Identification

Title

2017 Cornwall Inshore Fisheries and Conservation Authority (IFCA) Fal Oyster Survey

Abstract

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. Slipper limpets (Crepidula fornicata) were recorded at each site using a SACFOR style scheme. The aims of the survey were to investigate the relative abundance and distribution of native oysters (O. edulis) and scallops (queen scallop, A. opercularis; variegated scallop, M. varia) within the Fal Oyster Fishery. The distribution of substrate types across the fishery were also recorded at each site and species of bycatch were recorded across the survey area as a list of species present. In 2017, a total of 80 sites were completed and a total of 1481 oysters and 2952 scallops were recorded. The analysis was done by Geographic Areas; Harbour, Outer Harbour and River.

Resource type

dataset

Resource locator

Unique resource identifier

code

CIFCA_FAL_OYS_2017

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

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

Additional information source

Jenkin, A., Trundle, C., Street, K. and Naylor, H. 2017. Fal Oyster Survey. Cornwall Inshore Fisheries and Conservation Authority (Cornwall IFCA), Hayle.

Classification of spatial data and services

Topic category

biota

Keywords

Keyword set

keyword value

effective date

2015-04-07

Geographic location

West bounding longitude

-5.0653

East bounding longitude

-5.0063

North bounding latitude

50.2482

South bounding latitude

50.1554

water column

Temporal reference

Temporal extent

Begin position

2017-01-22

End position

2017-01-24

Dataset reference date

date type

publication

effective date

2019-04-09

Frequency of update

asNeeded

Quality and validity

Lineage

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. 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 and queen scallops 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. Slipper limpets were recorded on an abundance scale of 1-5. A list of bycatch species was made for the whole survey area. The bycatch recording in 2017 was a minor part of the oyster survey and the list of species recorded is shown in the report. 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. For a full methodology please refer to the report.

Conformity

Conformity report

specification

title

MEDIN data guideline for fish and benthos data by trawl or dredge

reference date

date type

publication

effective date

2018-10-08

degree

true

explanation

See the referenced specification

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

2021-11-24

Metadata language

eng