Crustacea Fisheries

Current projects


Paternity Tests for lobsters

Description: skid trials 044

Image: Harriet Salomonsen - Berried female Homarus gammarus

What: We are currently collecting tissue samples from berried females along with samples of their eggs. We will carry out genetic tests to reconstruct paternities and estimate the number of males contributing to the fertilisation of the females in an area. This will also allow us to see if females mate with more than one male - multiple paternity.
We are hoping to compare the number of males fertilising females from commercially fished areas to the number of males fertilising females in areas closed to commercial potting, such as Lundy Island.

Why: Understanding the reproductive and mating behaviour of a species is vital for fisheries management decisions. V-notching of females protects the reproductive females. However it can also result in a bias with a higher number of male lobsters being landed. This study will enable us to understand if V-notching changes the mating behaviour of lobsters when it alters the ratio of large females to large males.

In the future: This is a pilot study using samples collected from the Llyn Peninsula, and Ramsey Island over Spring and Summer 2013. We hope to have the results in the New Year.

Stock Assessments: On board camera catch composition monitoring

Traditionally to conduct stock assessments for pot fisheries on board observers are required. We realize that having observers on board is often unfeasible and only provides limited temporal and spatial coverage.

Aims: An on-board camera system is being developed for assessment of crab and lobster fisheries. The camera captures footage of all catch, both landed and undersized and the video is analysed to gather size, sex and abundance data which will form the basis of stock status assessment and be used to create an index of recruitment to the fishery. We are also hoping to trial this technology with the sea bass fishery.

Progress: The trials and validation of the camera system to collect abundance, sex and size data for crabs and lobsters are almost complete. We have piloted the system measuring crab abundance and sex data from a video of a day’s pot hauling from a vessel on the Llyn peninsula. This allowed us to identify and solve any problems with the procedure. Validation of the sizes obtained from the videos was carried out using crab and lobsters from the Lobster Pot on Anglesey. The results showed the video to be an accurate measure of size and sex in crabs and larger lobsters.
Ten crab/lobster fishers have already signed up to use this system on their boats and Bangor University’s workshop is currently making the housings. Each fisher with a camera system will be provided with a string of five standardised parlour pots to allow comparison between fishers and areas. These pots are ready to be distributed.

Once the camera housings are completed they will be fitted to the crab and lobster fishers boats who will record one days fishing per month. The camera memory cards will be returned to Bangor University for analysis.

Images taken from the on-board camera showing the measurements taken and how crab and lobsters are sexed


The on-board camera system has been providing us with large amounts of data. The videos below show the type of footage we receive from the fishing vessels. From this we can ascertain numbers of crab and lobsters that are caught, how many of those are above the MLS and how many are undersized and returned to the sea. In addition we can see the sex ratio of the catch, we can see if females are carrying eggs and we can calculate the size of each animal. Other data that we can collect is the type of bait used and the presence of any by-catch. All of this helps those fishermen involved move towards a fully documented fishery and provides us with the necessary data for calculating recruitment indices.

On-board camera update bulletin - September 2013


Video footage showing a berried female lobster in the catch

Video footage showing brown crab sorted in the catch


Lobster tagging

Image: (Clockwise top left to bottom) Leigh Howarth (University of York) - Lobster with tag between carapace and abdomen, The five colours of tags that we will use, Close up of a tag showing the number to call if found.

One really important study we need your help with is our tagging study. We are conducting research into the growth of lobsters around the Welsh coast. This information will be used to help predict numbers of lobsters that will be large enough for the fishing industry to catch in a year or two, which in turn will help fishers manage fishing effort and their local stocks sustainably.  

We will be individually tagging and measuring up to 5,000 lobsters around the whole coast of Wales. The size and sex of lobsters at the time of tagging will be recorded. When they are re-caught we can look at growth, moult rate, movement and abundance. The lobsters will also be “v-notched” so they will be illegal to land and therefore be safe-guarded for a few years until the notch grows out and the tag falls off.

The lobster will be tagged on their back between the carapace and the abdomen. Different areas within Wales will use different colours as, although the primary objective is to collect information on the growth of the lobsters, we can also use this data to look at lobster movement around the coast. The different colours allow us to quickly identify if a lobster has moved to a completely different area since being tagged.

If tagged lobsters are re-caught and not reported this can negatively influence our estimates of abundance so please get involved.

Tagging will start in late April to early May, if you catch any tagged lobsters please get in touch.


To date almost 1000 lobsters have been tagged throughout Wales, with a large effort occurring off of the tip of the Llŷn Peninsula. The carapace length of re-caught lobsters ranges from 66mm to 105mm, suggesting that larger lobsters are less likely to be re-caught. Plotting the GPS co-ordinates of tagged lobsters against the GPS co-ordinates of where they were re-caught shows that the majority of lobsters have moved less than 200m. These preliminary data agree with previous studies of the movement of the European lobster, with most lobsters staying close to their initial capture location whilst a few lobsters range further afield. A preliminary report is now available here.

Lobsters moved a median distance of 114m with the majority of lobsters moving less than 200m. Maximum distance moved was 3.6km

Dr Natalie Hold
Telephone: 01248 382850 or 07903 762466

Brown Crabs: Fecundity and size at maturity

Image: Berried Brown crab - Jodie Haig


This winter 2014/2015 we are undertaking a collaborative project with researchers from Scotland, Ireland, Isle of Man, Wales and England to assess the regional variation in size at maturity.
Between November and January samples of brown crab will be collected and assessed for maturity stage using morphometric, visual and histological methods. Additionally we will be collecting berried hens for fecundity estimates.

If you would like to contribute to this study, or you are interested in the results in any way please contact Jodie!

For details contact:
Dr Jodie Haig
01248 382606

Crustacean Fisheries Data Collection

National and EU legislation will soon require the burden of proof to show that fisheries are NOT having a negative impact on fish stocks or the environment.

As data for fisheries in Welsh waters are comparatively data poor, there are implications for current fishing practices. Our project aims to collect some spatially relevant data on the whelk fishery so that the fishery can continue into the future in a fair and sustainable way. Engagement with industry is vital. With the joint effort of scientists and fishers working together, this project has the best chance of producing representative data for a future stock analysis. This project will provide the industry with the data it needs to respond to, and partake in the management process.

Fish with a scientific pot!

Image: Prawn pot (left) and lobster pot (right)

We aim to provide fishers with 2-3 scientific prawn pots or a string of crab/lobster pots. Once a month we will collect the contents of a day’s fishing from these pots along with a short, easy to fill out data sheet. For the remainder of the month the fisher will be able to fish the scientific pots as part of their gear.

For more information and to take part in this study contact:

Dr Natalie Hold
01248 388425

Dr Jodie Haig
01248 382606

Flying array

Flying array.jpg
Images: Flying array underway 1m above the seabed

A flying array has been designed to film over the rough, rocky or fragile habitat-types that the usual camera sled is not appropriate for. It is an autonomous towed underwater video system fitted with a video camera, LED lights and lasers (which enable accurate measurements of organisms captured by the camera). The buoyancy and design of the unit enables it to respond to changes in slope, thus “flying” over the rocky bottom. This will allow us to film potential lobster habitat. It is currently being trialled and initial testing has shown successful results.

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Image: Footage of the seabed filmed using the array showing the lasers used to measure fauna

Footage from trials with the flying array - This has been designed to film over rough, rocky and fragile habitats.

Recreational potters

Click on the image to see it full size:

(English version)                                                               (Welsh version)


Lobster Escape Hatch Study in Cardigan Bay

In collaboration with the Cardigan Bay Fisherman’s Association (CBFA), we are undertaking a study investigating the use of lobster escape hatches in Cardigan Bay.

  • To determine the optimum size of lobster escape gaps that maximises the whole catch
  • To determine the percentage loss of bycatch with lobster escape gap use
  • To observe the behaviour of targeted species within and around pots with and without lobster escape gaps

In addition to these core aims, this study strives to determine the species proportions of the retained catch of pot fishers in this area, whether lobster escape gaps decrease sorting time, and the effect that the introduction of lobster escape gaps would have economically as, at present, much of the bycatch is of high value.

This study will be using the on-board camera system for data collection. All four on-board camera systems have been installed on the fishers’ boats and the fishers have started fishing the pots with escape hatches. Data collection will continue until each fisher has completed 12 fishing days using the on-board camera system.

Image: Two of the on-board camera systems designs – Julia Pantin

In order to address the study aim of observing the behaviour of targeted species within and around pots with and without lobster escape gaps, an experimental pot will be designed with an attached camera to film the inside of the pot. This portion of the study will attempt to answer the following questions:

  • Are undersized target species using the escape gaps?
  • What percentage of individuals entering a pot is actually caught?
  • Is cannibalism occurring on undersized target species in pots without escape gaps?

Due to the design of this pot, it will only be fished experimentally and not attached to a fleet of commercial pots. This camera system is currently being built and will hopefully be ready for deployment in Autumn 2014.


Very preliminary results have been collected and are based on data collected by 3 fishers over 8 fishing days using 110 pots in 2013. Each fisher was given 5 pots with 45x80mm escape hatches, 5 with 47x80mm escape hatches and 5 with no escape hatches.

The percentage of lobster/crab that were kept and the percentage that were discarded by type of escape hatch.

The preliminary results indicate that there are more lobsters of legal size found in pots with the largest escape hatch, however the difference between escape hatch and no escape hatch is more pronounced than between large and small escape hatches.

The percentage of pots with bycatch and the abundance of velvet crabs in pots with differing escape hatches.

Preliminary results on bycatch indicate that pots with no escape hatches may capture more bycatch, however the difference in bycatch between pots with small escape hatches and pots with no escape hatches is very small. With respect to velvet swimmer crabs, the preliminary results indicate that the abundance of velvet crabs decreases with the use of escape hatches raising concerns that escape hatches may reduce the catch for this species. Further investigation is needed to determine whether the increase in legal sized lobsters compensates for the loss of velvet swimmer crabs.

For more information on this study, please contact:
Julia Pantin
01248 382607

Juvenile crustacean survey

We have started our juvenile crustacean survey. We are aiming to identify the key habitat types for small juvenile lobsters and edible crab. Once we know the best habitat to find these juveniles in we will then start to monitor abundance throughout the year and at a variety of sites around wales. The hope is that this will be the start of a juvenile abundance index that can be measured every year and be used to manage the fishery for these species. We have been using the flying array to map the habitat around Hells Mouth and Aberdaron. We then deployed some specially made, small pots with small mesh in different habitat types to investigate which habitat type catches the greatest number of small crabs and lobsters.

We are piloting this survey in North wales as it requires the pots to be lifted every 2-3 days. Once we have the method developed we will then role this out across wales to see if there are any regional differences. This is very much an experimental survey at this point and we are trying potting in many different locations. If anyone has any suggestions or can show us a good area to catch small lobsters or crabs we would be very interested in hearing from you. It has been mentioned that prawn fishers may be able to help us with this – the smaller the better!


Juvenile brown crab (Cancer pagurus), and European lobster (Homarus gammarus) caught in our experimental pots.

The juvenile project has come to a close until next summer. We’ve had some eventful days on the sea this.  All the data and video footage is currently being analysed and should be available as a report on the website in the very near future.

Preliminary graph to show the habitat preference of juvenile crab and lobster seen in this study.

Please contact:

Natalie Hold : 07903 762466
Jodie Haig : 07593 635348



Lobster (Homarus gammarus) and  Edible Crabs (Cancer pagurus):

The lobster and brown crab are the biggest fisheries in terms of man power employing roughly 500 fishermen, bringing in landings worth £1,482,797 and £341,779 respectively. Potting is carried out from small vessels ~10m in size. A voluntary V-notching programme is in place, allowing fishermen to tag buried females by removing a small v shape from a tail paddle before returning them to the sea. V-notched individuals are illegal to land.

Cancer pagurus is caught in pots around most of the British isles. Catches have risen steadily over the past 40 years and most of the British catch is exported live to France and Spain. 

Prawns (Palaemon serratus)

The Prawn fishery in Wales employs 100 fishermen and brings in £293,662. The total landings are less than those of the scallop, whelk, lobster, crab and bass fisheries. However, there is a high demand for prawns in the UK with 37,852 tonnes reaching the retail market compared to just 863 tonnes for lobster and crab combined.  The prawn fishery in Wales is the largest of its kind in the UK. This species is fished throughout Britain for live export to Europe. It is caught in pots and is a seasonal fishery in Wales.

European Spider Crab (Maja squinado)


Species Ecology

The Brown Crab or Edible Crab (Cancer pagurus)

The edible “brown crab” has an oval, reddish brown carapace with a distinctive “pie crust” edge and black tipped pincers. Adults can grow to 25 cm wide, weigh up to 3kg and live as long as 30 years.

Habitat & Distribution

Brown crabs are abundant throughout British and Irish coastal waters; they can be found as far north as Norway and as far south as Africa. Brown crabs use a variety of coastal habitats during different stages in their life history, from intertidal algae beds to mixed coarse sediments and offshore in muddy sands in water as deep as 100m.

Life cycle

Male crabs will grab a female and guard her until she moults, which is when her carapace becomes soft, and she can be fertilised. After mating the female will retreat to soft sediments to brood her millions of eggs for anywhere up to nine months. The number of eggs will depend on the size of the mother and the development time is temperature dependant. Tiny larvae (1 mm) called zoea will hatch and go through several moults themselves before metaphorphising into a postlarval form called a megalopa. This megalopa stage will settle out of the water column and into juvenile habitats inshore. Juveniles will stay in the intertidal zone until they reach 60-70 mm at which point they will migrate to deeper waters. Size at sexual maturity appears to vary with region and a range of sizes has been reported for both males (101-117mm carapace width) and females (108-134 mm carapace width).

The European Lobster (Homarus gammarus)

Description: lobby

Image: Ben Lincoln - Homarus gammarus in a pot

The European lobster, Homarus gammarus, is a large lobster that can grow up to 1 m in length, but is more often is 60 cm. This lobster is blue on top and yellow below, with a large asymmetrical set of claws.

Habitat & Distribution

The European lobster can be found on rocky bottoms living in holes and excavated tunnels from the lower shore to depths of 60 m. These species are distributed from the eastern Atlantic Ocean, Mediterranean Sea and parts of the Black Sea. Although the European lobster is not known to migrate, they will roam to find food and typically have a home range of 2 km. Some individuals, however, have been found to move 10 km or more from their burrows. European lobsters have a varied diet which consists of crabs, molluscs, sea urchins, sea stars and polychaete worms.

Life Cycle

Female European lobsters reach sexual maturity between the ages of 5 and 7 and mating takes place between a soft-shelled female and a hard-shelled male. Spawning usually takes place in summer and the female carries the eggs on her abdomen for 9-12 months. These females are called “berried.” Once the larvae hatch and are released into the water column, they float in the surface layers and are at the mercy of the ocean currents. This period last 5-10 weeks and they feed on micro-organisms. After three moults, the body shape changes and the larvae look more like adult lobsters and adopt a life on the seabed. Once settled, the juveniles burrow in the seabed for approximately 2 years and move very little. At a carapace length of approximately 15 mm they leave their burrows and begin life as an adult.

Common prawn (Palaemon serratus)

Description: Copia (2) de DSCN5424

Image: Enrique Gonzalez - Palaemon serratus

Palaemon serratus is called the “Common Prawn” but, in fact, belongs to a family of shrimp. P. serratus is a large (11 cm) marine dwelling species which can be distinguished from similar species by its upwards curving rostrum (nose), which is bifurcated at the tip and has 6-7 teeth on top and 4-5 teeth below. Also notable is the red and yellow banding on the first two pairs of pereiopods (walking legs), which have chelae (claws). P. serratus are active nocturnal predators on mollusc, crustacean and gastropod species but will also consume carrion, making it possible to catch this species in baited pots.

Habitat & Distribution

Palaemon serratus has a broad distribution in the Atlantic and can be found in rocky marine habitats in shallow intertidal pools down to depths of 40m. Adults move offshore in winter and return to inshore habitats in spring. It has been recorded from around the British Isles but more frequently found on the south and west coasts of England, Wales and Ireland and the west coast of Scotland.

Life Cycle

Palaemon serratus live between 3-5 years. Females grow faster and larger than males. The number of eggs she will carry will depend on the size of the mother and the development time is temperature dependant. Females will carry the developing eggs for around 4 months. Tiny predatory larvae called zoea will hatch and go through several moults before metaphorphising into a postlarval. Postlarvae will recruit in July and August, and by February of the following years, will be mature. It is thought that P.serratus populations may experience a male bias sex ratio as females are preferentially predated on in nature and may also be landed in higher numbers than males due to their larger size (this is yet to be investigated).

The European spider crab (Maja squinado & Maja brachydactyla)

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Image: Harriet Salomonsen - Maja squinado/Maja brachydactyla

It has been revealed that the Mediterranean spider crab is distinct from the Atlantic with Maja squinado found in the Mediterranean and Maja brachydactyla more commnly found in the Atlantic. The spider crab is a large crab with a circular, convex carapace bordered with spines. It can be red, brownish-red or yellow in colour and is often covered in attached algae. This species can grow to be 20 cm long.

Habitat & Distribution

It is found on coarse sand mixed sediments and bedrock along the open coast, as well as in deep tide pools and in shallow water up to 50 m in depth. It is found in the north-east Atlantic and the Mediterranean Sea. It has a varied diet, with seaweed and molluscs dominant in the winter, and species such as sea urchins and sea cucumbers in the summer. They undergo seasonal migrations, leaving coastal nursery areas in autumn/winter. They then head to their overwintering sites offshore at depths of over 50 m and return to their nursery areas in spring.

Life Cycle

The life cycle of European spider crab is between 5 and 8 years, and consists of a growth phase and a reproductive phase. The growth phase lasts 2-3 years. The tiny larvae develop in the water column before settling as juveniles on the seabed. The reproductive stage begins after a final moult and the crab may live up to 6 more years.