Recovery of the critically endangered river pipefish
The Estuarine Pipefish is a very rare relative of the seahorse, which was once thought to be extinct. It is a small (maximum size 130mm) greenish-brown fish with close-set dark lines on the head and pale lines on the body. Like the seahorse, the male pipefish look after the embryos in a brood pouch and then give ‘birth’ to the young.
Dr Whitfield and his team are studying the population numbers and condition of the Kariega estuary in the hope of finding a stable community of these fish.
Dr Whitfield with his draw-net
The estuarine system requires pulses of freshwater to support the zooplankton community on which the pipefish depend for food however further inland the Kariega is utilised to supply water to the surrounding urban and rural communities and the fresh water seldom makes it downstream. The heavy rains provide the needed freshwater however they can negatively impact the habitat
Dr Whitfield’s study involved sampling at 60 locations with a specifically designed net being drawn through the plant beds along the shallow banks of the estuary to discover what species were occurring in the area. Any species found are measured and recorded to also monitor how diversity changes with dry and wet years.
The habitat of the estuarine pipefish is a submerged plant called Eelgrass. After the floods in 2012 most of the eelgrass beds were washed away and the population was dramatically affected. The remaining grass is cord grass which although suitable habitat when submerged it is often found higher on the river banks and so exposed during low tide.
The study in 2013 revealed that although the zooplankton community is thriving, the eelgrass beds have not recovered as quickly as the team were hoping and as a result there is plenty of food but very little suitable habitat remaining for the pipefish.
The 2012 study found one male estuarine pipefish though in 2013 no individuals were found. However the 2013 study did see an increase in the number of longsnout pipefish found.
Various other species were found during the study including cape stumpnose, groovy mullet, Garrick, sole and bass.
Sibuya’s staff are able to continue aiding the research throughout the year by collecting samples of the fish caught and kept. A second team are researching the carbon and nitrogen levels found in different species. This enables them to determine what level the species is in a food chain and the source of the food chain. They predict the source of the food chain will eventually be altered after the loss of the eelgrass habitat
Find out more about the esturine pipefish in the South African Journal of Science: Recovery of the critically endangered river pipefish, Syngnathus watermeyeri, in the Kariega Estuary, Eastern Cape province