Small no-take zones can help top predators
It’s difficult to protect large marine areas from fishing – a great deal of resources must be put into patrolling and enforcing such an area. However, new research suggests that small but well-targeted protection zones can have a significant effect all the way up the food chain.
African Penguins (Spheniscus demersus) are a vulnerable species of penguin restricted to South Africa. They are threatened by human activities, such as egg collection and oil spills. Their population dropped by about 90% in the 20th Century, and has continued to drop since. There are now fewer than 26,000 breeding pairs.
Top predators, such as these penguins, are important members of an ecosystem, and removing them from an environment can ripple throughout the web in drastic ways. Pichegru et. al. (2010) looks at the effects of a small no-take zone around a penguin colony has on the success of the colony, comparing it with another nearby colony which did not get a protected zone. They measured the duration and length of their hunting trips, diving time and dive depth to calculate the effort expended by the penguins in finding food.
Over just three months, the protection had a substantial effect on the penguins. Overall, the penguins in the protected zone spent less time hunting, travelled shorter distances and stayed closer to the colony, reducing their effort spent foraging effort by 25-30%. This meant that they were able to spend an extra 5 hours each day on their eggs. They also shifted their hunting patterns – before the protected zone was created, they foraged in it about a quarter of the time, but by the end of the study they were doing over 70% of their hunting inside the zone.
It is interesting that the penguins in the control colony lost weight and spent longer foraging during the study period. It’s possible that protecting the one area shifted more of human fishing into the area around the other island. However, the positive effects on the protected colony far outweighed the negatives on the control island, and in any case the fishing wouldn’t all be shifted to the other colony. This study also didn’t look at what effects the protection may have had on the breeding or survival of the penguins – which, of course, is an important question.
Pichegru, L., Gremillet, D., Crawford, R., & Ryan, P. (2010). Marine no-take zone rapidly benefits endangered penguin Biology Letters, 6 (4), 498-501 DOI: 10.1098/rsbl.2009.0913
July 25, 2010 at 10:13 pm