Presentation: State-of-Knowledge Initiative for the Special Committee on Sustainable Aquaculture of the British Columbia Legislature

Delivered November, 2006. (Updated with Volume 5, January 2009)

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Fish Health Research

[A full pdf copy for printing may be downloaded from the WAVES database.]

Background

Intensive mariculture of fish is a recent industry in Canada relative to farming of land animals. This newness raises a unique set of questions.

Some alteration to the natural environment is inevitable. In reference to fish health, concerns about the risk of detrimental effects to the environment and to wild fish populations through the inadvertent introduction or amplification of infectious disease associated with aquaculture needed to be addressed.

There has been a considerable increase in research on fish diseases which has focused largely on the interest in health management in the developing aquaculture industry (Snieszko 1974, Stewart 1998, Woo and Bruno 1999, OIE 2006). Consequently there is an accompanying extensive body of published data in the form of original research papers and specialist textbooks on farmed fish diseases. However, there is relatively little comparable information on diseases in wild populations, largely because of the difficulty in collecting samples and to the more limited scope for the practical application of data in terms of fish health management. This imbalance can lead to a disproportionate and misleading impression of the concerns and level of disease in farmed fish stocks.

Nevertheless, over the last 15 years, several reviews comprehensively assessed the available scientific literature on the potential for disease interchange between wild and farmed fish (Hastein and Lindstad 1991, McVicar 1997, Hedrick 1998, Amos et al. 2000, Amos and Thomas 2002, Olivier 2002, McVicar et al 2006).

Notably, none of these reviews has found evidence that fish farming has contributed to detectable adverse changes in wild fish populations. However, reports have indicated that a variety of pathogens are present in wild marine fish species, which may then act as reservoirs for pathogens of farmed fish (Kent et al. 1998).

Significance

The introduction of new infectious agents into an area previously free of the organism can lead to serious outbreaks of disease (Kent 1994, Noakes et al 2000). Trade of live fish or eggs between areas carries risk of disease transfers as do other human activities such as fish processing plants where substantial concentrations of viable pathogens may be present and possibly from distant locations.

Other human activities with the potential of transferring fish pathogens include bait fish, aquarium hobbyist and ballast water used in the shipping industry. Because the movement of aquatic animals used in aquaculture can be controlled and because this is a major avenue of disease spread with immediate impact on an industry that relies on the health of aquatic animals, there has been considerable effort in the development of guidelines, recom-mendations and regulations to at least reduce and hopefully stop this avenue of disease spread (Scarfe et al. 2006).

In Canada, control is attempted by mandatory government approval of virtually all introductions and transfers of aquatic animals to the country, provinces or smaller areas (Scarratt and Drinnan, 1992).

Canada has developed a National Code on Introductions and Transfers of Aquatic Organisms and recently funded a National Aquatic Animal Health Program (Olivier 2004). Both are directed towards protecting aquatic animals from infectious diseases.

In addition to the identification of procedures that can be employed to reduce the risk of accidentally importing pathogens along with transplanted animals, tools have been developed to assess the risks involved when adjudicating on proposals to move aquatic animals (Arthur et al 2004). Also, procedures for acquiring information on pathogens of aquatic animals that may occur in an area have been developed (Cameron 2002, Subasinghe et al. 2004).

The aquaculture industry will likely continue and expand because its economic benefits will often outweigh the known risks. Additional research is required to address the many unanswered questions pertaining to aquatic animal health.

Therefore to reduce the inherent risks, a cautious science-based approach towards the management of aquatic animal health during aquaculture development is in practice.

References

Amos KH, Thomas J. 2002. Disease interactions between wild and cultured fish: observations and lessons   
    learned in the Pacific Northwest. Bull. Eur. Assn. Fish Pathol. 22: 95-102.

Amos KH, Thomas J, Stewart B. 2001. Pathogen transmission between wild and cultured salmonids: risk
    avoidance in Washington State, United States of America. P. 83-89. In, Risk Analysis in Aquatic Animal
    Health. Proceedings of an International Conference held in Paris, France 8-10 February 2000, Rodgers CJ,
    (ed.). World Organisation for Animal Health, Paris.

Arthur JR, Bondad-Reantaso MG, Baldock FC, Rodgers CJ, Edgerton BF. 2004. Manual on risk analysis for the
    safe movement of aquatic animals (FWG/01/2002). APEC/DoF/NACA/FAO. NACA, Bangkok.

Cameron A. 2002. Survey Toolbox for Aquatic Animal Diseases. A Practical Manual and Software Package.
    Australian Centre for International Agricultural Research, Canberra.

Hastein T, Lindstad T. 1991. Diseases in wild and cultured salmon: possible interactions. Aquaculture 98: 277-
    288.

Hedrick RP. 1998. Relationship of the host, pathogen, and environment: implications for disease of cultured and
    wild fish populations. J. Aquat. Anim. Health 10: 107-111.

Kent ML. 1994. The impact of disease on pen-reared salmonids on coastal marine environments. Proceedings of
    the Canada-Norway Workshop on Environmental Impacts of Aquaculture. Fisken og Havet 13:85-96.

McVicar AH. 1997. Disease and parasite implications of the coexistence of wild and cultured Atlantic salmon
    populations. ICES J. Mar. Sci. 54: 1093-1103

McVicar AH, Olivier G, Traxler GS, Jones S, Kieser D, MacKinnon A-M. 2006. Cultured and wild fish disease
    interactions in the Canadian marine environment. In, A Scientific Review of the Potential Environmental
    Effects of Aquaculture in Aquatic Ecosystems. Volume IV Fisheries and Oceans Canada.

OIE. 2006. Aquatic Animal Health Code. Ninth edition. World Organisation for Animal Health, Paris.
    (http://www.oie.int/eng/normes/fcode/A_INDEX.HTM). and Manual of Diagnostic Tests for Aquatic      
    Animals. Fifth edition. World Organisation for Animal Health, Paris.
    (http://www.oie.int/eng/normes/fmanual/A_summry.htm).
 
Olivier G. 2002. Disease interactions between wild and cultured fish – Perspectives from an American Northeast
    (Atlantic Provinces). Bull. Eur. Assoc. Fish Pathol. 22: 103-109.
 
Olivier G. 2004. Canada’s National Aquatic Animal Health Program and Canada’s National Code on Introductions
    and Transfers of Aquatic Organisms. In, Capacity and Awareness Building on Import Risk Analysis (IRA) for
    Aquatic Animals. Proceedings of the Workshops held 1-6 April 2002 in Bangkok, Thailand and 12-17 August
    2002 in Mazatlan, Mexico. APEC FWG 01/2002 (JR Arthur, MG Bondad-Reantaso, eds.), p. 115-121, NACA,
    Bangkok.
 
Scarfe AD, Lee C-S, O'Brien PJE, (eds). 2006. Aquaculture Biosecurity: Prevention, Control and Eradication of
    Aquatic Animal Disease. Blackwell Publishing, Ames.

Scarratt DJ, Drinnan RE. 1992. Canadian strategies fro risk reductions in introductions and transfers of marine
    and anadromous species. In, Dispersal of Living Organisms into Aquatic Ecosystems (A Rosenfield, R Mann,
    eds.), p. 377-385, Maryland Sea Grant College, College Park.
 
Snieszko SF 1974. The effects of environmental stress on the outbreaks of infectious diseases of fishes. J.
    Fish Biol. 6: 197-208.
 
Stewart JE 1998. Sharing the waters: an evaluation of site fallowing, year class separation and distance
    between sites for fish health purposes on Atlantic salmon farms. Can. Tech. Rep. Fish Aquat. Sci. 2218-1
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Subasinghe RP, McGladdery SE, Hill BJ. 2004. Surveillance and zoning for aquatic animal diseases. FAO
    FISHERIES TECHNICAL PAPER 451. Food and Agriculture Organization of the United Nations, Rome.
 
Woo PTK, Bruno DW. 1999. Fish Diseases and Disorders, Volume 3: Viral, Bacterial and Fungal Infections. CABI
    Publishing, Oxon. 874 p.