Introductions and Survival of Nonindigenous Species in the Marine Environment

Nonindigenous Diseases in the Marine Environment

Sindermann (1990a) discussed the effects of principal diseases of marine fishes on wild populations, especially on wild populations of economic significance. Sindermann and Rosenfield (1967) and more recently Sindermann (1990b) discussed the principal diseases of commercially important marine bivalves, molluscs, and crustaceans (including microbial pathogens, parasitic invasions, and tumors). These publications did not provide information about the status of diseases as native or nonindigenous to the United States or Florida. Kern and Rosenfield (1992) discussed shellfish health and protection, and Sindermann (1992b, 1993b) discussed the risks of importing diseases with the importation of nonindigenous marine animals. He reported that the virus IHHNV in shrimp was probably imported from Southeast Asia into aquaculture facilities in Florida. Although other nonindigenous diseases that the authors mentioned may be in Florida waters, we could find no published information that confirmed such presence.

The subject of the diseases of cultured Penaeid shrimp (Penaeus monodon) in Asia and in the United States is presented by Brock (1992), Fulks and Main (1992), Lightner (1988), Lightner et al. (1983), 1992a,b), and Lightner and Redman (1990). The introduction of pathogens, especially of nonindigenous viruses, with the introductions of nonindigenous shrimp species is such a threat to Florida's shrimp populations that a major effort is necessary to reduce or eliminate any chances of introducing these injurious organisms. The transfer of stocks the health status of which is unknown may pose a threat to wild populations and could also harm shrimp cultures (Fulks and Main 1992).

To reduce the number of unwanted non-native disease species introduced into marine waters, Sindermann (1993b: 8,c) recommended:

(1) A substantial reduction in the global dissemination of diseases of aquatic organisms could be attained by the development of native species or species stocks by scientific management and aquaculture practices (including selective breeding and genetic manipulation) as an alternative to introducing nonnative species.

(2) A vigorous international program of marine disease research and control should be developed by the Permanent Commission for the Study of Fish Diseases of the International Office of Epizootics. This intergovernmental veterinary organization, based in Europe, is a logical focus for the kind of coordination that will be required (de Kinkelin et al. 1990). Included would be the development of models for inspection and certification programs, standardized protocols for disease examinations, and the implementation of an effective communication network.

(3) Regional maps should be developed and kept current for each host species, showing the presence and abundance of each disease that affects the species. Movement of infected animals from an area where the disease is present to one where it is absent should be prohibited.

(4) National and regional disease diagnostic centers, with supporting research capabilities, should be established to develop information about species proposed for introduction, or approved for introduction, or introduced accidentally.

(5) Specific pathogen-free stocks of marine fish and shellfish should be identified for aquaculture purposes; these stocks should be used as sources of seed. A program should be developed that is modeled on one developed principally by the U.S. Fish and Wildlife Service and already in use for salmonid hatcheries in the United States.

Sindermann (1993b:page 9,a) outlined a national policy to control the spread of all nonindigenous species. He recommended the following steps:

(1) A clear national policy on introduced species, whether the introductions are accidental or deliberate, should be developed and stated.

(2) A national system of inspection and quarantine, with adequate back-up research capabilities, should be developed and funded.

(3) An effective regulatory regime and an enforcement system to ensure that regulations are not circumvented should be developed.

(4) Proposed introductions should have clearly stated and demonstrated rational bases. Proposals that are without adequate rationale, poorly planned, or unnecessarily risky, should not be approved.

(5) Decisionmakers should be aware of, and sensitive to, the practical, economic, social, and political aspects of introductions, but should evaluate proposals principally on the basis of the available scientific data. Relevant scientific implications and viewpoints include, but are not limited to:

a) Ecological considerations -- including competition, predation, and community characteristics of species (diversity, carrying capacity);

b) Genetic considerations -- including the potential for hybridization, change in gene frequency (genetic diversity), and change or modification in disease or parasite resistance;

c) Behavioral considerations -- including interactions between native and exotic species; and

d) Pathological considerations -- including the potential for unintentional introduction of diseases and parasites.

(6) All proposed introductions should be accompanied by full and adequate procedures and provisions for post-importation (follow-up) monitoring.

Early consideration should also be given to national and international acceptance of a uniform code of practice for movements of nonindigenous marine species. A United States policy on introduced aquatic species and adoption of the precautionary principle proposed by Germany and accepted at the Second International Conference on the Protection of the North Sea in 1987 would be beneficial. That principle requires action to reduce pollution even in the absence of soundly established scientific proof for cause-and-effect relations. The principle could be applied especially for the control of accidental introductions (including pathogens) that clearly are forms of biological pollution.