Fig. 1

Sampling methodology. Biopsy excision and swab application was performed on the left and right sides of fish respectively. The first gill was sampled in situ for each methodology prior to fixation of samples. Biopsies were excised as full tissue thickness sections including supporting cartilage and filament tissue. Swabbing (A) was performed over a corresponding gill region to tissue excision (B). Samples were subsequently utilised in DNA extractions (C, D). Swabs were scraped using a sterile blade and extractions performed on this dislodged material as well as directly from the swab (C). A fraction (10 mg +/− 2 mg) of each biopsy tissue sample was processed for DNA extraction (D), with replication achieved through successive extractions from further biopsy sub-samples. This file was partially generated using BioRender