Exceptional abundance of the snake pipefish (Entelurus aequoreus) in the north-eastern Atlantic Ocean

Pipefish (Syngnathidae) have occurred with unprecedented frequency in Continuous Plankton Recorder (CPR) samples to the west of the British Isles from 2003 to 2005. Identification by mtDNA sequencing established that they were snake pipefish, Entelurus aequoreus. The geographical range of the records were from the outer continental shelf of the Celtic Sea and north-west of Ireland to the mid-Atlantic Ridge between 40° and 57°N, with the greatest abundance near the shelf edge and adjacent oceanic waters south of Ireland and west of Brittany. There were records in every month from February to November but most were in late spring and summer. A proposed mechanism for the increase in abundance of the species is that recent climate change has had beneficial impacts on the reproduction of adults and the survival of larvae and juveniles.

An increase in snake pipefish (Entelurus aequoreus) in the northeast Atlantic: possible causes and effects

Climate induced changes in the planktonic community have been reported in the North Atlantic in recent years (Beaugrand et al., 2002), and similar responses has been seen in higher trophic levels (eg fish, Brander et al., 2003). Many of these responses have been identified by the use of the Continuous Plankton Recorder (CPR), and here we discuss recent results from the survey concerning pipefish, numbers of which have increased dramatically around the UK in recent years. This has also been reported in both the scientific and popular press, and anecdotally by many divers. Pipefish are easily recognized, being vermiform with a long slender ‘snout’ and an armoured outer layer, much like an elongated seahorse. This increase has raised many questions, why has it happened and what affects will it have on the ecosystem?