Assessment of suitable substrates for lumpfish in sea pens

This study assessed the use of different types of substrates for lumpfish in sea pens. Observations were recorded in the early morning before first light, and the number of lumpfish attached to each surface type was recorded. The substrate was removed and another design was deployed if no lumpfish were attached to a substrate for more than 2 weeks. Lumpfish preferred flat and smooth vertical surfaces of plastic, as very few preferred to attach to stones and car tyres offered. Some lumpfish were also observed attaching to the floating seaweed placed into the cages, a more natural substrate used in the wild. It is concluded that lumpfish will easily adhere to artificial, smooth, plastic surfaces instead of natural surfaces such as kelp. Irrespective of the type of substrate offered, it is critical to the welfare of the fish that they have access to some form of substrate due to the need to rest and attach overnight.