Fish and Ships

Heritage consultancy Fjordr Ltd worked with Isles of Scilly Inshore Fisheries and Conservation Authority (IFCA) and marine ecologists from the University of Plymouth to start examining whether historic shipwrecks provide habitats for important fish species.

A towed underwater vehicle was used to obtain high resolution video of a First World War wreck in deep water during a wider habitat survey for fisheries management purposes. This is a step towards understanding the role that the marine historic environment may play in providing ecosystem services in relation to nature conservation, sea angling, recreational diving and commercial fishing.

Shellfish and shipwrecks

The Isles of Scilly, 28 miles off the tip of Land’s End, are well known for their shipwrecks. Over the centuries, countless ships have been snared around the rocky reefs and islets which make up the archipelago.

The wrecks are a poignant reminder of these dangers and serve as a permanent monument to the fishermen, sailors and travellers who have lost their lives around Scilly.

The last shipwreck was over 20 years ago, and today the seas around the islands are an important local fishery. Around 20 local boats use pots to catch lobster, crab and crawfish around the islands between March and November.

Wrecks provide a habitat for fish and shellfish who find protection from their predators amongst timbers, boilers or disintegrating superstructures.

Fishermen distinguish crabs that have been living around old metal wrecks by their very dark brown or black colour, thought to be caused by their proximity to ferrous metals.

Around the islands, the rocky seabed descends steeply and changes to a complex network of sand, shingle and low-lying reefs. Here, wrecks provide relatively rare upstanding features that offer habitat and shelter for fish and shellfish. For fishermen using nets and lines, these wrecks often become a target for bumper catches, but gear can also quickly become wrapped around their jagged edges. The Isles of Scilly IFCA is keen to understand how key shellfish species are using wrecks through their life history, and the extent to which they have an importance in the overall ecology of the Isles of Scilly and their surrounding waters.

Surveying habitats and heritage

Isles of Scilly IFCA contacted Fjordr and Historic England to explore the possibility of integrating a shipwreck survey with a seabed habitat survey that had already been planned. The survey, by the University of Plymouth, was to focus on obtaining high-definition video of transects of the seabed; still images from the video could then be examined for the species represented in the images. The results would then be mapped – together with sediment samples and the results of a geophysical survey carried out previously by Cornwall IFCA – to indicate the extent of different seabed habitats.

The video would be obtained using a towed underwater vehicle (TUV) deployed from a fishing boat.

The buoyancy of the TUV is balanced so that it ‘flies’ a little above the seabed while video images are transmitted through an umbilical cable to the surface, where they can be monitored and recorded.

Prior to the survey, desk-based information was collated about wrecks in the survey area from Historic England’s maritime record and other sources. Bathymetric data – which indicates the topography of the seabed – was also scanned to identify localised anomalies that might prove to be shipwrecks.

The seabed in the survey area is quite deep – typically 70-80 metres – so there are relatively few known wrecks despite the number of losses closer inshore. Several ‘targets’ were identified, including both known wrecks and more ambiguous anomalies.

Unfortunately, poor weather intervened in June 2019 when the archaeological element was due to take place, so the surveys directed towards wrecks had to be concentrated into one available day. Nonetheless, the method proved successful. Three targets were examined: one known wreck and two anomalies. In all three cases it proved possible to fly the TUV sufficiently close to the target to obtain video of sea life on the seabed and in the water column. This was no mean feat given the water depth and the localised character of the targets, reflecting the skill of the skipper and diligence of the University of Plymouth team.

One anomaly – which appeared in the bathymetric data to be the shape and size of a classic ‘three island’ cargo ship – proved to be an outcrop of boulders.

The wreck of the SS Beechcraft had a dense cover of marine life.

The other anomaly was characterised by more broken rock which again seemed more likely to be natural than a cargo. Fortunately, the known wreck was very definitely a shipwreck – the SS Beechpark, torpedoed in 1917 – and was successfully imaged in 90 meters of water. In contrast to the surrounding sandy seabed, the wreck had a dense cover of marine life, including plumose anemones, Devonshire cup coral, dead men’s fingers, encrusting sponges and ‘turf’ made up of hydroids and bryozoans (encrusting animals that form a kind of moss underwater).

Although its scope was quite limited, this piece of work demonstrated that methodologies for mapping seabed habitats could be combined with archaeological objectives, even in exacting conditions . It showed that it is possible to capture robust ecological data from historic wreck sites with equipment deployed from the surface using a relatively small vessel. Being able to quickly clarify the character of topographic anomalies – which might in other circumstances prove to be unrecorded wrecks – was also an advantage.

Shipwrecks as habitats

Management of the marine environment is increasingly discussed in terms of the benefits that it generates for society, framed as ‘ecosystem services’ arising from ‘natural capital’. As part of a wider set of case studies for Historic England, Fjordr has been examining historic shipwrecks in terms of natural capital and the ecosystem services that are obtained through nature conservation, sea angling, recreational diving, commercial fishing and so on.

Survey data on the character of shipwrecks as habitats is necessary to understand the contribution that marine heritage assets make to the biodiversity and productivity of our seas, and to the coastal communities that depend on them. The success of this trial is an important step towards more extensive interdisciplinary research that will help Isles of Scilly IFCA to achieve long-term sustainability of its local fisheries whilst conserving and enhancing the marine environment.

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