Meeting Report: Between the Tides

3 November 2017
Jim Logan

About eighty members and visitors gathered to hear a talk by marine biologist Jim Logan, entitled 'Between the Tides'. In his talk the speaker aimed to give an overview of the extraordinary variety of wildlife that can be found between the high and low watermarks on the Solway coast. Our area is particularly rewarding, partly because of the wide variety of coastal habitats, ranging from mudflats through sandy and shingle beaches to rocky shores, and partly because the tidal range, from 6 to 9 metres, is the second largest in Britain, thus providing a huge intertidal zone.

Salinity can vary considerably, due to freshwater streams and rivers that discharge into the Solway, and the speaker pointed out that some seaweeds, for example, can tolerate almost non-saline water, and also drying out, whereas others require a strictly marine environment. Rock pools, which might seem to provide a good place to observe wildlife, can be a difficult habitat for marine species as in hot weather the pool dries and salinity rises, whereas heavy rain will dilute the seawater.

The speaker then described the various types of molluscs to be found. These include the little winkle, which spends most of its life above the tideline but takes to the sea to breed, whereas the edible winkle requires daily immersion in seawater. The familiar limpet grips to rocks using a huge foot muscle, and scavenges weed by scraping the rock surface. Dog whelks feed on other sea creatures such as mussels or barnacles by drilling a hole in the shell and then liquifying the organism inside by injecting digestive juices. The native European oyster is no longer found on the Solway coast, but there is a thriving colony and oyster fishery at Loch Ryan.

Jim Logan then moved on to describe crustaceans, such as crabs, which range from the large edible crab (complete with piecrust-like shell!), to the tiny pea crab, which lives inside mussels, feeding on material gathered by its host. Barnacles, despite appearing to resemble small limpets, are in fact crustaceans which feed on plankton by opening up plates in the top of the shell. Other intertidal creatures include starfish, sea anemones, and sea urchins. Fish are generally observed in rock pools, and species include the blenny, goby and butterfish, the last so named because of its slippery slimy skin.

The speaker concluded by mentioning sea-creatures that may become stranded on the shore. Most notable are various species of jellyfish, some of which are harmless but others, such as the lion jellyfish, can inflict a powerful sting that can even be fatal for children.

The evening concluded with an extensive question-and-answer session, and it was suggested that the Society might ask Jim Logan to lead a sea-shore wildlife walk in the summer.