Identification

Title

2022 Cornwall Inshore Fisheries and Conservation Authority (IFCA) Fal and Helford SAC Drop Down Video Maerl Habitat and Classification Survey

Abstract

Cornwall Inshore Fisheries and Conservation Authority (Cornwall IFCA) carried out a survey between May and July in 2022 of the maerl feature of the Fal and Helford Special Area of Conservation (SAC). The aim of the survey was to get a better understanding of the varying types of maerl habitats present including: dense maerl (live and dead or dead), maerl sediment (live and dead or dead), sparse maerl (live and dead), scattered maerl (live and dead), maerl veneer (live and dead, static or live and dead, mobile) and areas of potential maerl which lack detail, and to provide and updated extent and distribution map within the Fal and Helford SAC. There were two parts to this survey and the current report details the second part. The first part consisted of an initial side-scan sonar survey in the Fal and Helford SAC, which was carried out by Cornwall IFCA in 2020 and 2021 (Sturgeon et al., 2021). The initial survey gathered acoustic data within the SAC, focusing on Falmouth Bay and covered an area from Pendennis Point to the Helford River out to the Fal and Helford SAC boundary from Zone Point towards Manacle Point. This second part uses the acoustic data gathered in part one to identify transitions between different acoustic signatures, with the aim of verifying habitat types represented by the given acoustic signals, using drop down video and stills. The survey is reported on by Jenkin et al., 2023.

Resource type

dataset

Resource locator

Unique resource identifier

code

2022_CIFCA_FAH_Maerl_DDV

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

urn:ogc:def:crs:EPSG::4326

Classification of spatial data and services

Topic category

biota

Keywords

Keyword set

keyword value

Keyword set

keyword value

Keyword set

keyword value

originating controlled vocabulary

title

GEMET - INSPIRE themes, version 1.0

reference date

date type

revision

effective date

2008-01-06

Keyword set

keyword value

originating controlled vocabulary

title

SeaDataNet P021 parameter discovery vocabulary

reference date

date type

revision

effective date

2009-11-16

Geographic location

West bounding longitude

-5.1223

East bounding longitude

-5.0132

North bounding latitude

50.1707

South bounding latitude

50.0880

Extent

Extent group

authority code

title

SeaDataNet vertical extent keywords

reference date

date type

revision

effective date

2010-01-01

code identifying the extent

water column

Temporal reference

Temporal extent

Begin position

2022-05-12

End position

2022-07-13

Dataset reference date

date type

publication

effective date

2023-05-04

Frequency of update

continual

Quality and validity

Lineage

Video and digital still imagery was acquired using a STR SeaSpyder drop camera system (Appendix 2). The survey was carried out in line with Mapping European Seabed Habitats (MESH) recommended operating guidelines for underwater video and photographic imaging techniques (MESH, 2008). The tows were planned at 200 m with a still image every 10 m at a speed of 0.5 knots aiming for 10 to 15 minutes per tow. Planned survey sites were loaded into Hypack Max Version 2019 for navigation purposes with 10 10 m radius rings around each site with the aim of having one still image at each ring. If the tide or wind moved the vessel off course a 10 m radius ring was added to each target so the officer would know when the vessel had moved 10 m. Prior to the deployment of the SeaSpyder for each tow, the video text overlay was checked and adjusted to display the survey name and tow number (e.g. “Cornwall IFCA_01/06/2022. Fal Bay_DDV_02_T1”) and the GPS, heading and depth info was checked to ensure that it was updating correctly. The .jpeg file name prefix was checked and adjusted to display the survey name, tow number, date, time (UTC) and automatic image number (e.g. “CIFCA_FalBay_02_T1_20220601__14_23_20__0094.JPG”). The SeaSpyder camera was deployed through the A-Frame at the stern of Tiger Lily and lashed securely to the starboard side of the vessel between tows. The video was set to record once the camera was just above the seabed. Com Port A was set to log to record all positional information from the USBL GPS antenna (Lat/ Long WGS84) for the entire tow. A target was created in Hypack to indicate the start of line (SOL); this was repeated at the end of line (EOL). The SeaSpyder was ‘flown’ with the frame legs just above the seabed for the tow. The camera frame was landed on the seabed every 10 m for a still image to be captured. Image separation varied slightly to ensure that the stills taken were of good quality (e.g. taken when the camera was focused on the seabed and the lens unobstructed) this sometimes led to a delay. Immediately upon having captured a still image a target was created in Hypack. Field notes were recorded for each target in Hypack such as image number, speed over ground and real-time observations of substrate and taxa (comma delimited) when possible. Hypack targets were used in data processing to obtain the exact time of each still image and the Easytrak Alpha USBL GPS log was used to obtain the exact location of each still image. All position information was recorded in the Lat/Long WGS84 projection and taken from a single GPS (USBL GPS antenna). GPS targets were recorded using the USBL GPS antenna set up on the wheelhouse roof of Tiger Lily. Hypack was set up to log a vessel position recorded every second and the Com Port A file was recording the USBL position from the camera for the duration of each tow. Hypack targets were extracted as a .txt file format and opened in Microsoft Excel (comma delimited). The Hypack ‘logging’ function was left running both survey days which outputs as a .RAW file. This data was opened with Microsoft Excel and cut to only include relevant strings of data such as date, time, position and depth. The data has not been extracted per tow but is available if required. Com Port A data was logged for the duration of each tow and saved in a .txt file format to the Topside PC. Still images from the SeaSpyder camera were initially stored on the internal computer (sub-surface), then on completion of each tow the still images were transferred to the SeaSpyder topside control unit using FileZilla and filed by site number. Video files were captured to the SeaSpyder topside unit data drive (D:/). The stills and video files were transferred from the topside unit to a WD Passport for transport and storage at the end of each survey day. The log sheets were worked on from the network and saved regularly throughout the day. Image analysis was carried out post-survey with each still image being assessed in terms of quality with categories good, acceptable or poor as follows; o Good: Clear, camera on seabed and sediment type and fauna distinguishable o Acceptable: Can make out the sediment type and what fauna are present but not the best quality o Poor: Can’t make out the sediment type or what fauna is present Any poor-quality images were not carried forward for further analysis. The position data for each tow were transferred to MapInfo Professional Version 17.0.2 and points were created to show the position of each still image (good and acceptable quality images only) and SOL/ EOL positions.

Conformity

Data format

name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Data is freely available for research or commercial use providing that the originators are acknowledged in any publications produced and permission must be sought if the data will be reproduced in full or part or if used in any analyses.

Constraint set

Limitations on public access

No restrictions to public access

Responsible organisations

Responsible party

organisation name

Cornwall Inshore Fisheries and Conservation Authority

email address

enquiries@cornwall-ifca.gov.uk

responsible party role

originator

Responsible party

organisation name

Cornwall Inshore Fisheries and Conservation Authority

email address

enquiries@cornwall-ifca.gov.uk

responsible party role

custodian

Metadata on metadata

Metadata point of contact

contact position

Data Officer Cornwall IFCA Research Team

organisation name

Cornwall Inshore Fisheries and Conservation Authority

email address

enquiries@cornwall-ifca.gov.uk

responsible party role

pointOfContact

Metadata date

2024-08-13

Metadata language

eng