A win-win-win? Habitat restoration key to improving stocks, catches and marine ecosystems.

Black, Belgian, or Dover? Preferring shallower depths at juvenile stage before moving towards offshore areas, young common sole typically inhabit sandy, muddy seabeds and estuaries along the North-East Atlantic. Long coveted by European markets on account of its delicious taste and by fishermen for the price it commands, conservation of the species has traditionally been placed in the hands of fishing quotas. However, recently published SEAwise research indicates that protecting the juvenile habitats of commercial species, like common sole, may be as beneficial as regulating fishing pressure, and could yield benefits for both fish and for those who make a living catching them.

How does loss and degradation of coastal nurseries affect fish stocks?

As part of SEAwise’s efforts to gather knowledge to support the roll-out of Ecosystem-Based Fisheries Management (EBFM) in Europe, the research team investigated how loss and degradation of essential habitats affects the productivity of commercial fish stocks. They did this to understand the benefits of restoring those habitats, alongside wider efforts to regulate fishing pressure. 

The team focused their efforts on coastal areas, which often act as ‘nurseries’, meaning many fish species depend on them for their growth and survival to adulthood. Long under pressure from pollution, these habitats are facing increasing threats from activities like land reclamation, and waste water discharge. A current lack of understanding of how these activities affect the productivity of fish species means these impacts are not accounted for within measures that seek to restore fish populations and regulate fishing, such as stock assessment, advice or management. 

Working to address this, led by French Institut Agro Rennes-Angers and carried out by SEAwise’s ‘Spatial Management Impacts on Ecological Systems and Fisheries’ team, the researchers analysed the nursery habitats of four commercially important species in the English Channel – sole, plaice, whiting and seabass.

Restoration gains of more than 50% for some species

Measuring area loss to estimate the effects of habitat degradation on young fish in the area, the team investigated an array of scenarios that showed the potential effects of restoring these important habitats on fish stocks. They found that restoration would lead to substantial increases in reproductively mature stocks (in other words, fish that have survived to adulthood and are now capable themselves of reproducing) – meaning more fish in the sea and more quotas for fishermen and women in the long run!

According to the analysis, restoration of both habitat areas and quality would mean sizeable gains for some species – up to 51.8% and 27.4% in the stock of reproductively mature seabass and sole, respectively. Good news for fishers, following a similar pattern, restoration would boost sustainably set catches for these species and see annual catch gains of 65.2% for seabass and 35.3% for sole, or  810 and 1990 tons. 

Though smaller, gains would also be realised for whiting and plaice, of 327 and 957 tons respectively. Not only this, the researchers highlight that increases in fish biomass would have beneficial consequences for the sustainability of fish populations and the wider ecosystem – suggesting a win-win-win for fisheries.

Habitats key to sustainable fisheries management

How can this information support implementation of EBFM across European seas? In a context of increasing pressure on (and competition for) marine space, particularly in coastal areas, the models developed as part of this research offer marine regulators valuable knowledge in support of devising management measures to mitigate against habitat degradation. These models could also be used to identify potential conflicts arising from spatial management strategies when exploring options and planning for future seaspace changes. 

Monitoring fishing pressure still remains central to the sustainable management of fish stocks. What this research shows clearly, however, is that maintaining and restoring essential fish habitats, and especially coastal and estuarine nurseries, is also a key component in the sustainable management of stocks, and in securing healthy fisheries, livelihoods, and ecosystems into the future.