Harmful algal blooms (HABs) are a threat to fish welfare, occurring suddenly and unexpectedly causing significant consequences for fish and salmon farmers worldwide. Norwegian farmers have been facing this challenge at irregular intervals since the very beginning of the industry. This report describes the events on the first fish farm affected by the spring HAB of 2025 in northern Norway. Specifically at the production site Fo...

Studying inflammatory responses induced by vaccination can contribute to a more detailed understanding of underlying immune mechanisms in lumpfish ( Cyclopterus lumpus ). Tissue samples from lumpfish intraperitoneally immunized with a divalent oil‐adjuvanted vaccine ( Aeromonas salmonicida and Vibrio salmonicida ) at water temperatures of 5, 10, and 15°C were collected at 630 day degrees and 18 weeks post injection. The relati...

The aim of this study was to evaluate histologic post‐mortem autolytic changes in farmed Atlantic salmon. The fish were either stored at room temperature (RT, 21°C), refrigerated (4°C) or frozen (−20°C), while fish necropsy was performed at 0, 1, 4, 24 and 48 h post‐storage (hps). In addition, gills were sampled at 0, 5, 10, 15, 30 and 45 min post‐storage (mps) at room temperature (RT). The haematoxylin and eosin‐stained tissu...

The definition of scavenger endothelial cells (SEC) is exclusively based on functional and structural characteristics. The following characteristics are common hallmarks for the vertebrate SEC: (a) All vertebrates examined are furnished with a population of special SEC that plays a role in the catabolism of physiologic and non‐physiologic soluble waste macromolecules. (b) From the ligands that are endocytosed, SEC in all seven...

Combating and controlling sea lice causes large economic costs for the farmers, with estimated values of more than 305 million euros (€) per year. Increased resistance against traditional chemotherapeutants due to evolutionary drivers in the sea lice combined with the lack of an effective vaccine and few other chemical treatments available are expected to cause these costs to increase. Several possible methods for managing sea...

Atlantic lumpfish were vaccinated by intramuscular (im) or intraperitoneal (ip) injection with a multivalent oil‐based vaccine, while control fish were injected with phosphate‐buffered saline. Four lumpfish per group were sampled for skin/muscle and head kidney tissue at 0, 2, 7, 21 and 42 days post‐immunization (dpi) for histopathology and immunohistochemistry (IHC). Gene expressions of secretory IgM, membrane‐bound IgM, IgD,...

In today's aquaculture of Atlantic salmon ( Salmo salar L.), a majority of viral disease outbreaks occur after seawater transfer. A relevant question is how the parr–smolt transformation influences the efficacy of viral vaccines and the innate resistance against viral diseases. In this study, vaccinated and unvaccinated A. salmon parr were exposed to different photoperiodic regimens (1‐, 3‐ or 6‐week continuous light—WCL). Fis...