Draft Fisheries Assessment – The Barra Fan and Hebrides Terrace Seamount NCMPA: Fisheries management measures within Scottish Offshore Marine Protected Areas (MPAs)

1. Introduction

1.1 Scope of The Barra Fan and Hebrides Terrace Seamount NCMPA assessment

The geographic scope of this assessment covers the whole of The Barra Fan and Hebrides Terrace Seamount NCMPA (Figure 1). The purpose of this assessment is to determine whether the current levels of fishing would or might hinder the conservation objectives of The Barra Fan and Hebrides Terrace Seamount NCMPA, and to help identify options for management measures.

In this assessment, Scottish Ministers use the best available evidence to review the site characteristics and current fishing activity (Part A), both taken alone and in combination with other relevant activities (Part C), to determine if the fishing activities are capable of affecting the protected feature. Any fishing activities capable of affecting the protected features, either alone or in combination with other relevant activities, are considered further to assess whether they would or might hinder the achievement of the conservation objectives (Part B).

Where there is the potential for the achievement of the conservation objectives to be hindered, management measures are identified for the site by the Scottish Ministers. These measures are considered in light of the conservation objectives, biological characteristics, current fishing, other activity levels and existing fisheries restrictions for The Barra Fan and Hebrides Terrace Seamount NCMPA. A final decision on which measures, if any, are to be adopted, will follow upon a statutory consultation exercise and will take into account all relevant statutory obligations incumbent upon Scottish Ministers.

A methodology document has been prepared to aid understanding of these assessments.

1.2 Site Description

Situated to the west of Scotland, adjacent to the boundary with Irish waters The Barra Fan and Hebrides Terrace Seamount Nature Conservation NCMPA follows the seabed from the top of the Hebridean continental slope as it descends into the deep Rockall Trough and beyond (Figure 1). The ‘Fan’ is a geological protected feature of the site that was created when a large build-up of sediments underwent a series of submarine landslides. These landslides have subsequently been modified by water currents, and were long ago gouged by icebergs grounding on the seabed during past ice ages. The Barra Fan is regarded as scientifically important because the morphology and sedimentary sequences have helped in furthering understanding of regional-scale palaeoceanographic changes as well as fluctuations in the extent of the last British Ice Sheet.

On the continental slope part of the NCMPA, mud, sand and gravel habitats are home to worms and other creatures that have adapted to living buried in and on the seabed. The base of the continental slope provides conditions for the establishment of burrowed mud habitat; specifically seapens and burrowing megafauna communities, which are considered Threatened and/or Declining across the North-east Atlantic by the OSPAR Commission. To the west of the site, the Hebrides Terrace Seamount rises to a height of almost 1km above the surrounding seabed and is thought to represent a remnant of an ancient volcano. The seamount supports a diverse range of marine life, including cold-water corals and deep sea sponges. These seamount communities are considered to be Threatened and/or Declining by the OSPAR Commission across the North-east Atlantic, as are orange roughy (Hoplostethus atlanticus); a long-lived deep-water fish found associated with The Hebrides Terrace Seamount.

The seamount is thought to be significant to the health of Scotland’s seas due to the effect it has on the movement of underwater currents, which bring a good supply of food to the area. The resulting rich diversity supports many fish species, which in turn attract larger marine animals, such as sharks and whales.

The Barra Fan and Hebrides Terrace Seamount NCMPA has been designated for the following protected features:

• Burrowed mud
• Offshore subtidal sands and gravels
• Offshore deep sea mud
• Orange roughy
• Seamount communities
• Continental slope
• Seamounts
• Geodiversity features – prograding wedges, continental slope turbidite canyons, slide deposits scour moat, continental slope, Hebrides Terrace Seamount, iceberg ploughmark fields

The Conservation Objective for The Barra Fan Hebrides Terrace Seamount Nature Conservation Marine Protected Area is that the protected features listed below:

• so far as already in favourable condition, remain in such condition; and
• so far as not already in favourable condition, be brought into such condition, and remain in such condition.

With respect to burrowed mud, offshore deep-sea muds, offshore subtidal sands and gravels and seamount communities, this means that:

• extent is stable or increasing; and
• structures and functions, quality, and the composition of characteristic biological communities (which includes a reference to the diversity and abundance of marine fauna forming part of or inhabiting each habitat) are such as to ensure that they remain in a condition which are healthy and not deteriorating.

Any temporary deterioration in condition is to be disregarded if the habitats are sufficiently healthy and resilient to enable their recovery from such deterioration. Any alteration to that feature brought about entirely by natural processes is to be disregarded.

With respect to orange roughy, this means that the quality and quantity of their habitat and the composition of their population are such to ensure that the population is maintained in numbers which enable them to thrive.

Any temporary reduction of numbers is to be disregarded if the population of orange roughy is thriving and sufficiently resilient to enable its recovery from such reduction. Any alteration to that feature brought about entirely by natural processes is to be disregarded.

With respect to the iceberg ploughmark field, prograding wedges, continental slope turbidite canyons, slide deposits, scour moat, continental slope and Hebrides Terrace Seamount representative of The Barra Fan & The Peaches Slide Complex Key Geodiversity Areas, this means that:

• their extent, component elements and integrity are maintained;
• their structure and functioning are unimpaired; and
• their surface remains sufficiently unobscured for the purposes of determining whether the points noted above are satisfied.

Any obscuring of the features entirely by natural processes is to be disregarded. Any alteration to the features brought about entirely by natural processes is to be disregarded.

With respect to the area of the continental slope and Hebrides terrace seamount large-scale features, this means that:

• their extent, distribution and structure is maintained;
• their function is maintained so as to ensure that they continue to support their characteristic biological communities (which includes a reference to the diversity of any species associated with the large-scale features) and their use of the site for, but not restricted to, feeding, courtship, spawning, or use as nursery grounds; and
• the processes supporting it are maintained.

Any alteration brought about entirely by natural processes is to be disregarded.

For burrowed mud (seapens and burrowing megafauna), seamount communities, offshore deep-sea muds, orange roughy, and offshore sands and gravels, and iceberg ploughmark field, the feature condition has been assessed by JNCC as being ‘unfavourable’. For Continental slope, seamount and, prograding wedges, continental slope turbidite canyons, slide deposits, scour moat, continental slope and Hebrides Terrace Seamount representative of The Barra Fan & The Peaches Slide Complex Key Geodiversity Areas, the feature condition has been assessed by JNCC as being ‘favourable’.

More information regarding the designation of The Barra Fan and Hebrides Terrace Seamount NCMPA is available in the Designation Order.

More information regarding the conservation objectives and feature condition for the protected features of The Barra Fan and Hebrides Terrace Seamount NCMPA is available within the site’s Conservation Advice package.

With regards to the scope of this assessment, JNCC considers that the large-scale features (seamount and continental slope) and the geological / geomorphological features are unlikely to be impacted by fishing activities within the site. As such, these features are not considered further in this assessment.

1.3 Activities assessed

The assessments consider the impacts of fisheries activities at each NCMPA in terms of the conservation objectives stated for the designated sites. This was deemed appropriate in order to assist in identifying potential management measures.

In this context, the implications of fishing activity in view of the conservation objectives for the NCMPA are being assessed through the fisheries screening stage (Part A), the fisheries assessment (Part B), and the in combination (cumulative effect) assessment (Part C).

Fisheries assessments use the best available evidence to fully consider potential impacts of commercial fishing activity, and in-combination (cumulative) effects with other activities, against the conservation objectives for the site. If the assessment concludes that use of certain fishing gear types would or might hinder the achievement of the conservation objectives of the site, management measures will be considered.

Commercial sea fishing activity has the potential to vary in nature and intensity over time. This assessment considers fishing activity based on activity levels and type between 2015-2019. This date range was considered to provide the best available data on current fishing activity levels for the assessment. Using a five year date range provides an average view of fishing activity within the site; latter years (2020 – 2021) were not considered representative of regular fishing activity due to the Covid pandemic. The selected date range (2015 – 2019) was used consistently across all assessments within the consultation package. Changes in fishing activity after this time period may be considered in future reviews of this assessment (see Section 6).