A new study led by the University of St Andrews, has found that Critically Endangered African penguins (Spheniscus demersus) are significantly more likely to forage in the same areas as commercial fishing vessels during years of low fish abundance, increasing competition for food and adding pressure to a species already in crisis.
Published today (17 November) in the Journal of Applied Ecology, the research introduces a novel metric called "overlap intensity" which for the first time, measures not just the extent of shared space between penguins and fishing vessels, but how many penguins are actually affected by this overlap.
The African penguin population has plummeted by nearly 80% in the past three decades, in part due to competition with the local fishery targeting sardines and anchovies a key prey for the penguins.
The local fishery is purse-seine, a large fishing net used to catch schooling fish by surrounding them.
Lead author of the study Dr Jacqueline Glencross from the Scottish Oceans Institute at the University of St Andrews, said: "We wanted a better way to assess how many penguins are potentially impacted when fisheries operate nearby — not just where the overlap occurs,"
Using tracking data from penguins on Robben and Dassen Island, the team, which included researchers from the University of Exeter, the South African Department of Forestry, Fisheries and the Environment, and BirdLife South Africa, found a sharp increase in overlap during food-scarce years. In 2016, a low fish biomass year, around 20% of penguins were foraging in the same areas as active fishing vessels. In contrast, during years with healthier fish stocks, overlap fell to just 4%.
These findings suggest that fishery-penguin competition can intensify when prey is scarce, posing the greatest risk during sensitive periods like chick-rearing, when adult penguins must forage efficiently to feed their young.
By quantifying overlap intensity at the population level, the study provides a powerful new tool to evaluate ecological risks and inform ecosystem-based fishery management. It also has practical implications for the design of dynamic marine protected areas that can respond to real-time changes in predator-prey dynamics.
The African penguin recently made headlines in a landmark South African court case, which challenged the lack of biologically meaningful fishery closures near penguin breeding colonies.
Earlier this year, the conservation and fishing industry sectors reached a high court settlement over the need for fishery closures near penguin colonies. In response, the South African government has reinstated a more biologically meaningful no-fishing zones around Robben Island, one of the key colonies studied.
Dr Glencross, added: "This research highlights why those closures are necessary. Previously unprotected areas with high overlap intensity are where the penguins were most at risk."
