An unsustainable & unethical practice
In an effort to reduce lice numbers and chemical use to control lice on salmon farms, other species of fish have been introduced to eat the lice.
It has some positive effect and has reduced chemical use in some farms.
However, as expected this practice is not without its drawbacks....
Cyclopterus Lumpus, Lumpfish or Lumpsucker is a ponderous swimmer. They are "community fish", forming bonds with neighbouring lumpfish and requiring protection and cover, where they cling onto rocks and reefs with their pelvic fins. The last place they should really be is in a barren salmon farm with salmon swimming at 2m/s+
Well, actually the last place they should be found is dead, in a mort bin along with dead salmon.
This is eventually what happens and the same lumpfish are not reintroduced to the new harvest after one production cycle - they are killed.
There has been a huge desperate push to try and farm these little fellows to provide a "sustainable" supply. In some cases it has worked but the mortalities are high and getting their diet correct in order that they will then go on to feed on sea lice and fish pellets is almost impossible.
The most widely used are Labrus bergylta or Ballan Wrasse.
As with Lumpfish, they are community fish, living in the kelp and reefs along the coastline.
They've a better chance of pecking off sea lice from a salmon but as it's not their natural habitat, they are stressed and they probably feed through desperation.
Unfortunately, they have been overexploited in Scotland as regulation has not been put in place to safeguard their extraction.
In 2018 a range of voluntary control measures for the wild wrasse fishery were agreed between Marine Scotland and the salmon farming sector on size and and recording - unfortunately this does not mean regulation.
As with most areas of salmon farming, the producers are asked to report everything, there is no independent monitoring.