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Lumpfish (Cyclopterus lumpus) are extensively used as part of the control measures against salmon lice in fish farms. In recent years, there has been an increased focus on lumpfish welfare, and how to increase survival of lumpfish during production. To survey lumpfish welfare and compare welfare between different fish farms, welfare indicators are necessary. Condition factor is an attractive welfare indicator since it depends only on the length and weight of the fish, which is easy to measure and does not require euthanisation. Fulton’s K is commonly used to assess body condition for fish. However, this condition factor assumes isometric growth, which has been found not to be a reasonable assumption for lumpfish. In this study, we suggest an alternative expression for lumpfish body condition, which is based on almost 30 000 lumpfish sampled from Norwegian fish farms during production. The resulting condition factor is given as 5.85 ⋅ W∕L2.5016, where Wis the lumpfish weight measured in grams, and Lis the standard length measured in centimetres. We demonstrate that our proposed condition factor is more suitable for comparing body condition of lumpfish than Fulton’s K, since Fulton’s K is negatively correlated to length such that small fish tend to have high Fulton’s K factors. We conclude that Fulton’s K is an inappropriate indicator of lumpfish welfare, and propose to rather use a condition factor tailored to lumpfish, like the presently proposed condition factor. We also illustrate why standard length (length up to the caudal fin) is more appropriate for measuring body condition than total length (i.e. length including the caudal fin). For condition based on standard length, we found that caudal fin erosion was less prevalent among the lumpfish with comparatively higher body condition. The same relationship was not found for body condition based on total length.

ABSTRACTIn southeastern Norway 1998–2000, the number of specimens, species richness and species diversity (measured by Simpsons diversity index) of Agromyzidae were investigated in biologically and conventionally grown spring barley and grass fields. Flies were caught by sweep-net in 1 × 10 m plots in the boundary, 0.5, 5, 15 and 30 m into the fields. A total of 5822 specimens of at least 66 species were caught during the 3 years. The pest species Chromatomyia fuscula(Zett.) and Cerodontha denticornis(Panzer) were most numerous in the fields, while most other species were most numerous in the boundaries. The species richness (for grass only) and species diversity (for cereals and grass) were significantly higher in biological fields, although the pest species (Ce. denticornisand Ch. fuscula) were less abundant in the biologically treated fields. In spring barley fields the species richness and species diversity were significantly reduced when moving from the boundary and into the field. In grass fields this was shown for species richness, but not for species diversity.