Whelk fishing has been increasing throughout the British Isles and there is a considerable lack of knowledge of biological parameters that inform sustainable management. They are a relatively slow growing species which reproduce late in life. As a result, this species is potentially vulnerable to overexploitation.
Since 2015, the Fisheries and Conservation Team here at Bangor University have increasingly focused on static gear fisheries and are collaborating with the UK and Manx fishing industries to better understand whelk resources within the Isle of Man territorial waters. By analysing landings-per-unit effort (LPUE) data from logbook records, we are able to monitor the general trends in productivity. It is also important to build upon this low-resolution information hence the team are developing several long-term projects.
Monthly Pot Samples
A Fish-Tec whelk pot given to commercial fishermen for samMpling (left). Researcher Jack Emmerson estimating the age of whelk samples in the laboratory (right).
Recent work by Jodie Haig and other Fisheries and Conservation team colleagues showed that the biological characteristics of whelk populations in Wales can vary significantly at different spatial resolutions. In order to understand whether this is the case in the territorial waters of the Isle of Man, we have set up a standardised fisheries-dependent sampling regime with both Manx and UK vessels. Fishermen land the contents of two pots (separately) once a month and provide basic catch information such as GPS, soak time, bait used and the haul date. From these biological samples, we will be able to gather data on:
- Catch per unit effort
- Population structure
- Sex-ratio (catch composition)
- Size at age
- Size at functional maturity
- Size at onset of maturity
A tagged whelk with unique ID (left). Whelk movements identified by MSc student Matt Robinson (right).
A tag-recapture experiment was conducted during the summer of 2015 as part of Matt Robinsons’ MSc project. Students tagged over 5000 whelk with a successful 15.5% recapture rate. The results provide insight on the site fidelity, movement and local abundance of whelk within the experiment area.
The tagging method was highly effective and researchers on the Isle of Man are collaborating with colleagues in Wales to further refine the methodology to maximise benefit so as to get the most from these experiments. We will be co-ordinating further tagging experiments on fishing grounds around the Isle of Man to study the connectivity of these populations and identify whether habitats and/or seabed features may be causing movement restrictions.
A whelk undergoing dissection (left) and genetic samples stored in ethanol (right).
The team have provided small tissues samples of whelks from around the island in a larger project looking at the connectivity of whelk resources in the Irish Sea. By collaborating with other fisheries scientists to compare the genetic structure of Manx whelks with that of populations elsewhere in the Irish Sea, we will gain insight into the connectivity of these populations. This allows decisions to be made about the necessity, or benefits, of local fishery management plans.