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Connecting the dots between land and sea

Estuaries have long suffered from the separation of management between the land/sea interface. This separation has historically damaged the interests of mobile fish species that straddle both habitats.

July 2018

The view that “the bit in the middle”, the estuary, is not a distinct and important habitat, but rather a form of conduit, is outdated and simplistic but has unfortunately been a longstanding issue in the UK.

Many studies from around the world have demonstrated that estuaries provide some of the most productive aquatic ecosystems on the planet. ‘Migratory’ fish species need to move though estuaries into freshwaters to complete their life cycles. The early life stages of important ‘marine’ species such as sea bass, sole, flounder and grey mullets also need to spend part of their early life history in fresh or brackish conditions. Estuaries provide critically important nursery grounds, and yet these facts are often unknown. For example, the Thames estuary is now the largest sea bass nursery in the south of England! Recent studies have demonstrated that saltmarshes may well be the optimal nursery grounds for early life stages of species like sea bass. Yet we have lost 80% of our saltmarshes across Western Europe over the past 250 years, without understanding the scale of ecosystem services lost.

Given the high value ecosystems theses habitats provide, we should be protecting them in every possible way. To do that, we need to turn the tide on the outdated approach of separating marine and aquatic environments and take a lead from countries such as Australasia and the USA who have been protecting these resources through established management measures for decades. Europe is behind the curve. Indeed, until the arrival of the Water Framework Directive, there was no general driver to study fish ecology in estuaries. We now have a wealth of data in the UK to demonstrate how important our estuaries and intertidal habitats are for fish life.

This growth in data is reflected in the consultation on the third and final round of Marine Conservation Zones (MCZs). MCZs are an effective means of providing protective management in Estuary habitats and fish spawning aggregations can be viewed as supporting features in candidate MCZs. Of the 41 new sites and 12 additional features proposed in the latest consultation, seven are estuary sites. These offer protection for a range of unique features including coastal marshes and saline reedbeds.

Unfortunately, the linkages between land and sea in the MCZ consultation are not replicated in other marine legislation. The current English Marine Plan process offers no evident link between the new marine planning process and its terrestrial equivalent, nor is there recognition of the overlap between requirements under the UK Marine Strategy and the Water Framework Directive (WFD).

It is clear there is much to be done if we are to succeed in protecting the unique estuary habitats in England. If all the estuary sites proposed in the MCZ consultation are taken forward, this will be a great step in the right direction. However, to ensure a lasting change the Institute of Fisheries Management believes we need to embed the idea that the whole aquatic environment is a continuum and demand the drawing together (or even integration where appropriate) of all relevant management regimes.

Steve Colclough, Chair of the Transitional and Marine specialist section at the Institute of Fisheries Management.

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The opinions expressed in this blog are the author's and not necessarily those of the wider Link membership.