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In earlier posts we have covered the unsuitability of tri butyl tin and copper related formulations for use in aquaculture antifouling applications.

A new patent document has identified phytochemicals as antifouling agents.

Biofouling presents a severe operational problem to aquaculture.

On fish cages, it restricts water flow through netting which reduces the supply of dissolved oxygen and the removal of excess feed and waste products.

A large mass of fouling can compete with the cultured species for food and space, and can overwhelm flotation capacity.

Current metal-based antifoulants are undesirable for aquaculture because of possible adverse environmental effects, and consumer concerns that may jeopardise market image.

Commercially available, but biodegradable compounds, or naturally occurring antifoulants extracted from marine organisms, may provide an acceptable solution by offering broad spectrum activity, and in the case of natural antifoulants, acting via chemical deterrence rather than toxicity. 

Commercialisation of antifouling technology other than paints is still in its infancy, and few field trials are reported in the literature.

Although there are many antifouling agents and compositions presently available, the methods typically used to protect an object from fouling in an aqueous environment involve applying some form of protective coating to the surface of the object.

Unfortunately, this approach is not suitable for all applications and there is a need for other means of protecting such objects from microbial- or macro-fouling.

New polymer compositions have been developed that contain antifouling agents which have surprising broad-spectrum antifouling characteristics over prolonged periods and at lower concentrations than were previously believed possible. 

Synthetic antifouling agents belonging to the families of isothiazolones, furanones, or combinations thereof have been found to be effective. This invention consists of an antifouling polymer comprising an isothiazolone or one or more furanone antifouling agents, the polymer capable of maintaining broad-spectruin antifouling activity for an extended period. The polymer is used to form a thread which may then be incorporated as part of the thread structure of a multi-stranded netting material. 

The discovery was made by researchers associated with the Aquaculture Cooperative Research Centre.

One of the patent documents related to the invention may be accessed here.

Fouling in aquaculture relates principally to the growth of marine flora and fauna on submerged installations, including the netting.

Severe fouling results in clogging nets and other cage elements, which impedes the passage of water through and around the enclosure.

The reduction in exchange of water which results can lead to depleted oxygen and elevated ammonia levels, affecting growth and animal health.

In severe cases, fish mortality can be high, severely impacting the economics of the operation.

Fouling affects current-induced drag forces on submerged equipment, representing a potential hazard to the fish cage installation overall.

The present approach to dealing with fouling suffers from a number of disadvantages because present approaches are both ineffective and expensive.

Hence, there is an urgent need either stop fouling altogether or alternatively, to develop cost-effective net and cage cleaning equipment suitable for the various cage systems commercially in use in the fish farming sector.

A consortium has been formed to investigate potential solutions. The consortium coordinator is identified below.

Organisation: SELOY UNDERVANNSSERVICE AS
Department: MAIN DEPARTMENT
Address: Hestoy, HEROY, NORWAY
Contact Person: Name: TROND, Olsen (Mr)
Tel: +47-75068400
Fax: +47-75068401

Further information is available via this link.