Richard J. Onders

Induced gynogenesis in black crappie.

Abstract This study reports the results of initial experiments on induced diploid gynogenesis in black crappie Pomoxis nigromaculatus. White bass Morone chrysops were an effective sperm donor for gynogenetic experiments with black crappies. White bass spermatozoa fertilized black crappie eggs, but hybrid larvae were not viable and died after hatching. In a series of experiments, we determined the ultraviolet (UV) light dose required to inactivate the sperm genome and the heat shock parameters needed to restore diploidy. Black crappie eggs were inseminated with white bass sperm irradiated with UV dosages ranging from 25 to 2,500 J/m2. A typical “Hertwig effect” in the yield of hatched larvae was observed with dosages greater than 100 J/m2. The genetic inactivation of paternal chromosomes was confirmed by flow cytometry measurement of DNA content in larval cells. Larvae resulting from sperm irradiated at a dose of 1,000 J/m2 were haploid. Time durations of mitotic interval (τ0) at different temperatures for...

Hormonal Sex Reversal and Evidence of Female Homogamety in Black Crappie

Abstract This study reports the results on hormone-induced sex reversal in black crappie Pomoxis nigromaculatus and the sex ratios of progenies obtained from test crosses of androgen-treated males with normal females. The androgen 17α-methyltestosterone (MT) was orally administered to fish with an artificial diet (30 mg/kg) for 30 d beginning 37 d after hatching; mean fish lengths were 35 and 55 mm at the beginning and conclusion of the treatment, respectively. The MT-treated group consisted of 95% males and 5% intersex fish, while the sex ratio in the control group was not significantly different from 1:1. Four males from the androgen-treated group were individually test-crossed with normal females to identify sex-reversed males according to the sex ratios in progenies and to reveal the chromosomal mechanism of sex determination in black crappie. Two out of three analyzed progenies consisted of females only, while one progeny had a sex ratio not significantly different from 1:1. The appearance of all-fem...

Reservoir Ranching of Paddlefish

Abstract Paddlefish Polyodon spathula (30–67 cm total length, TL) were stocked in six flood control reservoirs (<41 ha) in western Kentucky in January 1995 at a target stocking density of 10 fish/ha. Fish growth was monitored quarterly beginning in July 1995. The fish were implanted intraperitoneally with passive integrated transponder (PIT) tags. Chemical and physical variables and zooplankton biomass were measured monthly. Three reservoirs that had not been stocked were sampled monthly as controls. Of the 1,440 paddlefish stocked, 353 were recovered at harvest in the fall of 1996, and only two tags were found. Anecdotal evidence indicated some loss to predation by largemouth bass Micropterus salmoides and some to escapes through mechanical spillways. The total gross yield was 1,715 kg or 13.7 kg/ha; it ranged from 0.6 to 28.8 kg/ha. Gill nets of 102-mm-bar mesh were optimum for harvest. Mean harvest weights were significantly different among reservoirs. A positive correlation was found between relative ...

Effectiveness of the Minimally Invasive Surgical Technique (MIST) for Removal of Ovulated Eggs from First-Time and Second-Time MIST-Spawned Paddlefish

Abstract A minimally invasive surgical technique (MIST) for the removal of ovulated eggs from paddlefish Polyodon spathula was tested on broodstock that had been previously spawned using MIST to determine whether repeat spawning affected fecundity or hatching rate compared with broodstock than had not previously been induced to spawn. There were no significant differences in the number of eggs removed or in the hatching rate between first- and second-time MIST spawners. The oviducts from second-time MIST spawners appeared normal and had no scarring or blockage. The MIST approach is efficient, practical, and less stressful to broodstock during artificial propagation than other reported egg collection procedures.

Inheritance of Predorsal Black Stripe in Black Crappie

Abstract This study presents data on inheritance of the predorsal black stripe in black crappie Pomoxis nigromaculatus. Four progeny groups, obtained by crossing fish with certain phenotypes and of known origin, were investigated. Presence of the black stripe in all fish in two progeny groups, produced by crossing fish with and without the black stripe, indicated dominance of this trait. In two F2 progeny groups, segregations of fish with: without stripe did not differ significantly from the 3:1 Mendelian ratio. It was concluded from the data that the appearance of predorsal stripe in black crappie is under the control of a dominant mutation of one gene (St/st): fish with genotypes StSt and Stst have a stripe, while fish with genotype stst do not possess this trait. Presence or absence of the black stripe was not connected with sex of the fish. This indicates that gene St/st is located in an autosome but not in a sex chromosome. Distribution of fish with stripe in one F2 progeny group with regard to relat...

Application of a Temperature-Dependent Mitotic Interval (τo) for Induction of Diploid Meiotic Gynogenetic Paddlefish

Abstract We tested the application of mitotic interval (tau [τo]) unit in comparison with absolute time to help standardize preshock timing for a consistent production of diploid meiotic gynogenetic paddlefish Polyodon spathula. The diploid gynogenetic larvae were produced by applying heat shock (35°C; 2 min) at different times after activation of paddlefish eggs with irradiated sperm of shovelnose sturgeon Scaphirhynchus platorynchus at two different preshock temperatures (15°C and 20°C). When the timing of heat shock (minutes after activation) was expressed in absolute time, the yield of gynogenetic diploid larvae was distinctly different between the two preshock incubation temperatures. At 20°C, the highest yield was observed when the timing of the heat shock was 12- 13 min after activation, whereas at 15°C the highest yield was observed when the timing of the heat shock was 17- 22 min after activation. However, when the timing of heat shock was expressed in terms of τo, the yield of gynogenetic diploi...

THE ECONOMICS AND MANAGEMENT OF SMALL-SCALE FISH PROCESSING PLANTS USING PADDLEFISH PROCESSING DATA FROM KENTUCKY

Small-scale fish processing is the likely option available for Kentuckys aquaculture industry where market demand is limited, but the product prices are relatively high in restaurant and retail sectors and the seafood products are exotic and “in demand” by consumers. Paddlefish, a boneless freshwater fish with a meat texture similar to swordfish (Parr, 1999), is such an exotic product that enjoys a limited demand among local restaurant and retailers. This article investigated the optimal management parameters of a small-scale paddlefish processing plant using survey data from Kentucky. In addition, values of economic parameters such as profit, costs, and breakeven price, were also evaluated. Results of this article showed that 939 paddlefish could be processed per day into 1,891 kg of fillets, at a breakeven price of approximately

Reservoir Ranching of Paddlefish, Polyodon spathula : Results of a Public Opinion Survey in Kentucky

12.22/kg. Paddlefish steaks were found to be more profitable than fillets only if the steak price exceeded

Effect of Aeration Type and Circulation on Stress Indices of Paddlefish Held in Rectangular Tanks for 24 Hours

10.34/kg. At this price, 985 fish could be processed per day into 2,943 kg of steaks at a breakeven price of

Effect of Size-Grading and Feeding Frequency on Growth and Size Variation of Paddlefish, Polyodon spathula, Juveniles Reared in Ponds

8.27/kg. Current market demand for paddlefish in Kentucky indicates that fillet production will be the most profitable product form. However, given that paddlefish is cartilaginous and similar to shark, swordfish and sturgeon, and there is a demand for shark, swordfish, and sturgeon steaks, there is a potential for paddlefish steaks to be marketed profitably in the future.