Philip Boulcott

Sedimentation patterns caused by scallop dredging in a physically dynamic environment

Scallop dredging grounds in the Firth of Lorn, western Scotland, are juxtaposed with rocky reef habitats raising concerns that reef communities may be impacted by sediment disturbed by nearby scallop dredging. A particle-tracking model of sediment transport and settling is applied at two scales. In the near-field, a suspension of typical sand/gravel-dominated bed sediment is subjected to a steady current across the dredge track. In the far-field, silt particles, which may persist in suspension for multiple tidal cycles, are tracked in the context of a regional model of tidally-driven flow. The principal sedimentary risk to reef habitats is predicted to come from settling sand particles when dredge tracks approach within tens of metres of a reef. The cumulative effect of dredging at the relatively low intensities recorded in this region is not expected to have a significant long-term impact on suspended silt concentrations and settlement in this highly dispersive environment.

Variation in fecundity in the lesser sandeel: implications for regional management

The number of eggs produced by a parental stock is central to fisheries advice on recruitment potential. However, stock based estimates of egg production may give a misleading index of recruitment potential in stocks containing several reproductively isolated populations. This paper examines the ability of length, condition and oocyte developmental stage to predict levels of potential fecundity in the sandeel, Ammodytes marinus , in three important fished areas in the North Sea. Our results indicate that regional variation in this relationship exists, with fecundity in central areas of the North Sea being higher than those found just off the north-east UK. Oocyte diameter was also found to have a significant effect on potential fecundity, suggesting a down-regulation of oocyte numbers arising from pre-ovulatory atresia, however, this effect was not apparent in every model tested. Our findings have relevance to the local sustainability of spawning components and thus the regional management of the North Sea sandeel stock.

Effect of size on spawning time in the lesser sandeel Ammodytes marinus

Ovarian development was examined in relation to size and temperature in late pre-spawning Ammodytes marinus over 5 years. Oocyte diameter was positively related to length indicating that larger females spawned earlier. Age and temperature, whilst accounting for the effect of length, were not found to affect oocyte development, although the thermal range examined was only 1·3° C.

Identifying the larva of the fan mussel, Atrina fragilis (Pennant, 1777) (Pinnidae)

This work was funded by the Scottish Government project SP004 and a MSS PhD studentship to DS. Many thanks are due to the Crews of the MV Alba na Mara (MSS), RV Sir John Murray (SEPA) and the MV Lochnevis (Caledonian Macbrayne) for facilitating sample collection, John Dunn for assistance with the manufacture and installation of the ferry sampler, Marian Thomson and other staff at the University of Edinburgh for laboratory assistance, Anastasia Imsiridou, Sofia Galinou-Mitsoudi and Vassilis Katsares of the Greek Department of Fisheries and Aquaculture Technology for supplying reference adult A. fragilis DNA, Pablo Diaz and staff at the University of Aberdeen microscopy department for assistance with SEM analysis, the National Museum of Wales for allowing reproduction of the juvenile A. fragilis image, Keith Hiscock and Eve Southward of Plymouth Marine Laboratory for historical information on the identification of A. fragilis larvae, Colin McAlister and the staff of the Fishery offices in Mallaig and Fraserburgh for assistance in the transport of zooplankton samples and materials, and the British Oceanographic Data Centre for supplying data on the UK Tidal Gauge Network. Comments from Associate Editor Simon Cragg and two anonymous reviewers were greatly appreciated for improving the manuscript