Matthew E. McEntire

Chronic exogenous kisspeptin administration accelerates gonadal development in basses of the genus Morone.

The present study assesses the effects of chronic administration of peptides to fish, termed kisspeptins, which are the products of the KISS1 and KISS2 genes, and have been shown to control the development of puberty in animals. Using ecologically and commercially important species (white bass, Morone chrysops, striped bass, Morone saxatilis, and their hybrid) as comparative models, we determined that repeated bi-weekly injections (over 7 weeks) differentially accelerate puberty, as evidenced by increases in the prevalence of spermatozoa in the testes of juvenile fish. Moreover, in sexually mature fish, kisspeptin treatment led to increased gonad weight, gonadosomatic index, and spermatocrit in some white and striped bass. Additionally, mature white bass treated with kisspeptins showed an advancement in oocyte development as determined by histological examination. These gonadal changes occurred in the absence of any photothermal manipulation or hormone injections. To date, this is the first description of kisspeptin-mediated pubertal initiation in fish, and the first evidence that kisspeptins could modulate gonad maturation. Although it remains to be determined how kisspeptins may best be utilized in practice, our findings are a basis for future studies to characterize the molecular underpinnings of the KISS system in various fish species.

Effect of Contrasting Agents on Survival, Performance, and Condition of Larval Hybrid Striped Bass Morone chrysops x M. saxatilis in Tanks

Contrasting agents, either algae or inert soil, cause turbidity, which is important in the tank culture of larval cannibalistic fish. Optimization of turbidity is critical to successful tank culture of new larval fish, which should include 100 mg/L of sub-5 μm particle size in the assessed range. The optimum tested range of greenwater culture for hybrid striped bass using algae paste once daily was between 629 and 1127 mg/m3 (350–583 cell/mL). Dispersed kaolin worked as well as greenwater culture. Using contrasting agents improved fish length, condition, tail–length ratio (TLR), and uniformity of the fish at the time of weaning onto prepared diets. Increasing turbidity appears to negatively skew fish length and TLR. TLR shows promise as an early indicator of cannibalism. Increasing turbidity appears to decrease the size advantage of the largest fish in the tank, which allows the smallest fish to catch up.

Genetic Effects and Estimates for the Heritability of Size in Fingerling Hybrid Striped Bass Reared Indoors

Hybrid striped bass fingerlings were grown in replicated indoor tanks for 42 days to evaluate progeny performance of two growth-related traits. Analysis of variance demonstrated significant differences in length and weight of fingerlings among paternal and maternal half-sib families and high estimates of heritability for dams and sires. Based on significant sire and dam effects and high heritabilities, a substantial portion of the selection differential could be expected to be gained in offspring from selected pure-line parents. As demonstrated by these results, a breeding program could be used to select parental lines that produce faster growing hybrid offspring.

Safety of Copper Sulfate to Channel Catfish Eggs

Abstract Copper sulfate (CuSO4) is used in the catfish industry to control saprolegniasis (caused by the watermolds Achlya spp. or Saprolegnia spp.) on eggs. This study was designed to establish the margin of safety of CuSO4 at 10, 30, and 50 mg/L when applied for three times the normal treatment duration to hatching troughs containing channel catfish Ictalurus punctatus eggs in 26°C, flow-through well water. The safety of CuSO4 was indicated by the percentage of fry that hatched from the eggs. Eggs were treated daily until the embryos reached the eyed stage. The least-squares means ± SE of hatch rates were 40.8 ± 9.1, 80.9 ± 6.4, 64.2 ± 8.6, and 80.3 ± 6.6% for the 0-, 10-, 30-, and 50-mg/L CuSO4 treatments, respectively. The hatch rate for the 0-mg/L CuSO4 treatment was significantly different from that of all other CuSO4 treatments. Treating channel catfish eggs with five times the recommended dose of 10-mg/L CuSO4 for three times the recommended duration did not adversely affect the hatch rates in thi...

The Effect of PIT Tagging on Survival, Tag Retention, and Weight Gain in Fingerling White Bass

We tagged fingerling white bass, Morone chrysops, with passive integrated transponders (PIT) at two body locations (peritoneal cavity and dorsal musculature) and six weight classes to evaluate survival, tag retention, and weight gain during a 28-day experimental period. The probability of survival (as calculated by logistic regression) was >95% for fingerlings >19 g for both PC and DM. Retention of PIT tags varied between PC and DM tagged white bass in 6 g and 14 g fingerlings. The probability of tag retention was 100% in all sizes of fingerlings tagged PC, and >95% for fish >19 g tagged DM.

Effects of solids removal on water quality and channel catfish production in a biofloc technology production system

ABSTRACT Total suspended solids control was evaluated in a channel catfish (Ictalurus punctatus) biofloc technology production system. Settling chamber flow rates were 0.9 (LO) or 2.9 (HI) L/min to reduce total suspended solids to 300 mg/L; solids were not removed from control tanks. Channel catfish yields (7.6–8.7 kg/m3) were not affected significantly, but control fish were skewed toward smaller size classes. Control treatment channel catfish tolerated 1,410 mg/L total suspended solids without adverse effects. LO- and HI-treatment fillet geosmin concentrations were high enough to be designated as off-flavor. Water quality results suggested that nitrification was affected by solids removal.

Comparative water quality and channel catfish production in earthen ponds and a biofloc technology production system

ABSTRACT This 210-day study compared variation in water quality and fish growth for channel catfish (Ictalurus punctatus; 47 g/fish) stocked in earthen ponds (1.5 fish/m2, 14,820/ha) and in a biofloc technology (BFT) production system with high-density polyethylene-lined rectangular tanks (12.6 fish/m2, 126,000/ha). Feed input and culture environment affected water-quality dynamics. In ponds, phytoplankton uptake predominated and little nitrification occurred, whereas in the BFT system phytoplankton uptake and nitrification maintained low ammonia-nitrogen concentrations. Size classes of fish were skewed toward the larger market sizes in ponds and toward smaller market sizes in the BFT system. Mean final fish weight was 630 g/fish in ponds and 542 g/fish in the BFT system. Despite these differences, fish yield was higher in the BFT system (7.7 kg/m3 v. 1.5 kg/m3) because of the greater initial stocking rate.