The teleost integument (consisting of mucus, epithelium, and scales) forms a physical barrier between the outer and internal environment of fish. Physical trauma, which may happen even during brief routine handling in hand nets, can cause integumental damage and render fish vulnerable to pathogens and osmoregulatory stress. Movement of salmonids using hand nets is used in aquaculture, fishing and environmental monitoring activities. Therefore, refining physical handling of salmon is important to reduce stress and morbidity.

In previous research, we exposed Atlantic salmon (Salmo salar) to routine brief exposure to mesh using hand nets, showing that rubber coated mesh significantly reduced the number of lost scales compared to when a conventional knotless equivalent was used. The technique of counting scales also offered a simple method to compare fish handling techniques. However, net handling can also damage scale-less regions of fish integument (eyes, fins, potentially the head region), and remove mucus and epithelium above and adjacent to lost scales across the flanks. Fluorescein is a non-toxic dye used to visualise cryptic damage in mucus membranes.

To date, model (non-salmonid) species have been investigated using this method, and a comparison between rubber mesh and conventional equivalents remains untested in this taxon.

This project aims conduct an initial proof of principle by investigating the extent to which rubber mesh reduces loss of mucus and damage to epithelium, and reduces damage to scale-less areas such the fins and eyes when compared to commercial standard knotless mesh. In addition, to test if rubber mesh potentially improves hygiene during handling via reduced delivery of bacteria to damaged areas of the integument, inferred via in vitro assay.