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.
FV Boy Shayne PL777 alongside FPV Barrule during a collaborative tag-recapture study.
The common whelk is fished using specialised pots around the Isle of Man by local and UK vessels, with the main markets in Europe and Asia. The fishery has only developed very recently and has shown significant increases in quantities being landed. In 2011, 134.5 tonnes were landed from 7 Isle of Man vessels. In 2014, 589 tonnes (£507,916) were landed by Manx registered vessels alone (in addition to substantial effort and removal by UK vessels). At present there are 13 vessels licenced to fish for whelk within the Isle of Man’s 0 - 3 nautical mile limit (including 2 UK registered vessels) although very few boats exclusively target this species.
Other than landings data, which is collected by DEFA as part of the requirement for licence holders to submit Monthly Shellfish Activity Logs, there is no current, detailed information about the whelk stocks. However, fishing industry members recognise the imperative for creating an evidence base to ensure a viable future and have thus begun geo-referencing their landings per unit effort (LPUE) within preallocated regions.
The information available indicates the common whelk is widely distributed around the island, with spatial differences in growth rates. They are slow growing and reproduce late, making them potentially vulnerable to over-fishing. Some precautionary measures are built into the Isle of Man fishery management arrangements, including a minimum landing size (MLS) of 70mm which is significantlu larger than the standard EU MLS of 45mm.
The Common Whelk (Buccinum undatum)
The common whelk, B. undatum © Asbjørn Hansen (left). Right: The movement of whelk towards a baited trap in a tagging experiment in the Gulf of St Lawrence, Canada (Himmelman, 1988).
The common whelk is a large whelk that can grow up to 10 cm high and 6 cm wide. The shell is yellowish brown in colour and has 7-8 whorls.
Habitat & Distribution
Common whelks are found on sand, sandy mud or stony bottoms from below the tide line to a depth of 100 m. These species are common in the North Sea and other shelf seas surrounding the North Atlantic Ocean. Their southern boundary is Brittany and northern boundary is into the Arctic region. Common whelks are active predators that mostly feed on live polychaete worms and bivalves. They extract the flesh of bivalves by either using their own shell to pry open the bivalve shell or by drilling holes into the shell.
This species reaches sexual maturity at 5-7 years and breeding takes place from October to May. The eggs produced are attached to rocks, shells and stones in protective capsules. Each capsule contains as many as 1000 eggs, and many female’s egg capsules can be grouped together in groups of over 2000. After several months, crawling young emerge from the capsules. Common whelks are believed to live for 10 years.
MSc & PhD Theses
Robinson M. (2015), The abundance, movement and site fidelity of the adult whelk, Buccinum undatum, in the territorial waters of the Isle of Man
Bolger E. (2014), The abundance, movement and population characteristics of common whelk, Buccinum undatum (L.), in an area under consideration for an offshore windfarm development in the territorial waters of the Isle of Man.