Trends in New Records of Non-Indigenous Species Introduced by Human Activities

D2 - Non-Indigenous Species

D2.1 - Abundance and state characterisation of non-indigenous species, in particular invasive species

Non-indigenous species are not only a major threat to marine biodiversity, but can also have considerable socio-economic impacts. Newly recorded species have been encountered at a relatively constant rate in the areas assessed. Preventing the introduction of non-indigenous species is considered the most cost-effective approach to management.

Area Assessed

Printable Summary

Background

Non-indigenous species (NIS) introduced by human activities are organisms moved into new areas outside their natural range by, for example, transfer of ships’ ballast water, biofouling (accumulation of organisms on ships’ hulls) and aquaculture. Species that naturally increase their range are not taken into consideration, however, NIS that spread to neighbouring areas by natural means following introduction (secondary dispersal), are still considered to be NIS.

The presence of NIS can exert pressures on the marine environment with possible social, economic or environmental impacts. Invasive NIS are one of the most significant threats to global biodiversity. Removing NIS subsequent to introduction is very difficult, which means preventing their introduction is the most cost-effective approach to management, thus avoiding costs and the need for eradication measures.

This assessment focuses on trends in new records of NIS introductions into the OSPAR Maritime Area, to determine the effectiveness of measures aimed at reducing NIS introductions.

This assessment is based on new records of NIS provided by OSPAR Countries, acknowledging limitations in these data, such as discrepancies between when the presence of a new NIS was recorded and when it was actually introduced. New political initiatives (for example, the European Union Invasive Alien Species Regulation and the Marine Strategy Framework Directive (MSFD)) mean that monitoring programmes focused on detecting introductions of new NIS, are starting to be developed. These will, in time, strengthen the data available and therefore the assessment of this indicator.

The invasive sea squirt Didemnum vexillum covering a holding tank at an oyster rearing unit (courtesy of Cefas)

The indicator on which this assessment is based includes three parameters that are used to determine the effectiveness of a programme of measures designed to reduce the number of new non-indigenous species (NIS) introductions, their rate of establishment and their spread.

  1. Introduction parameter: This examines the number of new introductions of NIS into geographical areas, enabling assessments of trends in introduction over time.
  2. Community abundance parameter: This examines the total number of established NIS present within a geographical area, enabling assessments of trends in the NIS community over time.
  3. Dispersal parameter:This examines the distribution of established NIS, enabling an assessment of changes in the distribution of NIS over time.

Only the introduction parameter is used in this first assessment. The main reasons being that (a) because preventing NIS introductions is the most cost-effective management approach, assessing (rates of) new introductions themselves should have a higher priority than assessing their subsequent abundance and dispersal, and (b) the other two parameters require more detailed data on NIS which are currently not widely available for the period considered in this assessment, mainly owing to the lack of current monitoring for NIS.

Despite global recognition of the threat of invasive NIS, there has been no coordinated and sustained regional monitoring of new NIS introductions in the OSPAR Maritime Area. While some OSPAR Countries do monitor for NIS, others do not, and of those monitoring programmes that do exist none have been in place long enough to facilitate an assessment. Despite this, all OSPAR Countries record NIS detected. However, in some cases these records bear little relation to the time and place in which the species was initially introduced. This may be due to lack of monitoring effort or the reporting process.

First recordings of new NIS have been used for this assessment, being the only suitable data available. These records come from many different sources including monitoring programmes (some of which are specifically tasked to look for NIS), but the majority originate from secondary sources, such as scientific studies, citizen science or chance observations. These sources mostly lack the necessary geographic and temporal consistency in the methodology used for detection and recording needed to ensure data suitable for trend analysis. Using historical data from such a wide range of sources for this assessment may limit interpretation of results.

With various political drivers, such as the International Convention for the Control and Management of Ships' Ballast Water and Sediments (The International Maritime Organisation Ballast Water Management Convention), the European Union Marine Strategy Framework Directive (EU 2008/56/EC) (MSFD) and the European Union regulation on Invasive Alien Species (1143/2014), monitoring programmes focused on detecting NIS are starting to be developed. Given time, these should provide baselines and datasets that can be used to assess all three indicator parameters. It is essential however that there is consistency in approach, coordination and harmonisation of monitoring methods and quality assurance, recording processes, data flow and assessment at an OSPAR regional scale.

For the Quality Status Report (QSR) 2010, NIS were assessed by compiling a list of NIS considered problematic in the OSPAR Maritime Area, supported by information on range, first reporting, probable vector and possible impact. A quantitative assessment of trends in introduction was not possible. The development of an indicator on introduction of NIS makes it easier to identify change in the rate of new introductions of NIS and to assess the effectiveness of management measures.

Data

Each OSPAR Contracting Party was requested to provide data on new records of non-indigenous species (NIS) within their waters between 1 January 2003 and 31 December 2014 for each region assessed (Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast). The period assessed was selected because it represents two six-year periods (2003–2008 and 2009–2014), from which Contracting Parties are most likely to have complete data sets. The data therefore enable comparison of new NIS records between two six-year reporting periods. Data were requested on the date that NIS were first recorded within each of the regions and the location of the observation.

Data were provided by: Belgium, Denmark, France, Germany, Ireland, Portugal, Spain, Sweden, the Netherlands and the United Kingdom.

The data received were checked for taxonomic discrepancies and formatting issues, which were then addressed. For the purpose of this assessment, records before 2003 and after 2014 were removed.

Analysis

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 an NIS in the OSPAR Maritime Area. Duplicate records for any given species were removed such that numbers recorded for each of the three regions were not overestimates. Care was taken to ensure that it was the first record (i.e. earliest) for a given species in a given region that was used for analysis.

The following metrics were assessed using the data gathered for this assessment:

  • The total number of new records of NIS made per year, for each region assessed;
  • The total number of new records of NIS for each region between 2003 and 2014, calculated using the count function and cumulative function; and
  • A comparison of the mean number of new records of NIS between reporting period 1 (2003–2008) and reporting period 2 (2009–2014) for the Greater North Sea, Celtic Seas and Bay of Biscay and Iberian Coast. A T-test analysis (a statistical hypothesis test to determine if the two sets of data are significantly different from each other) was used to determine whether there was any significant difference between the mean number of new records made in reporting period 1 compared to reporting period 2. Box plots were used to illustrate the comparison between the number of new NIS records in reporting periods 1 and 2. Box plots are used to examine patterns in data sets as follows: the data are sorted and divided into quarters, the thick black line represents the median or the midpoint of the data, the middle box represents the middle 50% of scores, with 25% being above the median line and 25% below. The bars above and below the box (not always visible) represent the upper and lower 25% of data.

This analysis was used to identify potential emerging trends in NIS records, within those areas of the OSPAR Maritime Area assessed.

Results

The number of new non-indigenous species (NIS) recorded for the Greater North Sea, Celtic Seas and the Bay of Biscay and Iberian Coast over the period 2003–2014, varied by year and region (Figure 1), but showed no overall trend in the number of new NIS records over the assessment period.

The cumulative number of new NIS records (Figure 1) provides an indication of change in trends. In the Greater North Sea there was a relatively constant linear increase in the number of new NIS recorded over time, whereas the other two regions had particular years with relatively high numbers of new NIS records which meant a similar linear increase did not occur: Celtic Seas (2006, 2012) and Bay of Biscay and Iberian Coast (2004).

Data indicate that the numbers of NIS introduced into the Celtic Seas is lower than in the Greater North Sea, Bay of Biscay and Iberian Coast. It is difficult to speculate as to why this may be the case, given the nature of the data used.

For each of the three regions assessed, there were more new NIS records in reporting period 1 (2003–2008) than in reporting period 2 (2009–2014), as outlined in Table 1. There was considerably more in the case of the Greater North Sea and the Bay of Biscay and Iberian Coast, although this difference was not statistically different. In the Celtic Seas there is little difference between new NIS records between reporting periods 1 and 2, and no significant difference between the datasets.

There is moderate confidence in the method and low confidence in the data availability.

Table 1: Mean number of new NIS records in the Greater North Sea, Celtic Seas and the Bay of Biscay and Iberian Coast, and the results of a statistical comparison between the means for both periods, by OSPAR Region
OSPAR RegionMean number of new NIS recordsStatistically significant difference between means (p value of 0.05)
Reporting period 1 (2003-2008)Reporting period 2 (2009-2014)
Greater North Sea10.177.67No
Celtic Seas3.002.83No
Bay of Biscay and Iberian Coast38.833.67No

Figure 1: The number of new NIS records per year in each region assessed

Note the different scales used on each plot and on the two y-axes.

The number of new non-indigenous species (NIS) records per year varied for each of the three OSPAR Regions assessed (Figure 2). In total, there were 107 new records for the Greater North Sea, 35 for the Celtic Seas and 225 for the Bay of Biscay and Iberian Coast over the 12-year assessment period (2003–2014).

The number of new NIS records varied between years. These variations may reflect differences in monitoring intensity (in space and time), as well as the ad hoc nature of most of the data collected. In the Greater North Sea, the total number of new NIS records per year ranged from 4 (2013) to 14 (2004), for the Celtic Seas the range was 0 (2003, 2013, 2014) to 11 (2006, 2012), and for the Bay of Biscay and Iberian Coast the range was 0 (2014) to 111 (2004). It is possible that formerly undetected NIS were recorded in the first reporting period.

The average number of new NIS records per year was 8.92 for the Greater North Sea, 2.92 for the Celtic Seas and 18.75 for the Bay of Biscay and Iberian Coast.

In the Greater North Sea there was a relatively constant increase in new NIS records over the assessment period (Figure 2). In the Celtic Seas there were two years (2006, 2012) in which comparatively high numbers of new NIS were recorded, resulting in a non-linear increase in total NIS records. For the Bay of Biscay and Iberian Coast, the number of new NIS records was greater near the start of the assessment period (2004), resulting in an early increase followed by a plateau.

For each region assessed, there were more new NIS records in reporting period 1 (2003–2008) than in reporting period 2 (2009–2014). Specifically, 61 and 46 for the Greater North Sea, 18 and 17 for the Celtic Seas, and 203 and 22 for the Bay of Biscay and Iberian Coast. The lower number of new NIS records in reporting period 2 may reflect a decrease in monitoring intensity or delays in the reporting of data, as well as a real decrease in rates of new NIS introductions.

For each region assessed, although the mean number of new NIS records for reporting period 1 is greater than for reporting period 2, this difference is not statistically significant (Table 1). Figure a shows box plots of the number of new recordings of NIS made in reporting periods 1 (2003 to 2008) and 2 (2009 to 2014) whereby the thick black line represent the median or the midpoint of the data, the middle box represents the middle 50% of scores, with 25% being above the median line and 25% below. The bars above and below the box (not always visible) represent the upper and lower 25% of the data.

Figure a: Box and whisker plots comparing the number of new records of NIS per year between reporting periods 1 (2003–2008) and 2 (2009–2014)

Note the different scales used on each plot.

A T-test was used to compare the mean number of new NIS records between reporting periods 1 (2003–2008) and 2 (2009–2014). For future assessments, where multiple reporting periods will be used, more appropriate multi-variant analysis will be applied.

Confidence Assessment

The confidence in the methodology for this assessment is moderate. There is a common consensus for using the method among the regional seas commissions, with OSPAR, the Baltic Marine Environment Protection Commission (HELCOM) and the Barcelona Convention using similar assessment methodology. However, further work is required to develop the indicator, especially in relation to determining monitoring effort, NIS community abundance and NIS distribution.

There is low confidence in the data availability for NIS. There is no information on how data were gathered or monitoring effort applied. There are also spatial gaps in the data used.

Conclusion

Excluding a few years with high rates of NIS introduction, new species have been encountered at a relatively constant rate for the three regions assessed. Therefore, more effort to reduce the current rate of introduction should be considered. Differences in the rates of introduction are relatively small between regions, and not statistically significant between the two six-year reporting periods (2003–2008 and 2009–2014).

There are a number of limitations identified with the data used. There is a lack of data with which it is possible to make an accurate and reliable assessment of introductions of new NIS in each of the regions assessed. Nevertheless, this assessment demonstrates the functionality of the developed method.

The main conclusion is, therefore, that development and implementation of coordinated and harmonised monitoring should be considered to provide accurate datasets for future assessments. In addition, to accurately determine whether the rate of introduction of new NIS is stable or changing, longer term datasets are required and hence more sustained monitoring.

Emerging NIS are extremely difficult to detect, thus the development of monitoring should take into account the risk based approach and a proportional application of management options for NIS once detected.

Continued implementation of the European Union MSFD, Invasive Alien Species Regulation, and Water Framework Directive, and the International Maritime Organization Ballast Water Management Convention, should ensure some of the identified gaps in monitoring are addressed.

It is difficult to draw any clear conclusions from the results of the analysis except that, excluding a few exceptional years, the rates of introduction of non-indigenous species (NIS) have been relatively constant over the assessment period.

Several issues have been identified in relation to the data used for this assessment:

  • A lack of information on the monitoring effort applied to detect new NIS. The number of new NIS introductions reported may be positively correlated with monitoring effort, so years with high numbers of new NIS records may be the result of increased monitoring effort; equally a year with few new NIS records may be the result of little or no monitoring effort. For example, in the Bay of Biscay and Iberian Coast region more than 100 new NIS were reported in 2004. This is unlikely to be a true reflection of the number of new NIS introduced in 2004, especially in comparison to the number of new NIS introductions reported for other years in the same region; but may be the result of the reporting process or increased monitoring effort;
  • A lack of information concerning the methods used for NIS detection, in particular their sensitivity and / or suitability for detecting NIS. Without an understanding of the methodology applied it is difficult to determine the effectiveness of the methods used for detecting NIS;
  • Limited monitoring at locations considered to be at particular risk of new NIS being introduced, such as ports and marinas, therefore species will be missed at the point of introduction;
  • Potential discrepancy between when an NIS is first recorded and when the introduction actually occurred. This also raises issues with linking introduction events to specific pathways of introduction and management measures;
  • Potential discrepancy between where an NIS is first recorded and where it was actually first introduced. This may result from multiple NIS introduction events, where subsequent introductions are detected before the initial introduction, or where a secondary population resulting from spread is detected prior to the original founder population;
  • Data accessibility varies between countries, depending on internal processes for collating and storing data. This may result in missing data, resulting in an incomplete view of the number of new NIS introductions in a given year; and
  • Reliable data are not available for a long enough period to effectively examine trends in new NIS introductions over time.

Despite data limitations, this assessment does demonstrate how this indicator can be used to determine changes in the number of new NIS being introduced into the three regions assessed (and has synergy with other Regional Seas Conventions in Europe), with the provision of appropriate data. Development and implementation of coordinated and harmonised monitoring is required to address the issues listed above and to provide accurate datasets for future assessments. Any such monitoring will need to be integrated with other requirements such as those for the European Union Marine Strategy Framework Directive, the European Union Invasive Alien Species Regulation, and the International Maritime Organization Ballast Water Management Convention.

Knowledge Gaps

Strengthening of non-indigenous species (NIS) monitoring would improve the assessment of this indicator. Efforts need to focus on a cost-effective approach to:

  • Improve the baseline dataset, from available knowledge, for comparison against future assessment periods;
  • Consider approaches and methodology used by other organisations and for other regulatory requirements;
  • Coordinate and harmonise monitoring and response at the OSPAR regional level, in association with other Regional Seas Conventions;
  • Improve data flow and management processes; and
  • Investigate the development of additional methods to improve the speed and probability of early NIS detection.

Understanding of the contribution of different vectors to the introduction of NIS, would be improved through the development of complementary indicators.

In relation to NIS, consideration could be given to the following.

Develop Baseline Dataset:
  • A baseline is required from which future trends can be assessed. This could be achieved using secondary data (i.e. information collected from sources other than established monitoring programmes, such as rapid assessment surveys or citizen science) and validated against data collected from monitoring programmes as they are developed; and
  • The development of a baseline and the validation process would ideally be conducted at the OSPAR regional scale, but could also be coordinated between Regional Seas Conventions.
Improve Speed and Probability of Early Detection and Response to NIS, Notably in Areas at High Risk of Introduction:
  • Increase the quality and quantity of monitoring conducted for NIS;
  • Conduct vector-related monitoring at locations at high risk from the introduction of NIS, such as ports, marinas and aquaculture sites;
  • Investigate the applicability of different detection methods, such as molecular-based tools;
  • Develop methods whereby monitoring effort can be quantified and compared between Contracting Parties;
  • Develop standardised monitoring protocols to optimise detection of NIS;
  • Develop methods by which assessment results can be compared with effort undertaken in relation to the programme of measures to determine its effectiveness and how the programme of measures may need to be modified in the future;
  • Establish an early warning system to alert Contracting Parties, especially on the occurrence of potentially invasive NIS to enable joint consideration of possible eradication efforts as a rapid response action;
  • Improve the quality assurance of taxonomic identification Coordinate and harmonise monitoring at the OSPAR regional level, as well as at the level of other Regional Seas Conventions;
  • Ensure expertise and experience is shared between and within Regional Seas Conventions;
  • Develop standardised monitoring guidelines and procedures to ensure consistency;
  • Investigate and define optimised monitoring design for the European Union Marine Strategy Framework Directive, with potential applicability to other policy drivers, such as the International Maritime Organization Ballast Water Convention, the European Union Water Framework Directive and the European Union Invasive Alien Species Regulation; and
  • Identify a central body / group of representatives to coordinate monitoring and quality assurance, within and between Regional Seas Conventions.
Improve Data Flow and Management Processes:
  • Develop data management and data flow guidelines;
  • Identify a common repository for data management processes and storage; and
  • Standardise reporting format and procedure to the common repository.
See all acknowledgements