J. P. Harvey

The diets and parasites of larval and 0+ juvenile twaite shad in the lower reaches and estuaries of the rivers Wye, Usk and Towy, UK

This study assessed the diets and parasites of larval and 0+ juvenile twaite shad Alosa fallax fallax in the lower reaches and estuaries of the rivers Wye, Usk and Towy, UK. There were significant differences between the diets of larvae and co-habiting 0+ juveniles, and of larvae and 0+ juveniles among sites, both within and among rivers. In the Wye and Usk, the diets of twaite shad larvae were dominated by chironomid larvae, whereas those in the Towy specialised upon cyclopoid copepods. The diets of 0+ juvenile twaite shad from freshwater (River Wye) were characterised by chironomid larvae, while estuarine (Towy Estuary) individuals specialised upon calanoid copepods. Parasites infecting 0+ twaite shad were Apiosoma sp. (Protozoa), Gyrodactylus sp. (Monogenea), Proleptinae (Nematoda) larvae, Pomphorhynchus laevis (Acanthocephala), Spinitectus sp. (Nematoda) larvae and Trichodina sp. (Protozoa). Over 60% of estuarine 0+ juvenile twaite shad were infected with Apiosoma sp., with maximal estimated loadings in excess of 3,000 parasites per fish. Other parasite taxa were generally present in only small numbers. There were no significant differences in the intensity of parasite infections among sites, or the condition of parasitised and non-parasitised 0+ twaite shad.

Monitoring Sea Lamprey Petromyzon marinus Ammocoetes in SAC Rivers: A Case Study on the River Wye

The sea lamprey (Petromyzon marinus L.) is a designated feature of the River Wye and the Severn Estuary Special Areas of Conservation (SAC). This study assessed the conservation status of sea lamprey in the Welsh reaches of the Wye catchment. Sea lamprey ammocoete (larvae) and transformer (metamorphosing larvae) surveys were conducted at 54 sites following the established UK protocol. The mean density of ammocoetes was 2.20 m–2 and, where sufficient ammocoetes were obtained, at least two size (≈age) classes were present, indicating favourable condition status. It was impossible, however, to identify trends in condition status because of lack of historical data. Condition status should also ideally be linked with information on flow dynamics, habitat requirements and river-channel morphology to understand, and be able to respond to, changes in population dynamics. Modifications to the condition assessment criteria for lampreys should be made as more data become available.

Monitoring Fish Populations in River SACs

The EU Habitats Directive (92/43/EEC) on Conservation of Natural Habitats and of Wild Fauna and Flora stipulates that Member states maintain or restore habitats and species in a condition that ensures their favourable conservation status in the community. To comply with this Directive requires assessment of the conservation status of aquatic species in rivers designated as Special Areas of Conservations (SACs) against a predetermined set of objectives. This paper describes the protocols developed to determine the condition status of lampreys, bullheads, shad and Atlantic salmon in SAC rivers in the UK.