High Rainfall and flooding result in abalone and seahorse washouts

29th September 2023

The Department of Forestry, Fisheries and the Environment (DFFE) has noted concerns around large numbers of abalone, alikreukel and other shellfish washed up in Uilkraalsmond and Buffeljagsbaai (Gans Baai) over the past 24 hours. 

This is likely a result of the exceedingly high rainfall and flooding over the past week. The fresh flood water diluted the salty seawater in the nearshore. Fish tend to move away from these areas, but slower and sessile (non-moving) invertebrates cannot and become physiologically stressed by the fresher water. This is likely why mostly abalone and other molluscs washed up, while other species such as fish and rock lobster swam and/or walked away.

High rainfall and resultant increased water flow had similar effects in other regions of the country.  In the Garden route, a substantial number of seahorses washed up on Lookout Beach. 

DFFE would like to thank all volunteers from Save the Seahorse and Cape Nature for responding en masse to collect seahorses stranded on the beach. As with the abalone, high rainfall caused the Keurbooms and Bitou rivers to swell into the coastal area. This unusual water flow caused seagrass with seahorses to wash up onto the beach, flushed out by the high flow. Seahorses were collected and taken for rehabilitation. 

Knysna seahorses are endemic to the Garden route where they are only found in 3 estuaries, they are also the most threatened species of seahorse in the world and the first listed as Endangered on the IUCN Red List in 2004. 

It is likely that other unusual washouts will occur over the next week. 

 

Issued by The Department of Forestry, Fisheries and the Environment