Penguins and fishing boats clash over dwindling pockets of fish

African penguins are in trouble, and the pressure is not just from the weather or the waves. When their prey thins out, they often end up hunting in the same places as commercial boats.

A new study tracked where the birds searched for food near two South African islands and measured how tightly their paths matched those of purse seine vessels.

In 2016, a year with scarce anchovy, about 20 percent of penguin foraging locations overlapped with active fishing grounds.

The research team was led by Dr. Jacqueline Glencross, a seabird ecologist at the Scottish Oceans Institute at the University of St Andrews.

The researchers set out to investigate how often and how intensely penguins and boats used the same patches of sea. They also looked at how this changed between lean and plentiful fish years.

Where penguins and boats meet

The team introduced overlap intensity, a population-level measure that weighs how many penguins and how many fishing events share the same grid cells – not just whether they happen to cross paths.

This strategy helps reveal pressure points where many birds and boats converge at once.

To place fishing activity precisely, the team used signals from the Automatic Identification System (AIS).

The shipborne transmitter broadcasts a vessel’s identity and position for safety and monitoring. Earlier work showed how these data can map global fishing behavior at fine scales.

Penguins packed into fishing zones

In 2016, the overlap intensity was high because penguins and purse seiners concentrated in the same cells during a year of low anchovy recruitment.

The same analysis found that spatial overlap by area was small, yet many penguin locations still fell inside the zones where fishing occurred.

That difference matters. Spatial overlap can look modest if shared cells are few, but it misses how many birds are actually present.

Overlap intensity captures that population pressure, which is what determines whether chicks get fed.

Lean fish years raise the stakes

The African penguin is listed as Critically Endangered, a status confirmed by BirdLife. When prey shoals shrink or shift, adults must travel farther or search longer, and any extra competition with boats can tip a tough season into failure.

The 2016 spike fits that picture because anchovy recruits were unusually low that year. When prey is patchy, both birds and boats are drawn into the same productive pockets.

This situation squeezes a species that is already stretched by chick-feeding demands.

Fishing nets change everything

The local fleet uses purse seine gear, a wraparound net that encircles schooling fish and cinches closed at the bottom, capturing an entire shoal.

Even a single set can remove a lot of prey from a small area, which is why the fine-scale view is important.

“We wanted a better way to assess how many penguins are potentially impacted when fisheries operate nearby,” said Dr. Glencross.

Closures that follow the fish

South Africa has now put fresh limits on purse seining near key colonies. The move follows a legal settlement that established ten-year closures around six sites, including Robben and Dassen.

The court order mandates year-round no-take zones of about 12 miles and requires a review after six years.

This new map of protected waters lines up with the study’s finding that most risky overlap sits inside the experimental closure areas when they are open to fishing.

Better aligned boundaries can push effort off the hotspots where birds need quick, efficient foraging.

Guiding smarter penguin protections

Managers can update overlap intensity as new tracks and fishing records arrive, allowing them to tune closures to where pressure actually builds.

That is useful because penguins are central-place foragers (CPF), animals that must return to a nest site, which limits their range during chick rearing.

The metric also highlights predator-dominated overlap, cells where many more penguin locations than fishing events occur.

Protecting those places may deliver more benefit per square mile, especially in lean years when every successful trip counts.

People, penguins, and pressure

African penguins anchor local identity and tourism, and purse seine fisheries support coastal jobs.

A clear map of when and where they clash can reduce conflict, since low overlap, fishery-dominated cells can remain open with minimal conservation cost.

The method is straightforward. It uses GPS tags on birds, public vessel data, and a grid-based calculation that any management team with basic analytical capacity can run.

“This research highlights why those closures are necessary. Previously unprotected areas with high overlap intensity are where the penguins were most at risk,” concluded Dr. Glencross.

The study is published in the Journal of Applied Ecology.

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