Marine biologist and senior zoology lecturer Dr Nadine Strydom is the only scientist in South Africa working on the ecology of the larval stages of coastal fish, which may provide the key to preventing looming wild fish extinction.
Dr Strydom said that not enough was known about the fragile larval stage of marine fish. “The size and sustainability of any fish population is intricately linked to the success of its larval phase at the start of the fish life cycle, so it’s imperative to find out what’s needed for larval fish to be able to survive.”
She said most species of marine fish had a larval stage after hatching from the egg during which time they float around as part of the microscopic world of ocean plankton. Once the larvae have developed tail fins and can swim, they head for coastal nurseries such as estuaries, where they are safer from predators.
There, they feed and grow until they reach sexual maturity. For some fish, like the dusky kob, a popular food fish whose dwindling population is estimated to be just one percent of what it was 150 years ago, this means a five-to six-year waiting period, in which they grow to about one metre in size.
But this is a fish whose survival is doomed, said Dr Strydom, as line fish restrictions place the minimum length in which the fish can be legally removed at 60cm – before they have even had a chance to reach sexual maturity and breed at least once.
Dr Strydom’s doctoral student Paula Pattrick is documenting the various species of larval fish larvae found in the shallow waters of Algoa Bay, as part of a bigger collaborative project with the South African National Parks.