Weekend Argus (Saturday Edition)
Fleeting visitors shimmer in Aquarium’s underwater ballet
THEY are paying only a short visit, so don’t miss the large shoal of sardines that have just arrived at the Two Oceans Aquarium.
Their shimmering underwater ballet is quite breathtaking, says Two Oceans Aquarium sustainability manager Helen Lockhart.
She describes how the fish form a tight ball to protect themselves against potential predators in the exhibit, including yellowfin tuna, dusky kob and striped bonito.
“When the larger fish approach the shoal, the silvery fish move in the opposite direction in a single ribbon-like motion. Should an individual become separated from the shoal, it runs the risk of becoming a snack for one of the predators,” she explains.
“We would love to have them on display permanently as they are so beautiful to watch.”
The sardines will only be in the exhibit for the next few weeks.
Lockhart jokes that the other inhabitants of the I&J Ocean Exhibit will also miss the sardines once they’re gone, as they provide “such tasty snacks”.
The sardines were donated to the aquarium by the Santa Monica, a tuna-fishing vessel that uses live sardines as bait. Using seine nets, the crew collects shoals of sardines and keeps them alive in the ship’s hull. They then pump live pilchards into the surrounding water to attract tuna to the side of the boat.
As soon as there are sufficient numbers of tuna close to the boat, the crew switch to spraying jets of water on to the surface of the ocean to sustain the tuna’s interest. The tuna are then caught on baited hooks on short lines attached to bamboo poles, hence the term “pole-caught tuna”. This fishing method, Lockhart says, is probably one of the most eco-friendly and sustainable methods.