Striped Bass Eggs

Effects of Increasing Water Hardness on Egg Diameter and Hatch Rates of Striped Bass and Hybrid Striped Bass Eggs

STEVEN SPADE (Oklahoma Department of Wildlife, Byron State Fish Hatchery, Byron, Oklahoma 73722)

Historically at the Byron State Fish Hatchery there has been problems with striped bass and hybrid striped bass eggs floating out of the hatching jars. A review of literature indicated that the problem was probably soft water. Therefore this study was conducted to determine the effects of raising total water hardness of hatchery well water on the egg diameter and hatch rate of striped bass and hybrid striped bass eggs. Fertilized eggs from each of thirteen females were divided into two lots (control and treatment). One lot (treatment) from each female was incubated in hardened water (190 ppm) and the second lot (control) was incubated in untreated water (41 ppm). Both lots were incubated for 48 -50 hours. The initial egg diameter and total number of eggs for each lot was taken five minutes post fertilization and then again at 48 -50 hours post fertilization. Total hardness was also monitored so that the treatment water would maintain a 190 to 200 ppm level.

The results showed a statistically significant difference between the control eggs and treatment eggs in both egg diameter and hatch rate. The increase in egg diameter from initial to final measurement for the control eggs was 1.598 millimeters as compared to 0.91 millimeters for the treated eggs. The hatch rate for the control was 53.58 percent while for the treatment was 65.63 percent, a difference of 12.05 percent. These results indicate that on an average production year at the Byron Hatchery an additional 1,000,000 eggs will hatch if these methods are used. Since these methods will adapt very easily to full production we plan to do so in 1997. We also plan to experiment with differing lengths of treatment times since the water hardening stage for Striped Bass and their hybrids is approximately 2.5 hours.

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