An ultimate link for a deepening...

In the article "Några reflektioner" of Hans Kautsky, right at the end, you can find this authoritative link. It takes you to the Paper presented by Don Staniford at the European Parliament's Committee on Fisheries public hearing on 'Aquaculture in the European Union: Present Situation and Future Prospects', 1st October 2002. It's in english, and offers several considerations to think about. Some samples below.

(...) As Dr Sergei Tudela of WWF states: "Intensive industrial scale aquaculture has become synonymous with pollution and destruction of the marine environment, conflicts with other resource users, and high levels of toxins in the fish produced.  The spread of aquaculture, a cause of increasing concern and growing alarm, has been described as a cancer at the heart of the coastal environment" (Tudela:2002)

(...) The technology required for closed containment systems already exist (G3 Consulting: 2000) and is being commercially developed in Canada (Cutland: 2002) but it has not been adopted in Europe as farmers dismiss it as too expensive. (...)  In allowing sea cages to discharge contaminated wastes into the sea, however, countries are permitting farmers the free use of pristine coastal waters as an open sewer (Folke and Kautsky:1994). Closed containment systems would not only stem the tide of pollution from sea cages but would also prevent escapes, stop the spread of diseases and parasites to wild fish and reduce the need for chemicals.

(...) Reports by the World Health Organisation and GESAMP have highlighted the environmental and public health threats of chemical use on fish farms (GESAMP: 1997, WHO: 1999).  However, despite a reduction in the use of antibiotics and organophosphates in salmon farming (OSPAR: 1994) the use of synthetic pyrethroids, artificial colorants, antifoulants, antiparasitics and other 'marine pollutants' warrants serious concern (Staniford: 2002a).  The cocktail of toxic chemicals used on salmon farms, in particular, jeopardises not only the marine environment but also the safety of workers (Douglas: 1995, GESAMP: 1997, Kelleher et al: 1998, Connolly: 2002). In Danish trout farms, for example, the abuse of antibiotics has raised consumer and environmental concerns (Lutzhoft et al: 1999). Chemicals used on salmon farms include carcinogens, mutagens and a myriad of marine pollutants (Staniford: 2002b). Since many chemical 'treatments' are designed to kill sea lice (which are crustacea) shellfish farmers have raised concerns in relation to the negative effects other shellfish such as lobsters, crabs, mussels, oysters and scallops (Blythman: 2001, Ross and Holme: 2001).