HIGH RESOLUTION MAPPING AND NEW DISCOVERIES AT ROCKALL - THE OFFCON PROJECT

Introduction

Rockall, a tiny island just 19 metres high, sits on the

very extremity of Scotland’s marine environment. Some

180 miles due west of St. Kilda, it is buffeted year round

by the extreme winds and swell that the North Atlantic

weather generates. As such, it is Scotland’s only truly

offshore shallow water ecosystem. The islet of Rockall

is actually the only part of vast plateau of submerged

continent that remains above sea-level. In 2011-12,

as part of a research project (OFfshore Fisheries and

CONservation: OFFCON) that aims to map seafloor

habitats, fish distribution and fishing activities at

Rockall, two surveys on MRV Scotia were undertaken.

OFFCON project

The OFFCON surveys have shown that Rockall supports

stocks of haddock and monkfish and has a particular fish

fauna quite distinct from elsewhere in Scotland including

rare species such as the frilled shark, a living fossil. In

the deeper areas of the plateau video surveys have

revealed some of the most extensive coldwater coral

reefs in the north east Atlantic. Deeper still, at depths of

1200 m, species of bivalves and polychaete worms were

collecting with a benthic sampling net that turned out to

be new to science and are only found in association with

methane seeping from the sea-floor.

TOPIC SHEET NUMBER 92 V2

www.gov.scot/marinescotland

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DETAILED BATHYMETRY OF ROCKALL AND HELEN’S REEF AS REVEALED BY MULTI-BEAM ECHOSOUNDER SURVEY.RED AREAS ARE SHALLOWER, DARK BLUE DEEPER AND PALE BLUE AREAS THOSE AREAS TOO SHALLOW TO SURVEY.

Objective

A main objective of the surveys was to map the

shallow reef areas around the islet of Rockall

using a high resolution ‘swathe’ multibeam. This

technology allows the seabed to be mapped

to within a metre or two of spatial resolution.

What emerged was truly spectacular; numerous

previously uncharted pinnacles, trenches, mounds,

ridges and bedrock reefs were revealed. The Rock

itself turns out to be a minor feature, compared

with Helen’s reef that extends in a great sweeping

arc of fissures and ridges to the north-west.

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Between the rock and Helen’s reef is a deeper

trench which is frequented by fishermen targeting

squid.

The data collected are being used to build a better

basis for the spatial management of the area for

both fisheries and the conservation of vulnerable

and unique marine habitats. For example in

2013, data from the surveys were used by the

International Council for the Exploration of the

Sea (ICES) as a basis to protect certain areas from

potentially damaging bottom-contact fishing.

THE ISLET OF ROCKALL FRILLED SHARK

ALFONSINOS (BERYX DECADACTYLIS)