This is the latest in a series to mark World Oceans Day which looks at how plastics and other pollutants are affecting the marine environment. Here, Bermuda Marine Debris Taskforce member Jennifer Gray explains how plastic octopus traps threaten the survival of marine creatures as big as whales

Bermuda has seen an increase in plastic octopus pots washed up along our coastline. Most of us have likely seen them and have no idea what they are or where they came from.

Local beachcombers, driven by concern and curiosity, connected with Florida Fish and Wildlife Conservation Commission biologist Tom Pitchford who advised these were traps to catch octopus and that we can tell from pot shapes and markings where they come from. "Flat-topped" pots are from Portugal and can easily be traced to their respective fishing vessel by initials branded into the pots. "Round-topped" pots come from northwest African countries such as Morocco, western Sahara, and Mauritania and may also show branded initials.

The common octopus seeks refuge on the seabed to avoid predators and to spawn and protect eggs. Such shelters can be natural cracks in rocks, holes in the substrate, empty shells or man-made such as plastic bottles, buckets or barrels.

The tendency of this species to seek shelter has led to the development of a type of artisanal fishery using pots strung together sometimes several hundred at a time on long lines that can extend between five and 20 kilometres and are attached to a surface float.

The first pots designed were made of heavy terracotta clay and have been replaced over the years with plastic pots that are weighted with cement. The shift towards plastics has resulted in many pots breaking free, releasing the cement weight, and drifting on the currents.

The loss of full or nearly full lines of pots is usually due to heavy storms and to trawlers entering areas where pots are set. A study in the Gulf of Cadiz in the northeastern Atlantic calculated monthly losses of 9,520 octopus pots.

Once set loose on ocean currents, there is no telling where these pots will turn up. They have already been found along the US coasts of California and Florida, Cape Verde, Dorset in England, and in the Bahamas, Barbados, Bermuda, Cayman, Grand Turk and the US Virgin Islands.

Tracing the source of octopus pots and finding they have travelled halfway around the world on the sea is indicative of the persistent nature of plastic, and how much lost and abandoned fishing gear is being seen globally.

In False Bay near Cape Town a dead 12-metre Bryde’s whale was found after becoming entangled in octopus trap ropes. This was the sixth whale in False Bay that had died from drowning in octopus fishing trap ropes in a four-year period. Many more were freed from entanglements. Since 1998 the company that fished octopi in False Bay removed up to 50 tonnes of octopus -- every year. Think of the number of octopus pots needed to catch that many.

To assist efforts by conservationists to convince fishermen to revert to using clay octopus pots rather than the plastic versions, the Bermuda Marine Debris Taskforce will continue collecting data on octopus pot markings that wash up in Bermuda. We encourage people to remove the pots and other marine debris from the coastline and dispose of it responsibly. Take photos of any Octopus pot markings and post them on our Facebook page at https://www.facebook.com/bermudataskforce/

• Jennifer Gray is the founder of the Bermuda Turtle Project and a member of the Bermuda Marine Debris Taskforce, a group of environmental and research organisations that aims to promote awareness of the impact of marine debris landing on Bermuda’s beaches and affecting marine life and to propose solutions to the growing problem