Large flocks of fish are seen outside one of the rivermouths at Shenzhen Bay. Wang Haolan
Huge schools of fish leaped out of the waters near No. 12 outfall of Shenzhen Bay Park on Tuesday morning, marking the second time that jumping fish were spotted in the park this year, Shenzhen Evening News reported.
The almost three-minute spectacle was captured on video by Qin Xiaoxin, a member of Shenzhen Bird Watching Society, while he was photographing birds nearby. “I photographed birds at Shenzhen Bay frequently and captured a footage of fish leaping out of the waters before. However, this huge school of fish was the largest and most impressive sight,” he said.
Dr. Huang Honghui, a researcher from South China Sea Fisheries Research Institute, Chinese Academy of Fishery Sciences, told the News that the fish is Liza affinis, or eastern keelback mullet. Schools of Liza affinis usually throw themselves up through a series of jumps in the air, which indicates they are looking for mates.
“Notwithstanding, I would suggest keeping observation and see if there are a lot of dead fish following the jumping. If there are, the jumping indicates the fish’s stress reaction which can be caused by toxic pollutants in the water,” Huang said.
However, the theory about water pollution was disproved as two photographers who were taking bird photos in Shenzhen Bay the last two days told the reporter they found no dead fish.
Dr. Zhou Kai, deputy director of the city’s center for ocean monitoring and forecasting, mentioned Shenzhen Bay’s water treatments measures, further weakening speculation on water pollution. Shenzhen Bay has designated a restricted fishing area since May 1, 2014 to preserve the bay’s ecological environment and biological resources. The city also continues to monitor and improve the water quality of seagoing rivers and has closed 16 discharging outlets in Shenzhen Bay waters, which significantly improved the water quality of Shenzhen Bay.
“Shenzhen Bay’s low-velocity brackish waters are breeding grounds for Liza affinis. The fishing ban and water treatment efforts have produced visible outcomes, leading to a sharp increase in the fish population,” Zhou added.
Fishery experts listed several possible reasons why schools of fish jump out of the water, namely changes in water quality and temperature, dodging predators, mating and overly high fish density. Shenzhen Bay’s fish jumping could be very well explained as exhibiting mating behavior, according to the experts. ?