Blennies Seek Out the Dark

The Blenny (or Shanny, Lipophyris pholis) is a very common fish of the the North East Atlantic from Norway to Mauritania and the Atlantic islands, with some records in the Western Mediterranean (1). It is particularly widespread on the Western coast of Ireland. Found among stones and seaweeds in rocky gullies on the lower shore, it often becomes trapped in rock pools at low tide where the specimen pictured was spotted. While this is a small (c. 4 cm) example of the species, they can reach 10 cm in size (2).

Blenny, Lipophyris pholis, in a rock pool

Blennies show a preference for rocky over sandy substrata from an early age (3). The reason for this is unclear, but in such environments, Blennies will immediately make for the first dark area as soon as possible. Dodd et al. (4) have shown that in an artificial novel environment, they will move towards a black screen, pressing themselves up against it. Once they have gained experience of this environment, they will us the positions of large objects around them to relocate a refuge.

References

1. Steffani et al., 2006 Molecular Phylogenetics and Evolution 39 pp. 282–287
2. Sterry, 2003 Collins Complete Guide to Irish Wildlife p. 102
3. Almada and Faria, 2000 Journal of the Marine Biological Association of the UK 80 pp. 1143-1144
4. Dodd et al., 2000 Behavioural Processes 49 pp. 69-75