IMIS - Marine Research Groups

"This dataset contains a time series (2013 – 2018) of bycatch data from the AFBI Queen Scallop dredge research survey. It should be noted that the species of primary concern of this research survey was the Queen Scallop (Aequipecten opercularis); and as such the survey design, sampling protocol and technical equipment were designed to maximise the recording of the target species. Over the course of the time series there has been adjustments to survey design, sampling protocol, survey staff and technical equipment in response to changing requirements and latest novel developments in survey equipment. At the end of each research survey individual cruise reports are composed by the Scientist in Charge of (S.I.C.) that provide a summary of the individual survey design, sampling protocol, survey staff and technical equipment and are available on request. The below protocol outlines a general overview of the sampling protocol of the research survey. A bespoke survey report outlined the specification. Stations were selected at random from a fixed grid 0.03* 0.03 decimal degrees. The number of stations within strata were selected as a function of historic queenie fishery within that strata and strata area. At all stations the camera and sledge was deployed. Film data from 15-minute tows at each station were stored on DVDs. A USBL system was used to enable the course taken by the sledge during tows to be tracked. This information is an essential input to calculation of the area of seabed swept during each tow. The dredge is towed at 2.2kn for 15 minutes. Dredge samples were taken at selected stations across a spectrum of observed queenie densities. The fishing gear used four dredges towed abreast, the outer dredges were as used by the commercial vessels for targeting queen scallops (width = 725 mm). The inner dredges were as used to target king scallop (width = 745 mm), one of these was fitted with a fine mesh liner. All catch was processed separately from the each of these three dredge types. A beam trawl and net were used at selected stations. The otter trawl net is towed at 2.4kn for 30 minutes, beam trawl samples were collected from samples of 10 minutes with towing speed of 1 kn. Length frequencies of all queen scallops were taken and two from each length class (0.5cm) retained for biological sampling - length, breadth, and abductor muscle and gonad weights. Length frequencies of all finfish bycatch and counts of benthos were recorded. Paired sampling by otter trawl net and dredge at stations was undertaken to compare catch rates and gear selectivity. "