Researchers advocate shifting protected areas that move with species.

Unfortunately, it is still too common for endangered species – such as sea turtles, marine mammals or sharks – to accidentally become entangled in fishing gear and, for example, end up in fishing nets as bycatch. To address this problem, marine protected areas have been designated; permanent places in the ocean that are intended to preserve biodiversity and where, for example, fishing is not allowed. While that sounds promising, the criticism against such ‘permanently protected areas’ is mounting. Because according to researchers, this is a fairly inefficient way of protecting marine biodiversity.

Accidental Bycatch

It is far from a rarity that endangered animals inadvertently end up in fishing nets. “Unfortunately, all forms of fishing capture species other than just the target,” researcher Maite Pons said in an interview with Scientias.nl. “For example, the long-line fishery focuses on different tuna species, but sea turtles, sharks and rays can occasionally be caught. We are most concerned about the endangered species that will become entangled.”

A loggerhead turtle is accidentally caught during long-line fishing in Uruguay. Image: Philip Miller

Many countries are therefore calling for better protection of the world’s seas. The aim is even to protect about 30 percent of the oceans by 2030 against all forms of exploitation, including fishing.

Criticism

To achieve this, permanent marine protected areas have been created. But not everyone is happy about that. One of the criticisms is that many of the species that need to be protected by these areas – such as marine mammals, sea turtles and sea birds – are moving and thus swimming out of the protected areas. “The distribution of mobile species such as sea turtles and sharks changes from season to season and from year to year,” said Pons. “Many migratory species are often caught accidentally anyway.”

Shifting Protected Areas

It means that permanently protected marine areas are not sufficient to protect endangered species. But the researcher does have a solution to this problem: shifting protected areas. “Instead of static closures that only protect the species in an area where it occurs occasionally, shifting protected areas move with species,” says Pons. “In this way, they are protected throughout their range.”

Study

In the study the researchers studied 15 fisheries around the world — including the hunting of California swordfish, South African tuna and Alaska pollock. They then compared the impact of restricting fishing through both permanent and shifting protected areas. The results show that limiting fishing by 30 percent in a fixed area leads to a reduction in bycatch of about 16 percent. But in dynamically closed areas, bycatch can be reduced by as much as 57 percent. “We found that we can significantly reduce bycatch without reducing target catches,” says Pons. “And that simply by closing small fishing areas that can change from year to year. This dynamic approach is becoming increasingly important, especially as climate change is driving both animal species and fishermen to new areas.”

Confusing?

This shift will take some getting used to at first. But Pons is not so afraid that it will cause confusion. The benefits of shifting protected areas will also be significant, she says. “This does mean that there is good communication about this and that it must be enforced,” says Pons.

Predictive Model

However, according to the researcher, there is a price tag to this story. This is because it is necessary to properly map out where an animal that could accidentally become entangled in a fishing net as bycatch, is at a certain moment. The shifting protected areas are then determined on the basis of this. “Using historical data on bycatch and ocean conditions, it is possible to build a predictive model that provides insight into bycatch rates,” explains Pons. “On this basis, we can see where the bycatch will be greatest, based on things such as ocean temperature, oxygen and currents.”

Better alternative

Pons hopes the study contributes to the growing awareness that shifting protected areas may be a better alternative than permanent ones. Although the latter does not have to be completely overhauled. “Permanently closed areas are only more applicable to species that also live there permanently, such as coral reefs,” says Pons. “A key point of our paper is to show how ineffective permanently protected areas are when the goal is to protect biodiversity. And the main loss of biodiversity is due to accidental bycatch.”

According to the researchers, it is therefore time that we do our best to reduce this unintended bycatch. “We want to make the fishing community, marine conservationists and other stakeholders aware that dynamic closures can be much more effective to reduce unintended bycatch,” said Pons. “Especially when we talk about protecting mobile species. Policymakers should consider these results when considering strategies for protecting global marine biodiversity.”