The availability and quality of data for assessment in the UK's Great North Sea and Celtic Seas sub-regions meant it was not possible to produce a robust trend analysis, but it is possible to say, with low confidence, that there was no significant change over time (2009 and 2014) in numbers of newly recorded non-indigenous species in UK waters.
UK Target on Non-indigenous Species
This indicator is used to assess progress against the target set in the Marine Strategy Part One (HM Government, 2012), which requires a reduction in the risk of introduction and spread of non-indigenous species through improved management of high-risk pathways and vectors.
Key pressures and impacts
Non-indigenous species are organisms that have been moved into new areas outside their natural range by human activities such as shipping, recreational boating and aquaculture (for example, Figure 1). The presence of these species can exert significant impacts on the marine environment and may result in social and economic impacts.
Measures taken to address the impacts
Limiting the introduction of non-indigenous species is the most cost-effective way of reducing the pressures and impacts they can cause. Measures to reduce the number of new introductions have been set out in the UK Marine Strategy Part Three (HM Government, 2015) and include the implementation of a number of existing statutory and voluntary measures to manage key pathways and vectors.
Monitoring, assessment and regional cooperation
Areas that have been assessed
The assessment of newly recorded non-indigenous species took place in the UK portion of the Greater North Sea and the Celtic Seas.
Monitoring and assessment methods
This assessment is based on historical data. The majority of these historical records comes from secondary sources, such as scientific studies, citizen science or chance observations, although some come from dedicated programmes designed to look for non-indigenous species. A monitoring initiative for non-indigenous species was introduced in 2016 in recognition of the threat that they can pose.
No assessment threshold is currently set but work is underway in OSPAR to address this.
The UK is the indicator lead in OSPAR and the UK results are being used in the OSPAR Intermediate Assessment 2017.
The indicator on which the non-indigenous species target assessment will be based includes three parameters. Together, these parameters will be used to determine the effectiveness of the UK programme of measures designed to reduce the number of new non-indigenous species introductions, their rate of establishment and spread. Specifically, the parameters are:
- Introduction parameter: examines the number of new introductions of non-indigenous species into geographical areas allowing for assessments of trends in introductions over time.
- Community abundance parameter: examines the total number of established non-indigenous species present within a geographical area allowing for assessments of trends in those communities over time.
- Dispersal parameter: assesses the distribution of established non-indigenous species, allowing for changes in their distribution to be assessed over time.
Only the introduction parameter is considered for this initial target assessment. The main reasons are:
- preventing the introduction of non-indigenous species is the most cost-effective management approach, assessing rates of the new introductions should take higher priority than assessing their subsequent abundance and dispersal, and
- the other two parameters require more detailed data on non-indigenous species than are currently available.
The UK implemented a monitoring initiative in 2016, where existing biodiversity monitoring programmes were also tasked with the collection of data for non-indigenous species. Prior to this, monitoring of non-indigenous species was ad hoc and inconsistent, including elements of research studies, citizen science initiatives and chance observations. Marine Strategy Framework Directive monitoring and reporting in the UK for marine non-indigenous species is focused (but not exclusively) on two lists of high priority species. High priority species are those that have either:
- been identified as an invasive species (they have an environmental impact) and are recognised as established in UK waters, or
- have been identified as having the potential to be an invasive species or have been recorded as an invasive species elsewhere but are not yet established in UK waters.
The lists were compiled by risk assessment and horizon scanning processes established by the Great Britain Non-Native Species Secretariat. The species lists were established in 2015.
Despite the limitations of available information, data on new records of non-indigenous species from 2003 to 2014 are used in this assessment. The assessment refers to newly recorded non-indigenous species rather than new introductions to reflect the fact that new records may not actually refer to non-indigenous species recently introduced, for example, if there is a lag between introduction and detection or, detection is at locations outside the initial introduction site. Interpretation of analysis using these data should, therefore, be precautionary. Future assessments will use data from monitoring implemented in 2016 enabling a more accurate assessment with increased confidence in interpretation.
Use of an OSPAR-agreed common indicator facilitates comparison of UK target assessment with other contracting parties and increases our ability to understand the changes in the introduction and spread of non-indigenous species in the UK and in a wider context.
This assessment is based on data from new recordings of non-indigenous species made between 1st January 2003 and 31st December 2014 for UK Celtic Seas and UK Greater North Sea. The time period was selected as it represents two six-year periods (2003 to 2008 and 2009 to 2014) from which available data were. Data include the date that non-indigenous species were first detected and the location of the observation. The records were gathered from the Non-Native Species Information Portal for Great Britain, a UK government led initiative tasked with collating records of non-indigenous species. Records from Northern Ireland were gathered directly from the Department of Agriculture, Environment and Rural Affairs. This analysis provides a demonstration of the comparison of newly recorded non-indigenous species between two 6-year reporting periods.
Data were checked in Microsoft Excel 2016 for taxonomic discrepancies and formatting issues which were then addressed. All analysis was conducted using R Studio Version 0.98.994 (a programme for statistical computing and graphics). Analysis was based on the first newly recorded non-indigenous species in UK Celtic Seas and UK Greater North Sea. For this assessment, duplicated records for species within each UK sub-region were removed so that numbers recorded for each UK sub-region were not overestimated. Crucially, it was ensured that the first record (earliest) for a species was used. The following metrics were assessed:
- The total number of newly recorded non-indigenous species per year for UK Celtic Seas and UK Greater North Sea: the total number for each region between 2003 and 2014 was calculated using the count function and cumulative function.
- Comparison of numbers of newly recorded non-indigenous species between six-year reporting periods for UK Celtic Seas and UK Greater North Sea: a T-test (a statistical hypothesis test) was used to determine whether there was any significant difference between the mean number of new records made in reporting period 1 (2003 – 2008) compared to reporting period 2 (2009 – 2014). This analysis was used to identify any potential emerging trends in the number of new records of non-indigenous species.
Findings in the UK Initial Assessment in 2012
Around 60 non-indigenous species have become established in UK seas and this number is increasing. The impacts of most concern are those on intertidal and shallow subtidal habitats, particularly around the south and south-western coasts of the UK, where studies suggested there are more non-indigenous species compared to the rest of the UK.
More non-indigenous species were recorded in the Celtic Seas compared to the Greater North Sea during the assessment period, although there was no significant change over time in the number of new records in either region. These results for UK waters are comparable to those for the wider OSPAR Regions. Precautionary interpretation of the data below is required given the lack of consistent monitoring historically.
A total of 37 non-indigenous species, not previously reported in the UK Celtic Seas, were first recorded between 2003 and 2014, compared to only nine in the UK Greater North Sea. The number of newly recorded non-indigenous species was greatest in the Celtic Seas in 2012 (followed by 2006) and in the Greater North Sea in 2004 (Figure 2). No newly recorded non-indigenous species were reported in 7 out of the 12 years used in the assessment for the UK Greater North Sea and 2 out of the 12 years for the UK Celtic Seas. There is no clear trend in the years where none were reported for the UK Greater North Sea or the UK Celtic Seas, although the possible cyclic pattern observed in the UK Celtic Seas could be due to variations in monitoring effort. Data from the UK Celtic Seas showed approximately 3 new records of non-indigenous species being made each year of the reporting period, while for the UK North Sea only one new non-indigenous species was recorded each year. These results may be a result of variation in monitoring effort and/or reporting over time, rather than a change in the numbers of non-indigenous species being introduced.
In the UK Greater North Sea, two species (both sea squirts) of the nine non-indigenous species recorded within the assessment period are on the UK Marine Strategy Framework Directive’s priority species monitoring list and a further two species (both crabs) are on the Marine Strategy Framework Directive’s priority species surveillance list. In the UK Celtic Seas, 11 species of the 37 recorded within the assessment period are on the priority species monitoring list (1 shrimp, 4 molluscs, 1 toxic micro alga, 2 macro algae, 2 sea squirts and 1 bryozoan) and one species (a crab) is on the surveillance list.
The availability and quality of the data meant that it was not possible to produce a robust trend analysis, but it has been possible to say with low confidence that there was no significant change over time in the number of newly recorded non-indigenous species in either region.
- In the UK Greater North Sea, newly recorded non-indigenous species ranged from 0 per year (in 2006-2008 and 2010-2013) to 4 (in 2004), while in the UK Celtic Seas they ranged from 0 per year (in 2005 and 2013) to 12 (in 2012).
- The mean number of newly recorded non-indigenous species in each year was 3.083 for the UK Celtic Seas, and 0.75 for the UK Greater North Sea.
- The cumulative number of newly recorded non-indigenous species (Figure 2) provides an indication of changes over time. In the UK Greater North Sea sub-region there was very little change in the total number apart from between 2003 and 2004. In the Celtic Seas sub-region there were two years (2006 and 2012) where comparatively high numbers were recorded resulting in a non-linear increase in cumulative number of non-indigenous species records.
For the UK Greater North Sea there are fewer newly recorded non-indigenous species during period 2 (2009-2014) compared to period 1 (2003-2008). There are 6 newly recorded non-indigenous species in the UK Greater North Sea in period 1 compared to 3 in period 2. For the UK Celtic Seas there are more newly recorded in period 2 compared to period 1. Specifically, there are 17 newly recorded in period 1 compared to 20 in period 2. The differences in records between period 1 and period 2 may be due to a variation in monitoring intensity or delays in the reporting of data. The mean number of newly recorded non-indigenous species reported in period 1 is greater than that reported in period 2 for the UK Greater North Sea. For the UK Celtic Seas, the mean number newly recorded in period 1 is less than that in period 2. However, there is no significant difference between the number in reporting period 1 and reporting period 2 for either region. The results from the analysis are summarised in Table 1.
Mean number of newly recorded non-indigenous species per year
Significant difference between means
Reporting period 1 (2003-2008)
Reporting period 2 (2009-2014)
UK Celtic Seas
UK Greater North Sea
The number of newly recorded non-indigenous species was compared between two six-year reporting periods: 2003 to 2008, referred to here as reporting period 1 and 2009 to 2014, referred to as reporting period 2. In the UK Greater North Sea, fewer were reported during period 2 than during reporting period 1 (table 1). While the opposite occurred in UK Celtic Seas, with more reported during period 2 compared to period 1. However, these differences were not statistically significant in either region (Table 1).
- Two species from the priority species monitoring list (sea squirts: Didemnum vexillum and Asterocarpa humilis) were reported from the UK Greater North Sea. These species are reported here as they were introduced and became established during the period covered by this assessment. A further two species (crabs: Hemigrapsus sanguineus and Hemigrapsus takanoi) are on the priority species surveillance list. These species were introduced during the assessment period but are not yet considered to be established.
- In the UK Celtic Seas, 11 species reported are on the priority species monitoring list (shrimp: Caprella mutica; molluscs: Crassostrea angulata, Crassostrea gigas, Crepidula fornicata and Diadumene lineata; toxic micro algae: Heterosigma akashiwo; macro algae: Heterosiphonia japonica and Undaria pinnatifida; sea squirts: Styela clava and Didemnum vexillum and bryozoa: Watersipora subatra). These species are reported here as they were introduced and became established during the period covered by this assessment. One species (crab: Hemigrapsus sanguineus) is on the surveillance list, as this was introduced during the assessment period but not yet considered to be established.
It is difficult to say from this assessment if the UK target has been met. The numbers of newly recorded non-indigenous species in both UK sub-regions do not appear to vary a great deal over time. More have been recorded in the UK Celtic Seas than in the UK North Sea. The lack of consistent monitoring effort and/or reporting over the assessment period is likely to be the major compounding factor in interpreting these results. Introductions may have been recorded sometime after the introduction event occurred or was missed entirely. This may especially be the case at locations where introductions are most likely to occur, such as ports and marinas where there is limited monitoring effort. It is therefore difficult to say with confidence whether existing measures for the management of high risk pathways and vectors have had an effect in reducing the rate of introduction and if the UK target has been met. New monitoring initiatives for non-indigenous species instigated in 2016 should provide consistency in detection effort and may improve the quality of data and our confidence in future assessments of introduction, while also facilitating assessments of spread.
While the assessment indicates that the number of newly recorded non-indigenous species has not changed over time, and indeed it would appear that those newly recorded in the UK North Sea decreased from reporting period 1 (2003-2008) to reporting period 2 (2009-2014), although not significantly, there are issues associated with the data and therefore interpretation of the assessment results. These issues include:
- There is limited available information on monitoring effort applied to the detection of non-indigenous species in the UK Celtic seas and UK Greater North Sea during the assessment period. Without this information, it is not possible to determine whether the number is positively correlated with monitoring effort so that, years with greater monitoring effort see greater numbers, or conversely in years where there is less monitoring effort fewer new records were made. For example, monitoring for non-indigenous species and raising awareness was undertaken between 2008 and 2011 as part of a large-scale project (Cook and others, 2011) and may have contributed to the increase in the number reported in the UK Celtic Seas between 2008 and 2012 (assuming possible delay in reporting).
- There is limited information relating to the methods used for detecting non-indigenous species nor their sensitivity and/or suitability. Without an understanding of the methods applied it is difficult to determine their suitability, with some species not being detected even where monitoring was conducted, as suitable monitoring methods were not applied to detect certain non-indigenous species.
- A lack of monitoring for non-indigenous species at locations most at risk from their introduction, such as ports and marinas, may decrease the probability of them being detected at the location and time of their first introduction. In addition, a lack of monitoring at high risk locations limits accuracy with which we can attribute introductions of species to specific pathways and therefore assess effectiveness of individual pathway measures.
- Limited monitoring could lead to potential discrepancies between the location where a non-indigenous species is first recorded and where it was introduced. Differentiating between populations resulting from introduction events and populations resulting from spread events is therefore very difficult.
- Though interpretation of the assessment should be precautionary, it does suggest that current measures are not reducing the risk of introductions occurring in UK Celtic Seas and UK Greater North Sea.
- The data available for this assessment lack consistency in the methods used for detection and recording to enable robust observations and conclusions in relation to trends in non-indigenous species introduction. The analysis was conducted with the data available and the confidence in the method is moderate, but the confidence in the data availability is low and thus confidence in any conclusions drawn from the data is low.
- Monitoring: The UK still lacks monitoring programmes at high risk locations, which limits the power of detection at key points of introduction such as ports and harbours.
- Impact: There are knowledge gaps in relation to marine invasive non-native species in our waters, the level of impact they have and, in some cases, how they are introduced and spread.
- Spread: The current assessment only examines the introduction of non-indigenous species. Assessment of spread is also crucial to determining Good Environmental Status with respect to non-indigenous species.
- Measures: Our current Programme of Measures consists, in the majority, of current biosecurity. Although the assessment is inconclusive, it does indicate that there has been no change in the number of new records of invasive non-native species being made, suggesting that improvements in the Programme of Measures need to be made.
To expand further on the knowledge gaps identified above:
- The monitoring that is currently being undertaken is limited in its ability to detect invasive non-native species. This is partly as the programmes are not targeted towards these species as their primary objective, particularly those species of greatest concern (that is the listed species).
- There is very little monitoring conducted in ports and marinas for invasive non-native species and none that is consistent and persistent. This leaves a considerable gap in our understanding of where, and when, species are arriving. It also limits our ability to rapidly respond to new incursions.
- Our current understanding of monitoring effort in relation to invasive non-native species is limited and so it is difficult to distinguish between changes in the introduction rates of these species as a result of the Programme of Measures or, changes in monitoring effort and therefore ability to detect species.
- Greater understanding of the impacts that marine invasive non-native species cause would aid in identifying which species we need to target the most. This is particularly important with limited resources.
- Understanding how invasive non-native species impact key native species and habitats would greatly assist in the assessment of other descriptors under the Marine Strategy Framework Directive.
- Our understanding of the pathways of spread of non-indigenous species within UK waters, and those locations most at risk from spread, is limited.
- Spread has not been assessed here due to the lack of reliable data but with further monitoring effort and the creation of a baseline, it could be included in future assessments.
- Our current Programme of Measures focuses almost exclusively on managing pathways of introduction. More effort is required to implement measures to limit spread of key species.
- More robust measures to manage pathways of introduction are required.
- We need to increase our understanding of where, and to what degree, the Programme of Measures is being implemented. This will be important in using results of further assessments to inform the Programme of Measures to ensure that targets are met, and Good Environmental Status is achieved.
Cook EJ, Baker G, Beveridge, CM, Bishop, JDD, Brown L, Clark PF, Huys R, Jenkins S, Maggs C, McCollin T, Mieszkowska N, Mineur F, Wood C (2011). ‘Marine Aliens II – Controlling Marine Invasive Species by Targeting Vectors of Dispersal’. Final Report. SAMS Report Number 274
HM Government (2012) ‘Marine Strategy Part One: UK Initial Assessment and Good Environmental Status’ (viewed on 5 July 2018)
HM Government (2015) ‘Marine Strategy Part Three: UK Programme of Measures’ (viewed on 5 July 2018)
OSPAR (2017) ‘Intermediate Assessment 2017’ (viewed on 21 September 2018)
|Assessment Type||UK Marine Strategy Framework Directive Indicator Assessment|
Descriptor 2. Non-indigenous species do not adversely alter the ecosystem
Changes to non-indigenous species communities
OSPAR CEMAP Guidelines Common Indicator NIS3: Changes to non-indigenous species communities
|Point of contact firstname.lastname@example.org|
|Metadata date||Friday, June 1, 2018|
|Title||Trends in newly recorded non-indigenous species introduced by human activities in the United Kingdom’s Greater North Sea and the Celtic Seas sub-regions|
The assessment is based on evidence that suggests no significant difference in the number of new records of non-indigenous species detected between the two six-year periods (2003 to 2008 and 2009 to 2014) used in the assessment. This indicates no significant reduction in the risk of introduction of non-indigenous species over this time period as a result of the measures in place.
Work related to the wider implementation of Descriptor 2 of the Marine Strategy Framework Directive is available from the GB non-native species secretariat.
|Conditions applying to access and use|
© Crown copyright, licenced under the Open Government Licence (OGL).
The indicator used is a UK-lead OSPAR common indicator. The indicator has been developed with input from both the OSPAR non-indigenous species expert group and the UK Marine Pathways Group. Data was sourced from administrations across the UK.
Data are new records of non-indigenous species made between 1st January 2003 and 31st December 2014 for UK Celtic Seas and UK Greater North Sea. The time period used was selected as it represents two six year periods (2003 to 2008 and 2009 to 2014), from which data was complete and available. The data enables comparison of new records of non-indigenous species between two 6 year reporting periods to be demonstrated. Data include the date that new records of non-indigenous species were first made and the location of the observation.
Separate data were received from Great Britain and Northern Ireland. Data were checked in Microsoft Excel 2016 for taxonomic discrepancies and formatting issues which were then addressed.
All analysis was conducted using R Studio Version 0.98.994 (a programme for statistical computing and graphics). Analysis was based on the first new record of a non-indigenous species in UK Celtic seas and UK Greater North Sea. For this assessment, duplicated records for a species within each UK sub-region were removed so that numbers recorded for each UK sub-region were not overestimated. Crucially, it was ensured that the first record (earliest) for a species was used.
Stebbing and Tidbury (2019). Collated new Non-native species records for UK from 2003-2014 Cefas, UK. V1.doi: https://doi.org/10.14466/CefasDataHub.80
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Recommended reference for this indicator assessment
Stebbing, P.D. 1 & Tidbury, H.J.1 2018. Trends in newly recorded non-indigenous species introduced by human activities in the United Kingdom’s Greater North Sea and the Celtic Seas sub-regions*. UK Marine Online Assessment Tool, available at: https://moat.cefas.co.uk/pressures-from-human-activities/non-indigenous-species/newly-recorded-non-indigenous-species/
1 Centre for Environment, Fisheries and Aquaculture Science