SATELLITE MAPS WARN ABALONE FARMERS

Abalone farmers along South Africa’s coast are now using ocean colour maps to track marine algal blooms that could harm their export molluscs. Scientists from the CSIR have developed ocean colour and temperature data from satellites that is easy to access as an online tool. The work forms part of the country’s ocean economy plan to boost aquaculture jobs.

Dr Marie Smith, a marine observation expert at the CSIR, says the combination of upwelling, followed by calm conditions or marine heatwaves, can cause microscopic algae to proliferate. Abalone can be sensitive to certain species of bloom-forming algae.

Abagold is an aquaculture facility in Hermanus. Its research and sustainability manager, Sarah Halse, says there are different mechanisms of harmful algal blooms – some cause toxins which are harmful to certain species but not to others, and some are harmful in that they cause mechanical damage, for instance they might be spikey and stick in fish gills.

An abalone farm’s scientific team will routinely check for signs of harmful algae in incoming sea water. Now it is possible to use ocean colour maps from satellite data to track algal blooms before they even reach an aquaculture facility. The satellite information provides a much larger spatial scale of information that one could get by simply taking a single sample at the farm at the intake pipe.

In 2017, an algal bloom caused the death of millions of abalone in the Walker Bay area, killed as phytoplankton numbers got out of hand. Toxins that caused a harmful red tide throughout nearby bays were produced, but if satellite imagery had been available at the time, farmers would have had more time to take protective measures such as closing their intake pipes, changing their filters and adjusting feeding schedules to preserve the water quality for their abalone.

The Fisheries and Aquaculture Decision Support Tool interprets ocean colour and temperature data from the satellite, so that abalone farmers can monitor harmful red tides in near real time.

The aquaculture industry is a driver of the economy, and many jobs dependent on fisheries and the ocean have transferred to the aquaculture sector. Past, present and future satellite data is critical to safeguarding these jobs, particularly in the context of the climate crisis where frequent and intense environmental hazards like marine heatwaves could worsen red tides.

www.csir.co.za