Sealife doesn’t recognise legal boundaries and territorial borders, because our seas are fundamentally interconnected by the same body of water. Larvae of fish, molluscs, corals and other marine life can flow in ocean currents to settle elsewhere, miles from the source of their original dispersal. The populations of some adult fish populations in one area can depend on nursery grounds in an entirely separate marine habitat. It is therefore of limited use protecting a population of basking sharks in a place where they are known to aggregate at one time of year, if there is no complementary protection at a site important for another life history stage elsewhere. There are also connections with land to be considered: seabirds can be protected on their land-based colonies, but if their foraging grounds at sea are not safeguarded, then a decline in food source can mean ‘protected’ populations can still suffer. All these connections should be reflected in the design of a Marine Protected Area network.
Marine Protected Areas are a very useful tool to help establish and secure these important connections. By understanding the dispersal of larvae in prevailing currents, sites can be set up and managed to maximise the spread and regeneration of particular species beyond their now reduced range. However, we are only just beginning to understand the hidden connections between different species and habitats. Some recent research discovered shark eggs nesting in the safety of a cold-water coral reef in the Sea of the Hebrides. Until this research find, the life-cycle of this shark was simply not known.
For the purposes of MPA science, Marine Scotland has defined connectivity “as the extent to which animal aggregations in different parts of a species range are linked by the exchange of larvae, juveniles or adults (Palumbi, 2003)” and “in the OSPAR context it also includes dependence of one habitat type on another for structural integrity (Roberts et al., 2003).“
The Save Scottish Seas campaign believes that connectivity is a crucial aspect of marine protected area networks and planning at sea more widely. If we do not understand the connections between the sites we are protecting and with ecosystems and habitats outwith the sites, we are in danger of creating a network with broken links, unable to fulfil its purpose.
Time is ticking
Respecting connectivity is a fundamental part of the Scottish Government’s obligation to create an ecologically coherent network by 2016. (Read our Marine Protected Area Briefing 4: Ecologically Coherent Networks for more information). But – although there has been some excellent research into the connectivity of different sites – the scientific community believes there is still much work to do. Marine Scotland Science is currently assessing which features are relevant for connectivity-based network design and management, but this research is not due to be complete until 2014. We need to prioritise this research so that the sites selected are strategically placed and managed to allow the ecological connectivity between them, thereby helping to sustain and improve the network and Scotland’s seas overall.
 Scottish Marine and Freshwater Science Volume 4 Number 2: Connectivity of benthic priority marine species within the Scottish MPA network, Marine Scotland Science, Scottish Government