A cohort study of gill infections, gill pathology and gill‐related mortality in sea‐farmed Atlantic salmon (Salmo salar L.): A descriptive analysis

Abstract

Gill disease is an important cause of economic losses, fish mortality and reduced animal welfare in the marine and freshwater phase of salmonid farming in Norway and across the world (Shinn et al., 2015;Sommerset, Bang Jensen, Bornø, Haukaas, & Brun, 2021). Reduced gill health may also impact outcomes of, and decisions about, management operations, such as non-medicinal delousing and transport, because diseased fish might have reduced tolerance for handling and stress. Gill disease and gill injuries can be caused by infectious agents, environmental factors, management operations or a combination of these (Boerlage et al., 2020;Rodger, Henry, & Mitchell, 2011). Gill disease has been classified as either simple or complex/multifactorial based on a presumption of single or multiple causes and/or infectious agents involved in the disease process (Gjessing,

Effectiveness of functional feed ingredients to enhance gill disease in Atlantic salmon (Salmo salar, L.)

“…In literature, most of the studies are focused on describing the mechanisms behind the development of CGD, the role of each pathogen involved, and the use of histopathological gill assessment as a more in-depth investigation [ 23 – 26 , 58 , 59 ]. However, one aspect that has not been yet deeply explored is the investigation of alternative strategies to improve gill tissue conditions and fish health during CGD outbreaks, especially in absence of vaccines or specific treatments.…”

First detection of Flavobacterium psychrophilum in juvenile Siberian sturgeons (Acipenser baerii) and description of the pathological findings

“…Besides, several authors have suggested that the adhesion of F. psychrophilum to gill tissue may be an important initial step in the pathogenesis of the infection (Nematollahi et al, 2003). However, gill pathologies are not exclusively triggered by infectious agents, as environmental factors and management conditions are also involved in the development of gill diseases (Østevik et al, 2022). Regardless of the cause, the proliferation of the gill epithelium with fusion of the secondary lamellae significantly reduces the available respiratory surface causing gas exchange impairment, hypoxia and death.…”

High resolution longitudinal molecular and morphological tracking of planktonic threats to salmon aquaculture: new candidates and old players

“…The presence of a planktonic irritant on a given day may not result in an immediate impact on either gill integrity or fish health. Furthermore, gill damage is likely to be cumulative (Boerlage et al, 2020; Østevik et al, 2022) with the condition worsening over the course of spring/summer months, increasing the sensitivity of fish to mortality through physiological stress associated with feeding, medicine treatments and other handling events. Cumulative damage may be best reflected through PGD score, as AGD scores do seem to improve after freshwater treatments for N. perurans (e.g.…”

“…Nematocysts, stinging organelles associated with cnidarian epithelial cells, are also thought to drive gill damage and inflammation (Kintner & Brierley, 2019). Phytoplankton species may also have a role, either via toxin production or, in the case of siliceous diatoms, as direct damage to the gill via penetration of the siliceous spines in gill tissue (Bell, 1943; Østevik et al, 2022). Biological stressors on salmon gill health may synergistically interact to drive cumulative damage to gill tissue.…”