Africa’s only penguin species is being pushed into sharper competition with commercial fishing vessels during periods of low fish availability, placing the already-declining seabird under even greater pressure, a new study has warned.
The research, published Wednesday in the Journal of Applied Ecology by the University of St Andrews, introduces a new metric titled “overlap intensity.”
Unlike conventional mapping methods that simply chart where penguins and fishers cross paths, this metric estimates how many penguins are directly affected when purse-seine boats operate inside their foraging grounds.
African penguins (Spheniscus demersus) have witnessed an almost 80% collapse in their numbers over the past three decades. Scientists have long pointed to competition with sardine and anchovy fisheries both crucial to the penguins’ diet, as a major factor behind this dramatic decline.
Purse-seine vessels, which use encircling nets to target schooling fish, work extensively along the species’ coastal range.
“We needed a clearer way to understand how many birds are actually impacted when fishing occurs nearby not just how often the two overlap on a map,” said lead author Dr Jacqueline Glencross of the Scottish Oceans Institute.
Using high-resolution tracking data from breeding colonies on Robben and Dassen islands, researchers from St Andrews, the University of Exeter, South Africa’s Department of Forestry, Fisheries and the Environment, and BirdLife South Africa observed sharp contrasts between good and bad years for fish stocks.
In 2016, a year marked by low fish biomass, about 20% of tagged penguins were forced to forage in waters where purse-seine vessels were active. In years with healthier fish populations, overlap dropped significantly to roughly 4%.
According to the researchers, these spikes in competition are most dangerous during the chick-rearing period, when adults must complete shorter, more efficient feeding trips or risk failing to raise their young.
By applying overlap intensity at the population level, the team says the metric can help evaluate ecological risk more accurately and support ecosystem-based fishery management. It could also inform the design of adaptive marine protected areas that shift based on real-time environmental and prey conditions.
The study comes at a crucial moment for South Africa’s penguin conservation efforts. Earlier this year, African penguins were at the center of a high-profile court case over inadequate fishing closures near breeding colonies. Conservation groups and industry representatives ultimately reached a settlement supporting stronger, biologically justified no-fishing zones.
Following the ruling, the government reinstated expanded closures around Robben Island, one of the primary study sites.
