fc5f58fca24ea6b70f2cb425c7fb26a2 English dataset Cornwall Inshore Fisheries and Conservation Authority Data Officer Cornwall IFCA Research Team enquiries@cornwall-ifca.gov.uk pointOfContact 2024-07-22 MEDIN Discovery metadata standard 2.3.8 urn:ogc:def:crs:EPSG::32630 2019-2020 Cornwall Inshore Fisheries and Conservation Authority (IFCA) Scallop dredging Survey 2021-05-27 publication 2019-20_CIFCA_POR_DRE_SCA Cornwall Inshore Fisheries and Conservation Authority (CIFCA) is the authority responsible for the sustainable management of sea fisheries in the Cornwall IFCA district, which extends to 6 nautical miles from coastal baselines. Dredging for king scallops in the Cornwall IFCA district is currently subject to a number of byelaws, including; Shellfish Boats Byelaw, Scallop Dredge (Limited Fishing Time) byelaw and Methods of Fishing (Dredges) byelaw. These byelaws limit boat size to 16.46m in the district, prohibit scallop dredging between 7pm and 7am and stipulate gear requirements, including a limit of 12 dredges per vessel at any one time. Cornwall IFCA’s research team are preparing to start annual dredge tow surveys for scallops within the district. Currently the proposal is to conduct annual survey tows at a number of inshore sites within the district which were previously regularly surveyed by CEFAS along with some new sites. Data from these surveys, in conjunction with the larger current Cefas Stock Assessment program, would help to guide management of this fishery in inshore waters. Cornwall IFCA carried out this survey in preparation to start annual dredge tow surveys for scallops within the district. Currently the proposal is to conduct annual survey tows at a number of inshore sites within the district which were previously regularly surveyed by CEFAS along with some new sites. Data from these surveys, in conjunction with the larger current Cefas Stock Assessment program, would help to guide management of this fishery in inshore waters. The aim of the project was to develop a suitable method for repeat surveying for scallops from R/V Tiger Lily, to be used in multiple locations. The objectives of the survey were to trial the effectiveness of the N-Virodredge and tow bar for dredging for scallops from R/V Tiger Lily, to obtain measurement of all scallops (P. maximus) collect and to trial identifying and measuring the growth rings on individual scallop shells for ageing purposes. In 2019, five tows were completed with a total of 74 scallops recorded. In 2020, a total of nine tows were completed with a total of 105 scallops recorded. 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 Geographic Information System Marine Environmental Data and Information Network NDGO0005 Species distribution GEMET - INSPIRE themes, version 1.0 2008-01-06 revision Fish and shellfish catch statistics Shellfish abundance and biomass in water bodies Shellfish morphology, age and physiology 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. Permission must be sought if the data will be reproduced in full or part or if used in any analyses. This data is not suitable for use in navigation otherRestrictions No restrictions to public access English biota Charting Progress 2 Sea Areas 2009-06-18 creation Western Channel and Celtic Sea ICES Rectangles 2009-05-01 creation 29E5 International Hydrographic Bureau, Limits of Oceans and Seas 1954-01-01 creation English Channel SeaDataNet vertical extent keywords 2010-01-01 revision water column -4.8858 -4.8699 50.1987 50.2182 2019-02-28 2020-05-27 19.6000 34.2000 Research Team Cornwall IFCA Cornwall Inshore Fisheries and Conservation Authority enquiries@cornwall-ifca.gov.uk distributor dataset MEDIN data guideline for shellfish stock assessment data 2011-02-02 publication See the referenced specification true A single N-VirodredgeTM mounted on a custom designed tow bar was used during the survey. The N-Virodredge has the same width as a traditional scallop dredge (76cm), but uses individually mounted spring loaded tines, as opposed to a steel tooth bar to penetrate the sea bed. A shackle was used to connect the N-Virodredge to a central towing point on the custom made 1.8m tow bar. The winch on Tiger Lily’s A-Frame (Spencer Carter 0.5t) was used to deploy and recover the dredge. Dyneema cable from the winch was used for towing. The slave hauler on the starboard side of Tiger Lily was rigged around the front of the vessel to the davit in the port quarter position. This hauler was used to raise and lower the end of the dredge bag for emptying the contents on to the deck. GPS track data was recorded in Hypack®MAX for the duration of the survey and all targets / waypoints created in Hypack. All positions in Hypack are sourced from the dedicated survey GPS (Furuno GP-32) on board and times in Coordinated Universal Time (UTC) are taken from the same source. Vernier stainless steel callipers were used for all shellfish measuring on board. The N-Virodredge was deployed through the A-Frame at the stern of Tiger Lily, using the onboard winch, whilst the vessel motored slowly forwards. Once the dredge was clear of the deck and at the surface of the water winching was halted. A lowered towing point was then created by attaching a chain with a connected towing block across the bottom of the A-Frame. The Dyneema cable was then run through this lowered towing point. The winch was then used to lower the dredge onto the seabed. The length of Dyneema cable out varied slightly (70-95m) with each tow, but was approximately three times the water depth. Once the dredge was on the seabed a start-of-line (SOL) position was created in Hypack. R/V Tiger Lily motored forward at a speed of 2-3 knots for the duration of the tows. The first two tows were considered trial tows and not of a set length. The remaining three tows were a nautical mile in length and considered three replicates, with tows 3 and 5 running in the same direction and tow 4 running in the opposite direction. Once tows were completed an end-of-line (EOL) mark was created in Hypack. The winch was then used to recover the dredge to the stern of the vessel. The lowered towing point was removed, before the winch was used to recover the dredge and tow bar onto the deck. The tow bar wheels were chocked with wood to secure the equipment. A line from the slave hauler, run through the port quarter davit was then connected to the rear of the dredge bag. The hauler was used to raise the end of the dredge bag and empty the contents on to deck. Before any catch sorting the slave hauler was used to lower the dredge bag back onto deck and the winch then used to move the dredge and tow bar into the water at the stern of the vessel. The catch from each tow was photographed, before the scallops were sorted into a fish box. The height of all scallops was measured from the umbo to the mantle and a width measurement was taken across the widest point, all to the nearest mm. Scientific Officers then trialled recording the length of each growth ring from the umbo of the scallop. These rings each represent a year’s growth and can be used to age the scallops. The flat valve was used to determine growth rings, with lines on the curved valve used to confirm any uncertainties. Where rings were difficult to distinguish on the scallops a ‘low confidence’ mark was noted with the measurements. Scallop measurement data was entered in situ into a recording sheet which was set up in Microsoft Excel. At the end of the survey this spreadsheet was transported back to the office via a hard drive and stored on the Cornwall IFCA servers. All photographs taken as part of the survey were again transferred to Cornwall IFCA’s servers and stored in the same folder as the data, labelled with the survey title and date. At the end of the survey all track and target data was exported from Hypack in a .txt file format and stored on the Cornwall IFCA servers. The GPS tracks of all tows were plotted in MapInfo Pro v17.0 over hydrographic charts and side-scan sonar data of Veryan Bay. Microsoft Excel was used to plot charts of scallop height, width and age class.