Anchor-dredge samples of the benthos in Weymouth Bay and Poole Bay were taken after the severe 1962–63 winter to ascertain what changes in the fauna had occurred. The same station positions as had been previously sampled in 1958 and 1959 were re-sampled in 1963–64 and the results from each Bay compared.
Most species had survived the previous winter, when sea temperatures had probably been at 3° or below for about a month, but populations of the bivalve molluscs Venus verrucosa and Venerupis rhomboides, previously common in the area, had suffered severe mortalities, none being taken in the 1963–64 samples. The brittle star Acrocnida brachiata had also disappeared from the samples, and many other invertebrates appeared to have declined in numbers. Two cold-water species, Spisula elliptica and Buccinum undatum, showed if anything a slight increase, perhaps reflecting colder sea temperatures over the past few years. Crepidula fornicata also showed an increase in numbers.
Mortalities were not necessarily of species close to the limits of their range, some of the latter having survived with no noticeable decline in numbers.