Journal of the Southeastern Association of Fish and Wildlife Agencies

Hellige Water Testing Outfits and a La Motte TRL-05 Water Testing Kit were evaluated by comparison with standard analytical methods. The testing outfits and kit often gave values for variables which were 80-120 percent of values obtained by standard methods. However, for some variables, and especially for total ammonia nitrogen, the testing outfits and kit did not provide reliable data for all concentrations. Results of the present study and earlier studies are summarized in tabular form to provide an assessment of the reliability of seven water testing systems.

Hydrated lime is not as suitable as agricultural limestone for increasing pH and total alkalinity in soft water ponds. However, small amounts of hydrated lime may be applied during dry summer months to increase alkalinity for several weeks in ponds that have such high water exchange rates during wetter months that conventional applications of agricultural limestone are ineffective. Hydrated lime is an effective sterilant for damp pond bottoms. It will also remove carbon dioxide from water. Hydrated lime is not an oxidizing agent, so it will not destroy organic matter in mud or water. The biochemical oxygen demand (BOD) of water may be reduced by large applications of hydrated lime because the lime increases pH to levels toxic to microorganisms. The concentration of hydrated lime necessary to reduce BOD will retard photosynthesis and will harm fish. Although hydrated lime can be used to raise pH and kill fish, its potential as a fish eradicant needs further study.

Recirculating 2271-liter culture systems were designed and evaluated as potential fish production units. System components include a culture tank, sedimentation basin, and a biological filter. Three different biological filter types were compared: a commercially available plastic filter media, a rotating biodisc filter, and a submerged gravel filter. Each duplicated system was stocked with 5 cm fingerling channel catfish, lctalurus punctatus, which were fed daily. The experiment continued until maximum loading capacities were attained. In the 155 day growing period, the greatest standing crop attained was 41.2 kg using the rotating biodisc filter. Excepting one replication which exhibited 100 percent mortality due to an aerator failure, survival rate was 95 percent or greater, with feed conversions ranging from 1.27 to 1.62.

From an analysis of the trophic status and fish populations of 22 Florida lakes, total fish biomass is low in oligotrophic lakes, increases to a maximum in mesotrophic-eutrophic lakes, and fluctuates around the maximum value in hypereutrophic lakes. Total fish density likewise is low in oligotrophic lakes and increases to a maximum in mesotrophic-eutrophic lakes; but unlike biomass, fish density declines as lakes become hypereutrophic and gizzard shad becomes the dominant species of fish. Sport fishes reach maximum biomass and optimum densities in mesotrophic-eutrophic lakes with a total nitrogen concentration of 1.2 mgll and a chlorophyll a concentration of 11.0 ugll, but suffer adverse effects with further enrichment.

Genotypic male Tilapia aurea, previously treated for sex reversal to a female state, and their sex-reversed female (F') parent were stocked into aquaria with untreated females at various ratios. The reproduction of the 2 types of females with normal males was compared. None of the treated fish spawned; most were later found to have ovotestes. The PI sex-reversed female spawned repeatedly after she was paired with a male in a larger tank, indicating that the presence of normal females under confined aquarium conditions may have a repressive effect upon estrogen sex-reversed females.

Six groups of cage-grown channel catfish (lctalurus punctata) and Tilapia aurea were compared for body weight, total length, condition factor, carcass characteristics, and sensory quality. Catfish used in this study were the first generation progeny of brood catfish selected for increased and decreased body weight and for body weight variability at 48-week post-spawning age. A random-bred control line and a group of pond-raised catfish were also included in the experiment. Results indicated that I generation of divergent selection has increased body weight and body weight variability in the upward lines but no declines were observed in the downward lines. Selection for improved growth rate may also produce catfish more uniform in size. In the taste test tilapia were preferred over catfish.

From 3 May 1979 through 9 November 1979, cage culturing of fingerling white amur, Ctenapharyngodan ideUa was conducted utilizing alfalfa pellets, catfish pellets, alfalfa and bermuda grass hay or aquatic vegetation as feeds. Feed utilizations, feed conversion ratios and growth rates were analyzed. Feed conversion ratios ranged from 10: 1 to 30: 1. Fish fed the catfish pellets or hay yielded poor growth. Those fed the alfalfa pellets were larger and achieved the expected stocker size. Mortality was a problem throughout the study period. Handling stress, agonistic behavior, and bacterial and fungal infections appeared to have been the causative agents.

Duckweed (Family Lemnaceae) was incorporated into 6 isocaloric diets which were fed for 10 weeks to channel catfish (Ictalurus punctatus) fingerlings in aquaria. Three diets contained surplus essential amino acids while utilizing duckweed at 0, 15, and 20 percent of the diet. Three other diets had the same levels of duckweed, but contained borderline levels of amino acids. No significant difference in mean weight gain per fish was found within each group of 3 diets. Feed conversion and kcal of energy required per g of weight gain were not statistically different for the fish fed the 6 diets.

A survey of previous Arkansas fish farmer certificate holders was conducted during 1978-79 through the use of renewal questionnaires, telephone conversations, and personal contacts. This survey was compared to similar surveys from preceding years. Approximately 65.3 percent of the 13,540 intensively farmed hectares in 1978-79 was devoted to the production of bait fish, while 28.1 percent was utilized in food fish production. Total area in bait fish production has remained virtually unchanged since 1975-76, but the value of the bait fish industry has increased by 7.0 percent. A 30.8 percent increase in area intensively farmed for food fish has resulted in a 17.0 percent increase in food fish value since 1975. Area devoted to catfish fingerling production increased 130.2 percent over the 1975-76 survey, while the total value ofcatfish fingerlings increased 70.8 percent.

A survey designed to elucidate current farming practices and problems was sent to all known catfish farmers in Mississippi. Most farms are greater than 45.5 ha (100 acres) and stocking rate averaged approximately 7410 fish per ha (3000 per acre). Most farmers use tractor pulled feeders and feed floating feed. The vast majority of respondents sold their fish to processors. The majority of respondents would like to increase their catfish farm acreage. Slightly more respondents produced their own fingerlings than purchased them and most managed their own farm. Few respondents had pesticide kills while about one-third had serious parasite or disease kills and one-fourth had oxygen depletions. Chi square analysis was used to test the relationship between farm size and stocking rate, stocking rate and oxygen depletions, and stocking rate and parasite and disease kills. Only the relationship between farm size and stocking rates was statistically significant.

Stomachs of 240 adult largemouth bass (Micropterus salmoides) taken from a small impoundment with abundant aquatic vegetation, were evacuated and their contents examined. Thirty percent of the bass had empty stomachs. Crayfish, bluegill (Lepomis macrochirus), and young-of-year largemouth bass were the predominant food items. Electivity values (E) indicated negative selection for bluegill and positive selection for young bass. Dense, aquatic macrophytes are probably the major factor influencing the feeding behavior of these bass.

Alewife (Alosa pseudoharengus) were evaluated as a pelagic forage fish for southeastern reservoirs based on results of trophic and population ecology studies conducted in Claytor Lake, Virginia. Positive attributes of the alewife forage based included: a) establishment of a prolific and self-sustaining population, b) high desirability and availability to pelagic predators, and c) a positive impact on growth of pelagic sportfish. Negative attributes included: a) predation on larval fish, b) low desirability and/or availability to littoral sportfishes, c) rapid growth beyond a size vulnerable to most predators, d) fluctuating population levels, e) alteration of zooplankton size composition by selective predation on largest forms, and f) emigration to a downstream reservoir. Alewife are most suitable for introduction to waters managed primarily for pelagic piscivores on a put-grow-take basis.

A method was developed for estimating rate of exploitation from the rate of decline in catch per unit effort of tagged fish. The method was used to estimate exploitation of largemouth bass (Micropterus salmoides) at a 75-ha Chambers County Public Fishing Lake, Alabama. Fishing effort directed towards largemouth bass was estimated from an access creel survey employing nonuniform probability sampling. The estimated 58 percent rate of exploitation agreed well with an independent estimate made using catch records and an estimate of the number of harvestable-sized ( > 249 mm total length) bass in the. population.

This study was conducted to determine the effects of otter trawl tow length on variahility and catch rates, and to assess replicate sampling. Longer tows caught more individuals/minute, individuals/tow, and species/tow than the shorter tows. The total number of species caught per hour of sampling, however, were essentially equal for all tow lengths. No difference in precision hetween tow lengths were detected. The numher of replicates needed to detect changes within desirahle statistical limits were logistically impractical. We recommend that otter trawls he used strictly for qualitative purposes and conclude that a small number of replicated lO-minute tows would adequately descrihe hasic community structure.

During the 14 years after initial introduction, a viable striped bass (Morone saxatilis) sport fishery developed on Keystone Reservoir. Natural reproduction, first identified in 1970, continued through 1979 in tributary rivers. Selected endemic fish species showed no significant changes in standing crop estimates from cove rotenone studies 1971-73, 1976-79. Available prey-predator ratios (AP/P) showed a fluctuating availability of forage for small predators and ample prey for large predators.

The water level of West Point Reservoir is lowered 3 m from October to May for flood control purposes, exposing about 2,900 ha oflittoral zone. The effects of water level fluctuations on the benthic organisms inhabiting this zone were determined from samples taken at 2 bottom contours; the contour exposed during winter drawdown and the contour just below the winter drawdown that remained permanently inundated. During May and July, fewer organisms (P < 0.05) were collected from the contour exposed during drawdown than from the contour never exposed. By August there were no differences (P > 0.05) in the number of organisms inhabiting both contours, indicating that the community had recovered after about 4 months of inundation. Soil particle size analysis showed a smaller percentage (P < 0.05) of silt and clay and a larger percentage (P < 0.05) of sand in the contour exposed during winter drawdown than the contour that remained permanently inundated.

Arkansas has carried out an extensive program of chemical rehabilitation of lakes and reservoirs since 1953. In the 27-year period since the first renovation, over 220 major lakes and impoundments have been treated with 94,445 kg of 5 percent equivalent rotenone powder and 37,123 liters of 5 percent liquid rotenone. A total of 18,839 ha have been treated on these lakes. Chemical rehabilitation may be required every 3 to 5 years on some lakes in Arkansas. Gizzard shad (Dorosoma cepedianum) is usually the problem species but often sunfish, particularly Lepomis spp., and other species offish overpopulate, stunt and require thinning. Thirteen chemical renovations on 7 state lakes were evaluated. In II cases, desired goals were achieved. Generally, large gizzard shad populations can be significantly decreased by renovation with the black bass population often receiving the greatest benefit.

Juvenile gulf menhaden (Brevoortia patronus) data were extracted from otter trawl surveys conducted along the Louisiana coast since 1966. The relationships between various abundance indexes and commercial harvest of age-I fish were determined by correlation and linear regression analyses. Several indexes were significantly correlated at the 0.95 and 0.99 level with commercial harvest. The strongest indexes, involving frequency of occurrence of more than 25 or 50 gulf menhaden in samples, were used to predict commercial landings. Recommendations were made to continue monitoring the relationship between these abundance indexes and commercial harvest.

The age and growth of larval Atlantic croaker, Micropogonias undulatus, was determined from daily growth increments on their otoliths. Smaller and younger larvae were found offshore near probable spawning areas while larger and older larvae were found near shore and in the lower estuary. A Laird-Gompertz growth model, L(t) = 0.926 exp {2.876 [1-exp(-0.0428t)]}, described the growth of larvae to 62 days old. The agespecific growth rate, derived from this relationship, declined with fish age. Atlantic croaker spawned over a 5-month period from mid-September to late-February, with the majority probably spawning in October-November. Larvae were the same size, 9 to II mm SL, when they immigrated to the estuary in the period from late-October to mid-April, although mean age of fish entering in January and April (61 to 64 days) was almost twice that of fish entering earlier.

This study describes culture of Malaysian prawn (Macrobrachium rosenbergii) without feeding in brackish water ponds in Louisiana. Survival and average size increased with decreasing stocking densities. After 163 days, average production in kg/ha for stocking rates of 1.25/m2 , 2.5/m2 and 3.75/m2 was 159, 191 and 218, respectively. Orbit length-total length relationships were determined to be expressed by the linear equation: Orbit length = 1.498 + 0.736 (total length) with both sexes combined. Total length-weight measurements at harvest of both sexes resulted in the curvalinear equation Log Weight = -5.867 + 3.41O(Log Length). Measurements were in millimeters and grams.

Three marsh types (saline, brackish, and freshwater) in the Baratoria Basin were sampled with the Wegener Ring. Forty-four species were collected, representing 21 families. Overall species composition and within species abundance varied from saline to freshwater environments. Shannon-Weaver diversity and evenness diversity show a decreasing gradient from saline to freshwater marsh. Number of individuals collected had an opposite gradient. The order of sequence from highest to lowest for biomass was fresh, saline, and then brackish. The saline marsh had the highest species richness value, while freshwater marsh had a slightly higher value than the brackish marsh.

The long haul seine is a 1100-1450-m net about 3 m deep pulled by two 9.2 13.7- m boats for distances of up to 2 to 3 km. The fishery, unique to North Carolina, apparently started in the early 1900's. Since 1956, the number of haul crews has varied between 30 to 60 and there is no clear relationship between that number and the total annual catch. Since 1972 landings have tended to increase, with a record 1O,250t landed in 1979. Much of this increase can be attributed to croaker landings, which increased 45-fold from 1971 to 1979. Sixty-one long haul seine catches were sampled during April-October 1979 in Pamlico and Core Sounds and Neuse, Pamlico, and Pungo Rivers, North Carolina. A total of 53 species of fish, 4 species of invertebrates, and 2 species of turtles were observed in the catches. Together, spot, croaker, menhaden, and weakfish comprised 90 percent by number and 88 percent by weight of the samples.

Largemouth bass (Micropterus salmoides) are able to feed on relatively large prey. The relative size of prey, calculated as the ratio of prey length (or weight) to .predator length (or weight), changed only slightly witb increasing size of largemouth bass. Bluegills (Lepomis macrochirus), gizzard shad (Dorsoma cepedianum), and threadfin shad (D. petenense) were the most common fisbes consumed by largemouth bass in West Point Lake. Bluegills were more often eaten by small largemouth bass (3 to 15 cm TL), while shad were eaten by larger ones ( > 15 I'm TL). Regression equations for the sizes of bluegills and shad that largemouth hass consumed were calculated to p,"edict the average size of prey for different sizes oflargemouth bass. Largemouth bass could swallow bluegills at 0.4 times their length or shad at 0.5 times their length. The equations of Lawrence (1958) were corroborated by our study of size - selective predation in largemouth bass from West Point Lake.

Cross-sections cut from the articulating process (AP) of pectoral spines were used to determine age and back-calculate growth of 370 flathead catfish (Pylvdictis olivaris) from 2 Oklahoma reservoirs. The accuracy ofthis method was validated by the following: agreement between the number of annuli and known age of 16 fish; 1 new annulus formed in the pectoral spines of fish tagged in 1970 and recaptured in 1971; agreement between calculated length increments and known length increases of tagged fish; and agreement between assigned age and length frequencies of young fish. Pectoral AP sections were superior to dorsal AP sections for age determinations. Sole use of sections from the distal end of the basal recess of pectoral spines would have resulted in underestimation of age by 1 to 5 years in fish of 3 to 13 years of age.

Seasonal dynamics of metacercariae of Uvulifer ambloplitis (Hughes 1927), the black spot parasite of centrarchids, were monitored over a 12 month period for bluegill (Lepomis macrochirus) < 70 mm total length. Prevalence of infection ranged from 8 percent in April to 97 percent in September. Mean parasite density during September was 16 metacercariae per host although individual infections of over 100 per host were not uncommon. Prevalence and density of infection were greatest in bluegill 31 mm to 50 mm total length. Metacercariae were often localized in the caudal peduncle, gular plate, and isthmus of heavily infected fish. Analysis of variance indicated significant differences in weight and body condition (K) of heavily versus lightly infected individuals of the same length class (P < 0.05). Body condition was negatively correlated to parasite density (r = - 0.474, P < 0.01).