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

Abstract

Calcium chloride was used to increase total hardness of hatchery well water from 40 mg/L to 200 mg/L, and two experiments were conducted to evaluate effects on egg diameter and hatch rates of eggs from striped bass Morone saxatilis. In the first experiment, fertilized eggs were divided into two lots; one lot was incubated in untreated well water with a total hardness of 40 mg/L, the other lot was incubated in water hardened to about 200 mg/L. The eggs that were incubated in treated water hatched at a significantly higher rate (70.3%) than the control eggs (53.9%). The mean egg diameter of the treatment eggs (2.45 mm) was significantly smaller than the control eggs (3.14 mm). In a second experiment, eggs were incubated in hardened water for different durations. Fertilized eggs were incubated for 3, 6, or 48 h in hardened water then transferred to well water. Eggs incubated for 48 h in hardened water hatched at a significantly higher rate (44.7%) than those incubated for 3 h (25.3%) or 6 h (31.9%). No significant difference was detected in numbers of eggs per liter between treatments. The higher hatch rate will permit meeting production goals while using fewer broodstock and incurring lower production costs.