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The use of lumpfish (Cyclopterus lumpus L.) as cleaner fish in Atlantic salmon aquaculture has emerged as a promising solution to combat the issue of sea lice infestation, as they have proven effective under the right conditions. The aquaculture industry, however, is facing challenges in ensuring the welfare and survival of lumpfish in salmon cages. Part of the welfare monitoring of lumpfish is the estimation of body condition. Previous research on standard length-weight relationships for lumpfish has primarily relied on the growth patterns of lumpfish in salmon cages, which might not align with the natural growth patterns of the fish. In this study, we argue for another perspective: using the standard weight of wild lumpfish to estimate the body condition of lumpfish in salmon cages. We assert that this approach aligns more closely with the natural growth pattern of the fish and may offer a more accurate representation of their condition. Our findings show significant differences in growth patterns between wild lumpfish, which show positive allometric growth, and those in salmon cages, which show slightly negative allometric growth. The findings underscore the importance of using appropriate length-weight relationships for lumpfish in aquaculture to ensure an accurate assessment of their body condition. [ABSTRACT FROM AUTHOR]

In recent years, the salmon farming industry has grown significantly worldwide, and in the Faroe Islands, it has become a major industry with an annual production of over 94,000 tonnes, yielding 24% of the GDP. According to environmental regulations, the ocean floor is monitored during every production cycle at all farming sites, involving macrofaunal, sensory, and chemical analyses. However, the impact of farming activity on microorganisms in the Faroe Islands remains unknown. This study aimed to assess the impact of Atlantic salmon farming on benthic microbial communities, giving a better understanding of the effects on the foundation of the benthic food web and to assess if these are more prone to environmental impact than traditional macrofaunal biomonitoring. Sediment cores were sampled along a transect from directly below the salmon cages to a background reference site. The sampling occurred prior to the release of salmon into the cages ('before stocking') and immediately before the salmon were harvested ('peak biomass'). The 16S rRNA (V4-V5) gene was sequenced on an Illumina MiSeq from our sediment samples at the surface, 3 cm, and 10 cm depth. Significant shifts in microbial community composition were observed between 'before stocking' and 'peak biomass', as well as between different depth layers. Microbial diversity increased with increasing distance from the cages and was at its highest 'before stocking', indicating a significant impact of the salmon farming on the microbial community structure. In contrast to the regularly executed environmental monitoring, the results from this study showed an impact on the sediments by the salmon farming, underlining the powerful alternative of DNA-metabarcoding when biomonitoring an aquaculture area. [ABSTRACT FROM AUTHOR]