When we think about marine protected areas, we often think about protecting animals that don't move very far. Amongst other things, we might look to protect sedentary species like sponges or corals that themselves become home to an assortment of other marine life, or around a particular species like rockfish that tend to live in one location (have a small home range) as adults. But those very mobile species - the migrants, the nomads - don't they move far too much to gain any protection from all but the largest marine protected areas?
Creating effective spatial management measures for very mobile species is an interesting challenge - and one that I (and others) believe needs addressing. It is also the subject of my PhD thesis…
Before we get into the background, my PhD remit needs to meet certain conditions
Focus on marine protected area networks
Consider connectivity
Consider climate change
Be relevant to Canada
Great white sharks have huge home ranges, moving vast distances across the ocean. Credit Elias Levy (CC BY 2.0)
The background
The marine environment holds significant economic, ecological, and cultural importance for coastal regions like Newfoundland. To protect and ensure sustainable use of the ocean, managers and industry around the world are shifting their focus from single species management towards ecosystem-based approaches. This includes the creation of marine protected area (MPA) networks for conservation and fisheries sustainability.
Canada is a signatory to the Conservation of Biological Diversity, an international agreement that requires Canada to expand its MPAs from 1% to 10% of its territorial waters by 2020. One of the challenges facing the Canadian government is to create an MPA network that, by being greater than the sum of its parts, ensures species are adequately protected.
Rather than treat a population as a single isolated unit, an ecosystem-based approach takes into account biotic (living) and abiotic (environmental) interactions that influence the movement, distribution, and abundance of species. Many marine populations are interconnected through movement of adults, juveniles, and larvae. Furthermore, many species are highly mobile throughout their lives and may undergo migrations between key habitats. For these species, population persistence relies on the availability of a range of suitable habitats. Movement patterns and distribution is expected to be fundamentally altered by climate change and fishery pressure.
Stony corals like this one release their eggs and sperm into the sea in mass spawning events. Not all of these eggs will be fertilised, and only a small proportion of those that do will survive on ocean currents to find a new home somewhere else. Credit: Emma Hickerson/NOAA National Ocean Services (Public Domain)
Whilst the importance of understanding larval movement of largely sedentary species or those with limited movement is becoming increasingly recognised for ensuring populations persist, the spatial protection of species which exhibit greater mobility throughout their life cycle (e.g. migratory species) remains a challenge. MPA networks designed to incorporate the range of ‘essential habitats’ occupied throughout the life cycle of a species could provide critical protection and support population persistence.
For example, the protection of spawning or nursery grounds that are resilient to changing conditions may improve the chance of populations persisting in the long term. What’s more, the abundance and distribution of prey is a major driver of the movement and distribution of predators. MPA networks that include predators as conservation targets could benefit from considering the current and future distribution of major prey in their design.
By taking into account the movements of marine species at different stages in their lives and interactions between predators and prey, MPAs carefully placed into a network can ensure adequate protection for highly mobile/migratory species, maximising benefits MPAs can offer.
The thesis itself
My thesis seeks to understand how migratory/mobile species may benefit from spatial management measures like marine protected areas. I would like* to explore how connectivity is currently being considered in MPA network design and identify potential gaps that are pertinent to migratory species, and consider how current conservation planning theory is applicable to migratory species – including adapting or even creating new ‘rules of thumb’. I would also like to explore the idea of metapopulations and migratory species (two things that do not usually mix) and explore potential implications for MPA network design.
Then, homing in on some ‘real world’ scenarios, I would like to explore the movements and spatial interactions three key migratory species in the Newfoundland and Labrador ocean ecosystem - both now and under future climate scenarios:
Capelin which are recognised nationally and internationally as a keystone forage fish species in the region, and a species which has become the focus of calls for conservation management as a result of population declines.
Cod is a well-known keystone predator and (historically) commercially important species that relies heavily on capelin and has failed to recover from overfishing despite a moratorium being introduced in the early 1990s
Seabird species such as common murres and puffins which support their chicks with capelin during the breeding season.
Despite their small size, capelin can travel huge distances. This map roughly shows their movements around Iceland (until the turn of the last century). Take a look at the open-access paper by Dr. Gísli A. Víkingsson & colleagues where the maps came from.
Understanding the current and future movements of these interacting migratory species could give us insights into how we can optimise MPA networks for different migratory scenarios. For example, capelin may benefit from the protection of their spawning grounds (which are somewhat fixed in location), but equally adult and juveniles could benefit from the protection of either or both static and dynamic management – if we can identify them.
Cod may also benefit from a similar approach to capelin but with a key difference. Rather than just thinking about a single species (capelin), here we need to think about two species - cod, the predator, and capelin, the prey. Where the capelin are (or will be) could be key for cod survival. Here understanding the historic, current, and future predator-prey spatial match or mismatch between cod and capelin could offer insights into MPA network design for a migratory predator that is reliant on migratory prey.
The seabirds offer us a rather different scenario. During the breeding season, the birds are much more restricted with how far they can travel than the rest of the year, because they cannot leave their chicks for a long time. This gives us the opportunity to explore MPA network design for a spatially restricted species and mobile food source. If we want to protect the bird’s food – which is moving around - where should that protection be placed?
Stay tuned for more updates and explainers.
* PhD proposals typically evolve over time!