Includes the following papers:

Seaward, D.R. Ferrybridge reconstruction in relation to marine fauna

Holmes, N.T.H. Distribution of Zostera and Ruppia in the Fleet

Humphrey, E.C. A survey of the meiofauna of the Fleet

Dyrynda, P. Subtidal communities within the outer Fleet and Portland Harbour

Thompson, T.E & Seaward, D.R. Observations on the opisthobranch mollusc Akera bullata in the Fleet, Dorset

Ladle, M. The fishes of the Fleet with particular reference to the young stages of the bass (Dicentrarchus labrax L.)

Seaward, D.R. Ferrybridge reconstruction in relation to marine fauna. Short paper describing the changes observed during and after infilling of the old channel and construction of the new. The intertidal rare and local sea slug Aolidiella alderi, appeared to be unaffected by the development, but the local population (along with populations of other molluscs) was reduced by severe weather in January >85. A small area of interesting subtidal community with unusual fauna including the sea slug Doto millbayana under the old bridge was destroyed when the old channel was infilled - it was not known at this time whether this community would regenerate under the new bridge. Changes to the sand flats in Portland Harbour adjacent to the new channel were observed, but otherwise, no significant changes/impacts were observed.

Holmes, N.T.H. Distribution of Zostera and Ruppia in the Fleet. Report of the 1983 survey described above.

Humphrey, E.C. A survey of the meiofauna of the Fleet. Describes MSc project. Core samples were taken at low water at five sites within the Fleet, and analysed for macrofauna, meiofauna (i.e. retained on a 63µm sieve), temperature of sediment, particle size analysis and organic content, and salinity and temperature of the water. Water temperatures recorded during this survey were lower than those recorded by Whittaker in May 1968. Highest water temperatures were recorded at Moonfleet. pH measurements were higher than normal seawater (pH 8), as also recorded by Whittaker. It is suggested that this high pH may be contributory in the high preservation of empty Foraminifera tests. Greatest quantity of coarse material in sediments, with highest diversity and abundance of species was found at Moonfleet. High numbers of individuals were also recorded at Abbotsbury, where sediment sorting was greatest, although still relatively poorly sorted. The Fleet was shown to be a very rich area in terms of meiofaunal abundance and number of species, especially for Harpacticoida and Foraminifera.

Dyrynda, P. Subtidal communities within the outer Fleet and Portland Harbour. Summary of information included in Dyrynda 1984 and Dyrynda & Farnham 1985, covering surveys of the flora and fauna of sub tidal channels at the Narrows and Smallmouth (plus three stations in Portland Harbour for comparison).

Thompson, T.E & Seaward, D.R. Observations on the opisthobranch mollusc Akera bullata in the Fleet, Dorset. Paper describes the aspects of the taxonomy of Akera bullata. The variety Akera bullata subspecies nana of Jeffreys 1867 is the one found in the Fleet. It rarely exceeds 20mm in overall body length, swims only as a juvenile, has an obtusely rounded posterior pallial lobe, and lacks the ability to secrete offensive purple. It has existed in the Fleet since around 1850 at least. Densities of up to 120 m² were recorded by Seaward, 1978. As part of the studies into this species in the Fleet, temperature and salinity at the foreshore at Langton Hive Point were measured on a monthly basis from November 1984, and should continue until 1986. Salinity during 1985 varied widely, dropping to 22 ppt or lower in mid winter, rising to 35.5 ppt in summer (equivalent to open water in the English Channel). Temperature of the water was usually higher than that of the air, but this tended to reverse in the winter months.

The life cycle of Akera bullata in the Fleet is annual. Spawn masses are produced in April-June, spent adults die off in April-June to be replaced by newly settled young, which dominated the samples in June and July. Juveniles could swim until 2-3 months old. The benthic stages appear to be detritivorous. There was no evidence that Akera feeds on living Zostera, either the roots or the leaves. The Fleet population of Akera bullata is ecologically distinct from larger Akera bullata subsp. farrani found elsewhere, whether it should be considered a separate species was not concluded until completion of the sampling programme.

Next Section

Ladle, M. The fishes of the Fleet with particular reference to the young stages of the bass (Dicentrarchus labrax L.). Paper reports a study to establish whether bass spawn within the Fleet, or whether eggs, larvae or post-larvae enter the Fleet with each tide, and to attempt to establish the age structure, distribution and relative growth rates of young bass within the lagoon. The surveys were conducted in May-October 1983. The study provided no evidence of bass spawning in the Fleet. It was generally believed that they spawn chiefly in offshore situations and that larvae migrate inshore, often to shallow brackish water. The status of the Fleet as a nursery area was confirmed, but it was not possible to estimate the size of the population except to say that it was substantial. The young fish were relatively quick growing for a species nearing the northern limits of its geographical distribution. Gobies were found to be the most abundant fish during the survey, with sandsmelt (Atherina presbyter) the second most abundant. Sandsmelt eggs attached to algal fragments (indicating that they are benthic rather than planktonic), rarely observed in other British waters, were found in the plankton at the end of May on the ebb tide.

 Next Section