This blog post has now moved to my Marine Biology website, Marine-bio-images.com. It can be read at:
This post follows on from Lyme Bay Closed Area, a Marine Protected Area success? Part 1, which described the damage first noted on rocky reefs in Lyme bay, Southwest England, from scallop dredging during the 1990s. This post describes the voluntary agreements set up and the ongoing problems.
As described in Part 1, the condition of the reefs in Lyme Bay had begun to deteriorate markedly by the early 1990s, and this deterioration continued more or less unchecked over the next 12 or 13 years. It would however, be wrong to suggest that all reefs were suffering equally or that nothing was happening to change this situation. Some reefs were simply too rugged for any sort of mobile fishing gear to ever be towed across them, however even they suffered from degradation around the edges. Others that were more easily worked were devastated.
The Devon Wildlife Trust had been working hard with local fishermen since the early 1990s, and voluntary agreements had been set up voluntary agreements whereby trawlers and scallop dredgers would not work in the most fragile reef habitats. The first such agreement extended voluntary protection to two reefs (known locally as Lane’s Ground, a boulder reef rich in sponges, and The Saw-Tooth Ledges, a series of limestone ledges supporting abundant seafans, soft corals and sponges). Two additional reefs were added to this agreement in 2006, The East Tennants Reef, a boulder reef supporting high densities of large seafans, and Beer Home Ground, a reef of ledges and rocky promentories composed of softer mudtstone and sandstone amongst harder limestone that had suffered quite badly from reef erosion through the action of scallop dredges. However problems remained. The first was that however sincere most local fishermen were, there was always the problem that some from further afield would see no need to abide by this agreement and, it has to be said, not all local fishermen agreed with the closure. It only took one vessel operating within the voluntary closures, maybe late at night or early morning when they were unlikley to be spotted, to cause damage that would last for years. The second problem was that the four voluntary areas were small and in no way enclosed all of even the most vulnerable reefs. An example of this is the West Tennants Reef. This is an very extensive reef in Lyme Bay terms. It is a low limestone ledge, or series of ledges, that runs parallel to the shore, about 4 miles offshore and roughly 29 metres below sea level. Although only around 10-30 metres wide over much of its length, it runs east-west for over two miles. The ledge is fairly level and free of rocky protrusions, and drops less than a metre to the surrounding seabed, thus it was very easily worked from the top of the ledge, dredges running along, parallel to the edge before eventually dropping of the edge. Strong currents sweep along this ledge, and in the early 1990s a dense band of very large seafans grew along this ledge, along with significant numbers of large axinellid sponges.
The band was not wide, perhaps no more than 8-10 metres across, but extended for nearly two miles East-West. Although the East Tennants Reef nearby had higher densities of seafans but, simply due to its size, the west Tennants Reef supported more large seafans than any other reef in Lyme Bay. Indeed it was one of the most extensive continuous beds of large seafans in UK waters. Unfortunately, by 2007 most of these large seafans (and large sponges) had gone. As part of a wider study, I conducted a remote video survey along the reef in the summer of 2007. Instead of a dense continuous bed of seafans we found isolated patches and extensive areas of bare reef. We also saw many recently detached large seafans lying flat on the seabed and scallop dredgers working nearby. We returned a couple of days later to dive the reef and capture some better video. This can be seen here: West Tennants Reef, 2007.
It was clear that the situation in Lyme bay was continuing to deteriorate. Fortunately major changes to rectify this were also happening. Following a lengthy consultation process, with proposals submitted by the Natural England, Conservation NGOs (in particular the Wildlife Trusts) and the fishing industry, DEFRA announced that an area of some 60 square nautical miles in the central part of Lyme Bay was to be closed to mobile fishing gear by Statutory Order. There have undoubtedly been a few vessels that continued to work inside the closed area at night, especially during the first couple of years. However it’s fair to say that by and large this has been a success, in terms of maintaining an area free from the impacts of mobile bottom fishing gear. So how has that been reflected in changes, or recovery, of the fauna of the reefs within the closed area. In order to assess this two parallel studies were set up, one by Plymouth University using remote video, and one conducted by ourselves (that is my consultancy Marine Bio-images) with divers recording life at fixed stations. Data was collected over three summers; 2008, 2009 and 2010, and the findings of these studies have now been analysed and are about to be published. The next part of this blog will look in more detail at what we found and what seems to have changed since the closed area was established.
Update 10th July 2012, New blog: Lyme Bay, what makes it special?
All images and text (C) Colin Munro Photography.