Population dynamics of the ampharetid polychaete, Melinna palmata Grube, in Inner Galway Bay, west coast of Ireland

Abstract

The ampharetid, Melinna palmata is a common member of the polychaete infauna occurring along the north shore of Galway Bay, (O'Connor, 1981). A high density population at one location was the focus for a two year study (April, 1983 to March, 1985). Five samples were taken each month with a modified 0.12 m2 van Veen grab (hinged 0.5 mm mesh doors fitted to the top to reduce bow wave). Samples were sieved on a 0.5 mm mesh and fixed in 10% buffered formalin. They were subsequently divided into 2 mm, 1 mm and 0.5 mm fractions. M. palmata were sorted from the 2 mm and 1 mm fractions and measured (10th setiger width) for construction of size frequency histograms. Monthly examination of coelomic contents from anaesthetised worms revealed the principal events of the reproductive cycle. Melinnapalmata in Galway Bay was shown to be polytelic with a breeding season extending from May to July. This is earlier than reported for the Breton coast (Retiere, 1979; Guillou & Hily, 1983). Adult worms were gravid in May with spawning taking place until August when water temperatures were at their maxima, (approx. 17 OC). Simultaneously, proliferation of the following season's population of gametes commenced and increased