Influence of Stocking Densities on Walleye Fry Viability in Experimental and Production Tanks

Abstract

In 1992 at Rathbun State Fish Hatchery, experiments were conducted to evaluate the effects of stocking density on performance of larval walleyes (Stizostedion vitreum) in small (278-L) cylindrical tanks, and to compare fry performance in production-scale (6 79-L) and small tanks. Hatched fry were reared for 21 d and fed Fry Feed Kyowa B400 and B700 in all experiments. I>ensilies of 20, 30, and 40 fry/L were evaluated in two trials, and densities of 20, 50, and 60 fry/L were evaluated in another trial. Fry performance did not differ significantly among density treatments of 20, 30, or 40 fry/L. In the other trial, however, survival was significantly greater for fish stocked at 20 fry/L than for fish stocked at 50 or 60 fry/L, but the number of fry produced (yield) was 216% greater in the tanks stocked at 60 fry/L. Growth rate was not affected by density in any trial. For comparisons between 278-L and 679-L tanks, three 679-L tanks were stocked at 20 fry/L in each of the three trials. Survival and viability differences between tank sizes were inconsistent, but the highest survival was an average of 74.9% to 21 d posthatch in the three 679-L tanks in the second trial. Cannibalism and gas bladder inflation were more common in the small tanks. Incidence of cannibals was as high as 7.5% of the original number stocked in the small tanks, but did not exceed 3.5% in the large tanks. Over all three trials, from 98.5 to 100% of the survivors in the 278-L tanks, and from 88 to 96.3% in the 679-L tanks, had inflated gas bladders. The outstanding rate of gas bladder inflation is attributed to the use of a surface spray, which seems to clear the water surface of oil and debris. These experiments demonstrate the feasibility of mass culture of larval walleyes in production-scale tanks.

Effect of stocking density on survival and growth performance of pikeperch, Sander lucioperca (L.), larvae under controlled conditions

“…The relationship between stocking densities and fish biomass gain was statistically significant (P < 0.01) and expressed by a linear (Table 3). Moore et al (1994) observed similar effects with larvae of walleye, Sander vitreus (Mitchill), reared at initial stocking densities varying from 20 to 60 individuals l -1 under intensive culture conditions. Peterson et al (1997) also reported that an initial stocking density of a similar range (40-60 individuals l -1 ) had a decisive impact on the growth and biomass increment of walleye larvae.…”

Performance of Larval Walleye Cultured Intensively in Clear and Turbid Water1

“…In all cases, a rheostat was used to adjust the light intensity at the water surface to about 100 lx. Fry Feed Kyowa B-400 and B-700 diets (Biokyowa Inc., Chesterfield, Missouri, USA)3 were provided to all tanks for 22 h/d in amounts and ratios that changed with larval age (Moore et al 1994b). Feeding was suspended for 2 h/d while the tanks were cleaned.…”

“…Moodie et al (1 992) reported 47% survival to 30 d in a "trough" and 13% in a cylindrical tank, but GBI was only 16% in the trough and 69% in the tank. Further advances in culture techniques have resulted in survival greater than 50% and GBI exceeding 90% (Barrows et al 1993;Moore et al 1994a;1994b).…”

Effects of density, starvation and size difference on aggressive behaviour in juvenile yellowtails (Seriola quinquevadiata)

“…Density-dependent mortality by cannibalism was reported in many larval and juvenile fish under experimental conditions: for example in sea bass Dicentrachus labrax (Katavic et al 1989), carp Cyprinus carpio (v, Damme et al 1989; Hecht and Pienaar 1993) and pike Esox lucius (Giles et al 1986;Wright and Giles 1987). However mortalities from cannibalism were density-independent in the catfish, Clarius gariepinus (Hecht and Pienaar 1993) and walleye, Slizosfedion uifreum (Moore et al 1994). Hecht and Pienaar (1993) pointed out that territorial aggressive behaviour decreased with increase in fish density, whereas the rate of cannibalism increased.…”