CORNWALL WILDLIFE TRUST

Investigating the efficacy of citizen science relative to other methods for monitoring

marine non-native species

John Bishop, Lisa Rennocks, Francis Bunker, Christine Wood and Anna Yunnie

March 2014

Report on contract ME5214

1

Project Title

Investigating the efficacy of citizen science for monitoring marine non-native species

Report No

Final

Project Code

ME5214

Defra contract manager

Deborah Hembury

Funded by

Department for the Environment Food and Rural Affairs

Nobel House

17 Smith Square

London

SW1P 3JR

Authors

John Bishop (Marine Biological Association of the United Kingdom)

Lisa Rennocks (Cornwall Wildlife Trust)

Francis Bunker (MarineSeen)

Chris Wood (Marine Biological Association of the United Kingdom)

Anna Yunnie (Marine Biological Association of the United Kingdom)

2

Contents Page

Executive summary 4

1 Introduction 6

2 Materials & Methods 8

2.1 Locations 8

2.2 Target list for panels and RAS 8

2.3 Settlement panel assembly 8

2.4 Deployment of panels by volunteers 9

2.5 Additional settlement panel deployment and assessment by CWT/MBA staff 10

2.5.1 Photography of CWT/MBA-deployed panels 10

2.5.2 Panel preservation 11

2.5.3 Panel scoring 11

2.5.3.1 Preserved panels 11

2.5.3.2 Digital images 11

2.6 Rapid assessment survey (RAS) protocol 12

2.7 Algal survey 13

2.8 Statistical analyses 13

3 Results 14

3.1 Panels deployed by volunteers 15

3.2 Panels deployed by CWT/MBA staff 15

3.2.1 Panels scored in the Lab 15

3.2.2 Digital images: comparison of images made using different equipment 18

3.3 RAS 20

3.3.1 Repeatability of the RAS survey 20

3.3.2 Species repeatability 22

3.3.3 Adequacy of the 1-hour RAS search period 23

3.4 Comparison of detection for digital images, panels scored in the lab and RAS 24

3.5 Notable records during the work by CWT/MBA 24

3.6 Surveys of algae 26

3.7 Comparative costings of citizen science, panel deployment by staff, and RAS 26

4 Discussion 28

5 References 32

6 Annex 1 Seaweed inventory (available as Excel attachment)

2 Comparative estimated costs (Not for publication)

3

4

Executive summary

The project confirmed the general prevalence of non-indigenous species (NIS) in marinas: in

September 2013, 1-hour rapid assessment surveys (RASs) on the south coasts of Devon and Cornwall

recorded a mean of 9.6 sessile animal NIS per marina, while surveys dedicated to algae found 5.0 NIS

per marina on average. In total, 26 NIS were recorded in the ten marinas surveyed.

Three methods undertaken by CWT/MBA staff were compared for their ability to detect NIS: RAS;

the deployment and laboratory analysis of settlement panels; and analysis of whole-panel digital

images of the same panels. The last emulated the protocol requested in the parallel citizen scientist

project whereby volunteers deployed panels and submitted images for inspection by trained staff.

RAS visits detected on average 2 or 2.5 more NIS per marina than the laboratory inspection of five 15

x 17 cm settlement panels that had been exposed for 8 weeks at 1.5m, which in turn detected 2.5

more NIS per marina than scrutiny of the corresponding whole-panel digital images. Furthermore,

the panels failed to generate any records of the four algal species on the target list, while records of

three of these species arose during the RASs, generally from specimens growing nearer the surface

on pontoon floats or on other shallow surfaces.

Comparative costings, coupled with the respective rates of detection of NIS by the different

approaches, suggest that a RAS is the most cost-effective way of monitoring for NIS. Advantages of a

RAS include the requirement for a single visit to each site and the rapid availability of the resulting

data compared to the deployment, exposure and retrieval of panels. However, in assessing the

citizen science option, the potential very substantial benefit in raised awareness amongst

participants should be taken into account.

Three photographic setups of varying sophistication were employed for the panel images and little

difference was apparent in the resulting species records when whole-panel images were analysed. A

modern, basic compact digital camera on an automatic setting or mobile phone camera can take

satisfactory whole-panel images. Competent close-ups of relevant specimens could, however

improve the rate of species detection, given an understanding of what to photograph and perhaps

involving some manipulation of camera settings. Actual citizen-science images were sometimes

inadequate due to a range of failings.

Analysis of digital images of panels, coupled with laboratory scoring of the same panels to produce a

definitive list of NIS for each side, documented that species vary widely in their probability of

detection in the images. Scrutiny of whole-panel images is clearly not an efficient way to detect all

species, but works very well for some. It seems possible to tailor image-based citizen scientist

programmes to target only the most suitable species.

The first panel of a set of five close together on a pontoon had, on average, two-thirds of the species

recorded from the set as a whole, so the rate of detection of new NIS slowed considerably as more

panels were scored. Species composition on pontoons varied from place to place within a marina,

and the best detection rates for a site overall would be expected from panels spread singly or in

pairs throughout the marina.

The digital images submitted by citizen scientists were of widely varying suitability for the detection

of NIS. The colonization of the panels themselves was also more heterogeneous than of those

5

deployed by CWT/MBA staff, largely reflecting different timings and periods of immersion by

individual volunteers. Nevertheless, the ‘citizen’ panels collectively allowed eight NIS to be

detected.

There is potential for a combination of monitoring by scientists and citizen-science initiatives, each

with specific benefits, in a national NIS monitoring programme to meet MSFD requirements.

6

Introduction

The potential for non-indigenous species (NIS) to exert biological pressure on the environment is

gaining increasing recognition (The Millennium Ecosystem Assessment 2005; Convention on

Biological Diversity, 2009). This, together with a growing awareness of the economic impacts NIS can

impose (Williams et al., 2010), has seen legislative instruments and policy begin to incorporate

preventative measures to reduce the spread of marine NIS, calling for improved detection and

monitoring capabilities. The European Marine Strategy Framework Directive (MSFD) identifies

marine NIS as one of eleven high-level descriptors of good environmental status (GES) requiring

that levels of NIS introduced by human activities do not adversely alter the ecosystem.

A recent report suggests in excess of 70 marine NIS have become established in Great Britain (GB)

from around the globe, in particular from temperate Asia, North America and the Pacific region (Roy

et al. 2012).

Maritime traffic and aquaculture are thought to be responsible for the majority of marine NIS

introductions (Streftaris et al., 2005). As a result both commercial shipping and aquaculture have

seen the development of preventive measures to reduce their potential to spread marine NIS. These

include the IMO’s Ballast Water Management Convention (International Maritime Organization,

2005), which awaits ratification, and Biofouling Guidelines (International Maritime Organization,

2012). Aquaculture operators require authorisation under the Aquatic Animal Health Regulation

2009 and are subject to specific controls and conditions of licence designed to protect native species

and habitat under the Import of Live Fish Act 1980 and Wildlife and Countryside Act 1981 in

particular the Alien and Locally Absent Species in Aquaculture Regulations 2011. In addition, the

Centre for Environment Fisheries and Aquaculture Science have adopted the European non-native

species risk analysis scheme (ENSARS) described by Copp et al. (2008).

Recreational boating and the movements of smaller vessels however remain largely unregulated,

and have been implicated as both primary and secondary pathways of spread (Bax et al. 2002;

Hilliard 2004; Minchin et al. 2006; Hardiman & Burgin 2010; Murray et al. 2011). The Green Blue

(2011, 2012) have produced guidance documents for both marine operators and boat users in

recognition of the lack of regulation. Monitoring studies indicate that marinas provide suitable

habitat for marine NIS establishment (Arenas et al. 2006; Ashton et al. 2006), and from these initial

entry points secondary transfer can take place. There is an increasing risk of introduction through

this pathway as the numbers of boats, marinas and journeys between marinas increase (Murray et

al. 2011).

The earlier along the invasion pathway a species can be detected, the more cost-effective it is likely

to be to reduce its spread further, and surveillance regimes targeting primary transfer sites offer the

greatest chance for early detection. However, comprehensive surveillance in the marine

environment is inherently challenging and costly, especially when it requires the expertise of divers.

Cornwall Wildlife Trust, in collaboration with the Marine Biological Association of the United

Kingdom, has developed a citizen science programme as part of their Local Action Group work on

marine NIS surveillance. One aspect of the programme aims to build a network of volunteers to

gather data on marine NIS by recruiting boat owners to deploy settlement panels from the pontoon

at their marina berth. The Trust has also sought the involvement of local shellfisheries, an industry

7

both susceptible to the threats posed by NIS and implicated in unwittingly introducing them through

transportation of cultivated species. Participants in the panel project are required to submit digital

images of their colonised panels after a minimum period of eight weeks’ immersion. The images are

then inspected by experts for the presence of NIS. The project design aims to provide verifiable

biological data on the presence of a range of taxa across a wide geographical area but, equally

importantly, to raise awareness within the recreational boating community, with an aspiration that

their involvement could lead to behavioural change, and ultimately reduce the rate of spread of NIS

whilst also providing an early warning system for species introductions.

This project will evaluate the efficacy of using volunteers to provide photographic surveillance by

comparison with data from traditional sampling methods, and to explore its potential to play a role

in delivering monitoring requirements to aid evaluation of GES under Descriptor 2 of the Marine

Strategy Framework Directive (MSFD).

Aims:

To evaluate the adequacy of photographic images taken using a range of camera equipment

e.g. high specification and resolution vs. amateur equipment.

Comparison of photographic data vs. laboratory assessment of preserved panels.

Comparison and evaluation of Rapid Assessment Surveys (RAS) undertaken by experts vs.

settlement panel sampling.

Examine how techniques could be utilised as part of the MSFD monitoring programme

Provide guidance for spatial distribution of panels to provide effective detection of marine

NIS.

The project went relatively smoothly and the aims were largely achieved. Concerning the fourth

bullet-point above relating to MSFD monitoring requirements, we have included approximate

relative costings of the different methodologies additional to comparing their ability to detect NIS.

Rapid assessment surveys appear to be the best single monitoring option under these criteria, and a

separate 2-page document outlining an approach to RAS surveys covering the coast of Great Britain

was sent to D. Hembury (Defra) and P. Stebbing (Cefas) on 14-4-2014.

8

2 MATERIALS & METHODS

2.1 Locations

Locations and their three-letter codes are detailed in Table 1. Each participating marina was

contacted in advance for permission to deploy panels and undertake surveys, and to enable

preparation of any required documentation or safety requirements.

Table 1. Locations, environmental measurements, and dates of the study.

Site

Code, National Grid ref

Panel deploy-

ment RAS 1 Temp

°C Sal- inity RAS 2

Temp °C

Sal- inity

Mylor Churchtown, Mylor Marina

MYL SW821352

15/07- 17/09 15/07 17.8 35.0 03/09 17.2 35.2

Falmouth, Yacht Haven

FYH SW811326

15/07- 17/09 15/07 18.9 35.3 02/09 17.1 35.2

Falmouth, Falmouth Marina (Premier)

FPR SW798337

17/07- 18/09 17/07 18.2 35.0 03/09 17.2 34.5

Falmouth, Port of Pendennis Marina, inner silled basin

PIN

SW815323 17/07- 18/09 17/07 19.2 35.2 02/09 17.2 35.1

Falmouth, Port of Pendennis Marina, outer pontoons

POU

SW814324 17/07- 18/09 17/07 19.3 31.5 02/09 17.6 35.1

Plymouth, Queen Anne's Battery Marina

QAB

SX484537 10/07- 09/09 12/08 16.2 34.8 04/09 16.5 34.1

Plymouth, Plymouth Yacht Haven Marina

PYH SX492531

10/07- 09/09 30/07 17.9 31.4 04/09 17.1 34.2

Plymouth, Sutton Harbour Marina

SUT SX483543

10/07- 09/09 12/08 17.2 34.2 01/09 17.4 34.9

Plymouth, Millbay Marina

MIL SX470537

10/07- 11/09 12/08 16.4 34.6 01/09 16.9 34.9

Plymouth, Mayflower Marina

MAY SX459538

10/07- 09/09 31/07 17.3 35.0 04/09 16.9 34.8

All dates 2013. Temperature and salinity measured at 2m.

2.2 Target list for panels and RAS

A target list of 25 non-native species (21 animals and 4 algae) largely based on the revised

Identification guide for selected marine non-native species issued to the volunteer participants and

funded by the Environment Agency, was produced for scoring the panels and for use in the RAS (see

Table3). We also looked out for unexpected non-native species during the work.

2.3 Settlement panel assembly

Settlement panels were assembled using pre-punched black polypropylene Correx (‘corrugated

plastic’) panels size 170 x 150 x 4mm to which a 2mm diameter x 2m length of black polypropylene

braided cord was secured by a bowline knot to a cable tie at the top of the panel and an 8oz lead

9

clock weight at the bottom, attached by cable tie through the central hole (Fig. 1). The panels thus

hung vertically.

Figure.1. 17 x 15 cm Correx panel ready for deployment

2.4 Deployment of settlement panels by volunteer participants

Citizen scientists from the recreational boating community along the south coast of Cornwall were

recruited in a number of ways to deploy panels, including posters in marinas and Harbour Authority

noticeboards, at CWT-organised events, press releases to local press and Volunteer Marine

Conservation Area groups and via the CWT membership magazine. Not all volunteers had a boat or

mooring, in which case permission to deploy a panel was sought from the marina operator.

Participants were sent an information pack or asked to collect one from a drop off point e.g. marina.

The pack included an assembled panel ready for deployment, with instructions, identification

materials, recording sheets, background information including guidance on how to take suitable

images, and a Check Clean Dry information poster. All information resources were available online

together with a gallery of previous panel images.

The citizen scientists were requested to deploy their panel at a depth of 1.5m for a minimum of 8

weeks, then to remove and photograph the panel.

Panel details including location, dates of deployment and retrieval were submitted online with an

image of each panel side plus close-ups of species thought to be of interest (maximum of 5Mb per

image). The digital images were taken using a range of photographic equipment including mobile

phones. Participants were encouraged to attempt to identify the organisms and submit an online

recording form with their photographs. Panels were then either discarded or put back in the water

for further monitoring. Thus they were not preserved for scoring in the laboratory. On receipt, panel

details were logged and the images were scored for NIS by CWT/MBA staff.

10

2.5 Additional settlement panel deployment and assessment by CWT/MBA staff

Additional to panels deployed by stakeholder volunteers, identical units were deployed by

CWT/MBA staff to provide sets of replicate, uniformly treated panels allowing statistical

comparisons between techniques. Five settlement panels were deployed at each of the 10 selected

marinas during July 2013 (Table 1). Each panel was attached to a pontoon using a rubber sheath to

protect the cord from chafing. The five panels were positioned on the same pontoon, > 1m apart

and suspended approx. 1.5 m below the waterline.

The panels remained continuously submerged for approx. 8 weeks then, in September, they were

retrieved and prepared for species assessment as described below.

2.5.1 Photography of CWT/MBA-deployed panels

Photographs were taken at the marina with the panel out of the water. Each side of each panel

was assigned a reference number and whole-side digital images incorporating a tally counter

displaying the number were taken using three photographic set-ups, intended to produce a range

of image resolution:

1. A basic compact camera, Casio EX-Z, set on automatic, operated hand-held with instant

shutter release and with the panel propped against any convenient object (‘Casio’ below,

intended to emulate competent images submitted by volunteers) (Fig. 2A ).

2. A compact camera using more advanced features, Pentax Optio W60, set to shoot at an ISO of

50 and operated with delayed shutter release (self-timer) while fixed c. 40 cm above the

ground on a tripod and aligned accurately to frame the panel supported on a low ‘easel’ stand

(Fig. 2B).

3. A digital SLR, Nikon DS3100 with Nikkor 18-55mm lens, and set on manual to shoot at F13 (a

middle value in the available range at the focal length used) and an ISO of 100, and operated

with delayed shutter release while similarly fixed on the tripod facing the panel on the ‘easel’

stand.

Figure.2. Photography of panels. A, hand-held Casio EX-Z. B, tripod-mounted Pentax Optio W60, with panel on

stand.

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The Casio and Pentax were used for all panels, while the Nikon was used only at MIL. All

photography was by daylight (i.e. without flash), using autofocus, and produced JPEG files.

Characteristics of the cameras and of the images obtained are shown in Table 2.

Table 2. Imaging of panels: cameras and settings, and sizes of the resulting image files.

Camera Mega-pixels

Resolution (dpi)

F-stop Exposure (seconds)

Sensitivity (ISO)

Image file size (Mb)

Casio EX-Z 1080

3.2 72 vertical

72 horizontal

2.8-6 (mostly 2.8

or 5.1) 1/50-1/320

80-800 (mostly 80 or

100) 0.89-1.86

Pentax Optio W60

9.9

72 vertical 72 horizontal

3.5 1/6-1/80 50 3.39-3.80

Nikon DS3100

14.2

300 vertical 300 horizontal

13 1/4-1/13 100 6.43-7.50

2.5.2 Panel preservation

After photography, each labelled panel was carefully stored in cooled seawater for transit back to

the laboratory. On arrival panels were preserved in 70% Industrial Denatured Alcohol (IDA99) for

subsequent scoring.

2.5.3 Panel scoring

2.5.3.1 Preserved panels

Preserved panels were scored in a random order and each panel side was recorded

separately. Firstly, those NIS visible to the naked eye, without removal of any specimens, were

recorded. Then, specimens were removed to reveal any hidden understory. The panel was

next examined under a dissecting microscope for any additional target species. Where

necessary, samples were taken for later microscopic identification or confirmation. All

bryozoan and botryllid ascidian specimens were examined under the microscope.

2.5.3.2 Digital images

For each camera, a single, whole-panel image of each panel side was analysed, without

knowledge of the origin of the panel. The digital images were selected in random order and

scrutinized for the presence of NIS while viewed in Photoshop, which allowed selective

enlargement of the image, adjustment of brightness and contrast, sharpening, and marking

points of interest.

Two levels of certainty of occurrence were used, ‘probable’ and ‘definite’. A record was only

‘definite’ when visible detail would have been sufficient to support a significant record such as

a substantial range extension. A lesser degree of confidence, lacking some confirmatory

details, was recorded as ‘probable’.

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The ‘probability of detection’ of a species in digital images was calculated for each camera set-

up from occurrences per panel side (thus a total of 100 potential occurrences). The records

from inspection of the preserved panels in the laboratory were taken to represent the pattern

of genuine occurrences. Positive records from images were either ‘correct’ (true positive),

matching a record for the corresponding panel side in the laboratory, or ‘incorrect’ (false

positive) if no matching record was noted in the laboratory. Probability of detection was the

proportion of positive records from laboratory inspection that were also recorded from the

digital image (thus ‘correct’, either as ‘probable’ or ‘definite’ records). However, some

apparently incorrect occurrences were also recorded from the images, and a figure for ‘false

detection rate’ for records of each species was calculated, being the proportion of total

records from images that were incorrect in light of the panel inspection data.

Specific criteria were adopted in advance for a few taxa, based on previous experience:

Specimens appearing to be the erectly branching bryozoan Tricellaria inopinata were

recorded only as ‘probable’ unless sufficient zooidal detail could be seen to exclude

similar taxa such as Scrupocellaria and related genera.

The non-native bryozoan species Bugula simplex and B. stolonifera could not be

distinguished from other, native, species of Bugula without microscopical

examination, and so could not be recorded from the images. In contrast, another non-

native Bugula species, B. neritina, was sufficiently distinctive to be definitely

recognisable.

For the taxonomically problematic colonial ascidian genus Botrylloides, well-grown

single-colour colonies (lacking contrasting colour patterns) were scored as ‘probable’

B. violaceus. If the characteristic large, brooded larvae of B. violaceus were confirmed,

a definite record could be noted. B. diegensis could be scored as definite based on the

very distinctive contrasting pattern of solid colours shown by many colonies of this

non-native species.

2.6 Rapid assessment survey (RAS) protocol

RASs were undertaken at any state of the tide, from the surface (i.e. from floating pontoons, without

diving or snorkelling). A team of three (comprising JDDB and CAW plus LR or ALEY) visited each

marina to conduct the RAS. Surveys of the 10 marinas were carried out in July-August (RAS1) and

repeated in September (RAS2) (Table1).

At each site, the available pontoons were apportioned equally between the three staff, who worked

independently for one hour. In addition to inspection of the pontoons themselves, submerged

artificial substrates such as hanging ropes, keep cages, fenders, etc., and natural substrates such as

kelps were pulled up and examined. Hooks and scrapers were used if necessary to access material

for inspection. The 15-minute interval (1-15, 16-30, 31-45, 45-60 min) in which each target species

was first encountered was recorded independently by each surveyor, and an estimate of abundance

made on a three-point scale (Rare-Occasional, Frequent-Common and Abundant-Superabundant) at

the end of the observation period.

13

Specimens were collected to substantiate significant findings, or for discussion. At the end of the

hour the staff gathered to compare notes and specimens, and summarize their joint observations on

a standard form.

If required for laboratory identification or as tokens of significant records, specimens were relaxed

using menthol or propylene phenoxetol prior to preservation in 70% IDA. Salinity and water

temperature at 2m were recorded using a YSI 30 meter.

An assessment of the adequacy of the one-hour search interval was made by checking that the rate

of discovery of new taxa had fallen to a very low level by the fourth 15-minute interval. (Additional

time could be added if species discovery was continuing at a substantial rate at the end of the hour

or if necessary to complete coverage of larger or more complex sites).

The preserved specimens requiring identification were examined in the laboratory, if necessary

under the microscope.

2.7 Algal survey

During the September RAS surveys, FB accompanied CWT/MBA staff to provide additional algal

expertise. FB conducted a survey of algae from the surface at each marina, noting species and

collecting specimens for identification in the laboratory. Roughly an hour was spent searching at

each site, during which time at least two contrasting regions of the marina were visited. A

substantial quantity of specimens was collected, necessitating preservation of a large proportion in

formalin for subsequent identification after the surveys.

2.8 Statistical analyses

Species accumulation curves were derived, PERMANOVA analysis performed, similarity coefficients

calculated, and Principal Co-ordinates plots produced using PRIMER v.6 incorporating

PERMANOVA+. Friedman’s and Wilcoxon’s signed-rank tests were performed in MINITAB 15. Other

calculations were done in EXCEL 2007.

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3 RESULTS

Of the initial list of target species, Amphibalanus amphitrite, Ficopomatus enigmaticus, Botrylloides

diegensis, Didemnum vexillum and Codium fragile fragile were not encountered during the project,

leaving totals of 16 sessile animal and 3 algal species recorded by the CWT/MBA team (Table 3).

Table 3: List of target NIS and their occurrence in different phases of the project.

Panels

Species RAS1 RAS2 ID in lab

Pentaximages

Casio images

Volun-teers’

images

Diadumene lineata (anemone)

Austrominius modestus (barnacle)

Amphibalanus amphitrite (barnacle)

Crepidula fornicata (gastropod)

Crassostrea gigas (oyster)

Ficopomatus enigmaticus (tubeworm)

Tricellaria inopinata (bryozoan) () () ()

Bugula neritina (bryozoan)

Bugula simplex (bryozoan)

Bugula stolonifera (bryozoan)

Watersipora subtorquata (bryozoan)

Schizoporella japonica (bryozoan)

Styela clava (ascidian)

Asterocarpa humilis (ascidian)

Ciona intestinalis ‘A’ (ascidian)

Corella eumyota (ascidian)

Botrylloides violaceus (ascidian) () () ()

Botrylloides diegensis (ascidian)

Didemnum vexillum (ascidian)

Perophora japonica (ascidian)

Undaria pinnatifida (brown alga)

Sargassum muticum (brown alga)

Grateloupia turuturu (red alga)

Codium fragile fragile (green alga)

TOTAL species 18 19 11 8 7 8

TOTAL animal species 15 16 11 8 7 8

(): Probable identification, necessary characters not all visible

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3.1 Panels deployed by volunteers

Whole-panel images for 73.1% of panels distributed by CWT for deployment from pontoons were

received from citizen scientists for scrutiny. 19.2% of panels were lost or removed and 7.7% were

unaccounted for.

The panels had been deployed for varying periods, including redeployment overwinter following

monitoring in 2012. Deployment was from pontoons in marinas or from visitors’ pontoons and other

floating structures on the open river. This degree of variability provided a wide range of assemblages

from heavily fouled panels dominated by Ciona intestinalis and Ascidiella aspersa to ones with more

open communities consisting of both solitary and colonial ascidians, bryozoans and barnacles. In

total eight NIS animal species from the target list were recorded, of which two were “probable” due

to brooded larvae in the case of Botrylloides violaceus or zooidal characteristics for Tricellaria

inopinata not being visible.

No NIS algal species were recorded from images submitted by citizen scientists.

Images submitted varied from high to low resolution, over- to under-exposure and large to small

subject to image ratio. The length and timing of deployment also affected the degree to which NIS

could be detected from the images, with species on the surface layer on heavily fouled panels

obscuring an understorey layer, while some panels were dominated by a particular species due to

seasonal recruitment. A range of images submitted by citizen scientists in Fig. 3 illustrates the

varying levels of suitability.

3.2 Panels deployed by CWT/MBA staff

A wide range of colonizing assemblages was observed on the panels, including complete coverage by

Ascidiella aspersa individuals about 4cm tall with a few Ciona intestinalis of similar size (QAB and

SUT; Fig. 4A), domination by sheet-forming botryllid and/or didemnid (Diplosoma listerianum)

ascidians (e.g. PIN and MAY; Fig. 4C), and more open communities with numerous small solitary

ascidians and scattered barnacles plus small encrusting bryozoan colonies but also substantial bare

space (MIL; Fig. 4B). In FPR vigorous growth of hydroids had occurred (Fig. 4D). A basal layer of the

barnacle Austrominius modestus was sometimes present on panels (especially notable at MAY), but

if so was generally overgrown and obscured by other organisms.

3.2.1 Panels scored in the Lab

Eleven species of the non-native sessile animal on the target list were recorded on the panels as a

whole, but none of the algae (Table 3). The species recorded and their total occurrences in the 10

marinas are shown in rank order in Table 4. Species absent from the panels but recorded during

the RAS were: Diadumene lineata, Crepidula fornicata, Crassostrea gigas, Schizoporella japonica

and Styela clava.

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Figure.3. Examples of panel images submitted by citizen scientists. A, good quality image taken at high

resolution, appropriate exposure and high subject to image ratio. B-D problematic images. B, low subject to

image ratio. C, over-exposed image. D, panel heavily fouled after prolonged exposure, only allowing

detection of NIS on surface layer.

Table 4. NIS recorded during laboratory inspection of panels, ranked by the number of panel sides occupied

(out of 100 in total).

Species No. of sides

Austrominius modestus 89

Bugula neritina 86

Tricellaria inopinata 84

Bugula stolonifera 46

Corella eumyota 35

Botrylloides violaceus 31

Bugula simplex 26

Asterocarpa humilis 21

Watersipora subtorquata 5

Perophora japonica 2

Ciona intestinalis type ‘A’ 2

A B

C D

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Figure.4. Representative panels photographed by CWT/MBA staff from SUT (A), MIL (B), PIN (C) and FPR

(D), taken with Pentax photographic set-up.

Species accumulation plots for the five panels in each of the 10 marinas are shown in Fig. 5 (right

panel). A single panel at a site had on average 71% of the NIS listed from all five panels (mean

proportion 0.711, s.d. 0.127), while the fifth panel of a set contributed on average less than 4% of

the total records from the set (mean proportion 0.036, s.d. 0.033).

At MIL, very small Schizoporella colonies occurred on the panels but could not be attributed to S.

japonica because the necessary characters were not yet developed, although S. japonica was

found to be common at this site in the RASs.

Botrylloides violaceus was recorded only if confirmed by its distinctive larvae (distinguishing it

from B. leachii); on several panel sides no brooded larvae were seen in the Botrylloides colonies

18

0

2

4

6

8

0 1 2 3 4 5

Spe

cie

s re

cord

ed

Panels scored

PYH

QAB

SUT

MIL

MAY

FYH

PIN

POU

FPR

MYL

Panels scored in the lab

0

1

2

3

4

5

6

7

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present, so B. violaceus was neither discounted nor confirmed. B. diegensis would have been

recognisable from zooidal characteristics, but, as stated above, was not encountered.

Figure.5. Species accumulation curves from the 120 possible permutations of panel order for five panels at

each of ten marinas. Panels were scored from digital images (‘Pentax’ setup) and by direct inspection in

the laboratory, as indicated.

3.2.2 Digital images: comparison of images made using different equipment

The three camera set-ups did produce clear differences in resolution in the manner intended (Fig.

6, in which c. 2% of a panel side is shown).

Figure.6. Comparison of resolution of digital images. The same 2.3 cm-wide region of a panel at MIL,

enlarged from whole-panel images taken with a hand-held Casio EX-Z (A), a tripod-mounted Pentax Optio

W60 (B) and a tripod-mounted Nikon DS3100 (C) (see Materials and Methods for details). The section

includes at least two species of encrusting bryozoan (one of which is recognisable as Electra pilosa in the

Nikon image) and the barnacle Austrominius modestus. The same panel is shown in Fig. 4B.

19

Three species identified on the preserved panels were not reported from panel images: Bugula

stolonifera and B. simplex (both requiring microscopical examination), and Ciona intestinalis type

‘A’; as with direct panel inspections, none of the target-list algae were recorded.

The probability of detection of species in digital images and false detection rate of the records are

shown in Table 5 for the six species recorded in the images for which more than five occurrences

were noted in the laboratory inspections (see Table 5).

Table 5. Detection probability and false detection rate of six non-native species recorded in digital images

of settlement panels taken with two camera set-ups (Casio and Pentax).

Species Detection probability

False detection rate

Casio Pentax Casio Pentax

Austrominius modestus 0.52 0.54 0.04 0.00

Bugula neritina 0.81 0.87 0.00 0.00

Tricellaria inopinata 0.87 0.93 0.01 0.02

Corella eumyota 0.66 0.63 0.12 0.00

Botrylloides violaceus 0.71 0.77 0.31 0.33

Asterocarpa humilis 0.48 0.52 0.00 0.08

Across species, detection probability was slightly higher (with marginal significance: paired t-test,

p = 0.061) in the Pentax images than in the corresponding Casio images, while no trend emerged

between photographic set-ups concerning false detection rate.

The barnacle Austrominius modestus and the medium-sized solitary (unitary) ascidians Corella

eumyota and Asterocarpa humilis, all of which have low growth forms and tend to grow closely

applied to the substrate, had relatively low probabilities of detection of approximately 0.5-0.6,

while the erectly branching bryozoans Bugula neritina and Tricellaria inopinata had higher values

of 0.8-0.9. The sheet-forming colonial ascidian Botrylloides violaceus had an intermediate value of

detection probability (0.7-0.8), but differed from the other species in having a relatively high false

detection rate: a substantial proportion of ‘probable’ records of this species was not confirmed

by the laboratory inspection of the corresponding surface. However, this shortfall in part

reflected the absence of brooded larvae needed to confirm the species’ identity during the

laboratory investigation. Examples of these trends are shown in Fig. 7.

The Nikon DSLR (MIL only) did provide enhanced resolution (Fig. 6), but this did not result in an

obvious enhancement in detection rate of NIS in the whole-panel images, with one exception: it

was possible to identify young colonies of the encrusting bryozoan Watersipora subtorquata in a

higher proportion of cases than with the Pentax, while the images from the Casio compact

camera did not allow recognition of W. subtorquata at all. However, in the Nikon images it was

still not possible to identify many other encrusting bryozoans, in which the zooids were not as

large and distinctive as those of W. subtorquata. It was not possible to confirm the zooidal

characters of Tricellaria inopinata in images by the Nikon (or either other camera), so all records

of this species from digital images were classed as only ‘probable’. Nor were the brooded larvae

of Botrylloides violaceus discerned with certainty in any of the digital images.

20

Bugula neritina Corella eumyota Botrylloides violaceusN

um

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ProbableDefinite

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Figure. 7. Scoring success of ‘Casio’ and ‘Pentax’ photographic setups for three NIS on each side of 100

panels. Records from the images were scored as probable or definite based on the certainty of the

identification and were classified retrospectively as correct or incorrect (i.e. false positive) based on

occurrence data from laboratory examination of the preserved panels.

Species accumulation plots (for Pentax images) of the five panels in each of the 10 marinas are

shown in Fig. 5 (page 18, left panel). A single panel at a site had on average 67% of the NIS listed

from all five panels (mean proportion 0.674, s.d. 0.174), while the fifth panel of a set contributed

less than 6% of total records from the set, on average (mean proportion 0.055, s.d. 0.040).

3.3 RAS

In RAS1, a mean of 10.20 NIS per marina was recorded (range 6-16, s.d. 2.75); for animals only, the

mean was 8.9 NIS per marina (range 6-13, s.d. 2.02). In RAS2, a mean of 11.20 NIS per marina was

recorded (range 7-14, s.d. 1.83); for animals only, the mean was 9.6 NIS per marina (range 7-11, s.d.

1.11).

3.3.1 Repeatability of the RAS survey.

Eighteen species from the target list were recorded during RAS1 (July-August), and 19 during

RAS2 (September), but the similarity of these overall figures gives a slightly misleading

impression. Across the 19 species and 10 marinas, the two RASs provided 124 species–site

records, but in 34 of these (27%) the species was only recorded on one of the RASs, rather than

both.

Two-way unreplicated Permanova analysis based on a matrix of pair-wise Jaccard’s similarities

between the species lists from the marinas in RAS1and RAS2 (Table 6) attributed the great

majority of variation to the factor ‘Marina’ and very little to ‘Survey’. However, an interaction

term could not be calculated in the absence of replication, limiting the scope to interpret the

non-significance of ‘Survey’ in this analysis. To examine the trends further, a principal co-

ordinates plot (PCO) of the data was produced (Fig. 8), and indicated the absence of a consistent

overall shift between the surveys. There was a mixture of sites, some showing good agreement

between surveys and others with greater displacements between surveys (particularly MAY and

POU) but in a variety of directions on the first two axes of the plot. Thus the low variance

21

component attributed to ‘Survey’ by the Permanova analysis was probably not attributable to

relatively close similarity between the repeat surveys at each site. Rather, the differences

between the surveys are appreciable at some sites, but varied in nature between the different

marinas, giving no overall effect of ‘Survey’.

Table 6 Results of unreplicated 2-way PERMANOVA

Unique

Source df SS MS Pseudo-F P(perm) permutations

Marina 9 13991 1555 3.689 0.001 999

Survey 1 543.2 543.2 1.289 0.306 995

Residual 9 3792 421.3

Total 19 18327

Estimates of components of variation

Source Estimate Sq.root

S(Ma) 566.6 23.80

S(Su) 12.18 3.490

V(Res) 421.4 20.53

Figure. 8. Principal co-ordinates plot of RAS results for ten marinas visited on two occasions (RAS1 and

RAS2) at an interval of 3-7 weeks. Arrows link the same marina.

22

Values of Jaccard’s coefficient of similarity between RAS1 and RAS2 for individual marinas are

included in Fig. 9 (mean of individual marina values = 0.731, s.d. = 0.127), and represent the

proportion of species recorded on both occasions (as opposed to in only one survey) at the

marina. Again a range is apparent, from marinas with near-perfect agreement between repeat

RASs to others showing substantial differences.

0

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Figure.9. Number of NIS recorded in RAS of ten marinas repeated after 3-7 weeks. Blue parts of columns

indicate species recorded on both occasions, red shows species recorded only on one visit. For each

marina, Jaccard’s coefficient of similarity between the species lists from the two occasions is indicated.

3.3.2 Species repeatability.

The similarity in the pattern of occurrence of a particular species over the ten marinas in RAS1

and RAS2 was also assessed using Jaccard’s coefficient of similarity, representing the proportion

of occupied marinas in which the species was recorded in both surveys as opposed to just once.

This can be regarded as an index of the species’ ‘repeatability’ in the two surveys; values are

given in Table 7 and occupy the full range of the coefficient, from 0 to 1. Clearly these values

might in part reflect the species’ overall abundance, with highly abundant species unlikely to

escape detection; it seems probable that Corella eumyota, Bugula neritina and Austrominius

modestus are examples of this. The maximal repeatability of Schizoporella japonica arose

somewhat differently: this conspicuous newly arrived species was recorded on both occasions in

the only site at which it was known at the time of the surveys. The opposite phenomenon, low

repeatability, could reflect genuine changes in abundance (or detection probability) between the

two surveys. The anemone Diadumene lineata was undetected at Port Pendennis Marina in RAS1

and in several previous visits, but was seen by all three observers in the inner basin in RAS2: it

seems to have undergone a sudden change at this site, either rapid colonization or a sharp

increase in detection probability, between the two surveys, but was still not recorded elsewhere.

Ciona intestinalis type A shows a strong pattern of seasonal occurrence, becoming evident in late

23

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RAS1 RAS2

summer, and this aspect of its biology may be reflected in low repeatability between the first and

second surveys: it was found at a single site in RAS1 but also at two additional sites in RAS2.

Table 7. Values of Jaccard’s coefficient for similiarity between RAS1 and RAS2 in the

occurrence of 19 NIS in 10 marinas.

Species Jaccard coeff. Species

Jaccard coeff.

Styela clava 0.889 Diadumene lineata 0.000

Asterocarpa humilis 0.900 Austrominius modestus 1.000

Ciona intestinalis type ‘A’ 0.333 Crepidula fornicata 0.286

Corella eumyota 1.000 Crassostrea gigas 0.333

Botrylloides violaceus 0.571 Undaria pinnatifida 0.833

Perophora japonica 0.500 Sargassum muticum 0.600

Tricellaria inopinata 0.900 Grateloupia turuturu 0.429

Bugula neritina 1.000

Bugula simplex 0.625 Mean 0.647

Bugula stolonifera 0.375 s.d. 0.300

Watersipora subtorquata 0.714 Range 0-1

Schizoporella japonica 1.000

3.3.3 Adequacy of the 1-hour RAS search period.

In both RAS1 and RAS2, c. 70% of first encounters with target species were in the first 15 minutes

of the survey at a site (Fig. 10). The final 15 minutes accounted for only 2.7% (RAS1) or 4.8%

(RAS2) of first sightings.

Figure. 10. Frequency distribution of timing, in 15-minute intervals, of first sightings of NIS at each site

by each of three workers during RASs of ten marinas. RASs were undertaken in July-August (RAS1) and

September (RAS2)

24

3.4 Comparison of digital images, panels scored in the laboratory and RAS for detecting NIS

Friedman tests with ‘Method’ as treatment blocked by ‘Marina’ were used to compare the number

of NIS per marina (n = 10 marinas) recorded by 1) RAS, 2) scoring of preserved panels in the lab and

3) scoring of panels from digital images. Within these three-way comparisons, RAS could be

represented by RAS1 or RAS2, the digital images could be those from the Casio or the Pentax set-up,

and the species counts could include the algae on the target list or be animal-only. For all eight

combinations of RAS1 or RAS2, Pentax or Casio images, and species count including or excluding

algae, ‘Method’ was highly significant (p < 0.0005) (see also Fig. 11). This test does not provide pair-

wise comparisons to identify the source of significant differences, so separate Wilcoxon signed-ranks

tests on number of NIS recorded per marina were performed on selected pair-wise comparisons of

methods, with additional comparisons between photographic set-ups and between RAS surveys, as

shown in Table 8.

Table 8. Results of Wilcoxon signed-ranks tests comparing the number of NIS detected per

marina (n = 10 marinas) by different protocols.

Comparison (higher value in bold if significant) P-value

Panels in lab vs. Pentax images 0.006

Panels in lab vs. Casio images 0.006

RAS1 vs. Panels in lab, all species 0.006

RAS1 vs. Panels in lab, animals only 0.018

RAS2 vs. Panels in lab, all species 0.006

RAS2 vs. Panels in lab, animals only 0.006

Casio vs. Pentax images 1.000

RAS1 vs. RAS2, all species 0.155

RAS1 vs. RAS2, animals only 0.441

Thus, the abilities to detect NIS differed significantly between methods as follows: RAS >

Examination of 5 panels in lab > Images of 5 panels. No significant difference was demonstrated

between the two main photographic set-ups, or between RAS1 and RAS2.

3.5 Notable records during the work by CWT/MBA

With the exception of Falmouth Yacht Haven, we had surveyed all of the sites in recent years.

Nevertheless, some notable new observations of particular species were made. As mentioned

above, a new population of the anemone Diadumene lineata was discovered at Port of Pendennis

Marina (inner basin), Falmouth, during the second RAS, suggesting some form of rapid increase

there by this species, which is not commonly encountered by us in south coast marinas.

Specimens of an apparently undescribed Botrylloides species were encountered in Port of Pendennis

Marina (inner) during the RASs. This entity, currently referred to as Botrylloides species ‘X’, has only

recently been distinguished from other Botrylloides species and is the subject of studies by MBA staff

in collaboration with the Station Biologique de Roscoff. This record is the furthest west that the

species has been found, representing a substantial extension of the known range on the south coast.

25

PYH SUTQAB

MAY

MIL

PINFYH

FPR

POU

MeanMYL

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pec

ies

The bryozoan Schizoporella japonica was discovered in MIL in November 2012, its first recorded

occurrence in England. The surveys in 2013 during this project confirmed its persistence since then,

and documented an increase in abundance to Frequent-Common.

The Japanese kelp Undaria pinnatifida was discovered in the Fal estuary in 2010 and has been the

subject of eradication attempts by Cornwall Wildlife Trust, Natural England and the Port of Truro. At

the time of RAS1 there were no known populations in the Fal. A very small group of thalli (algal

fronds) was found on a single pontoon in Falmouth Yacht Haven during RAS1 and all thalli visible

from the surface were removed. A few thalli were again seen in the same spot in RAS2 and were

also removed.

Figure.11. Number of NIS recorded at each of ten marinas by scoring digital images of settlement panels

(‘Pentax’ setup), by inspecting the same panels in the laboratory, and during two RAS visits at each site (RAS 1

July-August, RAS 2 September). Mean values across all marinas for each method also shown.

26

3.6 Surveys of algae

A limited number of algae easily recognised in the field were targeted in the RAS protocol. The

parallel surveys by FB specifically targeting algae resulted in material which received a total of 87

hours of subsequent scrutiny in the lab. A list of 109 native and non-native taxa resulted (Annex 1).

Between 21 and 42 taxa were listed per marina. Three NIS new to the UK, Chrysymenia wrightii,

Dictyota cyanoloma and Griffithsia schousboei, were recorded, although final confirmation of these

identifications is awaited at the time of writing. Ten NIS already known in the UK were also noted

(Table 9), giving an average of 5.00 NIS per marina (range 3-7, s.d. = 1.49).

Table 9. NIS recorded during the surveys specifically targeting algae.

Species PYH QAB SUT MIL MAY FYH PIN POU FPR MYL

Antithamnionella ternifolia Antithamnionella spirographidis

Asparagopsis armata

Caulacanthus okamurae

Chrysymenia wrightii

Dictyota cyanoloma

Grateloupia turuturu Griffithsia schousboei

Heterosiphonia japonica

Neosiphonia harveyi Sargassum muticum

Umbraulva olivascens Undaria pinnatifida

Total algal NIS 4 6 7 5 6 7 3 3 5 4

3.7 Comparative costings of citizen science, panel deployment by staff, and RAS

Costs were estimated for conducting an assessment of NIS in the 10 marinas studied here by each of

four methods in isolation (Annex 2 – Not for publication):

1) deployment and retrieval of panels by volunteers, images submitted for analysis by staff;

2) deployment and retrieval of panels, photography and analysis of images by staff;

3) deployment, retrieval, preservation and laboratory analysis of panels by staff;

4) rapid assessment survey by staff.

Travel costings were for a local laboratory (distances similar to the current project). For 1)-3),

deployment and scoring of 5 panels per marina was costed. Two members of staff were involved in

deployment and retrieval of panels in 2) and 3), and three members of staff performed the RAS (4).

For the citizen science option (1), all communication with volunteers was assumed to be via e-mail,

internet, post or phone. Relative costs in rank order were as follows: Method 3, 1.00; Method 1,

0.76; Method 2, 0.72; Method 4, 0.63.

27

Given the potential influence of travel costs and staff time spent travelling, and the relatively local

scope of the present project (two clusters of five marinas separated by about 80 miles), the costing

was repeated for 10 marinas spread along a coast at distances (arbitrarily) of 200-400 miles from the

laboratory. Again, all communication with volunteers was assumed to be remote, by electronic

media or post. Relative costs in rank order were then as follows: Method 3, 1.00; Method 2, 0.77;

Method 4, 0.63; Method 1, 0.61.

28

Discussion

The project confirmed the general prevalence of NIS in marinas: in September, 1-hour rapid

assessment surveys recorded a mean of 9.6 sessile animal NIS per marina on the south coast of

Devon and Cornwall, while parallel surveys of similar duration dedicated to algae found 5.0 NIS per

marina on average. In total, 26 NIS were recorded in the ten marinas surveyed.

RAS detected on average 2 or 2.5 more NIS per marina than the laboratory inspection of 5 panels

that had been exposed for 8 weeks at 1.5m, which in turn detected 2.5 more NIS per marina than

scrutiny of whole-panel digital images of the same panels. Furthermore, the panels failed to

generate any records of the four algal species on the target list, while records of three of these

species arose during the RASs, generally from specimens growing nearer the surface on pontoon

floats or on other shallow surfaces.

The comparative costings, considered alongside the respective rates of detection of NIS by the

different approaches, suggest that a RAS is the most cost-effective way of monitoring for NIS, both

on a relatively local scale as in the present project and, arguably, for more remote or scattered sites

if the likely greater return of records of NIS from RASs compared to the citizen science protocol is

taken into account. Our costing for the citizen science option is based on the questionable

assumption that such a programme can succeed without face-to-face contact with the volunteers

(and thus zero travel expenses), but in assessing this option, the potential substantial benefit in

awareness raising amongst stakeholders should be taken into account. Advantages of a RAS include

the requirement for a single visit to each site and the rapid availability of the resulting data

compared to the deployment, exposure and retrieval of panels. The relative costings presented by

Campbell et al. (2007) are in agreement with ours in suggesting that the per-site costs of RASs and

the exposure of settlement panels are very broadly similar.

Technology relating to digital photography is now such that even modest equipment on default

automatic settings can produce good images, and no major benefit was apparent from using

relatively high-end equipment in the form of a digital SLR camera. However, it should be noted that

this conclusion relates to whole-panel images (requested as the primary submission in the citizen

science project). Supplementary close-up images would be expected to improve the detection of

NIS, particularly combined with clearing taller organisms out of the way to reveal others underneath,

and would benefit from equipment with good macro capability and, preferably, flexible options for

the focus and exposure modes. This could require some additional attention to the process of taking

pictures, compared with ‘arm’s-length’ shooting. Perhaps just as importantly, it would need

understanding of what to photograph—submission of numerous ‘scattershot’ close-ups would not

be efficient.

Images submitted by citizen scientists did indeed reflect varying capability and understanding of

what was required. Some images were of good quality, with high resolution and correct exposure

and focus, and with the panel filling the whole of the frame, to allow for maximum detail, while

others were of low resolution, limiting the amount of enlargement possible during analysis, or had

incorrect focus or exposure. In others, little could be discerned due to the reflecting surface of the

wet panel, or the panel occupied only a small part of the frame. Thus, the level of competence in the

basic ‘Casio’ set of images we produced is not always realized in the genuine citizen scientist

submissions that this set was intended to emulate.

29

In addition to this, the ‘citizen’ panels varied substantially in their period of exposure and hence

degree of growth, some panels having been redeployed over winter after monitoring in 2012. The

inclusion of a NIS identification guide to prompt the user what to look out for and direct their choice

of macro shot was utilised by some participants, however the study has highlighted that this could

be better directed and improved photographic guidance may help to increase the quality of images

submitted .

Not all of the panels distributed to volunteers led to results, for several potential reasons. The

panels could be lost either as a result of poor fixing or being snagged by passing debris. In some

circumstances volunteers reported that their panels had been cut free, which tended to be more

likely in open public areas outside of marinas. There was also a degree of drop-out whereby

volunteers disengaged with the project. Striking the right balance of communication to ensure that

volunteers continue to engage with the project through to image submission can be tricky given the

extended period while panels are deployed. Social media posts, newsletters and email provide good

options for maintaining contact and interest without being intrusive.

Different strategies for volunteer engagement in recognition of varying levels of commitment and

capability are already being trialled by CWT as part of their citizen science programme. In 2013 a

few selected volunteers took responsibility for monitoring a number of panels and were mentored

by the project officer providing one to one on-site training. However, it is noteworthy that this more

intensive approach would reach a far smaller audience in terms of raising awareness, an intrinsic

factor to changing attitudes within the boating community. CWT envisages that both approaches run

concurrently.

Our analysis of digital images of 50 double-sided panels, coupled with laboratory scoring of the same

panels to produce a comprehensive list of NIS for each side, documented that species vary widely in

their probability of detection and ease of recognition in the images. Scrutiny of whole-panel images

is clearly not an efficient way to detect all species, but works very well for a few. The distinctive,

erectly branching bryozoan Bugula neritina is the prime example of the latter, with a high probability

of detection and a low false-detection rate. The project thus generated very useful insight related to

the probability of detecting the target species, and it seems possible to predict how easily detected

other species would be by considering their growth form, dimensions and shape, and the nature of

their key identification features. It would thus be feasible to tailor citizen scientist programmes

relying on digital photography to target only the most suitable species, although these may not be

the main focus of interest under other criteria, such as risk.

The first of a set of five 15 x 17 cm panels on a pontoon had, on average, two-thirds of the species

recorded from the set as a whole, both for inspection of the panels themselves and when scoring

images of them. The rate of detection of new NIS slowed considerably as the remaining panels were

scored.

In the RASs undertaken here and in our previous projects it was clear that species composition on

pontoons varied from place to place within a marina. A clear example is Perophora japonica at QAB,

where the species was first found on the visitors’ pontoon in 1999 (its first UK occurrence); the

species continues to thrive along this pontoon but is still rarely, if ever, seen on other pontoons in

the marina. Extensive panel deployments by the MBA for the EU Interreg IVA ‘Marinexus’ project

(joint with Station Biologique de Roscoff) documented differences in the faunal assemblage on

30

replicate panel sets at ‘outer’ (close entrance from the open sea) and ‘inner’ (far from the entrance)

sites within the same marina. The best detection rates for a site overall would thus be expected from

panels spread singly or in pairs throughout the marina, although this would require careful mapping

to allow the panels to be found efficiently at the end of their exposure. The placing of test panels on

a single pontoon in the present work allowed a clear estimate to be obtained of the rate of

decreasing returns from the species pool in a single spot, but it would have been informative, had

time and resources allowed, to deploy additional panels in other regions in each marina.

Of the species on our target list that were not encountered during the present work, Botrylloides

diegense is established further east on the south coast of England and has recently colonised

marinas in Torquay and Brixham, so it is expected soon in south-west Devon and Cornwall.

Amphibalanus amphitrite was present in Plymouth 3 or 4 years ago but has not been noted by us

more recently. Didemnum vexillum was seen in PYH in 2008 and 2010, but again has not been noted

more recently. Ficopomatus enigmaticus is predominantly a brackish-water species, and is a

possible occurrence in the Plymouth marinas that sometimes experience substantial freshwater

input. Codium fragile fragile has occurred in QAB and FPR (Arenas et al., 2006), but was not noted

by us during the RASs or recorded by FB during the algal surveys in September 2013. The absence on

our panels of Styela clava could be attributed to the late breeding season of this species, with

recruitment predominantly in autumn. Accordingly, S. clava was detected from images of citizen

science panels that had been left over the winter. Schizoporella japonica was probably present on

panels at MIL (the only site in the project at which this species is known to occur), but the colonies

were too small to identify positively given the possibility of other Schizoporella species.

The exercise of repeating RASs at an interval of a few weeks was informative. Recording the

discovery of NIS at each site in 15-minute intervals suggested that very little remained to be found

after an hour. Nevertheless, at some sites there was a lack of complete agreement in the species list

obtained on the two occasions. Some variation is explicable by genuine changes between surveys:

appreciable changes in the density of invertebrate populations can occur in this time frame. Changes

in the recorded presence of Diadumene lineata and Ciona intestinalis type A apparently reflected

this situation. Otherwise stochastic variation in detecting less common species or those with

inherently low detection probability must undoubtedly have played a part. Also, the recording of

species most apparent on intertidal surfaces in marinas, such as Crassostrea gigas, was affected by

the state of the tide during a survey, which we did not harmonize between visits.

The rapid assessment surveys undertaken here were a relatively streamlined version of the RAS

protocol, with just three staff with similar general skills working separately during the observation

period, and a focus on sessile animal taxa. This enables relatively comprehensive spatial coverage of

the pontoons at a site. A variant approach involves a dozen or so specialist taxonomists who travel

as a group and between them cover a larger proportion of the total fauna and flora (e.g. Cohen et

al., 2005; Arenas et al., 2006). RASs provide immediate results in assessing species distribution and

the detection of new introductions, dependant on frequency of surveying. Prioritising particular

pathways of introduction would help focus effort and the chance of detection. Work to highlight

hotspots for introduction would help to inform monitoring effort (Pearce et al. 2012). However,

success of this method alone would largely depend on gaining access to sites. Operators may be

reluctant to participate and deny access, fearing the consequences should a high-risk species be

31

detected. Reassurance from an authoritative source that this would not lead to a loss of revenue or

liability for costs may be required.

Alternatively, opposition of site owners and operators towards monitoring may be reduced if the

citizen scientist approach was adopted using boat owners who already have access to the marina

from which they rent a mooring. Reliability of detection may be improved with better resources,

and participation of the boating community may facilitate the process of raising awareness within

the marina as a whole, contributing to the long-term goal of changing behaviour to prevent the

spread of NIS.

This suggests that there is potential for a combination of monitoring by scientists and citizen-science

initiatives, each with specific benefits, in a national NIS monitoring programme to meet MSFD

requirements.

Acknowledgements

We wish to thank the marina operators for allowing access to the pontoons and accommodating the

deployment of panels, both by volunteers and by CWT/MBA staff.

32

REFERENCES The Alien and Locally Absent Species in Aquaculture (England and Wales) Regulations 2011. Available at http://www.legislation.gov.uk/uksi/2011/2292/contents/made

ARENAS, F., J. D. D. BISHOP, CARLTON, J. T.,DYRYNDA, P. J., FARNHAM, W. F., GONZALEZ, D. J., JACOBS, M. W., LAMBERT, C., LAMBERT, G., NIELSEN, S. E., PEDERSON, J. A., PORTER, J. S., WARD, S., WOOD, C. A. (2006). Alien species and other notable records from a rapid assessment survey of marinas on the south coast of England. Journal of the Marine Biological Association of the United Kingdom. 86: 1329-1337.

ASHTON, G., BOOS, K., SHUCKSMITH, R. COOK, E. (2006). Rapid assessment of the distribution of marine non-native species in marinas in Scotland. Aquatic Invasions 1: 209-213.

ASHTON, G., BOOS, K., SHUCKSMITH, R., COOK, E. (2006) Risk assessment of hull fouling as a vector for marine non-natives in Scotland. Aquatic Invasions 1: 214-218

BAX, N., HAYES, K., MARSHALL, A., PARRY, D., THRESHER, R. (2002). Man-made marinas as sheltered

islands for alien marine organisms: Establishment and eradication of an alien invasive marine

species. In: Veitch, C.R. and Clout, M. N. (Eds.) Turning the tide: the eradication of invasive species.

IUCN SSC Invasive Species Specialist Group. IUCN, Gland, Switzerland and Cambridge, UK, pp. 26-39.

CAMPBELL, M.L., GOULD, B., HEWITT, C.L. (2007). Survey evaluations to assess marine bioinvasions.

Marine Pollution Bulletin 55: 360-378.

Convention on Biological Diversity. Causes and impacts of invasive alien species. Available at:

https://www.cbd.int/idb/2009/about/causes/default.shtml

COHEN, AN, HARRIS, LH, BINGHAM, BL, CARLTON, JT, CHAPMAN, JW, LAMBERT, CC, LAMBERT, G,

LJUBENKOV, JC, MURRAY, SN, RAO, LC, REARDON, K, SCHWINDT, E. (2005). Rapid assessment

survey for exotic organisms in southern California bays and harbors, and abundance in port and non-

port areas. Biological Invasions 7, 995-1002.

COPP, G. H. BRITTON, J. R. JENEY,G. JOLY, JP.GHERARDI F.GOLLASCH, GOZLAN R. E.JONES, G. MACLEOD A. MIDTLYNG, P.J.MIOSSEC,L. NUNN, A D, OCCHIPINTI-AMBROGI A, OIDTMANN, B. OLENIN, S.PEELER, E. RUSSEL, I.C.SAVININ D.TRICARICO, E.THRUSH, M (2008) Risk assessment protocols and decision making tools for use of alien species in aquaculture and stock enhancement. Centre for Environment, Fisheries & Aquaculture Science available at http://www.cefas.defra.gov.uk/our-science/ecosystems-and-biodiversity/non-native-species/decision-support-tools.aspx

HARDIMAN, N., BURGIN, S. (2010). Recreational impacts on the fauna of Australian coastal marine ecosystems. Journal of Environmental Management 91, 2096-2108.

HILLIARD R. (2004) Best practice for the management of introduced marine pests. URS Australia Pty.

Ltd on behalf of Global Invasive Species Programme. GISP Secretariat.

Import of Live Fish Act 1980. Available at http://www.legislation.gov.uk/ukpga/1980/27/contents

International Maritime Organization (2005) Ballast Water Management Convention. International

Maritime Organization, London, 141 pp.

33

International Maritime Organization (2011). Marine Environment Protection Committee: Guidelines

for the control and management of ships’ biofouling to minimize the transfer of invasive aquatic

species. Resolution MEPC.207 (62). MEPC 62/24/Add.1 Annex 26. Available at:

http://www.imo.org/blast/blastDataHelper.asp?data_id=30766

Millennium Ecosystem Assessment (2005). Ecosystems and Human Well-being: Biodiversity

Synthesis. World Resources Institute, Washington, DC.

MINCHIN D., FLOERL O., SAVINI D., OCCHIPINTI AMBROGI A. (2006). Small craft and the spread of

exotic species. In: J. Davenport, Davenport J.D. (eds). The Ecology of Transportation: Managing

Mobility for the Environment. Chapter 6: 99-118 pp.

MURRAY C. C., E. A. PAKHOMOV, THERRIAULT, T.W. (2011). Recreational boating: a large unregulated vector transporting marine invasive species. Diversity and Distributions 17: 1161-1172.

PEARCE, F. PEELER, E. STEBBING, P. (2012) Modelling the risk of the introduction and spread of non-indigenous species in the UK and Ireland. CEFAS. Project Code E5405W

ROY HE, BACON J, BECKMANN B, HARROWER CA, HILL MO, ISAAC NJB, PRESTON CD, RATHOD B, RORKE SL, MARCHANT JH, MUSGROVE,A, NOBLE D, SEWELL J, SEELEY B, SWEET N, ADAMS L, BISHOP J, JUKES AR, WALKER KJ, PEARMAN D (2012) Non-Native Species in Great Britain: establishment, detection and reporting to inform effective decision making. NERC Centre for Ecology & Hydrology, 110 pp.

STREFTARIS, N., ZENETOS, A., PAPATHANASSIOU, E. (2005). Globalisation in marine ecosystems: The story of non-indigenous marine species across European seas, in: Gibson, R.N., Atkinson, R.J.A., Gordon, J.D.M. (Eds.), Oceanography and Marine Biology - an Annual Review 43: 419-453.

The Green Blue (2011) Biosecurity for submerged structures. Available at:

http://www.thegreenblue.org.uk/boating_businesses/antifoul_and_invasive_species/best_practice_

invasive_species.aspx

The Green Blue ( 2012) The Green Guide to Coastal Boating. Available at:

http://www.thegreenblue.org.uk/leaflets__resources.aspx

The Green Blue (2012) The Green Guide for Marinas. Available at:

http://www.thegreenblue.org.uk/leaflets__resources.aspx

Wildlife and Countryside Act (1981) (Variation of Schedule 9) (England and Wales) Order 2010. Available at: http://www.legislation.gov.uk/ukpga/1981/69

WILLIAM S. F., ESCHEN R., HARRIS A., DJEDDOUR C., PRATT C., SHAW R. S., VARIA S., LAMONTAGNE-GODWIN J., THOMAS S. E., MURPHY S.T. (2010) The economic cost of invasive non-native species on Great Britain. CABI, Wallingford, Oxfordshire. OX10 8DE. CABI Project No. VM10066.