Crayfish Nursery Behavioural Study Week 3

February 5, 2019
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The Ballan Wrasse (Labrus bergylta)

Last week we released a Ballan Wrasse, Labrus bergylta, that had been a resident in our largest marine tank at our testing facility in Brixham, Devon, back in to the local waters where it was caught. This individual was very sociable and would often come to the front of the glass to greet passers-by. Although some may see fish as unintelligent animals, this one had a sense of curiosity that seemed to prove otherwise.

L.bergylta gets its name from the Latin term ‘Labrum’ which means lip, rim or edge, as it is common for species of this genus to have large lips. Commonly found around the shores of Britain and Ireland as well as parts of Europe, it can be found hiding and foraging amongst the rocks, seaweed and reefs. The diet of L.bergylta is composed mostly of crustaceans and molluscs (such as mussels, cockles, limpets and winkles). As mentioned in our previous Tank Tuesdays article on the Snakelocks anemone, many species have an ecosystem role. The Ballan wrasse is no exception, taking up the helpful role of cleaner. It eats the sea lice from the bodies of other fish and is so good at it that it’s been introduced into aquaculture pens by humans to clean up salmon. The wrasse gets a free meal and the salmon are kept healthy, free from pests. There is even a potting fishery for wrasse here in Devon to transport the fish to aquaculture sites elsewhere in the UK.

Figure 1: Ballan Wrasse hiding within a natural reef

Not the largest of fish, L. bergylta commonly grows to around thirty centimetres in length but has been seen up to 50 cm. Ours was a bit on the smaller side sitting at around 10 cm. All individuals of this species start their lives as a female and remain female for around 4-14 years. After this period they change sex; becoming male, so a larger wrasse is likely male.

Our wrasse lived in a tank with four 12.5cm Reef Cubes. Interestingly it preferred to rest in one particular cube, where it would spend most of its time. When travelling in the tank it would swim around and through the cubes, using them as cover. Sometimes it even seemed like the fish was showing off (See video below).

Figure 2: A video showing the Ballan Wrasse  swimming through Reef Cubes within the ARC Marine laboratory.

Species like the Ballan wrasse are likely to colonise artificial reefs because they replicate their natural rocky habitats. Lots of species use areas of hard habitat, some more than others. Ballan wrasse have a particularly close association to rocky hard-bottom habitats and spend most of their lives in such areas. Theory suggests that these are the species most likely to benefit from an artificial reef because they are often limited by a lack of suitable habitat (Fabi et al., 2015). Introducing new hard habitat like Reef Cubes gives them the space and suitable resources to grow, thrive and reproduce; increasing their abundance. So, it is encouraging and as expected to see the wrasse utilising the Reef Cubes in our tank.

We have had to release our Ballan wrasse back in to waters around Brixham as we had to clear out the tank for future projects. Now it’s free to grow and live a life in its natural environment. It may even make its way to our larger 25cm cubes, on the edge of the harbour nearby.

By Sam Hickling and Jamie Matthews

Tank Tuesdays is a series of mini articles describing the marine life here at ARC Marine’s aquaria; and their interactions with our artificial habitats.


Fabi, G., Scarcella, G., Spagnolo, A., Bortone, S.A., Charbonnel, E., Goutayer, J.J., Haddad, N., Lök, A. and Trommelen, M., 2015. Practical Guidelines for the use of artificial reefs in the mediterranean and the black sea. General Fisheries Commission for the Mediterranean. Studies and Reviews, (96), p.I.