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Cleaner-Fish Technology : Parasite control, alternative to pesticides, and creating a new fishery.

Objective

The proposed work would assess the potential benefits for, and problems in, using native wrasse to remove parasites in intensive finfish culture in northern and southern Europe. More specifically, the project would compare the cleaning abilities of different wrasse species, study the ectoparasites of finfish being cultured at present and being developed for culture, determine the most practical and least ecologically damaging method of wrasse collection, determine the abundance and distribution of wrasse (so as to be able to focus fishing effort in certain areas, and estimate the size of the wild fishery), conduct experimental work on factors which may affect wrasse cleaning activity.

Should wrasse technology prove feasible, the final report would describe the methodology for wrasse technology and compare the economic costs of biological (wrasse) versus chemical control of sea-lice on salmon and sea-bass.

The study can be divided into two main areas, namely Commercial Trials and Field Studies. The former focuses on fish arms and developing wrasse technology. The latter focuses on the wild wrasse populations, where they occur, their abundance, and fishing techniques.

Commercial trials would study the relationships between cleaning efficiency and number and size of host fish (e.g. salmon, sea-bass), environmental parameters (e.g. visibility, temperature, day length), cage or pond conditions (e.g. size, depth, cover), the species, sex, age, size and number of wrasse, the species of parasite(s) and its life-cycle, condition and health of the wrasse (e.g. weight, maturity, parasites, disease).

Field studies would aim to determine reliable methods for quantifying the size and structure of wrasse populations, define the habitats of the species and age groups, study activity patterns (e.g. seasonal, diel, tidal) and behaviour (e.g. territorial, cleaning) in undisturbed and fished populations, test the relative effectiveness of different wrasse capture methods, examine effects of fishing on wrasse populations so as to estimate the sustainable catch.

TCD will coordinate the project, although each partner will be responsible for the collection of the data in their area. Trials and experiments at each institute would be designated at coordinating group meetings to ensure that data collected would not only be compared but avoid unnecessary duplication of effort. Studies at fish farms in northern Europe will concentrate on salmonid species whereas institutes in Portugal and Greece will concentrate on sea -bass, with limited work on other cultured marine species such as bream.
An investigation was made of the potential of cleaner fish (wrasse) to remove sea lice from farmed Atlantic salmon under commercial conditions.
Wrasse were cheaper and more effective than dichlorvos in lice control on first sea year salmon. Effectiveness on second sea year salmon remains to be shown although several Norwegian and British farms claim positive results. The current limitations on cleaner fish technology are:
availability of wild stocks near some farms;
absence of a fishery from March to May which exposes salmon to lice for 2 months;
sustainability of supply of greater than or equal to 10 cm wrasse from local populations (excepting southern Norway);
concerns over transmission of wrasse diseases and parasites to salmon.

Cultured wrasse, which are certified as disease free, may overcome these limitations. Additional research is also required to reduce wrasse escapement, improve understanding of factors affecting cleaning activity (eg presence of hides, alternative food, social status, salmon aggression), and predict the transmission potential of wrasse (and other wild fish associated with farm cages) diseases and parasites to salmon.

Topic(s)

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Call for proposal

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Funding Scheme

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Coordinator

Trinity College Dublin
EU contribution
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Address

Dublin 2
Ireland

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Total cost
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Participants (5)