|Marine Protected Areas and Sandeels (Ammodytes marinus & A. tobianus)|
Due to their limited movements and dependence on areas of well flushed sands, sandeels are vulnerable to localised depletion. MPAs may be necessary to promote resilience within this important prey resource.
Sandeels are a priority for the North and West MPA regions (within OSPAR Regions II and III respectively) and, because of their regional ecological significance, have also been considered in the east MPA region (within OSPAR Region II).
On the basis of information on contribution and connectivity among sandeel aggregations, five important sandeel areas have been identified. It is recommended that these be included within new single or multi feature MPA search locations (see Figure 1 overleaf). One of the sandeel areas already has protective measures in place.
In the west, an area north of Lewis is proposed because it is associated with:
locally high density of larvae
presence of suitable sediment
export of larvae to other north west sandeel grounds
In the north, an area west of Orkney is proposed because it is associated with:
very high larval densities
presence of suitable sediment
extensive export of larvae affecting recruitment from Shetland to the Moray Firth
Areas off the Shetland coast in the vicinity of Mousa and south to Boddam Voe are proposed since these are the preferred areas for young of the year in the Shetland region and protecting this region would therefore minimise mortality on the recruiting fish when year class strength is low.
In the east, part of Turbot bank is proposed since this area has been subject to occasional intensive sandeel fisheries and there is little potential for re-colonisation from the Firth of Forth banks that are currently protected by a temporary closure and it can supply recruits to other east MPA grounds.
Given the protection provided by the current temporary closed area covering most Firth of Forth grounds, consideration should be given to making this closure a permanent measure.
Figure 1 MPA search locations that could make a contribution to the protection of the sandeel MPA search feature
NB this map does not show the full suite of MPA search locations in Scottish waters
Purpose of document
This interim position paper has been produced to support identification of MPA search locations suitable for conserving sandeels.
Sandeels are search feature priorities throughout the North and West MPA regions (OSPAR Region III) but none of the search locations discussed at workshop 3 include significant sandeel aggregations. Aggregations off Lewis and the north-west mainland coincide with areas used by priority cetaceans and breeding seabirds. Whilst sandeels were not included as a search feature priority in the East MPA region, some sandeel aggregations outside the current fishery closure may be important to protect due to their size and isolation from protected grounds as well as the role they play in supplying recruits to other sandeel grounds.
Distribution in Scottish waters
Following settlement, sandeels spend much of their life buried in coarse sands1 and so their settled distribution reflects the distribution of such habitat2,3. Marine Scotland Science has information on the distribution of early hatched larvae in the plankton, pre-settled pelagic 0-group and settled A. marinus. This data was collected over a range of geographical scales from ICES rectangle level (0.5° latitude x 1.0° longitude) down to < 1 km for particular banks. Detailed maps of fished areas are also available through collaborative work with Scottish and Danish fishers. Data on seabed sediments and bathymetry have been used to model the extent of potential habitat in Scottish waters. In the west region, data on areas previously fished, trawl records and suitable sediment indicate aggregations are typically < 25 km2 (Figure 2).
Figure 2 Distribution of sandeels and predicted habitat in the West MPA region
In the north, the only previously fished grounds are similarly small patches of suitable habitat around the Shetland Isles, although there is a large spawning area to the west and north of Orkney. The maximum annual landings by ICES rectangle for this region are shown in Figure 3. The east region has larger aggregations and fishing was previously concentrated around Turbot and Firth of Forth banks, although the later are mostly now protected by the north east UK precautionary fishery closure that extends out to 1°W (Figure 4). There are records from plankton and trawl surveys on the distribution of A. tobianus, although far less is known than for A. marinus as this species mostly occurs in bays from the mid-tide level over sandy shores to shallow sub-littoral depths of 30 metres.
Figure 3 Distribution of sandeels in the North MPA region. Numbers refer to maximum landing per ICES rectangle by Scottish vessels
Figure 4 Distribution of sandeels and fishing grounds in the East MPA region
Role of MPAs for sandeels
Marine Scotland’s Marine Nature Conservation Strategy advocates a three pillar approach to conservation in the marine environment; with the three pillars representing species-specific measures, site protection and a wider seas policy approach. ICES provide management advice for North Sea sandeels at a population scale, one of which (SA4, north-west North Sea) corresponds to the East MPA region4. The precautionary north east UK sandeel fishery closure (Article 29a from Council Regulation No 850/98) within this region, limits fishing on most of the Firth of Forth sandeel grounds. Turbot bank is the other major fished bank in the east region. Scottish coastal fisheries were regulated under national legislation and local plans but no landings have been made in recent years.
Due to their importance in North Sea food webs, it is important to maintain sandeel abundance at a level high enough to provide food for a variety of predator species. A number of marine predators are reliant on sandeels at particular locations and times of year and so past concerns over this species have tended to be locally focussed. The most abundant sandeel species in Scottish waters, A. marinus, is characterised by bank affiliated resident juvenile and adult life stages2,5 coupled to specific areas of sediment1 with dispersal to other areas confined to a drifting larval stage6-10 and a short pelagic juvenile phase10. This life strategy renders sandeel aggregations potentially vulnerable to localised depletion by fishing or other pressures. In addition, sandeel growth rate in Scottish waters is low relative to that of most North Sea grounds12 and areas of habitat are small relative those in the central and eastern North Sea3. Together, these factors appear to make Scottish sandeel aggregations more vulnerable to collapse than those further south and east. For these reasons temporary or permanent closures may be necessary to promote sustainable populations of this important prey resource.
To evaluate the impact of an MPA it is important to have an understanding of connectivity and the spatial scale of population processes affecting productivity. This information is available for A. marinus from a number of EU and nationally funded programmes. Tagging studies5,13 have found that recapture rate declines sharply with distance from release with very few recaptures beyond 10 km. Further evidence for limited movements of settled sandeels comes from an analysis of length composition variation across habitat patches that found aggregations > 28 km apart, even on the same bank, could have different rates of growth and mortality following settlement14. Simulations of larval duration and observations of larval and pelagic juvenile distribution indicate that young produced on Firth of Forth banks and close to the north west coast tend to be retained and that for other grounds there is generally little exchange beyond 100 kms8,9. Hence, it is possible to define the spatial scale of protection needed to reduce local mortality on settled sandeels and consider the potential export of recruits from a protected area to other aggregations.
Christensen and colleagues (2009)15 simulated the effect of an ICES rectangle scale MPA for A. marinus in the central North Sea. Their simulation indicated a net benefit to regional abundance and fishery yield by around 6 to 10 years after protection. This benefit arose from the increase in mature fish abundance in the protected area and spill over and export to adjacent banks. The implementation of the Scottish east coast closure in 2000 was associated with a reduction in sandeel mortality and an increase in availability to seabirds16,17. However, it is also important to recognise that protecting areas can only help to mitigate the natural variability in population dynamics, as fluctuations in abundance around Shetland and off the east coast have continued following fishery closures. Indeed, these natural fluctuations have led to the maintenance of the precautionary north east closure.
For areas that are currently or were historically important to sandeel fisheries, there is information on density distribution and trends in abundance. This includes an annual MSS trawl recruit survey of the 19 Shetland grounds conducted between 1985 and 2007 and an annual dredge survey of the east region since 2008. There are also various data sources for the Firth of Forth grounds going back to 1997. Annual fishery landings data are available at the ICES rectangle level. Outside these fished areas, there are records of sandeel occurrence, data on potential habitat and some records of larval distribution. Records of A. tobianus in Scottish waters largely support the view that this is a coastal species. Several process based studies since 1990 have provided a detailed understanding of population dynamics.
MPA search locations
OSPAR Region III Celtic Seas (West MPA region)
None of the existing search locations coincide with previously fished areas which are all found north of 57°N. The main areas targeted by the sandeel fishery when in operation were mostly off Lewis, north Minch and off North Rona. These areas also correspond to concentrations of newly hatched larvae in icthyoplankton surveys conducted north of 57°N. Larval transport modelling8 suggests there is no significant exchange between aggregations around Lewis and the north-west mainland with aggregations south of the Minch or east of 4°W (Figure 5). Larvae produced around North Rona tend to be advected more than 100 kms and generally to the east.
Figure 5 Density distribution of newly emerged A. marinus larvae (n.m-2 water column) corrected for cumulative mortality. Polygons give indication of extent of larval transport based on duration of 70 days. See Proctor, Wright and Everitt (1998) for further details
Sandeels are a prey to some priority species and seabirds. Former fished areas off Lewis and the north-west mainland coincide with high densities of guillemots and kittiwakes at sea during the breeding season18 and concentrations of minke whales in June, when sandeel are active19 as well as Risso and white beaked dolphins (Figure 6). Very little is known about sandeels south of the Minch, although the seabed sediments are largely unsuitable (Figure 2). Records of sandeel presence and suitable habitat within the Skye to Mull search location has been linked to Minke whale foraging aggregations near Eigg19 and Coll and Tiree20 but only in the spring when sandeels are active in the water column.
Figure 6 Area of overlap between sandeels, priority cetaceans and breeding seabird concentrations in the West MPA region
OSPAR Region II Greater North Sea - (North and East MPA regions)
During the 1980s the sandeel fishery in this region operated on 19 grounds around the Shetland Isles11. Extensive investigations of this area indicated that the habitat extent was comparatively small compared to North Sea regions and both empirical and modelling studies indicate this area is likely to be a net sink for recruiting sandeels, dependent on occasional influx of young of the year from the large spawning area to the west and north of Orkney7,11,21.
The Fetlar to Haroldswick MPA search location (formerly Bluemull Triangle to Holm of Skaw), partly contains the Balta fishing grounds (Figure 7). This ground was never particularly productive when the fishery was in operation. However, due to the isolation from grounds to the south these grounds were important to sandeel reliant seabirds breeding nearby. The waters around Mousa were an important fishing ground and the area of most persistent sandeel recruitment in Shetland10.
Figure 7 Location of sandeel grounds (orange shaded polygons) in relation to the Fetlar to Haroldswick MPA search location (green polygon) and the Mousa Special Area of Conservation (blue shaded area)
None of the previously proposed MPA search locations are likely to offer significant protection to sandeels and so new locations should be considered for long-term protection of this important forage species. These new locations need to be based on local productivity and connectivity. Local abundance, estimated from larval production, adult density or fishery landings provide an indication of local productivity. Connectivity and replication can be assessed from the magnitude and spatial extent of larval transport from sandeel grounds. Given the evidence base described above, a number of new areas of importance to sandeels can be defined as presented in Table 1.
Given that sandeels are only vulnerable to specialised fine meshed trawls and potentially scallop dredges, it is unlikely that area protection would have much impact on other fisheries. Other pressures that might alter their habitat would have to be considered.
Table 1 Summary of areas where sandeels were assessed as a potential driver in the identification of new MPA search locations
Other mobile species
Comments / Evidence
Cellar Head off Lewis
White beaked and Risso’s dolphin
Locally high density of larvae near to the presence of suitable sediment and the highest maximum annual landings of any west coast sandeel ground (11 k tonnes). Significant potential for larval export to other north west grounds8.
West of Orkney
Greater North Sea
Very important area of larval production6. Extensive presence of suitable sediment. Importance to larval export to grounds from Shetland and south to the Moray Firth8.
Mousa and Boddam Voe
Greater North Sea
Preferred areas for young of the year in the Shetland region as indicated by persistent 0-group settlement regardless of year-class strength11. Accounted for highest fishery landings.
Greater North Sea
Part of north west North sub-population (ICES SA4). Subject to occasional intensive sandeel fisheries with summed landings from 1984-1997 of 49204 and 94319 tonnes in ICES rectangles, respectively. Larval export south and east but potential for exchange from Firth of Forth banks is sporadic and low that are currently protected by a temporary closure.
Eastern extent of sandeel fished ground (east of 00° 10’ E) corresponds to the edge of the bank, with a predominantly mud sediment (Scotia 2000 survey).
Firth of Forth banks
Greater North Sea
Part of north west North sub-population (ICES SA4). Much of this area is currently protected by the precautionary north east UK sandeel fishery closure (Article 29a from Council Regulation No 850/98) which requires re-opening criteria to be agreed between the UK and Denmark.
Issues and opportunities
Sandeels were not considered a search feature priority in the East MPA region largely because of the precautionary closure presently in force. The most important area in terms of historical landings and as a foraging area for marine predators is the Firth of Forth banks. However, sandeels from the protected Firth of Forth banks are rarely likely to provide a source of recruits for areas such as the Turbot bank7 because the local hydrographic conditions tend to retain larvae. Turbot and the associated banks have been subject to occasional and intensive fishing pressure and little is known about the local consequence of this17. Therefore, whilst the sub-stock approach to management implemented by ICES17 since 2011 reduces that risk, it is worth considering closing part of the fished grounds to minimise any risk of localised depletion and promote re-colonisation from adjacent areas. However, Turbot and the associated banks are not especially important to breeding seabirds or cetaceans.
The new proposed locations would provide sufficient replication in the MPA network for sandeel based on model estimates of larval transport. Further research by MSS is ongoing to test past model estimates of connectivity, using otolith microchemistry.
The north east UK sandeel fishery closure closed area has had a positive benefit to sandeel abundance16 and reliant predators17. However, as this is a temporary measure it is worth considering whether more permanent protection is warranted.
Where possible, locations important for sandeels will be integrated with other search feature priorities to develop new MPA search locations for presentation to workshop 4. Other important areas form new MPA search locations that are specific to this species.
Following discussion at the MPA workshop 4, there may be revisions to the search locations to take account of any new information on this species or related search feature priorities.
1. Wright, P.J., Jensen, H. and Tuck, I. (2000). The influence of sediment type on the distribution of the lesser sandeel, Ammodytes marinus. Journal of Sea Research 44(3-4): 243-256.
2. Wright, P.J., Pedersen, S.A., Donald, L., Anderson, C., Lewy, P. and Proctor, R. (1998). The influence of physical factors on the distribution of lesser sandeel, Ammodytes marinus and its relevance to fishing pressure in the North Sea. ICES, Copenhagen (Denmark).
3. Freeman, S., Mackinson, S. and Flatt, R. (2004). Diel patterns in the habitat utilisation of sandeels revealed using integrated acoustic surveys. J. Exp. Mar. Biol. Ecol. 305(2): 141-154.
4. ICES. (2010). Report of the Benchmark Workshop on Sandeel (WKSAN), 6-10 September 2010, Copenhagen, Denmark. ICES CM 2010/ACOM:57.
5. Kunzlik, P.A., Gauld, J.A. and Hutcheon, J.R. (1986). Preliminary results of the Scottish sandeel tagging project. ICES, COPENHAGEN (DENMARK).
6. Munk, P., Wright, P.J. and Pihl, N.J. (2002). Distribution of the early larval stages of cod, plaice and lesser sandeel across haline fronts in the North Sea. Estuarine Coastal and Shelf Science 55(1): 139-149.
7. Wright, P.J. and Bailey, M.C. (1996). Timing of hatching in Ammodytes marinus from Shetland waters and its significance to early growth and survivorship. Marine Biology 126(1): 143-152.
8. Proctor, R., Wright, P.J. and Everitt, A. (1998). Modelling the transport of larval sandeels on the north-west European shelf. Fisheries Oceanography 7(3-4): 347-354.
9. Christensen, A., Jensen, H., Mosegaard, H., John, M.S. and Schrum, C. (2008). Sandeel (Ammodytes marinus) larval transport patterns in the North Sea from an individual-based hydrodynamic egg and larval model. Canadian Journal of Fisheries and Aquatic Sciences 65(7): 1498-1511.
10. Jensen, H., Wright, P.J. and Munk, P. (2003). Vertical distribution of pre-settled sandeel (Ammodytes marinus) in the North Sea in relation to size and environmental variables. ICES Journal of Marine Science 60(6): 1342-1351.
11. Wright, P.J. (1996). Is there a conflict between sandeel fisheries and seabirds? A case study at Shetland. In Aquatic predators and their prey. Edited by S.P.R. Greenstreet and M.L. Tasker. Fishing News Books, Blackwell Science, Oxford. pp. 154-165.
12. Boulcott P., Wright P.J., Gibb F., Jensen H. and Gibb I. (2007). Regional variation in the maturation of sandeels in the North Sea. ICES Journal of Marine Science, 64: 369-376.
13. Gauld, J.A. (1990). Movements of lesser sandeels (Ammodytes marinus Raitt) tagged in the northwestern North Sea. J. Cons. Ciem. 46(3): 229-231.
14. Jensen, H., Rindorf, A., Wright, P.J. and Mosegaard, H. (2011). Inferring the location and scale of mixing between habitat areas of lesser sandeel through information from the fishery. ICES Journal of Marine Science 68: 43-51.
15. Christensen A., Mosegaard H. and Jensen, H. (2009). Spatially resolved fish population analysis for designing of MPAs: influence on inside and neighbouring habitats. ICES Journal of Marine Science, 66: 56-63.
16. STECF/SGMOS 07/03 (2007). Working group report on evaluation of closed area schemes.
17. Daunt, F., Wanless, S., Greenstreet, S.P.R., Jensen, H., Hamer, K.C. and Harris, M.P. (2008). The impact of the sandeel fishery closure on seabird food consumption, distribution, and productivity in the northwestern North Sea. Canadian Journal of Fisheries and Aquatic Sciences, 65: 362-381.
18. Wright, P.J. and Begg, G.S. (1997). A spatial comparison of common guillemots and sandeels in Scottish waters. ICES Journal of Marine Science 54: 578-592.
19. Anderwald, P., Evans, P.G.H., Dyer, R., Dale, A, Wright, P.J. and Hoelzel, A.R. (in press). Spatial Scale and Environmental Determinants in Minke Whale Habitat Use and Foraging. Marine Ecology Progress Series.
20. Macleod, K., Fairbairns, R., Gill, A., Fairbairns, B., Gordon, J., Blair-Myers, C. and Parsons, E.C.M. (2004). Seasonal distribution of minke whales Balaenoptera acutorostrata in relation to physiography and prey off the Isle of Mull, Scotland. Marine Ecology Progress Series 277:263-274.
21. Poloczanska, E.S., Cook, R.M., Ruxton, G.D. and Wright, P.J. (2004). Fishing vs. natural recruitment variation in sandeels as a cause of seabird breeding failure at Shetland: a modelling approach. ICES Journal of Marine Science 61(5): 788-797.