4th lake, characterized by good recruitment and low forage levels, the proportion of quality did not increase and length-weight relationships remained undesirable.

Estimates of abundance, production, growth, survival, and mortality of largemouth bass were derived from spring electrofishing samples in the upper, middle, and lower sections of DeGray Lake from 1975 to 1979. Mean population estimates ranged from 86 to 163 bass per hectare; the populations were dominated by bass of ages I and IT (73% to 96%). Population estimates of the 3 coves based on surface area were biased because there were large differences in the ratio of shoreline length to surface area. Population estimates were adjusted to correct for this bias. Production was highest in the midlake section each year. Mean production estimates, based on spring electrofishing samples, ranged from 19.1 to 30.9 kg/ha. The greatest production of tissue and highest mortality occurred during the 2nd year of life. Harvest data indicated that 29.3% of the estimated spring standing crop of largemouth bass was taken by angling in 1977, and 26.8% in 1978.

Seasonal biomass estimates of largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus ), and longear sunfish (L. megalotis ) were made during 3 growing seasons (1977 - 79) by cove rotenone sampling in May, June, August and September. Substantial mortality of young-of-the-year (YOY) largemouth bass during late summer suggests that this period was critical in determining year-class strength. Overwinter mortality was 88, 87, and 71%for the 1977-, 1978and 1979-year classes, respectively. Biomass of bluegill increased from May to August and decreased in September, probably as a result of predation. Biomass of longear sunfish was lowest in June and peaked in September in 2 of the 3 growing seasons. Longear sunfish seem to feed more in littoral areas than do bluegills, and are therefore probably more susceptible than bluegills to early summer predation by largemouth bass, and less susceptible than bluegills to late summer predation.

In pond predation studies, 4 total length (TL) groups (152 - 406 mm TL) of Florida largemouth bass (Micropterus salmoides floridaiu.Ls) were each provided 4 length groups (51 - 140 mm TL) of blue tilapia (Tilapia aurea) as forage. Estimated maximum length of tilapia that 38 - 500 mm TL bass can swallow ranged from 36 61% of the bass's total length. Bass <254 mm TL ate tilapia which approximated the maximum estimated length they could swallow. Bass >381 mm TL rarely ate tilapia >27% of their total length. Regression analysis of blue tilapia total length (mm) versus body depth (D; mm) was D = 0.322TL - 2.68 (r = 0.99). Due to the importance of the bass fIshery in Florida, the impact of blue tilapia may ultimately be judged largely on its value as bass prey.

From 1977 to 1979 largemouth bass (Micropterus salmoides) were collected in spring from Lake Higgins in North Carolina and tagged with Floy FD-67 internal anchor tags. Tagged fish were released back into the lake and a recapture effort was made the next year. During the year following tagging, tagged bass generally achieved a smaller length increment than untagged bass of a comparable size. Weights of tagged bass tended to be less than similar size untagged bass, but only in the 326- to 350-mm size interval was the difference significant (P < 0.05).

The North Carolina Largemouth Bass Catch Survey was initiated in 1975 to monitor angling success for largemouth bass (Micropterus salmoides) in the state's waters. The survey relies heavily on the participation of organized bass fishing clubs and reflects primarily tournament fishing results. Individual participants and clubs are asked to maintain catch records for each trip on a fishing log sheet. At the end of each month, the accumulated statistics are summarized by the participant and reported by body of water on preaddressed summary postcards. All materials are provided by the North Carolina Wildlife Resources Commission. The data are consolidated annually by body of water and season of year. The number of largemouth bass (TL ≥ 30 cm) caught per hour fished declined steadily in North Carolina reservoirs from 0.26 in 1977 to 0.18 in 1980. During the same period the catch rate in rivers and streams remained stable at between 0.23 and 0.25 fish per hour.

The largemouth bass(Micropterus salmoides) fishery in the Ocmulgee River, Georgia was studied to address concerns about overexploitation. A significant decline occurred over time in overall success, fished-for success, and average weight of largemouth bass in the creel. The annual exploitation rate was calculated to be 0.11 and was estimated in the year of low bass harvest. The annual survival rate was calculated to be 0.47. A Kolmogorov-Smirnov two sample test showed a significant decrease in the percent frequency of larger bass in electrofishing samples from fall 1976 to fall 1978. The high bass harvest from spring 1976 to fall 1977 is believed to be the primary cause of decline in the bass fishery. Low bass recruitment to harvestable size also contributed to the decline. Management strategies for enhancing the bass fishery include stocking of advanced fingerlings and better enforcement of the 305 mm size limit.

Water and benthic samples were collected quarterly, May 1980 to May 1981, from 21 sedimentation ponds on the Ollis Creek strip mine in Campbell County, Tennessee. Water samples in general were low in pH and high in sulfate, hardness, iron, and manganese. A total of 63 discernable chironomid taxa was collected and identified. Low pH ponds were generally dominated by Chironomus attenuatus and Tanytarsus, while higher pH ponds contained variable chironomid assemblages. Diversity values (richness) were significantly correlated with pH values. The polar ordination of chironomid assemblages showed a distinct linear arrangement of stressed ponds to those containing viable Centrarchid populations.

Postlarval and juvenile prawns (Macrobrachium rosenbergii) were exposed to 7 mirex concentrations plus control for 96 hours. Static acute toxicity tests were conducted at 28 C using deionized water reconstituted to hardnesses of 11, 42, 160 and 300 mg/l as CaC03 with postlarvae and 42 mg/l with juveniles. No statistical differences were observed in survivals of postlarvae or calculated median lethal mirex concentrations among hardnesses. A 96-hour LC50 for all postlarvae was 33.9 µg/l and for juveniles 900.8 µg/l mirex. Postlarvae and juveniles exposed to 1000 µg/l accumulated mirex up to 513X and 88X control levels. Mirex residues in juveniles were greater in nerve tissue than abdominal muscle or remaining carcass.

The status of the fish populations of 8 North Florida rivers and their relationships to major quality parameters were explored in an effort to better understand potential effects of man's activities. Of the 10 water quality parameters analyzed, only conductivity, total dissolved solids and total nitrogen were found to have significant predictive capabilities for the total fish population Rivers in the Florida Panhandle, which are low in nutrients, pH and organic carbon and high in turbidity, support a high biomass of rough fish, a moderate biomass of sport fish, and a low biomass of commercial and forage fishes; however, numerically, these rivers are dominated by forage fishes. The rivers of northern peninsular Florida generally have equally high biomasses of rough and sport fishes and low biomasses of commerical and forage fishes; however, sport fishes dominate these rivers numerically, comprising more than 70% of all fish encountered.

Various concentrations of dissolved oxygen were tested against normal embryonic development of striped bass, Morone saxatilis, eggs. Lowest level of dissolved oxygen necessary for normal development was established as 3.0 ppm. Abnormalities associated with suboptimal levels of dissolved oxygen are described, and the number for each concentration quantified.

Concentrations of chlorophyll a, soluble orthophosphate, dissolved nitrate and nitrite, and associated water quality parameters were measured biweekly from May 1979 to May 1980 in 3 sequential ponds located on a dairy farm. Pond number 1 was located in the immediate vicinity of the barn and feedlot, and demonstrated limnological characteristics of a sewage settling pond Chlorophyll a and soluble orthophosphate averaged 298 mg/m3 and 10.1 mg/l respectively. Dissolved oxygen in pond 1 averaged 3.4 mg/l at the surface but was never present at a depth of 1 m. The presence of a settling pond as the primary recipient of wastes produced by a herd of cattle resulted in downstream impoundments having limnological characteristics highly desirable for the culture of herbivorous fishes. Chlorophyll a in ponds 2 and 3 averaged 103 and 77 mg/m3 respectively. In contrast to pond 1, dissolved oxygen at the surface and 1 m in ponds 2 and 3 averaged 7.0 and 4.2, and 10.1 and 7.8 mg/l respectively.