Abstract
: This study evaluated water quality variations in an artificial deep pool (ADP), which is an underground artificial structure built in a shallow pond as a fish shelter. The water temperature, pH, dissolved oxygen (DO), and electrical conductivity (EC) were measured on an hourly basis in the open space and inside the ADP, and a phenomenological study was performed, dividing seasons into normal and rainy seasons and environments into stagnant and circulating conditions. The results showed that the water quality parameters inside the ADP exhibit lower fluctuations and diurnal variations compared with the open space. On average, the water temperature inside the ADP is lower than outside it by 1.7–3.7 °C in stagnant conditions, and by 0.6–0.7 °C in circulating conditions during early summer. Thermal stratification occurs inside the ADP but is temporarily disturbed due to the mixing from the forced circulation and the rainwater input through rainfall events. The ADP provided a constant and optimal water temperature for living and spawning for bitterling (i.e., 15.0–21.0 °C), which dominated in experimental pond during spring to summer. Most importantly, the ADP was able to significantly reduce the thermal stress of the fish in the study site, and as a result, the bitterling, a cool water fish species, could successfully become dominant. Finally, the deployment of the ADP appears to provide a practical alternative for effective fishery resources management to improve species diversity and fish communities in an artificial freshwater ecosystem (garden pond, park pond, other artificial wetlands, etc.).
Highlights
Fish are exposed to many stress factors throughout their lifetime [1]
Since the experimental results in this study revealed that the water temperature inside the artificial deep pool (ADP) was lower and more stable than that in the open space, the monitored fish were observed to migrate into the ADP
To evaluate the function of a fish shelter in mitigating the impact of accumulated stress, the water quality inside the ADP was investigated for two consecutive years during the early summer period when thermal stress tends to rise in fish
Summary
Fish are exposed to many stress factors throughout their lifetime [1]. As water is the sole living space for fish, the aquatic environment is a directly limiting factor that influences the survival of fish [2,3].In particular, water quality parameters such as water temperature, pH, and DO, whose optimal ranges differ from one fish species to another, determine the changes in the physiology of fish [4,5,6,7].In particular, fish are very sensitive to water temperature [6,8]. Fish are exposed to many stress factors throughout their lifetime [1]. Water quality parameters such as water temperature, pH, and DO, whose optimal ranges differ from one fish species to another, determine the changes in the physiology of fish [4,5,6,7]. Fish are very sensitive to water temperature [6,8]. High water temperatures or high diurnal variations cause thermal stress in fish, and this can be aggravated through accumulation [9]. Fish are exposed to continuous cycles of stress and de-stress depending on the rise and fall of the water temperature [10]. Cheung et al reported that approximately 24% of fish species worldwide face the threat of extinction as a result of increases in
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