INTRODUCED FISHES IN MARINE SYSTEMS AND INLAND SEAS

The number of introduced marine and estuarine fishes is small compared to that of freshwater introductions. Nevertheless, the number now exceeds 120 species and the list is growing. Many have been intentional introductions to enhance fisheries, but the majority are the unintentional result of canal construction and ballast-water transport. While ballast-water transport of fishes and other organisms is a 20th century phenomenon that deserves immediate attention, inadvertent introductions related to shipping have been occurring for centuries. They have obscured the biogeography of many fish and invertebrate species, and have profoundly affected the community structure of many coastal ecosystems. Most intentional introductions either did not establish populations, did not achieve their objectives, or had deleterious effects if the species became established. In several cases, introduced species have contributed to the extinction of native fishes, particularly endemic species.