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Monitoring the consequences of the northwestern North Sea sandeel fishery closure
... During early operation of the North Sea sandeel fishery it was suggested the fishery had no impact on breeding seabirds (Furness, 2003). However, concerns about the potential impacts of fishing sandeels on seabird breeding success have occasionally led to temporary or long-term closures of fisheries (Greenstreet et al., 2010). A small, inshore sandeel fishery at the Shetland Isles opened in 1974, with annual landings peaking at just 52,000 tonnes (Dunn, 1998). ...
... Despite its small size, the fishery overlapped substantially with foraging areas of internationally important seabird colonies breeding at Shetland (Dunn, 1998). Collapse of the Shetland fishery and the subsequent decline in seabird breeding success around the Shetland Isles in the 1980s led to the precautionary closure of the fishery in 1990 (Hamer et al., 1993;Dunn, 1998;Rindorf et al., 2000;ICES, 2005;Greenstreet et al., 2010). However, although the sandeel population declined during fishery operation and recovered following its closure, this may have been caused by variation in 0-group immigration and survival rather than changes in fishery pressure (Wright, 1996). ...
... The closure appears to have caused an immediate recovery of sandeels within the area, with an observed increase in the biomass of 0-group and 1+ sandeels on the Wee Bankie within the first year (Greenstreet et al., 2006). However, by 2007 the spawning stock biomass (SSB) had declined to levels similar to those when the fishery was operating (Greenstreet et al., 2006;Greenstreet et al., 2010). This decline indicated that, even without fishing mortality, sandeel abundance will decline if recruitment cannot compensate for natural mortality (Greenstreet et al., 2006;Greenstreet et al., 2010). ...
A technical report by the RSPB on the diet of tern chicks around the UK and Ireland. This report reviews variation in tern diet across the study region, identifying three key prey species. It then reviews the ecology and distribution of these fish species, and considers current and potential future changes to their populations in response to climate-driven changes in the marine environment.
... Sandeels are important prey for many seabirds, piscivorous fish and marine mammals (see The importance of sandeels as prey, below), but are also the target of the largest (by weight) singlespecies commercial fishery in the North Sea (ICES, 2004). Due to the potential impacts on sandeeldependent species of local and regional depletion of stocks by industrial fisheries, and to ensure longterm sustainability of the fishery, it is important to monitor sandeel abundance (ICES, 2010;Greenstreet et al., 2010b). ...
... Additional evidence suggests that estimates based on different survey methods may not be directly comparable. When monitoring sandeels on the Wee Bankie before and after closure of the East Scotland sandeel fishery in 2000, Greenstreet et al. (2010b) found that, although both the acoustic survey and dredge survey showed sandeel biomass initially increased following the closure and then declined, the annual variation in biomass estimated from the two survey methods was uncorrelated (R 2 = 0.087). This is perhaps due to dredge surveys estimating sandeel biomass within the sediment while acoustic surveys estimate sandeel biomass in the water column (Greenstreet et al., 2006). ...
... van Deurs et al. (2009) showed that in years with a large population of 1-group sandeels, the positive relationship between spawning stock biomass and recruitment was decoupled. Further, following the initial recovery in sandeel abundance after closure of the fishery off Northeast Scotland and Northumberland in 2000, abundance then declined to very low levels (Greenstreet et al., 2010b). However, this decline coincided with increased survival of larvae ≤20 days old, implying that mortality rates of hatchlings increased as densities of older fish declined (Heath et al., 2012). ...
Technical report by the RSPB on the lesser sandeel, Ammodytes marinus, including a review of its ecology, population trends and importance in the food chain, causes of spatial and temporal variation, and threats to the species including climate change.
... Following closure of the sandeel fishery the north-western North Sea (Forth region) in 2000, Greenstreet et al. (2010) documented an initial and immediate marked increase in sandeel biomass. This was immediately followed by a steady decline. ...
... There was an indication of the biomass stabilising in 2005-06, at a level higher than that of 1997-99 when the fishery was operational, but 2007 saw the biomass decline again, to levels similar to those in 1997-99. Biomass was still low in 2008, but again showed evidence of recovery in 2009, likely related to a stronger juvenile group than the two previous years (Greenstreet et al., 2010). Results from monitoring the piscivorous fish showed no correlation between their biomass and the biomass of their sandeel prey. ...
... The fluctuation observed by Greenstreet et al. (2010) in the north-western North Sea (Forth region) suggested that the local abundance of sandeels is strongly dependent on recruitment, which is subject to environmental influence. Results from monitoring the piscivorous fish showed no correlation between their biomass and the biomass of their sandeel prey. ...
Background
In order to better understand the recovery process of temperate marine habitats and
species, Scottish Natural Heritage commissioned a literature review, leading to a framework
for assessing recovery potential, with a particular (but not exclusive) focus on features within
Marine Protected Areas (MPAs) which have been identified as having a conservation
objective to ‘recover’ or ‘conserve (uncertain)’. This will enable a consistent approach to
recovery (including the way it is defined and the goals for recovery) and will help to inform
and standardise the SNH approach to managing the species and habitats within MPAs in
order to maximise recovery potential.
A number of species and habitats of national and international importance have been
identified in the seas around Scotland through the Scottish Marine Protected Areas Project.
A number of these are classed as threatened and/or declining under OSPAR, and draft
conservation objectives for these features have been presented to the Scottish Government
by SNH and JNCC. However, where a ‘recovery’ conservation objective has been assigned,
further development of the potential approaches that could be followed for achieving this
objective is required. Approaches under consideration can be characterised as including the
reduction or removal of pressures and consideration of the extent over which management
might be applied in relation to the extent of the features within MPAs. However, a better
understanding of the effectiveness of these, and other, management options will enable
SNH to optimise their approach.
Main findings
A review of the literature indicated a high degree of variation in the use and interpretation
of the term ‘recovery’. It is proposed that ‘recovery’ should refer to a process or
trajectory and ‘recovered’ should refer to an end point. Separate definitions of
recovery and recovered have been proposed for individual species, communities
(including biogenic species) and habitats.
COMMISSIONED REPORT
Summary
ii
Of the species, communities and habitats reviewed, many show limited recovery potential
and of those which could recover, the timescale for recovery is likely to be long (tens to
hundreds of years). There are examples of recovery, or indications of recovery, having
been achieved as a result of pressure removal.
Factors limiting recovery included anthropogenic influence, together with aspects of the
biology of individual species and communities and environmental conditions. Of key
importance is the scale of the disturbance, the degree of habitat
homogenisation/fragmentation, species removal and the longevity of physical
modifications to the habitat. Recovery is reliant on environmental and biological
connectivity between populations or species patches and on the suitability of the habitat
in terms of substratum type, depth, water quality and sediment quality. For some species
(particularly those inhabiting soft sediments), subtle change in the sediment structure,
consolidation, stability and chemistry are of importance. Superimposed upon this are the
life history traits of the individual species, which may or may not enhance recovery
potential. These include reproductive strategy and frequency, growth rate, longevity and
dispersal ability, coupled with biological interactions between species which may
influence the direction and timescale of the recovery trajectory.
A brief review of restoration techniques indicates potential for application to a limited
number of species, particularly bivalves. However, the long-term success is unknown and
restoration should not be attempted at the expense of other management to enable
recovery and/or prevent further decline.
Management should take account of both environmental and biological connectivity and
should aim to protect the interaction between populations and sub-populations (e.g.
sources and sinks of propagules). Therefore, management should be targeted at both
physical and biological processes and management may have to be applied between
MPAs and/or beyond MPA boundaries if recovery is to be achieved.
Management needs to account for direct (near-field) and indirect (far-field) pressures.
... Indeed, sprat might actually represent a higher-quality prey resource than sandeels (Smout et al. 2013). For example, in 2000 the guillemots in the Firth of Forth switched to sprat even though they were two orders of magnitude less abundant than sandeels (Greenstreet et al. 2010a). ...
... Other fish species responding to climate change may have indirect effects on birds by interfering with the relationship between sandeels and seabirds. This interference may take the form of competition for sandeels as prey (Greenstreet et al. 2010a) or being present as an abundant but less-nutritious alternative prey. The much-reported influx of snake pipefish Entelurus aequoreus into European waters in 2003 , Kloppmann & Ulleweit 2007, Harris et al. 2008, van Damme & Couperus 2008) represents an example of the latter. ...
... The most notable example of such a measure is the sandeel fishery closure off the eastern coast of Scotland in 2000. Established with the aim of avoiding depletion of the sandeel stock, a substantial area covering approximately 21,000 km 2 was closed to sandeel fisheries (Frederiksen et al. 2008b, Greenstreet et al. 2010a). However, closing the area to fishing has not been sufficient to ensure high sandeel abundance (Figure 4). ...
After flourishing during the second half of the twentieth century, many North Sea seabird populations are now in decline. Much evidence is accumulating that climate change is driving these negative trends in growth rate. Climate-driven changes in the physical environment may affect seabirds both directly and indirectly. Direct impacts such as increasingly common extreme weather events will result in negative physiological responses. However, climate effects on seabirds are more likely to be indirect and mediated by prey quality and availability. Mounting evidence suggests that climate impacts on lower trophic levels are altering the pathway of energy to seabirds. While the basis for changes in primary production are complex and uncertain, climate-driven changes in the availability of sandeels (primarily Ammodytes marinus) and the copepod Ca/anus finmarchicus, key prey species in adjacent trophic levels, appear to be causing a reduction in breeding success and growth rate in several British seabird species.
... To obtain the true biomass of sandeels in the study area, correction factors must be applied to biomass-at-age-and-length matrices. Greenstreet et al. (2010a) measured the biomass of Firth of Forth 0-group and 1+ FIGURE 3 | Schematic of the method to estimate sandeel abundance. Input data and modelled data are highlighted in green and grey, respectively. ...
... Obtaining credible estimates of sandeel abundance-at-age is extremely challenging as fish are constantly in motion between the sediment and pelagic during summer surveys. Four different survey methods are commonly employed to measure sandeel abundance -acoustic, dredge, trawl, and grab surveys (Greenstreet et al., 2006(Greenstreet et al., , 2010a. However, it is unclear which method is most efficient. ...
Sandeels Ammodytes marinus are a crucial forage fish species in the North Sea, transferring zooplankton energy to higher trophic levels. However, there has been a sustained decline in sandeel abundance in the northwestern North Sea since 2000. Here we use field data to analyze year-to-year changes in A. marinus growth rate between 1997 and 2009 and assess whether variation in growth rate corresponded with variation in abundance. The signature of the reduction in abundance between 2000 and 2009 was a decline in age 1 sandeels, while no other age class declined. Analysis of age-length data showed that the decline in abundance coincided with a period of low growth. Growth performance indexes were correlated with zooplankton and phytoplankton biomass but not temperature. Further, we observed a significant correlation between larval growth rate and 0-group sandeel length during a period when hatch dates were relatively fixed; suggesting recent changes in length were influenced by food availability.
... When a sandeel fishery operated off eastern Scotland in the 1990s, sandeel abundance declined and black-legged kittiwakes Rissa tridactyla (hereafter 'kittiwakes') in the region showed reduced breeding success and survival (Daunt et al., 2008;Frederiksen et al., 2004;Rindorf, Wanless, & Harris, 2000). A closed area encompassing much of Scotland's east coast was established in 2000 to protect the sandeel stock: sandeel biomass initially rebounded, but has since continued to decline, likely due to worsening environmental conditions (Greenstreet, Fraser, Armstrong, & Gibb, 2010). The closure, which is still in place, appeared to provide some benefit to kittiwakes, although other seabird species showed less response to the fishery and its closure, possibly because diving or prey-switching ability may have reduced their sensitivity (Daunt et al., 2008;Frederiksen et al., 2004). ...
... Meanwhile, a more precautionary approach to management should be considered. There is a precedent for altering sandeel fishery management to mitigate predator impacts: the fishery off the east coast of Scotland was closed in 2000 in response to its impact on kittiwakes (Daunt et al., 2008;Greenstreet et al., 2010 . To aid SSB recovery and account for the needs of predators, it may therefore be appropriate to limit fishing mortality to a maximum of 0.5. ...
• In the North Sea, sandeels provide a vital food source for breeding seabirds, but are also the target of an industrial fishery. GPS tracking suggests that the most productive fishing grounds overlap with foraging areas of black‐legged kittiwakes from eastern England, raising the prospect that the fishery could affect the birds. Rising sea temperatures also threaten sandeels, so kittiwake food supplies could be affected by local and larger‐scale processes.
• Drivers of kittiwake breeding success at Flamborough Head and Bempton Cliffs Special Protection Area, the UK's largest colony, and one of the closest to the sandeel fishing grounds, were examined. Relationships between sandeel stocks, sea surface temperature and kittiwake breeding success were analysed with generalized linear mixed models and generalized linear models, with model performance assessed using the Akaike Information Criterion and R².
• Higher kittiwake breeding success was associated with higher sandeel spawning stock biomass (SSB; biomass of sexually mature fish) the preceding winter (R² = 21.5%) and lower sandeel fishing mortality two years previously (R² = 22.3%). After temporal trends were removed, only the fishing mortality effect remained. Models with multiple predictors supported the importance of fishing mortality. Higher sandeel SSB was associated with lower temperatures (R² = 15.2–38.6%) and lower sandeel fishing mortality (R² = 24.2–26.1%).
• Hence, lower temperatures and fishing mortality were positively associated with sandeel biomass, and higher sandeel biomass and lower fishing mortality were positively associated with kittiwake productivity. In light of worsening environmental conditions and declining sandeel and kittiwake populations, careful consideration should be given to the requirements of sandeel‐dependent predators when making fishery management decisions.
... Consistent with this view, Lynam et al. (2013) found that the abundance of A. marinus larvae was correlated with that of later life stages. However, estimates of A. mar-inus biomass in June off the Firth of Forth (east coast of Scotland), derived by combining data from both sediment and water column samples, indicated differences in relative YCS between age 0 and older ages (Greenstreet et al. 2010). This led Heath et al. (2012) to propose that YCS was established between June and the successive year. ...
... 6), where Loss rate iy is the loss rate for cohort i in year y. α, β 1 and β 2 are the parameters for the fixed effects on the linear and quadratic terms, u y represents the random effects, and ε iy represents the error term Greenstreet et al. 2010), suggested that variations in abundance were determined between the first summer and the following spring. As juvenile sandeel form pelagic feeding schools in June (Winslade 1971, Wright 1996, pelagic gears appear to be the most relevant sampler available to provide an index of age-0 sandeel abundance in early summer. ...
Understanding the mechanisms responsible for variability in fish recruitment can improve our ability to predict the response of marine species to environmental change. The synchrony between fish hatching and zooplankton productivity is widely considered to be a major driver in recruitment failure, but studies considering variability in the phenology of both predator and prey are scarce. Using otolith microstructure and a time series of predator and prey abundance, we studied the influence of the mismatch between fish hatching and the timing of egg production in 2 copepod prey species on recruitment variability in lesser sandeel Ammodytes marinus, a key trophic link in the North Sea. We found that year-class strength is established during early larval development in sandeel, and depends on the degree of synchrony between hatching and Calanus helgolandicus egg production. Therefore, this study identifies the critical life stage at which year-class strength is established and provides empirical support for the mismatch hypothesis in a key forage fish.
... Initial studies suggested that the closure had been partially effective, with an increase in sandeel abundance and a limited recovery in breeding success of black-legged kittiwakes (Rissa tridactyla, hereafter 'kittiwake'), the seabird species that had shown marked reductions in breeding success while the fishery was in operation (Greenstreet et al., 2006;Frederiksen et al., 2008;Daunt et al., 2008). However, subsequent work by Greenstreet et al. (2010) suggested that recoveries in sandeel abundance and kittiwake numbers at sea may have been short-lived. This fishery closure has now been in place for over two decades, yet no comprehensive assessment of the long-term impact of closure on breeding success of kittiwakes and other seabirds breeding in the region has been made since the initial studies, which were based on only six years of data post-closure (Frederiksen et al., 2008;Daunt et al., 2008). ...
... Habitat was classified as "inshore", "sandbank" or "offshore"; trawl stations within the coastal 50 m depth contour were classed as "inshore"; beyond this point, stations were classed as "offshore" unless they were , 50 m deep, in which case they were classed as "sandbanks". Annual 0-group sandeel biomass estimates were the modelled data derived from a combination of acoustic survey and demersal trawl survey data given in Greenstreet et al. (2006Greenstreet et al. ( , 2010. First, a model was fitted with all the explanatory variables included as main effects (Model 1). ...
Reilly, T. O. M., Fraser, H. M., Fryer, R. J., Clarke, J., and Greenstreet, S. P. R. 2014. Interpreting variation in fish-based food web indicators: the importance of “bottom-up limitation” and “top-down control” processes. – ICES Journal of Marine Science, 71: 406–416.
Proposed indicators for the Marine Strategy Framework Directive (MSFD) food webs Descriptor focus on structural elements of food webs, and in particular on the abundance and productivity of top predators. However, the inferences that can be drawn from such indicators depend on whether or not the predators are “bottom-up limited” by the availability of their prey. Many seabird populations appear to be “bottom-up limited” so that variation in their reproductive success and/or abundance reflects changes in lower trophic levels. Here we find that gadoid fish predators off the Firth of Forth, southeast Scotland, do not appear to be “bottom-up limited” by the biomass of their main prey, 0-group sandeels; gadoid biomass and feeding performance was independent of sandeel biomass. Variability in food web indicators based on these gadoid predators seems to impart little insight into underlying processes occurring at lower trophic levels in the local food web. The implications of this in terms of how the currently proposed MSFD food web indicators should be used and interpreted are considered, and the ramifications in terms of setting targets representing good environmental status for both fish and seabird communities are discussed.
Fisheries in all of the earth’s oceans entail direct and indirect effects on marine food webs and on seabirds in particular. Fisheries that target forage species are associated with precipitous declines of seabird populations in the eastern boundary currents of the Pacific and Atlantic Oceans. Uncertainties and variation in physical and biological conditions and in prey and predator distributions however make the attribution of fishing effects to seabird responses extremely difficult. Cascading effects associated with the removal of large piscivorous fishes and other apex predators have had both positive and negative indirect trophic influences on seabirds by either increasing or decreasing the availability of small fishes and other prey in temperate and tropical ocean systems, respectively. Fishery discards and wastes have provided otherwise inaccessible demersal food sources that have benefitted surface-feeding seabirds. Their low nutritive value (“junk food hypothesis”) and subsequent reduction and termination is however having negative effects on inflated populations of scavenger species. Bycatch in fishing gear kills hundreds of thousands of birds annually, though limited collection of systematic data underestimates total mortality. Pelagic long-lines, that target tuna, swordfishes, and sharks in tropical and temperate regions, hook and drown surface feeders (albatrosses, tube-nosed seabirds) many of which are threatened with extinction. Demersal long-lines set for groundfish in temperate, subpolar and polar waters kill large numbers of fulmars and shearwaters. Gillnets in temperate and subpolar regions entangle and drown numerous diving species (auks, penguins, seaducks). Disturbances created by light-based fishing activity for squid and forage and pelagic fishes attract nocturnal seabirds, escalating risks of collisions and gear entanglement. Marine and freshwater aquaculture sites displace and attract seabirds that are often shot, and at times, they provision predatory birds such as eagles. The feed requirements of the expanding aquaculture industry, which produces more fish than capture fisheries, will likely increase the value and intensity of forage fisheries. Increasing consumer demands for wild seafood will ratchet fishing pressure in warming oceans subject to more frequent heat waves and other extreme weather events. These circumstances will create further challenges for the behavior and ecology of marine birds and their populations and diversity. The incorporation of seabird and other predator requirements and information from seabird indicators in ecosystem management would improve biological conservation and fishing sustainability.
The UK Fisheries Audit provides an evidence-based snapshot of the status of UK fish stocks and the UK fishing sector’s recent exploitation history of those stocks, by the time the UK leaves the EU fisheries policies. In doing so, the report provides a baseline for future evaluations of the UK’s progress and/or setbacks in sustainable fisheries management.
Intense fishing of a stock of sandeels (Ammodytes marinus) on the sand banks off the Firth of Forth, northeast Scotland, during the 1990s led to a decline in catch per unit effort to uneconomic levels and collateral failures of piscivorous seabird breeding success at nearby colonies. A prohibition on fishing in 1999 was followed by a short-term recovery of stock biomass, but then a sustained decline to very low levels of abundance. Demographic survey data show that despite the decline in stock, recruit abundance was maintained implying an increasing larval survival rate, and that the stock decline was not due to recruitment failure. To verify this hypothesis we analysed a 10-year long data set of weekly catches of sandeel larvae at a nearby plankton monitoring site to determine the patterns of larval mortality and dispersal. We found that the loss rate of larvae up to 20d age decreased over time, corresponding with the trend in survival rate implied by the stock demography data. The pattern of loss rate in relation to hatchling abundance implied that mortality may have been density dependent. Our study rules out increased larval mortality as the primary cause of decline in the sandeel stock.
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