Critically endangered penguins are directly competing with fishing boats

A new study from the University of St Andrews has found that 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 increasing pressure on a species already in crisis.

Published in Journal of Applied EcologyThe study introduces a new metric called “overlap intensity,” which for the first time measures not only the extent of shared space between penguins and fishing boats, but how many penguins were actually affected by this closure.

Over the past three decades, the African penguin population has declined by almost 80%, partly due to competition from local fisheries targeting sardines and anchovies, the penguins' main prey.

The local fishery is the purse seine, a large fishing net used to catch schooling fish by encircling them.

Lead author Dr Jacqueline Glencross, from the Scottish Oceans Institute at the University of St Andrews, said: “We wanted to find a better way to estimate how many penguins are potentially exposed when fishing takes place nearby, rather than just where the overlap occurs.”

Penguins forage for food at the same time as fishing boats

Using penguin tracking data from Robben and Dassen Islands, the team, which included researchers from the University of Exeter, the South African Department of Forestry, Fisheries and Environment and BirdLife South Africa, found a sharp increase in overlap during years of food shortage.

In 2016, when fish biomass was low, about 20% of penguins foraged in the same areas as active fishing vessels. In contrast, in years with healthier fish stocks, the overlap dropped to just 4%.

These findings suggest that competition between fishers and penguins may increase when prey is scarce, posing the greatest risk during sensitive periods such as chick rearing, when adult penguins must forage efficiently to feed their young.

Implications for conservation and policy

By quantifying the intensity of overlap at the population level, the study provides a powerful new tool for assessing ecological risks and informing ecosystem-based fisheries management. This also has practical implications for the design of dynamic marine protected areas that can respond to changes in predator-prey dynamics in real time.

The African penguin recently made headlines in a landmark South African court case that challenged the lack of biologically significant fishery closures near penguin breeding colonies.

Earlier this year, the conservation and fishing sectors reached an agreement in the High Court to close fisheries near penguin colonies. In response, the South African government reinstated more biologically significant no-fishing zones around Robben Island, one of the key colonies being studied.

Dr Glencross added: “This study shows why such closures are necessary. Previously unprotected areas with high occlusion rates are where penguins are at greatest risk.”