Movement and Growth of Commercially Important Juvenile Fish in Shetland Waters
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A series of funded projects have enabled a programme of fish tagging studies to be undertaken by the NAFC Marine Centre since 2013. The Shetland Fisheries Local Action Group (FLAG) provided funding for the last round of tagging, which occurred in 2017. In such studies fish are tagged and released and over the following months and years, a proportion of the tagged fish are recaptured within the commercial fishery. Tagging studies rely on fishermen and processors reporting recaptured fish to the scientists involved in order that data on movement and growth can be obtained for the period between the release and the recapture of those fish. This report details the work that was undertaken through the FLAG funded project and sets it within the context of the preceeding tagging projects.
The overall aim of the series of tagging projects has been to increase our understanding of the growth and movement of commercially important data limited stocks such lemon sole (Microstomus kitt), anglerfish (Lophius spp.) and megrim (Lepidorhombus whiffiagonis). Plaice (Pleuronectes platessa) were also included in the tagging studies because, although the stock is not considered as data limited in terms of analytical assessment, relatively little research has been undertaken on the species locally. The focus of the FLAG project was to, via tagging juvenile fish, obtain movement data from inshore grounds into the commercial fishery.
In each tagging project, the fieldwork occurred during the summer and at various locations around Shetland. The species, total length (cm), catch and release coordinates, depth, and unique tag identifier number were recorded for each fish that was tagged and released.
During the FLAG project 4899 fish were tagged and released in the summer of 2017 with 260 of these recaptured by 31st December 2018. Since 2013 a total of 13427 fish have been tagged and released with 1014 reported recaptures by 31st December 2018.
Results from the tag returns can be summarised as follows: lemon sole show a high degree of site fidelity with 88% being recaptured within 10 km of their release position; plaice were recaptured up to 172 km from their release site, with 79% of recaptures within 20 km of their release position and monkfish were mainly recaptured north of their release positions. Three of the 172 megrim that were tagged have been recaptured, and this appears to be the first report of successful tag-release-recapture in the species. Recaptures of skates were almost entirely within 5 km of the initial tagging point suggesting high levels of site fidelity.
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