Introduction and Survival of Nonindigenous Species in Marine Environment

Baltz (1991) estimated that 120 species of marine and euryhaline fishes were introduced around the world. He summarized that most introductions did not establish populations or had deleterious effects or, if they were deliberate, did not achieve the objectives of the responsible parties. Because marine introductions usually cannot be controlled or prevented from spreading, all introductions into marine systems must be carefully evaluated before their implementation (Sindermann 1986). To reduce future problems from introductions, the International Council for the Exploration of the Sea (Sindermann 1992a) developed a code of practice for the introduction of species. The code is generally accepted by European countries but not by New World countries (Sindermann 1992a). Mann (1979) and Sindermann (1993a) summarized the use of exotic species in mariculture.

Pathways of introduction of nonindigenous marine organisms into North American waters were reviewed by Carlton (1985, 1987, 1989, 1992a,c,d). He demonstrated that most significant introductions by humans have been organisms on the outside (fouling species) or on the inside (boring species) of ships, namely, organisms inside vessels in solid ballast such as rocks, sand, and detritus; oysters or other shellfishes and organisms on their shells or in associated sediments and detritus; intentionally released species for fisheries; and larvae, juveniles, or adults of marine organisms in the ballast water of coastal, transoceanic, and interoceanic vessels. Carlton (1985, 1987, 1989, 1992a,c,d) reviewed the relative importance of each of these mechanisms to established introduced mollusks in North America (Carlton 1992b). Another major pathway of introduction is the escape of marine species and their pathogens from mariculture operations in the coastal waters (Kohler 1992).

The recent appearances of the South American fouling bivalves Mytella and Perna in Florida and Texas suggested that the global increase in ballast-water-mediated invasions (Carlton 1985, 1987) may be a mechanism that will continue to add to the nonindigenous mollusks of the Gulf (Carlton 1992b).

Information on the present ranges of introduced marine or estuarine organisms in North American waters is incomplete, scattered, or completely lacking. A review of the literature revealed introductions of several nonindigenous species into Florida's marine or estuarine waters, not all of which survived. Four exotic fish species of the genus Tilapia, three plant species, five invertebrate species, and at least two disease organisms were introduced into Florida's marine waters (Table 11). Some were introduced directly into coastal waters of the state, and some entered the marine or estuarine waters indirectly after they were introduced into freshwater ecosystems and migrated into the coastal waters. Kohler (1992) provided an overview of management principles and objectives for a marine- species introduction policy.