Slipper Limpets

The slipper limpet (Crepidula fornicata) is a species of sea snail They are known by a wide range of other names such as slipper shell, boat shell, slipper snail, American slipper and Atlantic slipper, but it is the slipper limpet name which seems to have stuck in the United Kingdom. They have been used as an effective sea fishing bait in the UK, but are a non-native invasive species. For this reason, it has been prohibited to use slipper limpets as a sea fishing bait in Britain since 2015.

Description and Life Cycle

Slipper Limpet Chain

A chain of slipper limpets.

Slipper limpets consist of a soft pale fleshy body inside a hard shell. This shell looks somewhat like the hull of a boat or a slipper leading to many of the common names for this species. They filter-feed by straining microscopic food and plankton through their bodies. A fully grown slipper limpet can be around 6cm long but most are smaller than this. Slipper limpets bury themselves into soft sand and filter-feed by straining microscopic food and plankton through their bodies. Slipper limpets are often found together in chains or stacks which can consist of ten or more slipper limpets. This is due to the unusual way in which they reproduce. The slipper limpet at the bottom of the chain will be female and the rest males. However, if the bottom slipper limpet dies the next one up will continue to cling to the empty shell and will transform into a female, allowing it to reproduce with the next limpet in the chain. Eggs are fertilised internally and the larvae will spread out and swim away from their birthplace, starting new chains elsewhere and quickly spreading slipper limpets along a coastline.

Distribution and Invasive Species Status

Slipper limpets are native to the coast of North America. It is believed they were first introduced to Europe in shipments of oysters in the late 1800s and have since spread across Europe. Today they are present throughout much of the south-east and southern coasts of England, as well as the southern parts of Wales. They have also been reported in parts of the Republic of Ireland, Spain, France, Portugal, the Netherlands and Belgium, as well as in Australia and Japan. As they are a warmer water species is thought that the colder seas of northern England and Scotland prevent this species from spreading further, although global warming and rising sea temperatures mean that they may soon be able to inhabit the whole coastline of the UK. The Marine Management Organisation classes slipper limpets as a damaging invasive species as they can smother oyster beds and out-compete other native shellfish species such as scallops for food. Although they are edible slipper limpets are not widely eaten and they have little to no commercial value.

In March 2015 the UK government made it an offence to release live or fresh slipper limpets into the sea, as this may spread the eggs and larvae into areas of the UK which are currently free of the species. This also includes using slipper limpets in angling, meaning that it is now an offence to use slipper limpets as a sea fishing bait. Read the official government news story on this released by the Marine Management Organisation by clicking here.

The Use of Slipper Limpets as Bait

When it was permitted to use slipper limpets as bait anglers could collect them by looking around rock pools and throughout the intertidal zone. However, the most effective way of collecting them was after a storm or period of bad weather when slipper limpets would have dislodged from rocks and could simply be collected from a beach by hand. Slipper limpets could be taken from their shell by scooping them out with a blunt mussel knife. Many anglers sprinkled them with a little salt to toughen them up prior to using them as bait. Slipper limpets could also be frozen for future usage and some tackle shops and online bait dealers would offer them pre-shelled in frozen form.

Chain of slipper limpets

A chain of slipper limpets dislodged from the rocks and onto a beach.

There was a belief among many anglers that slipper limpets are a better bait when left for a day or two to go off before being frozen or used as bait, as the slipper limpets would contain higher levels of scent to attract fish. While slipper limpets were best collected after a storm this was also the time that they were best used as bait and could account for species such as cod, whiting, pouting, flounder, dab, Dover sole and bass.

Note: This article was originally uploaded in 2012 when it was legal to use slipper limpets as bait. It has been revised several times to explain that it is now an offence to use slipper limpets as a sea fishing bait. All information on using slipper limpets as bait contained within this article is for reference only.

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