African penguins on the brink of extinction: fishing vessels take away their food

A new study led by the University of St Andrews has found that critically endangered African penguins (Spheniscus demersus) are significantly more likely to hunt in the same areas where fishing vessels operate.

This increases competition for food and further increases pressure on a species already in crisis.

The work, published in the Journal of Applied Ecology, introduces a new metric called overlap intensity. For the first time, it estimates not only the area of space where the paths of penguins and fishing vessels overlap, but also exactly how many birds are affected by the overlap.

Over the past three decades, African penguin numbers have fallen by almost 80 per cent. One reason is competition with local fisheries focused on catching sardines and anchovies, the penguins' key prey. The local fishery uses purse seines - large nets used to surround schools of gregarious fish.

Lead author of the study, Dr Jacqueline Glencross from the Scottish Oceanographic Institute at the University of St Andrews, explains:

"We needed a more accurate way to estimate how many penguins are potentially affected by nearby fishing activity - not just where exactly the overlap occurs."

Using satellite tracking data on penguins from Robben and Dassen Islands, the research team, which also included experts from the University of Exeter, South Africa's Department of Forestry, Fisheries and Environment and BirdLife South Africa, found a dramatic increase in overlap during years of food shortages.

In 2016, when fish biomass was low, about 20 per cent of the penguins foraged in the same areas where active fishing vessels were operating. In years with better fish stocks, the proportion of this overlap fell to about 4 per cent.

According to the authors, this shows that competition between penguins and fisheries increases when prey becomes scarce. The highest risks occur during the most sensitive periods, such as during chick rearing, when adult birds must be particularly efficient at finding food to feed their offspring.

The quantification of 'overlap intensity' at the whole population level provides a new tool for ecosystem-based ecosystem risk assessment and fisheries planning. In addition, the results can be used in the design of dynamic marine protected areas that account for changes in predator-prey relationships in real time.

African penguins have recently been in the spotlight due to a precedent-setting lawsuit in South Africa. The lawsuit challenged the lack of "biologically justified" fisheries closures in areas near penguin colonies.

Earlier this year, conservation organisations and fishing industry representatives reached a settlement agreement in the High Court to require fishing restrictions near penguin colonies. In response, the South African government reinstated more biologically significant fishing exclusion zones around Robben Island, one of the key colonies studied in the paper.

Dr Glencross emphatically states: "Our study shows why these closures are so necessary. Previously unprotected areas with high closure rates are exactly where penguins were most at risk."