e464132b92aa4c4fe90e8c504a2143cc English series Cornwall Inshore Fisheries and Conservation Authority Data Officer Cornwall IFCA Research Team enquiries@cornwall-ifca.gov.uk pointOfContact 2024-07-23 MEDIN Discovery metadata standard 2.3.8 urn:ogc:def:crs:EPSG::4326 2021 - Present Cornwall Inshore Fisheries and Conservation Authority (IFCA) Multi-year intertidal Edible Crab (Cancer pagurus) survey 2024-04-12 publication CIFCA_GRE_INT_EDC_2021-2023 "Cornwall Inshore Fisheries and Conservation Authority (IFCA) have been investigating ways to survey the abundance of edible crab (Cancer pagurus), also known as brown crab, within the Cornwall IFCA district. Shallow water, cobble nursery habitats are likely to represent a major source of recruitment to offshore fisheries (Robinson and Tully, 2000). Juvenile edible crabs, C. pagurus settle from July to September (Robinson and Tully, 2000) and inhabit the intertidal zone until they reach a carapace width 6-7mm (which takes approximately three years), before they migrate to subtidal areas offshore (Hunter et al., 2013). In 2020, Cornwall IFCA carried out two exploratory survey days at Prisk Cove, near Mawnan Smith on the south coast of Cornwall. This site was chosen due to high records of edible crab numbers during past Seasearch surveys (Matt Slater, pers. comm. 2020). These two surveys trialled different sampling methods: one using a 5 m2 grid at different stages down the shoreline from the high water mark to the low water mark and the other doing a walkover along the length of shore at the low water mark parallel to the shoreline. The walkover method proved more suitable to the survey and has been used by Cornwall IFCA in subsequent surveys presented in this data. Due to the low numbers of edible crabs at the Prisk Cove site from the two preliminary survey days, it was decided that repeating the survey at Greeb Point, Portscatho which is the location Cefas used for their surveys would be more beneficial. The site at Portscatho provides optimal habitat and shelter for juvenile edible crabs and consists of coarse sand, pebbles, cobbles, boulders and bedrock with overhangs. This survey involved multiyear intertidal edible crab surveys, between 2021 and 2024, 14 survey events were conducted at Greeb Point one mile south of Portscatho on the south coast of Cornwall. The survey events were carried out within a window 1.5 hours either side of low spring tides between April 2021 and June 2024 . Cornwall IFCA carried out fourteen survey days (between: April to October in 2021 (4 survey events - 29th April 2021, 27th May 2021, 23rd June 2021 and 8th October 2021 ), March to July in 2022 (4 survey events - 3rd March 2022, 31st March 2022, 15th June 2022 and 14th July 2022), March to June in 2023 (3 survey events- 21st March 2023, 20th April 2023 and 5th June 2023) and March to June 2024 (11th March 2024, 23rd April 2024 and 7th June 2024) to sample juvenile edible crabs at Greeb Point. Position tracks of the surveys were were loaded into a handheld Garmin GPS 60 unit using latitude and longitude. Officers walked towards the EOL position from SOL covering as much ground as possible in a 1.5h window either side of low tide. If crabs were found, these were picked up carefully and their abdomen was photographed with an Olympus Tough TG-5 or an Olympus Tough TG-6. The crabs were measured across the width of the carapace (mm) using vernier callipers and carapace width recorded on a log sheet. A total of 569 juvenile edible crabs were recorded during the four year survey." Research Team Cornwall IFCA Cornwall Inshore Fisheries and Conservation Authority enquiries@cornwall-ifca.gov.uk originator Research Team Cornwall IFCA Cornwall Inshore Fisheries and Conservation Authority enquiries@cornwall-ifca.gov.uk custodian asNeeded Marine Environmental Data and Information Network NDGO0005 Species distribution GEMET - INSPIRE themes, version 1.0 2008-01-06 revision Shellfish abundance and biomass in water bodies SeaDataNet P021 parameter discovery vocabulary 2009-11-16 revision 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. otherRestrictions No restrictions to public access English biota International Hydrographic Bureau, Limits of Oceans and Seas 1954-01-01 creation English Channel -4.9727 -4.9720 50.1640 50.1655 2021-04-29 2024-07-23 Research Team Cornwall IFCA Cornwall Inshore Fisheries and Conservation Authority enquiries@cornwall-ifca.gov.uk distributor series MEDIN data guideline for timed search data 2022-02-11 publication See the referenced specification true The start of line (SOL) positions from the survey carried out by Cefas in 2012 was used as the SOL position in the Cornwall IFCA surveys. The end of line (EOL) position was modified for all surveys from 2022 onwards due to time constraints and habitat type which consisted mainly of bedrock with overhangs which made it hard to record edible crabs. Positions were loaded into a handheld Garmin GPS 60 unit using latitude and longitude and work mobile phones using the what3words app. All times were recorded as Universal Time Coordinated (UTC) unless otherwise stated. Officers initially recorded the weather and tide times into a log sheet (water temperature was also recorded from 2023 onwards) and then proceeded to the SOL position. Officers walked towards the EOL position covering as much ground as possible. At the given survey positions, stones, cobbles and boulders that were deemed safe (not too heavy or in an awkward position) were overturned and checked for edible crabs hiding underneath. If crabs were found, these were picked up carefully and their abdomen was photographed with an Olympus Tough TG-5 or an Olympus Tough TG-6. The crabs were measured across the width of the carapace (mm) using vernier callipers and carapace width recorded on a log sheet. Determining the gender of immature edible crab is difficult as the differences in the abdominal flaps are not as distinct as in adult edible crabs (personal pre survey observation). As such crab gender was recorded as U (unsexed) for crabs less than 60mm carapace width and recorded as either male or female if they were greater than60mm and morphological features allowed a clear gender assignment. Once measured, the crabs were returned to the place they were found and the habitat was returned to as found, by replacing stones and cobbles to their original positions. The survey metadata, GPS positioning and crab data were transferred into Excel. Length frequency and density, box and dot plots were created in R (using R studio version 4.3.2) to visualise trends in data. However given the exploratory nature of this work the survey results have been compared with caution. The GPS track for all survey days were plotted using MapInfo Professional Advanced (Version 17.0.4) over aerial footage from drone photography of the survey site supplied by Vertical Horizons Media and was used as a base layer for surveys positional data.