All about crawfish 

Crawfish populations

Crawfish (crayfish/spiny lobster, Palinurus elephas) are one of the largest crustaceans found in British and Irish waters. Many populations suffered a dramatic declines towards the end of the last century. They are identified as a priority (formerly Biodiversity Action Plan, BAP) species because of the small numbers that remain.

Crawfish are found mainly around the west coast of Ireland, Wales, the north and west coasts of Scotland and the south-west of England, though there are some records from the east coast. They live in and around rocky reefs and wrecks, usually deeper than 20m. Their most obvious feature and one that divers usually spot first are the distinctive long, striped antennae. Smaller animals usually hide in crevices and you may not see the whole body. If you are lucky enough to see a large adult, it may be out in the open.

Recording crawfish 

Since 2015, there has been some revival in the population, particularly in the southwest of England.  One of our specialist projects, currently assuming greater importance than ever in light of that population recovery, has been to collect more data on crawfish in SW Britain and beyond. To date there have been a number of reports arising from this work all of which can be downloaded from this webpage.

Our records for crawfish are available from the National Biodiversity Network Atlas (note that this does not include sizes, habitats or exact positions).  

You can help boost our knowledge about crawfish by submitting a record if you see one.  This can be done in one of two ways:

1) as part of a standard Seasearch records form.

2) If you are a diver or snorkeller who is not yet part of Seasearch, we would still love to receive your records. These should be submitted to the iRecord crawfish webpage.  

We ask you to provide a simple set of information about the crawfish.

• Site name and location: Be as specific as you can.
• Position: This is essential information. It should be given in Lat/Long. The iRecord webpages allows you to select easily a position from a map.
• Depths: the shallowest and deepest depth where you saw crawfish.
• Date/time: this enables us to correct your given depths to chart datum.
• Number: how many crawfish you saw in total.
• Habitat and substratum: for each entry, select from the options available.
• Size: for each entry, select a size from the options available. Guidance on estimating size is provided below.
• Additional notes: Please record anything unusual or interesting.

Thank you for your records!

Estimating crawfish size

When estimating the size of a crawfish, the best measure to use is the  length of the carapace (shell) in centimetres (not the length of the whole animal including tail or antennae).

Crawfish SHOULD NOT BE DISTURBED when  you estimate their size. We provide a series of photographs for you to estimate the size compared to surrounding features. Recording this information should tell us whether the population is breeding on a yearly basis or whether the output of one or two good breeding years are now growing up.

"Very large" crawfish (carapace 16-20 cm)

Once animals reach this size, they are well above the minimum landing size (MLS) and are bold enough to emerge from the reef into the open.

"Large" crawfish (carapace 11-15 cm)

Once animals reach this size, they are above the minimum landing size (MLS) and may be seen out in the open.

"Medium" crawfish (carapace 6-10 cm)

At this size, the animals seem to be bold/confident enough to be seen out and about. Only those at the upper end of this size -class are large enough to be legally fished (MLS is 9.5-12cm carapace length depending on area).

"Small" crawfish (carapace 3-5 cm)

These animals are too small to be legally fished  (MLS is 9.5-12cm carapace length depending on area) and seem to be generally found hiding rather than out in the open.