Long Forties OMR

Location and physical characteristics

Figure 1: Long Forties Offshore Marine Region. The thicker white line delineates the extent of the Long Forties OMR. For a map of all SMRs and OMRs, see Figure 5 here

Sea area (km2 34,508
Deepest point (m) 178
Shallowest point (m) 32
Average depth (m) 80
Tides (m)  0.8 – 3.9
Salinity  34.67 – 35.53
Sea surface temperature (°C) 6.9 – 15.0

The Long Forties OMR includes parts of the northern North Sea. It borders the Forth and Tay and North East SMRs to the west, and the Fladen and Moray Firth Offshore OMR in the north. Its other borders are the edges of Scottish waters.  The Long Forties OMR is the most South-Eastern Offshore Marine Region (Figure 1).

As a shallow sea, the North Sea’s temperature range within a year can be large with the sea surface temperature range in the Long Forties OMR being 6.9 – 15.0 °C, the largest of any Scottish region.

The tidal currents in the Long Forties OMR are mainly directed in a north-south direction. The residual flow is generally southward but seasonal variation in circulation exists in both strength and positioning, due to changing wind patterns. In summer, the water column in much of the OMR becomes vertically stratified due to the heat input at the surface.  At the boundary between these seasonally stratified water and permanently mixed conditions (near to the boundary with the North East and Forth and Tay SMRs), frontal jets occur which are associated with density fronts.

The Long Forties OMR lies within a relatively shallow sediment plain of the North Sea and includes sandy sediments, shelf banks and mounds that support a range of benthic species. The area immediately adjacent to the Forth and Tay SMR is considered to be a relatively closed system where localised productivity is enhanced. Diverse and fine-scale current patterns result in a mosaic of different sedimentary habitats. These include the Berwick Bank and Wee Bankie, which comprise sand and gravel habitats suitable for colonisation by sandeels. The Wee Bankie is a large offshore moraine complex environment. It comprises a series of prominent submarine ridges, around 20 m high found in water depths of around 30-50 m.


The Long Forties OMR, as with other OMRs, does not have the activities associated with an SMR such as water abstraction, salmon and seatrout fishing and aquaculture. However, the Sectoral Marine Plan for offshore wind energy draft Plan Options (2019) shows areas for development within this OMR. This means that there is a similarity between this OMR and the Fladen and Moray Firth Offshore OMR, situated to the north the Long Forties OMR.

There are further similarities between these two OMRs in terms of their historical contribution to the Scottish marine economy. Both have been significant contributors to the offshore oil and gas industry for many years. In 2018, 23.2 million tonnes of oil, natural gas liquids and gas were produced from the Long Forties OMR. Over the years, significant infrastructure associated with the oil and gas industry has developed in the Long Forties OMR including a number of hydrocarbon pipelines which ultimately make landfall in the north east of Scotland (see Oil and Gas Assessment].

Historically, there has been a significant demersal fishery in this OMR. Such a fishery continues today with current landings from one of the International Council for the Exploration of the Sea (ICES) rectangles within this OMR exceeding 2,000 tonnes in 2018.

The Productive Assessment was undertaken, with a focus on 2014-2018, on a sectoral basis. However, for four sectors, fishing, renewables, oil and gas and subsea cables, there were changes over the period 2014 – 2018 (Figure 2).

Figure 2: Changes that have taken place in the Long Forties OMR by Sector. Although the period 2014 – 2018 inclusive has been used where possible, there are some entries when a slightly different time period has been used.

Pressures from human activities

As part of SMA 2020, an assessment of the main pressures from human activities in each of the Scottish Marine Regions and Offshore Marine Regions was undertaken through a MASTS-led workshop. The process and outcomes are presented in detail in the Pressure from Activities section. Five main pressures identified for the Long Forties OMR ordered as per the MASTS-led Pressure Assessment Workshop were:

Priority [1] Pressure (FeAST classification) [2] Main healthy and biologically diverse components affected [3] Main contributing FeAST activity /activities to pressure [4] Associated productive assessments [5]
1 Surface abrasion
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Demersal seine netting (SSC, SDN, SPR)
  • Fishing - Scallop dredging (DRB)
2 Sub-surface abrasion/penetration
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Scallop dredging (DRB)
3 Removal of target species (including lethal)
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Demersal seine netting (SSC, SDN, SPR)
  • Fishing - Pelagic trawling & purse seining (OTM, PTM, TM, PS, PS1, PS2)
  • Fishing - Scallop dredging (DRB)
4 Removal of non-target species (including lethal)
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Demersal seine netting (SSC, SDN, SPR)
  • Fishing - Pelagic trawling & purse seining (OTM, PTM, TM, PS, PS1, PS2)
  • Fishing - Scallop dredging (DRB)
5 Litter
  • Fishing - Bottom otter trawling and pair trawls (OTB, OTT, PTB, TB, TBN)
  • Fishing - Demersal seine netting (SSC, SDN, SPR)
  • Fishing - Pelagic trawling & purse seining (OTM, PTM, TM, PS, PS1, PS2)
  • Fishing - Scallop dredging (DRB)
  • Infrastructure - Offshore (oil & gas platforms)
  • Shipping

Clean and safe

The assessments cover eutrophication, hazardous substances, marine litter, noise and microbiology and algal toxins which have the potential to have an impact on habitats and species as well as being a consequence of human activity. Although sources of litter or contaminants may be local, there are cases when the source is some distance from the impacted area. The main findings for the Long Forties OMR are:

Hazardous substances

Hazardous substances (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and heavy metals (Hg, Cd and Pb)) assessments in sediment and biota (fish and shellfish) were undertaken at the scale of the five Scottish biogeographic regions: Atlantic North-West Approaches, Irish Sea (Clyde and Solway), Minches and Western Scotland, Scottish Continental Shelf and Northern North Sea. Long Forties OMR is in the Northern North Sea biogeographic region. Contaminant concentrations in the Northern North Sea biogeographic region were generally above background but below concentrations where adverse effects could occur. In addition, concentrations in sediment and biota were stable or declining for all hazardous substances measured. One biota and one sediment site are the in Long Forties OMR, these sites were typical of the Northern North Sea biogeographic region, with no major concerns.

A number of biological effects were also measured and assessments undertaken at the scale of the five Scottish biogeographic regions. The contaminant specific biological effects (PAH bile metabolites and 7- ethoxyresorufin O-deethylase (EROD) activity) in the Northern North Sea biogeographic region were consistent with the hazardous substances and showed a limited exposure to contaminants. There was one fish site assessed for these biological effects and results were typical of the Northern North Sea biogeographic region.

The Northern North Sea biogeographic region showed an increase in fish disease in some years but this could not be linked to exposure to contaminants. There were two fish sites assessed for fish disease in the Long Forties OMR, results from one site at Montrose Bank were typical of the Northern North Sea, biogeographic region, although there is considerably less data for this site.

Marine litter

Due to the lack of assessment criteria for marine litter and microplastic, status assessments were not possible. However, litter and microplastics are present in all sampled OMRs. Long Forties OMR has a relatively low concentration of microplastics in surface water(< 5,000 microplastics per km2 of sea surface).

Seafloor litter was assessed at the scale of the biogeographic regions; Long Forties OMR is included in the Northern North Sea biogeographic region. The evidence indicates that there is no consistent trend in seafloor litter density between 2012 to 2018 inclusive for the Northern North Sea biogeographic region.

Healthy and biologically diverse

This section summarises the information from the Marine Protected Areas (MPAs) and intertidal and continental shelf habitats assessments from SMA2020. It also provides information from the relevant case studies relating to Priority Marine Features (PMFs), with a focus on habitats.  Further work is required to enable assessment at a regional scale for most species; this will be included in Scotland’s next marine assessment.

At a regional scale for MPAs the focus is on the number of new MPAs, MPAs with new spatial management measures, and MPAs in which spatial management measures are in discussion, as well as recognising monitoring that has been undertaken between 2012-2018.  For the marine habitats, the focus is on interpreting the relevant intertidal and continental shelf habitat assessments – biogenic habitats, predicted extent of physical disturbance to the seafloor  (BH3) and intertidal seagrass beds.  For PMFs, a summary is provided of the changes in our understanding of the habitats of most relevance to the Long Forties OMR, including changes in distribution and extent.

Marine Protected Areas

Progress in developing the Scottish MPA network

There are 3 MPAs in the Long Forties OMR that contribute to the Scottish MPA network (see Table 1).

Some of these MPAs overlap completely or partially in terms of their spatial coverage and/or the features (habitats, species, etc.) they were set up to help conserve. They are counted as separate MPAs because they have been established under different legislation which influences the way in which they are managed. Also note that there are MPAs that straddle the boundaries between different OMRs or SMRs or in some cases overlap each other. Where this is the case, these MPAs have been counted as contributing to the MPA network in all of the OMRs/SMRs in which they are present.  This means that the total number of MPAs in Scotland cannot be calculated through combining the SMR/OMR totals. Please see the Marine Protected Area assessment which contains statistics for the Scottish MPA network as a whole.

Table 1. Numbers of types of MPAs in the Long Forties OMR that contribute to the Scottish MPA network, including the number of new MPAs introduced since 2012.

Type of MPA


Total no. of MPAs

No. of new



Nature Conservation MPA




Note: The Outer Firth of Forth and St Andrews Bay Complex SPA was also established in 2020.

Progress in Managing MPAs

The progress in implementing management measures for MPAs is summarised in Table 2. This includes information on where spatial management measures are in place and where they are under discussion. It also includes information on the number of MPAs that have been monitored by statutory bodies.

Table 2. Summary of progress in managing Marine Protected Areas in the Long Forties OMR .

Type of MPA

No. of MPAs with spatial measures in place pre-2012

No. of MPAs with new spatial measures in place 2012-2018

No. of MPAs with spatial  measures under discussion 2012-2018

No. of MPAs monitored by statutory bodies 2012-2018

No. of MPAs monitored by citizen scientists 2012-2018

Nature Conservation MPA






Progress is ongoing with fisheries management options being developed in the three MPAs (Turbot Bank MPA, Firth of Forth Banks Complex MPA, and the East of Gannet and Montrose Fields MPA).

Progress in Monitoring MPAs

Information on the evidence base used to characterise the offshore MPAs in the Long Forties OMR and any subsequent monitoring is given in the Site Information Centre web page ( https://jncc.gov.uk/our-work/offshore-mpas/ ) for the following MPAs:

  • Firth of Forth Banks Complex NC MPA,
  • Turbot Bank NC MPA,
  • East of Gannet and Montrose Fields NC MPA.

For links to the MPA Surveys and monitoring reports in the East of Gannet and Montrose Fields NC MPA, see MPA Monitoring Survey Reports | JNCC - Adviser to Government on Nature Conservation

Priority Marine Features

The assessments focus on individual/ grouped habitats and species with a number of case studies reflecting more detailed research and monitoring as outlined in ‘What is assessed’. A key component of an OMR is the number and type of Priority Marine Features (PMFs) present in the region and the associated protected areas. In addition, there is concern about invasive non-native species and the impact that they are having region. With respect to these three aspects, the principal findings of SMA 2020 that are most relevant to the Long Forties OMR are summarised below.

Number of Priority Marine Features and birds (non-PMF) recorded

The Long Forties SMR / OMR is the location for a range of PMFs Table 3.

Table 3. Summary of Priority Marine Features in the Long Forties OMR .

PMFs – grouped habitats and species

No. of species/habitats recorded

Intertidal and continental shelf habitats




Mammals (regularly occurring)


Shellfish & other invertebrates


Seabirds (non-PMF) - breeding


Seaducks, grebes & divers (non-PMF) – non-breeding


  • There are 37 PMFs recorded in this region, including a range of reef and sedimentary habitats, shellfish such as ocean quahog, fish and marine mammals.
  • The region contains one of the few examples of Atlantic-influenced offshore deep-sea mud habitats on the continental shelf. The deep-sea mud is habitat to a variety of bottom-dwelling species such as bristleworms and molluscs which are an important food source for fish. Larger animals such as sea urchins and sea spiders roam the mud surface.
  • The sandier areas of the region are important for the life history of sandeels, particularly as a source for the export of larvae to the surrounding seas. Sandeels are a small fish species associated with sandy sediment that play an important role in the wider North Sea ecosystem, providing a vital source of food for seabirds such as Atlantic puffin (Fratercula arctica) and black-legged kittiwake (Rissa tridactyla), fish such as plaice (Pleuronectes platessa), and marine mammals such as dolphins. 
  • Ocean quahog is a bivalve species, living mainly in sandy and gravelly sediments. They are one of the longest living creatures on Earth and can reach an age of more than 400 years.

Climate change

There is good evidence that climate change is driving changes in the physical, chemical and biological conditions of the marine environment but the current evidence base limits the ability to draw conclusions at the scale of the individual marine regions, including Long Forties OMR. This is a combination of the lack of comprehensive spatial coverage of key monitoring programmes, the relatively short time series, and the complex linkages of climate change impacts in the marine environment.

Increasing concentrations of atmospheric greenhouse gases have caused more energy to be trapped within the Earth’s atmosphere, land and ocean. Approximately 90% of this excess energy has been absorbed by the ocean, resulting in warming ocean temperatures (see Temperature assessment and Climate change Sea temperature assessment).

The increasing concentration of carbon dioxide, one of these greenhouse gases, has the additional consequence of driving a reduction in the pH of the ocean, a process known as ocean acidification (see Ocean acidification assessment and Climate change Ocean acidification assessment).

Mean sea level is rising due to increased contributions of freshwater from melting of land-based ice (glaciers and the polar ice sheets) and due to thermal expansion of water (see Sea level and tides assessment and Climate change Sea level assessment).

The warming temperatures also result in lower oxygen concentrations due to fact that warm water holds less oxygen and changes in stratification further influence oxygen concentrations (see Dissolved oxygen assessment and Climate change Dissolved oxygen assessment). Together with increased metabolic rates in organisms resulting in increased respiration, oxygen depletion has a severe impact on marine organisms due to the impact on metabolic processes.

These changes in the physical environment are also having an impact on marine life, such as changes to their metabolism, changes in seasonality and the timing of events in natural cycles, and changes in their distribution. These changes have consequences for the growth, survival and abundance of species, including those of commercial importance or critical to conservation objectives.

At present, most of these impacts are assessed at scales greater than marine regions. The Community Temperature Index combines species temperature affinity and their abundances. This index has the potential to inform how communities change due to climate change. An example of changes in the Community Temperature Index from bottom-living fishes can be found in the Fish section within Biological Impacts of Climate Change, where more information on other impacts in marine food webs can be found (such as seabirds and marine mammals) on large regional scales in Scottish waters.

Sea surface temperature in the Long Forties region has increased since 1870 by 0.06 °C per decade on average.  The rate of increase has not been constant, and in the last 30 years (1988-2017), the rate change in temperature was +0.15 °C per decade.

Detecting and understanding long-term change in biological time series is complex and resolving that which is due to climate change remains a challenge. Data from the Continuous Plankton Recorder (1958-2017; see Plankton Assessment) show significant decreasing trends for dinoflagellate, small and large copepod, holoplankton (those plankton species who spend their entire life in the plankton community) and crustacean life forms. Meroplankton (those species who spend part of their life cycle in the plankton community) and fish larva life forms show an increasing trend. Only changes in meroplankton are significantly correlated to trends in sea surface temperature, used as a proxy of climate change.


The Long Forties OMR has seen a 29% decrease in the value of the fisheries catch over the five years from 2014-2018.  Combined hydrocarbons production increased by 52% (i.e. 8 million tonnes oil equivalent) over the five years 2014-2018.  Subsea cables length increased by 49% over the five years 2015-2019. There was 30 MW of installed wind capacity in 2018.

The five main pressures affecting the OMR are Surface abrasion, Sub-surface abrasion/penetration, Removal of target species, Removal of non-target species, Litter.  Other pressures identified are Death or injury by collision above water, Hydrocarbon and PAH contamination, Introduction or spread of non-indigenous species, Physical change, Physical removal, Reduction in availability or quality of prey, Siltation rate changes (light), Synthetic compound contamination, Transition elements & organo-metal contamination and Underwater noise.

One contaminants (i.e. PAHs, PCBs, PBDEs and heavy metals) sampling site each for sediment and biota were sampled from the OMR and were typical for the Northern North Sea with no major concerns.  There was a relatively low concentration of microplastic in the surface water and there is no consistent trend in seafloor density between 2012-2018..

Three new MPAs were designated between 2012-2018, and no new spatial management measures were put in place. Spatial fisheries management measures are under discussion for three MPAs.  One MPA was monitored by statutory bodies during the period 2012-2018.

In the last 30 years sea temperature has risen by 0.15 °C per decade.