Douglas E. Colle

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%.

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.

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 growth rates in Lake Wales, Florida

Abstract Grass carp (Ctenopharyngodon idella) were collected from Lake Wales, Florida, a hydrilla (Hydrilla verticillata) infested lake, for a 4-year period. Average daily growth per year ranged from 10.0 to 10.4 g/day. Grass carp averaged 962 mm total length and 15.0 kg after 48 months.

Utilization of Selective Removal of Grass Carp (Ctenopharyngodon idella) from an 80-Hectare Florida Lake to Obtain a Population Estimate

Abstract Selective removal of grass carp was attempted in an 80-hectare Florida lake by means of a 0.1-mg/liter treatment of rotenone. A mark-recapture procedure was used to obtain a population estimate. Prior to the lake treatment, a field bioassay conducted in large polyethylene bags containing lake water and suspended in the lake, revealed that a 0.1-mg/liter concentration of rotenone killed grass carp but had little effect on sport fish. Fish collected from block nets set within the lake revealed lake-wide rotenone treatment removed more than half of the threadfin shad (Dorosoma petenense), grass carp, and golden shiners less than 100 mm. Appreciable numbers (20-50%) of largemouth bass (Micropterus salmoides), lake chubsuckers (Erimyzon sucetta), larger golden shiners, and redear sunfish (Lepomis microlophus) less than 100 mm were affected. Larger redear sunfish, bluegill (Lepomis macrochirus), warmouth (Lepomis gulosus), and black crappie (Pomoxis nigromaculatus) were abundant within the lake, as sho...

Controlled Spawning of the Neon Tetra

Abstract The neon tetra Paracheirodon innesi is one of the most valuable species in the ornamental fish trade. Most neon tetras available in the United States are imported from Southeast Asia, where they are farm raised, or from South America, where they are collected from the wild. In this study, we describe a method for artificially breeding the neon tetra that can be adapted to domestic commercial production. Broodfish pairs were routinely spawned in acidified, soft water at 25°C (pH, 5.5–6.5, adjusted with phosphoric acid; total alkalinity, 3.2 mg/L, and total hardness, 6.0 mg/L, as CaCO3). The water was also conditioned with humic acids (0.04%). A spawning substrate (nylon brush) was available for egg deposition. Fish reared in the laboratory had a significantly higher number of larvae (82 larvae/female) than broodstock collected from the wild or cultured abroad (28 larvae/female). The domestic population reached sexual maturity at 5–6 months of age, and broodfish pairs produced an average of 82 larv...

Processing Yields for Meat of Russian and Siberian Sturgeons Cultured in Florida, USA

ABSTRACT Cultured Russian and Siberian sturgeons were processed and analyzed to estimate meat yields and proximate compositions. Sturgeons were approximately 18 to 24 months in age and weighed 2.3–2.6 kilograms (lower and upper intervals, 95% level of confidence) in total body weight. Dressed fillet yields in sturgeon appear to vary by species. The skinless fillet yields for Russian sturgeon and Siberian sturgeon were 26% and 32%, respectively. The proximate composition of edible portions in Russian and Siberian sturgeons may range from 70–76% moisture, 17–19% protein, 5–10% lipid, and 1–2% ash; some 116–151 calories per 100 grams of fresh, uncooked meat. However, the lipid content in Siberian sturgeon may be higher than in other sturgeon species.