Important Species On The Isles of Scilly

The Isles of Scilly is located as the Atlantic Ocean divides into the English Channel and the Celtic Sea. The mixing currents create oceanic fronts which are highly productive, forming a foundation for plant plankton, which are the basis for a food chain that draws in species such as puffins, basking sharks and blue sharks. The habitats around the islands are distinctive to different locations, varying according to the underlying geology, depth and level of exposure to the waves.

Certain species have been highlighted as ‘conservation features’ because of they are rare or vulnerable, or play a significant ecological role.

Seagrass beds

Seagrass beds are found in the shallow sand areas around the islands. This is a species known as eelgrass (Zostera marina) and is found in bays, lagoons and estuaries across the northern hemisphere. Seagrasses are flowering plants (unlike seaweeds) which also grow through extension of their roots (rhizomes). They play a vital role in binding and stabilising sediments and have an extraordinarily high rate of primary production. Eelgrass is incredibly important as a nursery ground and habitat for hundreds of species. We have approximately 195 hectares of seagrass, concentrated in the channel between St. Mary’s and Tresco and around St. Martins.

sea grass

Sponge and Anthozoan Communities

The Isles of Scilly are granitic outcrops and away from the islands and islets, there are incredible landscapes of canyons, pinnacles and large boulders. In areas where they are protected from the full force of the waves and tides there are incredible communities of sponges, anemones and anthozoans. Anthozoans are a group which includes sea fans, cup corals and anemones. Many underwater pictures from the Isles of Scilly show carpets of rocks covered in densely packed communities of different coloured sponges, sea fans and anemones.

sponges and anthozoans

Crawfish

The European crawfish or spiny lobster does not have the claws that are found on a European lobster, this species has two long antennae, small hook-like claws and numerous sharp spines around its body. It is likely that many of the adults found around the Isles of Scilly are carried as larvae across the Bay of Biscay and western approaches from the coasts of France and Spain. In turn, eggs and larvae from here are carried up through the Celtic Sea. This species is mostly active at night and females will move to deeper waters during the development of the eggs. During the 1970s this species was caught commercially around the coasts of South West England, but declined suddenly in the 1990s. The Isles of Scilly are one of the few places in the UK where this species is still found and caught commercially. Some of the MCZs around Scilly have crawfish listed as one of the key species within the site.

crawfish

Stalked jellyfish

Unlike most jellyfish that drift on the ocean currents, most stalked jellyfish attach themselves to seaweed and eelgrass in shallow water. They are very small in size, reaching 5cm or so in height. Their tentacles are above their body and they use stinging cells to stun their prey and as a defence mechanism against predators. The two species identified within the Isles of Scilly MCZs are Haliclystus auricula and Lucernariopsis campanulata

stalked jellyfish on seagrass

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