Improving the environment for kelp hatchery culture in tanks with bottom aeration using a skeleton collector

Abstract

Hydrodynamic and light conditions may be affected by the frame system that carries the string (collector) used to produce kelp seedling strings in kelp hatcheries. However, no studies have analysed the effect of the collector type on these key environmental factors to assess hatchery suitability. In this study, two experimental set-ups were designed to evaluate the hydrodynamic environment and light availability using two distinctive collectors that have been used for kelp hatchery cultures in tanks with bottom aeration. A standard collector of walled PVC pipe was compared with an alternative collector consisting of a steel skeleton with a fully open frame structure. The results show that the two types of collectors produced different environmental effects. The skeleton collector displayed a significantly lower reduction in the water velocity compared with the pipe collector, and therefore, its design favours water circulation and exchange through the system to a greater extent. This effect was more significant as the aeration level increased. The skeleton collector also provided better light availability, with a significance that depended on the illumination source positions at different faces of the collector. The differences were greater on the inside faces and with illumination from the sides of the collector. The findings are discussed based on prior experience and the literature on kelp hatchery practices.