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1st October 2009

Recent wildlife sightings by members of the PNHS


1st October 2009
Glen Lee, Clyde
22.9 & 29.9,09
Whooper Swans
Arkleston Hill
Pale bellied goose
Brent goose
Lunderston Bay
Red Admiral
Greylag/Canada Geese
Paisley Town Hall
Greylag Geese
Newshot island
Last week Sept


The Clyde River Foundation  Dr Willie Yeomans

Aquatic life is not a topic with a large regular following in our Society, so we were amazed at the huge turnout to Dr Yeomans’ talk. As well as our regulars, advertising in the museum and local newspaper had attracted several new members. There were also several fishermen, and a large group of Boy Cubs, who had come to hear the talk as part of their Science badge!
Dr Yeomans identified the Clyde River Foundation as a charity devoted to the study of the ecology of the Clyde. He then demonstrated the size of the remit of his organisation: he and his colleagues are responsible for surveying the river system from its small beginnings at Crawford, near Abington in the Cheviots to the west coast at Inverkip.  The river itself is 106 miles long, but encompasses 4,000 kilometres of tributaries as well as the main river. Their work has been ongoing for 20 years.

The main body of their work is surveying the fish populations, the habitat and the invertebrates that live in the Clyde waters. With 220 sites to visit each year, and each site taking one man-day to complete, they collect a lot of data!  Dr Yeomans describes one of the interesting methods they use to study the fish: electro-fishing. This involves stunning the fish to allow time to study them, then returning them to the water unharmed. The team also aims, for example,  to sample the same site each year and compare the number of first and second year fish to determine survival rates.
We were shown photographs of the major species that inhabit the Clyde, 33 in all. Brown Trout is the most common species, and Salmon famously returned to the Clyde in 1983 when the waters became clean enough.  The density of fish is between 50 and 200 fish per 100 square metres, that is, a lot. Sticklebacks are a useful species to study.

The White and Black Cart and the Gryffe are the main rivers in Renfrewshire. Ten species have been found at the Hamills in Paisley, including Salmon; the Gryffe also has Salmon. Renfrewshire is known for a particular fish that was probably introduced as bait, the Bullhead. Because these fish compete with Trout, they are regarded as a threat to indigenous species.

Dr Yeomans then went on to talk about the main problems facing the Clyde Waters: invasive non-native species, and pollution. As well as the Bullheads, the main invasive species is the American Crayfish. Introduced right at the headwater of the river at Crawford, it poses a major threat.  Pollution consists of silting of the river, high temperatures, possibly related to climate change, and discharge into the river by industries. The recent decimation of the Eel population, probably as a result of an introduced parasite, is puzzling, because the reason is uncertain.

Dr Yeomans clearly gave a lot of useful information to fishermen, and gave the rest of the audience a new focus for natural history.

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