2019 Cornwall Inshore Fisheries and Conservation Authority (IFCA) Fal Oyster Survey
Cornwall Inshore Fisheries and Conservation Authority (IFCA) conduct annual dredge surveys within the Fal Oyster Fishery since taking over management of the fishery in 2014. The purpose of the survey was initially to assess the distribution and abundance of native oysters (Ostrea edulis) within the Fal Fishery management area in the River Fal, Cornwall. Since 2016 the survey has been developed to also assess queenies (queen scallop, Aequipecten opercularis; variegated scallop, Mimachlamys varia) distribution and abundance. In 2018, an addition to the survey was made to record the number of individual slipper limpets (Crepidula fornicata) at each site. The aims of the survey were to investigate the relative abundance and distribution of native oysters (O. edulis), scallops (queen scallop, A. opercularis; variegated scallop, M. varia) and slipper limpets (C. fornicata) within the Fal Oyster Fishery. The distribution of substrate types across the fishery and species of bycatch were also recorded at each site. In 2019, a total of 83 sites were completed and a total of 1710 oysters, 7015 scallops and 11412 slipper limpets were recorded. The analysis was done by Geographic Area; Harbour, Outer Harbour and River, and Management Areas; A, B and C so that the survey data corresponds with the Fal Fishery Shellfish return statistics.
dataset
CIFCA_FAL_OYS_2019
eng
urn:ogc:def:crs:EPSG::4326
Jenkin, A., Trundle, C., Owen, K., Sturgeon, S. and Naylor, H. 2019. Fal Oyster Survey. Cornwall Inshore Fisheries and Conservation Authority (Cornwall IFCA), Hayle.
biota
revision
2008-01-06
revision
2009-11-16
creation
2015-04-07
-5.0653
-5.0063
50.2482
50.1554
creation
2009-06-18
Western Channel and Celtic Sea
creation
2009-05-01
29E4
creation
1954-01-01
English Channel
creation
2014-05-16
VIIe
revision
2010-01-01
water column
1.4000
9.6000
urn:ogc:def:crs:EPSG::5861
2019-01-15
2019-01-18
publication
2020-12-14
asNeeded
The positions of the survey sites were based on previous survey positions from surveys carried out by Cefas/ Cornwall Council prior to Cornwall IFCA taking over management of the fishery in 2014. The survey was carried out onboard research vessel Tiger Lily VI. The oyster dredge used was an Essex-style oyster dredge with a 72 cm blade, rigged with 34 mm diameter steel belly rings and a 45 mm (twin 3 mm nylon twine) mesh back. The dredge was deployed and recovered using the A frame on the stern of Tiger Lily VI. A target was created in Olex for each site position and a radius ring was added to ensure each tow was 50 m in length. A tow haul method was adopted, similar to that used by the oyster punts. This allowed the dredge tow to be of a known distance and to be easily and consistently replicated. At each survey site the survey vessel was anchored and 60 m of anchor line was let out. The dredge was shot by hand and the slave hauler winch was used to take up 50 m of marked anchor line, resulting in a 50 m dredge tow at a steady 0.5 to 1 knots. The towing warp was run via the A frame mounted hydraulic winch. The towing warp was marked off so that the length (m) of cable deployed at any time was known; this was generally fixed for an average depth and altered only if a depth change was sufficient to cause the dredge to fish too heavily or lightly. The dredge was recovered using the hydraulic winch and/ or A frame. Once recovered, the dredge contents were emptied on to the sorting table. If the dredge did not fish, due to being blinded or flipped over, or the sample appeared smaller than it should be for particular areas, the dredge haul was repeated. A target was created in HYPACK MAX to indicate the start of line (SOL) and end of line (EOL). All positions were recorded using WGS84 projection and all times are recorded as Coordinated Universal Time (UTC). Each sample was photographed on the sorting table alongside a clapper board prior to sorting. Live native oysters, queen scallops and slipper limpets were removed and set aside as the sample was sorted. All live oysters and queen scallops were counted and measured across the widest point, to the nearest mm using Vernier callipers. The weight (g) was recorded for oysters where possible to the nearest 0.1g. All slipper limpets were counted, as individuals and as part of a chain. An abundance scale of 1-5 was used to categorise substrate content of each dredge. A list bycatch species was made for each survey site. Photographs were taken of species when it was not possible to identify them on the spot for later identification. Data was entered in situ into a recording sheet set up in Microsoft Excel. The size frequency distribution was graphed in Microsoft Excel and density maps were created in MapInfo Pro Advanced Version 17.0. Analysis was carried out comparing data from the geographic areas; outer harbour, harbour and river and management areas; A, B and C to ensure compatibility of the data with the oyster permit returns. For a full methodology please refer to the report.
publication
2011-02-02
true
See the referenced specification
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.
No restrictions to public access
Cornwall Inshore Fisheries and Conservation Authority
enquiries@cornwall-ifca.gov.uk
originator
Cornwall Inshore Fisheries and Conservation Authority
enquiries@cornwall-ifca.gov.uk
custodian
Data Officer Cornwall IFCA Research Team
Cornwall Inshore Fisheries and Conservation Authority
enquiries@cornwall-ifca.gov.uk
pointOfContact
2021-11-24