Research

1 - A Pan-European baseline

From February 2005 to April 2007, partners in the CRAB project monitored biofouling at finfish and shellfish production sites throughout Europe.

The main objective of this “baseline study” was to produce the first European overview of the biofouling problem, in terms of the differences in the biofouling communities that affect aquaculture producers at different sites, as well as their changes over time.

Aquaculture production sites use a wide range of materials (plastics, metals, etc) in various forms (nets, cages, buoys, trays, etc) and biofouling affects these materials in different ways. In order to produce results that were comparable, a standard protocol was designed, based on the use of identical 20x20cm PVC panels, vertically attached to plastic frames, and submerged at a depth of 2m on each site.

 

The panels were studied and fouling species were identified and weighed at a monthly interval. The photos were analysed using digital image analysis. Short-term studies showed the settlement or recruitment of species (Monthly Spatfalls), and the long-term study showed the succession of the different fouling species over time (Community Development).

An overview of the results for each site is presented in the Case Studies section.

2 - Testing Materials

Only low tech, low cost antifouling paints are used in aquaculture. These coatings are effective for 4-6 months depending on the leaching rate of the biocide(s), water temperature and fouling pressure. Copper based net coatings are not effective against all fouling types as some algae and hydroids can grow on treated netting.

At present, copper based net coatings are the only cost effective treatment available. This is particularly true for farmers with large cages (70m circumference or more) and located at exposed or high energy locations, where manual, air drying or mechanized cleaning methods are inappropriate. The current cost is approximately 4 Euro per litre paint/kg netting. Cost of treatment varies with location and is likely to increase with the increasing demand for copper as raw material.

Cleaning stations must strip the copper from the residue from net washing to minimize environmental impact. Farmers should also monitor the copper concentration in sediments around their farms. Legislative pressure on biocidal antifoulings is increasing but there are no clear indications that copper based products will be prohibited in the near future for aquaculture.

In recent years significant effort has been put into the development of low toxicity or biocide-free antifouling coatings for shipping. Some of these developments are relevant to aquaculture and have been trialled as part of the CRAB Project. The results with three major coating alternatives are summarised in Testing Materials.

More details are available in the Best Practice Guidelines produced by the CRAB project. The guidelines are available to download from the website in English and Spanish.