The effect of water-off events on the growth, survival, and biochemical stress indicators of the South African abalone Haliotis midae.
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Date
2025-03-18
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Publisher
University of Fort Hare
Abstract
South African abalone farms are dependent on seawater from the surrounding environment which occasionally may experience the occurrence of harmful algal blooms (HABs). To avoid HABs entering the abalone tanks, the farm may implement water-off events, resulting in ammonia accumulation which potentially stresses the abalone, influencing the metabolism, growth, and survival. This study aimed to better understand how long the water-off interruptions might be implemented before they have a negative impact on the survival, growth, and health of the abalone, Haliotis midae.
The study involved placing baskets of abalone in different raceway tanks (control and experimental) where the water was switched off for 24, 48, and 96 hours. Prior to, during and after the exposure to the different water-off periods, haemolymph and muscle tissue were taken from abalone and were used to assess haemolymph glucose, muscle glycogen, dopamine, superoxide dismutase, and total haemolymph protein content, as indicators of abalone health. There were differences in the water quality parameters over the sampling period period. Four months after the start of the experiment there was a 100% survival for the abalone across all the treatments with no differences in their growth. There was no difference in the concentration of glycogen, glucose, dopamine, and superoxide dismutase over time in any of the treatments. Total protein concentration in the treatment tanks showed differences
between 6h and 84h fluctuations, however, it did not show any differences between the treatments.
Despite fluctuations in the water quality parameters over the 96-hour time period, the water quality parameters remained within a safe range for H. midae. The results of this study therefore show that it is safe for farm managers to turn the incoming seawater off for up to 96-hours without any negative effect on the health, growth, and survival of H. midae.
Description
Masters dissertation
Keywords
Aquaculture -- South Africa, Glycogen, Dopamine