Wrasse exploitation for aquaculture raises questions


The use of wild-caught wrasse as cleaner fish in Scotland’s salmon industry has raised concerns that the population might be being too heavily exploited. The Fish Site website comments on why Marine Scotland want more research into this topic.

Dr Nabeil Salama, a stock assessment specialist with Marine Scotland Science, explains why it seems that exploitation levels may not have changed that radically, and more research is required before the full impact of the recent wrasse fishing boom is understood.

When did wrasse first become recognised for their ability to pick ectoparasites off other fish?

Cleaning behaviour by fish has been observed most frequently in tropical fish, however it was Potts who first reported in 1973 that several wrasse species in the UK had the ability to clean parasites from fish kept in aquaria. This was confirmed by observations in the field in the early 1980s by Hilden.

When was this trait first exploited by the Scottish salmon industry?

The first commercial trials [using them to control sea lice numbers] took place in the Shetland Islands in 1989 and the first successful commercial trials in mainland Scotland in 1990. By 1991, seven companies were using wrasse as cleaner fish.

Why did the initial phase of using wrasse come to an end?

Well, it is not quite evident whether the use came to an end as such. From speaking with the Marine Scotland fish health inspectors, there has been continual use in the aquaculture industry since the late 1980s. The introduction of emamectin benzoate [sold as Slice] in 2000 may have tapered the expansion, but there remained on average some 17,000 kg of wrasse caught each year between 2000 and 2013 by UK-registered vessels.

What other fisheries are exploiting wrasse in Scotland and what are those wrasse caught by other fisheries used for?

The data that is submitted does not list the intended destination of wrasse. It could be for cleaner fish use in salmon farms or, perhaps, for human consumption.

Read the full article at The Fish Site.

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