Durban – The South African Association for Marine Biological Research (Saambr) has revealed that uShaka Sea World has been assisting Durban Point Waterfront Management Association with the management of the Point Waterfront Canal ecosystem.
This is done through the supply of filtered water flow at a rate of 250-300m3/hour every hour, as well as daily water quality checks by its internal microbiology team, and through managing the fish within the canal.
Saambr’s Ann Kunz said: “There are more than 50 species of fish in the canal, with many species selected to manage marine algal growth (thus grazer fish) as well as sediment-sifting fish such as spotted grunters and sand steenbras. The fish thus not only add to creating a natural ecosystem but can also be viewed by the public as an ‘outside aquarium’ at no cost.”
Kunz said that the water quality in the canal is very good and due to its natural state does, from time to time, experience algal blooms. These are not harmful to the inhabitants and are a natural occurrence due to temperature increases and sunlight.
She said the animals are not impacted by these blooms, if anything they contribute to higher oxygen levels during the day and often to higher zooplankton presence, natural food to some of the fish, especially the smaller fish and larval fish.
uShaka Sea World’s aquarium curator, Dr Justin Hart, said: “In 2013 permission was granted to build a 25m² enclosure for growing out various species, from striped bonito to little hammerhead sharks.
“The sharks have actually thrived in this environment and their presence offers a great educational opportunity. They are released once our scientists feel they have reached a size where they are less likely to be at risk from other predators (mainly other shark species) as well as when we feel they are reaching a maximum size for the enclosure.
“The sharks, which are monitored daily, are fed four times per week. In the ocean, the survival rate of juvenile sharks is very low due to predation and this enclosure thus offers a safe space for the juvenile sharks to ‘outgrow’ the most sensitive and risky phase of their life-cycle.”
Kunz added that the current hammerheads have grown really well over the last year and are nearing release time. The hammerheads are listed as threatened or protected species and we make sure that we offer them optimal care.
She said they work closely with the Department of Forestry, Fisheries and Environment and inform them of planned releases.
Last year, Saambr removed two giant trevally (kingfish) from the Point Waterfront Canal and released them into the ocean at Vetch’s Pier.
In 2018, four kingfish were introduced into the Point Waterfront Canal with the intention of helping to control the large numbers of small fish in the canal.
They had done really well in the canal over the past four years and had more than doubled their size. Based on their large size, the decision was made to catch, tag and remove them from the canal, Kunz said.
“In a carefully planned operation, the aquarists used a ‘drag’ net to encircle the kingfish in the shallow section of the canal near the pedal boats. Once they were netted, they were carried on a stretcher to the waiting transport tank on a trailer,” Kunz said.
“We only managed to catch two of the four. They were tagged with a yellow ORI spaghetti tag, weighed and measured before they were released.”
Daily News