Painted panorama of Gloucester harbor and the sea serpent by John Ritto Penniman, from a drawing made by Captain John Beach.

Hundreds of people in the nineteenth-century United States reported seeing the Gloucester Sea Serpent (above), which was probably a marine creature bedecked with fishing debris. Credit: Museum of Fine Arts, Boston


The grim truth behind eyewitness accounts of sea serpents

Centuries-old ‘unidentified marine objects’ hint that sea creatures have been getting entangled in fishing lines since before the invention of plastic.

‘Sea serpents’ spotted around Great Britain and Ireland in the nineteenth century were probably whales and other marine animals ensnared in fishing gear — long before the advent of the plastic equipment usually blamed for such entanglements.

The snaring of sea creatures in fishing equipment is often considered a modern phenomenon, because the hemp and cotton ropes used in the past degraded more quickly than their plastic counterparts. But Robert France at Dalhousie University in Truro, Canada, identified 51 probable entanglements near Great Britain and Ireland dating as far back as 1809.

France analysed 214 accounts of ‘unidentified marine objects’ from the early nineteenth century to 2000, looking for observations of a monster that had impressive length, a series of humps protruding above the sea surface and a fast, undulating movement through the water. France says that such accounts describe not sea serpents but whales, basking sharks (Cetorhinus maximus) or other marine animals trailing fishing gear such as buoys or other floats.

Such first-hand accounts could help researchers to construct a better picture of historical populations of marine species and the pressures they faced, France says.