Jerome V. Shireman

Coefficients of Condition for Largemouth Bass, Bluegill, and Redear Sunfish in Hydrilla-Infested Lakes

Abstract Coefficients of condition were calculated seasonally for largemouth bass (Micropterus salmoides), bluegill (Lepomis macrochirus), and redear sunfish (Lepomis microlophus) for three years from two hydrilla-infested Florida lakes, Baldwin and Wales. Hydrilla coverage was altered with aquatic herbicides and grass carp (Ctenopharyngodon idella) during the study period in both lakes. Bluegill and redear sunfish condition was not adversely affected until hydrilla occupied the majority of the water column. The reduction in condition which occurred with near total occupation of the water column by hydrilla was probably due to the elimination of a foraging gradient between the submersed macrophytes and open water. Harvestable (creelable) largemouth bass had low condition values once hydrilla coverage was above 30%; however, smaller largemouth bass were not as adversely affected until percent coverage exceeded 50%.

Use of Otoliths to Determine Age and Growth of Largemouth Bass in Florida

Abstract The annual formation of otolith annuli was validated through age 5 for Florida largemouth bass Micropterus salmoides floridanus. Sectioned otoliths (sagittae) gave more reliable ages than whole otoliths. Beginning at age 2, at least one annulus was obscure in some whole-otolith mounts, a problem that worsened with fish age. By age 5, over 20% of the whole otoliths gave under-estimates of true age; otoliths producing these errors came from fish with slower than average growth rates. Sectioned otoliths gave poorer regressions (lower coefficients of determination) of otolith radius on body length than intact structures because the sectioning plane varied slightly among otoliths. Nevertheless, back calculations of fish size and growth from sectioned and correctly aged whole otoliths were equally accurate. Otolith sectioning is the procedure of choice for age-and-growth analysis of Florida largemouth bass. Whole otoliths, however, require much less time for analysis than sectioned ones and may be used...

Influence of Hydrilla on Harvestable Sport-Fish Populations, Angler Use, and Angler Expenditures at Orange Lake, Florida

Abstract An infestation of hydrilla Hydrilla verticillata caused an 85% reduction in angler effort at Orange Lake, Florida, in 1977 when plant coverage exceeded 80% of the lake. Nonlocal anglers were only 3% of the total number of anglers fishing the lake in 1977, but were 37% of the anglers during 1978 and 1979, when hydrilla coverage was less than 19%. Although angler use of Orange Lake was greatly reduced during the peak 1977 hydrilla infestation, the number of fish caught per hour during 1977 was equivalent to or greater than that of all other study years for all species of sport fish. The almost complete plant coverage did not lower the population of harvestable largemouth bass Micropterus salmoides or black crappie Pomoxis nigromaculatus. Numbers of harvestable bluegill Lepomis macrochirus and redear sunfish Lepomis microlophus were, however, negatively correlated with hydrilla coverage. Reduction in angling caused a 90% loss in revenue from the Orange Lake sport fishery that is valued at approximat...

Food Selection by Grass Carp Fingerlings in a Vegetated Pond

Abstract Five thousand grass carp (Ctenopharyngodon idella) fry were stocked into a 0.81-hectare pond in Marion County, Florida. The fry grew from 48.2 mm to 186 mm total length in 6 months with a survival rate of less than 7%. Food consumption decreased to near maintenance ration when water temperature fell below 14 C and growth was reduced. The 76 grass carp which contained food (63-220 mm) were strict herbivores, and ate animal material only in trace quantities (<0.1%). Mean electivity indices indicated positive selection for Sagittaria graminea, slight selection for Eleocharis sp., and discrimination against Najas flexilis, Ceratophyllum demersum, and Potamogeton illinoensis.

Evaluation of aquaculture effluents

Abstract Water quality data were collected from six Department of Fisheries and Aquatic Sciences (FAS) aquaculture ponds at the University of Florida and two ponds at each of four private farms. Effluents from four of the FAS channel catfish (Ictalurus punctatus) ponds were treated by pumping the water into a retention pond or vegetated ditch. At the stocking rates used, little relationship existed between harvest densities (kg·ha−1) and water quality parameters; however, harvest densities were lower than in most intensive production systems. Total suspended solids (TSS) were elevated by seining; however, if pumping did not occur immediately after seining, the TSS settled prior to pumping. Passing water through a retention pond or vegetated ditch reduced TSS. Mean water quality parameters in channel catfish fingerling ponds and sportfish (largemouth bass, Micropterus salmoides; bluegill, Lepomis macrochirus; redear sunfish, L. microlophus) fingerling ponds were generally lower than in the food-size channel catfish ponds except for dissolved oxygen. This study was conducted to develop a water quality database from a variety of soil types and cultured species. These data along with data from one catfish farm located in Northwest Florida were evaluated to determine if effluents from these farms meet Florida water quality standards. Using these data, the Florida Department of Environmental Regulation (FDER) developed a general permit for fish farms. Sufficient data from ornamental fish farms were available, and therefore ornamental fish farms were included in the permit without additional data collection.

Comparison of three live foods and two dry diets for intensive culture of grass carp and bighead carp larvae

Abstract Grass carp ( Ctenopharyngodon idella ) and bighead carp ( Hypophthalmichthys nobilis ) larvae fed freshwater rotifers ( Brachionus rubens ) were consistently longer and heavier at the end of the 3-week feeding trials than those fed the other foods tested. The final length of grass carp fed nematodes ( Panagrellus sp.) was the lowest of the live foods tested, however, the length of bighead carp fed Panagrellus was not significantly different from those fed brine shrimp nauplii Artemia salina . Growth of grass carp fed the two commercial dry diets (Ewos Larvstart and Fry Feed Kyowa A) was less than those fed the three live foods. Bighead carp grew well on the commercial diets, but results were somewhat inconsistent. Construction of a simple, inexpensive airlift sponge filter is described. This filter provided adequate water quality, resulting in excellent survival at densities as high as 57 individuals/l with no addition of freshwater. The airlift sponge filter has great potential for intensive larval rearing.

Distribution of Florida Largemouth Bass in a Lake after Elimination of All Submersed Aquatic Vegetation

Abstract Distribution of 16 Florida largemouth bass Micropterus salmoides floridanus was monitored weekly for 1 year by radiotelemetry in 80-hectare Lake Baldwin, Florida. The lake contained grass carp Ctenopharyngodon idella, which had elminiated all submersed aquatic macrophytes. Six of the largemouth bass stayed predominantly (87% of tracking locations) in water deeper than 3.5 m (60% of lake surface area), where they established home ranges averaging 21.0 hectares (range, 0.6–39.5 hectares); the offshore region had no natural or artificial structures. The other radio-tagged fish were relocated a majority of times in water depths of 3.5 m or less. Five of these fish established year-round home ranges averaging 4.1 hectares (range, 1.0–9.8 hectares) in the inshore region where water depths were less than 2.0 m, and had significant (P < 0.05) preferences for habitats with water tupelo Nyssa aquatica. The remainder of the largemouth bass used both the inshore region and water depths out to 3.5 m and had s...

Size Limits to Predation on Grass Carp by Largemouth Bass

Abstract The external distance between the cleithrum bones was used to estimate the sizes of grass carp (Ctenopharyngodon idella) that could be ingested by Florida largemouth bass (Micropterus salmoides floridanus). The equations for mouth width vs. total length (TL) of largemouth bass were: Mouth (mm): 0.0968 (mm TL) for bass 200 mm (r2 = 0.95). The equation for body depth vs. total length of grass carp was: depth (mm) = 0.629 + 0.204 (mm TL), r2 = 0.98. Five thousand grass carp fingerlings were stocked in a 0.81-hectare vegetated pond. Initial predation was high in the sportfish pond, as only one grass carp was recovered at termination. Stocking of grass carp >450 mm is necessary to totally eliminate the possibility of piscivorous predation in lakes with established Florida largemouth bass populations.

Efficiency of Rotenone Sampling with Large and Small Block Nets in Vegetated and Open-Water Habitats

Abstract The sampling effectiveness of rotenone applied within large (0.41 hectare) and small (0.08 hectare) blocknetted areas was compared at open-water and vegetated sites in Orange Lake, Florida. Eighteen fish species were collected within the large nets and 21 species within the small nets; 16 species were common to both nets. Total fish biomass (kg/hectare) and abundance (number/hectare) estimates did not differ significantly (P ≤ 0.10) between areas in either open-water or vegetated habitats; abundance estimates (number/hectare) did not differ between large and small open-water areas. Significantly higher abundance estimates were obtained in the smaller nets in vegetated habitats due to more efficient pickup of small fish. For larger size game fish, total abundance, biomass, and individual species estimates were not significantly different between sample areas in either habitat. The smaller experimental nets provided inventories of fish populations that were as accurate as those from large-area samp...

Grass Carp: Effects of Salinity on Survival, Weight Loss, and Muscle Tissue Water Content

Abstract Fingerling grass carp (Ctenopharyngodon idella), 100-120 mm total length, were exposed to various hypotonic and hypertonic waters to determine tolerance, body weight loss, and muscle tissue water content. After acclimation at 8.0‰, LD50s for 24, 48, and 96 h were of 15.7, 15.1, and 15.1‰ salinity, respectively. No mortalities occurred in fish exposed at 14.0‰ for 96 h; at 12.0 and 14.0‰, decreases of 8.5 and 11.3% in total body weight occurred. At lower salinities, declines in body weight were only 0.8-1.7%. As salinity increased, the water content of muscle tissue declined from 80.0% in fresh water to 74.4% at 14.0‰. Death at salinities higher than 14.0‰ was attributed to the failure of cellular processes to adjust to dehydration.