The research was only possible due to a three-year closure of commercial fisheries 20km around Robben Island, and it was discovered that the way in which adult African penguins fish and the physical condition of their chicks are directly linked to local fish abundance.
Penguins, among other marine predators, are considered indication species, meaning their success indicates the condition of their habitat. The fisheries closure was an opportunity to see how the colony would respond to natural changes in local abundance of their prey.
They found that local availability of anchovy and sardine was directly linked to penguin foraging behaviour and chick offspring condition. This has previously been a common assumption about predator-prey relationships that has rarely been tested in the absence of fishing.
“Understanding how African penguins forage to feed their chicks in their variable marine environment can help us identify conservation measures for these endangered populations,” said Dr Kate Campbell, who led the research at the University of Cape Town. “Since these short-term changes will likely have knock-on effects for chick survival and penguin population size, they could be used as powerful early warning signs to inform fisheries’ policies and marine conservation efforts.”
The results suggest that the condition and behaviour of these penguins could act as an indicator of local fish abundance, which helps make the case that they should be included in the monitoring of local ecosystem health.
“Interestingly, the variation in foraging behaviour between individuals also increased when prey fish were scarcer,” said Dr Richard Sherley of the University of Exeter. “Once food gets harder to find, more individuals will start to struggle and work harder, but they will do so at different rates, increasing the variation we see in foraging effort.”
“Technological advances also means there’s exciting potential to better understand how these endangered penguins behave when prey resources are scarce,” added Dr Campbell.
The hope is that an effective balance between fishery management and the needs of resident penguins could be implemented in the near future, ensuring a reduced impact on the economy while still benefiting the ocean environment.
The study, ‘Local forage fish abundance influences foraging effort and offspring condition in an endangered marine predator’, was published in the British Ecological Society’s Journal of Applied Ecology.
Photographs by R. B. Sherley, courtesy of the British Ecological Society.
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