Mechanical stress and injuries during handling and treatment are major risks to fish welfare in today's salmon industry. Inert sensor packages can track motion and impacts during pipe passage and could be used to assess handling systems such as delousing units. However, to relate these measurements to actual mechanical impacts experienced by live and potentially moving fish, verification is needed.This field study used gastric data storage tags (DST) in live and euthanized Atlantic salmon (Salmo salar) passing through a delousing system at three flow rates to locate areas of the pipe system where fish are particularly exposed to impacts and shocks (e.g., valves, splitters). The tags registered passage time as well as frequency and intensity of mechanical impacts. Additionally, welfare scorings related measured impact to observed injuries. In parts of the system the number of impacts increased significantly with faster flow rate for live and dead individuals. For live fish, increased water flow rate also resulted in increased impact intensity. While welfare scores showed mild eye damage as a risk of system passage, effects of flow rate could not be assessed in detail due to methodical issues and limited sample size.This study confirms the potential for using inert sensor packages in dead or “sensor fish” (artificial dummy fish) as objective welfare documentation and as a tool for detecting critical areas in pipe-based handling systems. Replacing live fish in welfare documentation could reduce the number of experimental animals while providing valuable insights into the treatment system.
Water hyacinth is among the world’s most damaging aquatic invasive plants, forming dense mats that disrupt ecosystem functioning, fisheries, navigation, and livelihoods across tropical and subtropical freshwater systems. Its rapid spread is driven by clonal propagation, short life cycles, and prolific seed production, particularly under nutrient-enriched conditions. Although mechanical, chemical, and biological control methods are widely applied, their long-term effectiveness remains uncertain when underlying eutrophication persists. Here, we present a large-scale, one-time water hyacinth removal campaign in Lake Tana, Ethiopia’s largest lake and a UNESCO Biosphere Reserve, as a representative nutrient-rich tropical freshwater system. Using high-resolution satellite imagery, we quantified coverage one month before removal, one month after removal, and one year later. We integrated SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis with a socio-ecological system map to assess mitigation mechanisms and identify sustainable management pathways capable of providing long-term solutions to halt water hyacinth proliferation in freshwater bodies. The campaign removed over 75
Maintaining sufficient levels of biosecurity at the farm level is crucial to prevent the introduction and spread of pathogens. However, data on biosecurity awareness and implementation in small-scale or backyard (hereafter referred to as small-scale) holdings across Europe are lacking. While the risk posed by these farms is generally regarded as limited, they represent a diverse group of farmers and do play a role in disease introduction and spread. The aim of this study was to explore veterinarians' perspectives on small-scale farming in Europe, including the frequency of farm visits, the definition of small-scale farming, the current status of biosecurity, and the most important measures to prevent pathogen introduction and spread. A multidisciplinary team developed a comprehensive survey to collect veterinarians' perspectives on biosecurity in small-scale farms. The survey was translated into 16 languages, digitalised, and distributed online between July and December 2024 by participants of COST Action BETTER. Data were analysed descriptively, and clusters of veterinarians were distinguished using multiple correspondence analysis. In total, 346 veterinarians from 23 countries participated in the survey. There is no standard definition of small-scale farming throughout Europe. According to the participating veterinarians, a small-scale farm was defined as having a median number of fewer than 20 cattle, 30 small ruminants, 13 pigs, or 99 heads of poultry. Three clusters of veterinarians were identified based on geographical location, field experience, biosecurity training, and perceived biosecurity awareness within the small-scale farming community. Biosecurity measures already applied in small-scale farming included fencing, carcass management, and biosecurity measures related to purchasing and feeding practices. According to the participating veterinarians, the most important biosecurity measures for small-scale farms to prevent pathogen introduction and spread included factors related to the introduction of animals, such as quarantine facilities, testing for health status, and purchasing animals from farms with a high health status. Besides factors related to the introduction of animals, hygiene measures and fencing were also frequently indicated as the most important biosecurity measures. Nevertheless, significant differences were found between the clusters regarding the importance of specific biosecurity measures. This study provides valuable insights into the perceived awareness, implementation, and desired biosecurity measures in European small-scale farming and underscores the importance of integrating small farms into "One Health" strategies, given their potential role in the spread of infectious diseases.
Renibacterium salmoninarum is the causative agent of bacterial kidney disease (BKD) and has been isolated from northern European salmonid farms since the 1960s. The bacterium has been detected only sporadically in Norway during the last few decades, but the country has experienced several geographically spread outbreaks since December 2022. The phylogenomic relationships of R. salmoninarum isolates associated with the epizootics ongoing on the West Coast and in Mid-Norway were explored using draft genomes generated by whole-genome sequencing. A broad overview of the phylogeography of this pathogen was gained through sequencing and analysis of a collection of isolates from Norway (n = 67), Iceland (n = 12), Denmark (n = 12), and the Faroe Islands (n = 1), along with a collection of 109 publicly available sequences. We identified two distinct contemporary clades of R. salmoninarum causing BKD in Norway in the period 2022-2024. Both clades belong to the expanding, aquaculture-associated Lineage 1. The epidemiological picture appears consistent with contemporary aquaculture operations, raising questions on the effectiveness or practice of current biosecurity practices toward R. salmoninarum. This work also describes a hitherto undescribed lineage (Lineage 3), predominantly from Iceland, where BKD is considered endemic. The detection of endemic reservoirs of R. salmoninarum in European water systems underscores the potential for ongoing pathogen circulation independent of acute outbreaks. This finding emphasizes the importance of further investigation of the mechanisms of pathogen persistence, particularly within environments related to aquaculture, where chronic infection reservoirs could compromise disease management and biosecurity.IMPORTANCERenibacterium salmoninarum, the causative agent of bacterial kidney disease (BKD), is a salmonid pathogen that often presents as subclinical, chronic infections, complicating detection and control. Effective management of BKD is crucial for sustainable aquaculture and wild fish conservation. Recognizing the need for comprehensive sampling, previous studies have underscored the importance of a global isolate collection to better understand the pathogen's epidemiology. While the slow genetic evolution and highly conserved genome of the bacterium have reduced the resolution of conventional typing methods in the past, applying whole-genome sequencing has enabled its molecular tracing at the outbreak level. Here, we present the largest phylogenomic analysis of R. salmoninarum to date, including sequences from Denmark, Iceland, and the Faroe Islands for the first time. This expanded data set elucidates past and present movements of the pathogen in European waters, providing actionable insights to support development of targeted BKD management and biosecurity strategies.
Introduction: Antibiotics are commonly used to treat infections and promote fish welfare in Aquaculture. Reports suggest that the use of antibiotics in fish farming often breaches established protocols, frequently accumulating in fish muscles and sediments. These residues are known to be detrimental to the fish, altering antioxidant activity and immune responses, and posing environmental risks. In this study, we aimed to investigate the presence, types and quantify, quantify the levels of antibiotic and residues in Nila tilapia (Oreochromis niloticus) fish muscles and sediment samples, and evaluate the associated health risks to humans and the aquatic ecosystem in Stratum II of Lake Volta, Ghana. Methodology: Muscles of table-sized fish and sediment samples were collected from cage aquaculture farms along the Stratum II of the Lake Volta, Ghana, and analysed using Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) for the presence of antibiotic residues. Variations in residual antibiotic concentrations and basic sediment properties throughout the various strata of the Lake Volta were examined using analysis of variance (ANOVA) with a general linear model (GLM). A post-hoc test for multiple comparisons with a significance level of p < 0.05 was performed using Tukey's HSD technique. Potential antibiotic sources were examined using principal component analysis (PCA). Possible risks to human health and the environment were estimated using risk quotients described in the European Technical Guidance Document on Risk Assessment. Results: Four antibiotics, namely ciprofloxacin, tetracycline, chloramphenicol, and azithromycin, were identified in both fish muscle and sediments, with Azithromycin, tetracycline, and ciprofloxacin residues being the most frequently detected antibiotics. Except ciprofloxacin which showed higher concentration midstream, the rest showed higher concentrations of the detected antibiotic residues from downstream sites. Risk analysis of antibiotic residues in fish muscle tissues and sediments revealed risk quotients that ranged from 0.0024-0.0382 for humans and from 0.0200-0.5713 for the aquatic ecosystem in the Lake. Discussion and conclusion: The detection of antibiotic residues in both fish muscle and sediment from aquaculture farms along Lake Volta suggests evidence of antibiotic use or contamination in fish farming in the Lake Volta. Though current antibiotic levels may not pose immediate risks, their accumulation, particularly Chloramphenicol, which has been banned for use in aquaculture, could contribute to antimicrobial resistance making it difficult for future treatment of human infection as well as compromising the food quality and safety. Antibiotic residues in fish and sediments from Lake Volta aquaculture signal contamination risks and a potential threat to future infection treatment
