Les Minquiers – A Natural History. Part 2

minquiers-30-7-2016-photo-by-hgyoung-27Marine habitats

Intertidal habitats

The intertidal habitat map has been compared with aerial photographs taken in 1944, 1980, 2003 and 2005. This suggests that the intertidal area at Les Minquiers is in good condition and there has been little measurable change in the type, size and location of its habitats. With the exception of some sand movement, the reef’s intertidal ecology seems to have remained stable during the past 70 years.

Unfortunately, not measurable from historical aerial photography is small scale ecological damage that can result from activities such as low water fishing and boating, such as not returning boulders. In 1956 it was reported that ormer fishermen were not returning rocks and that this was killing off under-boulder fauna to such an extent that it was affecting shellfish stocks on the reef. Survey work at Les Minquiers since 2013 suggests that while some ormer fishermen still do not return rocks, this is not happening enough to cause widespread habitat and species destruction.

Low water fishing activities should periodically be quantified to avoid some of the problems that have occurred on the nearby Chausey Islands. Compared with the French coast, pursuits such as raking, digging and ormering are at a low level on Les Minquiers and much that does occur tends to be within the anchorage at Maîtresse Île or on adjacent sandbanks. Raking has the potential to disrupt or destroy stable infaunal communities and is especially problematic in areas of eelgrass but when conducted on a small scale, habitats can recover and be repopulated from nearby areas. Promoting good practice regarding low water fishing will assist with the conservation of key intertidal habitats. Other potential but currently minor problems include the placing of moorings in eelgrass areas, the dumping of fishing gear and the threat from oil or other chemical spillages.


The intertidal environment at Les Minquiers is diverse and mostly pristine. From Les Minquiers – A Natural History

Subtidal habitats

Assessing the nature and quality of subtidal habitats at Les Minquiers has been problematic and there is much work left to do in this area. Diving, aerial photography and fisheries data all suggest that the seabed from chart datum to around five to ten metres in depth is probably in good condition with little obvious evidence of degradation. An exception to this is an eelgrass area to the south-west of Le Rocher du Sud which, in 2003, showed clear evidence of having been heavily dredged causing considerable damage.

Deeper water areas have not been assessed since the 1970s but modern fisheries data indicate that the seabed to the east, south-east and north-east of the plateau has been regularly fished using mobile gear. The state of these seabed areas has not been ascertained but it is possible that they may have been damaged by commercial fishing and be in a degraded condition and/or affected by the accumulation of the American slipper limpet (Crepidula fornicata).

Some form of seabed survey, possibly by remote camera, is desirable, especially in areas that the PhD study of Retière (1979) records as having had maerl. Non-mobile métiers, such as potting and line fishing, do less harm and, apart from instances of lost gear, are unlikely to cause long-lasting seabed damage.

Rocky subtidal habitats are of less interest to dredgers and trawlers and evidence from divers, and the fisheries data, suggest that there has been little damage to rocky reefs or large areas of exposed bedrock on the seabed. Subtidal rocky habitats contain many delicate species such as sea fans, sponges and anemones and should be conserved whenever possible.


A sponge on Les Sauvages – a particularly important underwater site to the south-east of Les Minquiers. From Les Minquiers – A Natural History

Marine Species

A general lack of data pre-1992 makes it difficult to discern any population trends for marine species found at Les Minquiers. There is sufficient anecdotal information to suggest that a number of species have either disappeared from the reef or have noticeably declined. This includes the conger eel, sea bass, common octopus, slipper lobster, flat oyster and eelgrass, although their decline is probably related to factors outside of the reef such as regional overfishing, disease and climatic events. A severe decline in the ormer population is related to a combination of historical overfishing and, in 1999, disease. There has been some recovery since the 1990s but the population is at an historical low and further conservation measures may be needed to assure the ormer’s long-term regional future.

The reef has also gained some new species, some of which have migrated up from southern Europe and there are seven invasive species that have arrived from neighbouring coasts. Invasive species can present a real threat to the local marine environment and some, such as wireweed (Sargassum muticum), have permanently changed habitats within Les Minquiers. Fortunately, the Plateau des Minquiers seems to have fewer invasive species than neighbouring coasts although it is possible that the American slipper limpet may be affecting deeper water sediment areas. It is only through international regulation and meaningful biosecurity measures that future arrivals can be minimised in the north-west European area.


Over 600 marine species are known from Les Minquiers. From Les Minquiers – A Natural History

Biodiversity on Les Minquiers

The table below summarises the number of species recorded from Les Minquiers from three separate periods of time: pre-1950; 1950 to 1999; post-1999. These periods broadly reflect elevated levels of recording that occurred either side of World War II and individual surveys during the 1950s, 1970s, 1990s and at the start of the current century.

It is probable that the number of species recorded on Maîtresse Île is an accurate reflection of the island’s overall biodiversity and that there has been a loss of plant and breeding bird species since the end of World War II. The resident arthropods have probably remained stable and may even have increased with the renovation of the huts from the 1970s onwards. Microscopic animals, such as mites and diatoms, and lichens have only recently been studied.

It is probable that the number of recorded marine species in the table is an underestimate with the total diversity probably being double or treble this total. Further targeted research will produce more records, especially in subtidal areas. Historical records are not good enough to discern whether there has been a decline in most marine species although this it is suspected in some cases.


A summary of biodiversity on Les Minquiers for three time periods: pre-1950; 1950-1999 and post 2000 together with the total number of species recorded overall. From Les Minquiers – A Natural History

Environmental threats, causes and solutions

The information gathered during the course of this project suggests that Maîtresse Île is under considerable environmental pressure. Of particular concern is the issue of soil erosion which presents an immediate threat to the island’s wildlife and infrastructure. Addressing it is primarily a matter of awareness, stakeholder cooperation, management and infrastructure maintenance although there are some factors, such as rising sea levels, that cannot be tackled solely at a local level.

In the marine realm the greatest threat is from the fishing industry and especially the use of mobile gear (such as dredges and trawls) on the seabed which can cause serious and irreparable damage to habitats and species. A review of ecosystem services suggests that Les Minquiers is an area of high biological productivity with habitats that make it an important nursery area for commercial fish and shellfish species. This has been suspected for some time and as early as the 1930s it was suggested that the reef was important to regional fish stocks.

It is probable that conserving the nursery function of Les Minquiers will have a greater long-term economic return for the fishing industry than the short-term rewards gained from damaging its benthic habitats. It is, therefore, important that as much of the reef as possible is designated as a no mobile fishing gear zone but especially the shallow marine habitats on the Plateau des Minquiers most (but not all) of which are at present undamaged.

Some other common solutions include the need for increased management, monitoring and awareness and there are a number of major potential threats (such as climate change, oil slicks and invasive species) that require international cooperation. However, in the short term it is local and regional management that offers the best and most immediate means of conserving the key ecological, infrastructural and cultural attributes of Les Minquiers.

Historically Les Minquiers has been managed via an informal relationship between the States of Jersey, the Crown, hut owners and regional fishing authorities. However, in recent years other organisations and groups have been founded whose remit covers the reef including the Ramsar Management Authority, the National Park and the Maîtresse Île Residents’ Association. Exactly how the reef should best be managed and how this may best be accomplished without becoming intrusive or overbearing to its stakeholders, remains a matter for discussion.

About Les Minquiers Project

The project to study Les Minquiers was begun in 2012 by three members of the Société Jersiaise’s Marine Biology Section. They had been working on Les Écréhous and Paternosters and were aware of the importance and fragility of Jersey’s offshore reefs. They were aware that little was known about Les Minquiers and decided that they would take a look to see what could be done to rectify this.

The initial plan was to just look at the reef’s marine biology (its most obvious natural asset) but it became quickly apparent that almost every aspect of Les Minquiers needed documenting. The team soon expanded to include botanists, ornithologists, entomologists, divers, geologists, archaeologists, meteorologists and all manner of other specialists. Every conceivable thing was studied, from single-celled organisms through to the reef’s complex political and cultural history. In the end the project had nineteen principal contributors plus over 50 others who assisted with fieldwork, data crunching, logistics and archive research.

The projects results have been written up into a book which is available in a limited edition hardback (from Société Jersiaise only here) and a paperback. Any profit from the hardback edition will be used to pay for the project’s cost, most of which has been funded by the participants themselves.


Le Minquiers – A Natural History