Roger W. Rottmann

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.

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.

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.

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...

Eliminating Adhesiveness of White Bass Eggs for the Hatchery Production of Hybrid Striped Bass

Abstract The adhesiveness of eggs of white bass (Morone chrysops) can be eliminated with a tannic acid treatment, facilitating jar incubation. Fertilized eggs are added to a tannic acid solution of 150 mg/L in a McDonald jar, and the mixture is aerated with compressed air for 10–12 min. The air stone is removed, the center tube of the jar is inserted, and the water flow is adjusted to keep the eggs in motion. This treatment has been used in the production of reciprocal hybrids with striped bass (Morone saxatilis).

Environmental manipulation to stimulate rotifers in fish rearing ponds

Abstract Four treatments were established in eight small ponds not stocked with fish: a control group (untreated and not fertilized) and three groups treated with organophosphate insecticide (Dylox). One group of Dylox treatment ponds was treated with chemical fertilizer, the second group with chemical and organic fertilizer, and the third group with chemical-organic fertilizer and paddlewheel water agitation. Water analysis and zooplankton samples were collected twice weekly. Rotifers increased in numbers in all treated ponds but no correlations were found between 16 hydrochemical and biological parameters and rotifer numbers. The application of rotifer management techniques for rearing larval fish is discussed.

Tank spawning of grass carp

Abstract Induced spawning of grass carp in indoor tanks without hand stripping of gametes is described. Circular tanks (1.83 m diameter) with biofiltration units were utilized for conditioning and spawning. This method was found to be successful and has several advantages over the dry-fertilization method: (1) preliminary ripening and spawning is conducted in small systems where the environment is controlled; (2) manpower requirements are reduced; (3) handling of brood fish is reduced, thereby minimizing mortalities; and (4) spawning occurs when the fish is physiologically ready, insuring good egg quality.

Hatching Jar That is Inexpensive and Simple to Assemble

Abstract Construction of an inexpensive hatching jar is described. The jar is made from a disposable plastic soft-drink bottle and plastic pipe components. Each unit can be assembled in approximately 5 min at a cost of less than

Technical Notes: Multiple-Tank Aquarium System with Recirculating Water for Laboratory Studies of Freshwater Fishes

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Growth of grass carp fed natural and prepared diets under intensive culture

Abstract A recirculating-water aquarium system for laboratory studies of freshwater fishes is described. The system consists of 216 glass tanks (3.5 gal each), two particle filters, a multistage biofilter, two ultraviolet-light sterilizers, and a regenerative blower for auxiliary aeration. Each tank is connected separately to the recirculating-water supply through inflow and outflow manifold pipes. Water flow to individual tanks is adjustable and can be varied from 0 to 10 gal/h (0–3 water exchanges/ h). The system was designed to minimize environmental variation among tanks and families in genetic studies of tropical aquarium fishes but would be useful for other studies in which replicated treatments or experimental units are required.