Effects of collision shock on semi-buoyant fish egg hatchings in high-speed streams

Abstract

During downstream drifting in high-speed steams, semi-buoyant fish eggs can run onto rocks, boats, and other surfaces. This will result in the abrupt and severe collision shock to the fish eggs, causing damage to fish eggs and potentially leading to their death. For protection of fish stocks and river management, it is crucial to understand the impact of collision shock on their hatching and to clarify the upper threshold of collision velocity. Through an indoor free-fall experiment, we quantified the influences of collision shock on semi-buoyant fish eggs. We discovered that, when fish eggs collided with a rock at a speed of 4.4 m/s, about 70% of the eggs did not successfully hatch. Forty-five percent of the egg envelopes were broken when the collision velocity was 4.4 m/s and collided with water. Development stage, particularly when the eggs were at the cell cleavage stage, was the most susceptible factor to collision shock. Our results offer new insights for preserving fish stocks in high-speed streams and can be used to inform river management strategies.