Fish disease and biomarker studies
External and internal diseases of dab, (Limanda limanda) were assessed at the South Cardigan (Site 1) and Red Wharf Bay (Site 4) stations. Tissues for biomarker analysis (including liver and gonad DNA adducts, metallothionein, bile PAH metabolites, gonadal apoptosis, liver metabolomics and red blood cell comet assay) were collected from the first 20 dab (10 male, 10 female) captured at each site. In addition, histological samples (of liver, gonad, spleen and kidney) were collected from these fish and a subsequent 30 (total n=50). Biomarker samples were snap frozen in liquid nitrogen while histological specimens were fixed in 10 % neutral buffered formalin. In addition to the 50 dab sampled for histopathology, an additional 49 and 25 dabs were examined at Site 1 and Site 4 respectively.
External diseases were assessed in accordance to ICES guidelines on all dab caught from the South Cardigan and Red Wharf sites. Fish captured from South Cardigan Bay displayed a relatively higher prevalence of external diseases compared to those captured from Red Wharf Bay. Figures in parenthesis refer to the prevalence (%) of external diseases recorded from South Cardigan and Red Wharf Bay respectively: Lymphocystis (0,0), skin ulcers (2,2), epidermal hyperplasia/papilloma (0,0), skin hyperpigmentation (8,0), liver tumours (6,0), anasakid nematode infections (2,2), Stephanostomum sp. (8,12), Lepeophtheirus sp. (8,2), Acanthochondria sp. (2,0), and Glugea stephani (8,8).
Visible liver nodules were only observed at the South Cardigan site. Three fish displayed lesions of above 2mm, with two of these displaying lesions of approximately 10mm. These lesions were sampled for histological diagnosis of type (according to BEQUALM liver pathology diagnosis categories) and additional samples were removed and snap frozen for proteomic and metabolomics analysis. In addition to tumour tissue, a portion of normal tissue (non-tumourous) was also dissected and frozen for analysis. No visible liver nodules were observed at the Red Wharf Bay site.
Photo of Dab © B.Picton, www.habitas.org.uk
