The North Atlantic Ocean: Need for proactive management

Among the major oceans of the world, the North Atlantic presents a unique problem in regard to the management of its commercial and recreational fisheries. Almost all of its populations of large-sized, predatory fishes have collapsed to the extent that they no longer play an effective rote in the ecosystem. There is a fundamental difference in the biodiversity and present state of the fisheries between the North Atlantic and the North Pacific. Much of the difference is attributable to their contrasting geological and climatic histories. The two oceans had been effectively separated until about 3.5+ million years ago, when the Bering Strait was formed permitting the Great Trans-Arctic Biotic Interchange. During the interchange, hundreds of Pacific species migrated to the Atlantic but only a few in the opposite direction. Although the Atlantic benefitted from the interchange, its species diversity remained relatively low. Today, the North Atlantic, in comparison to the North Pacific, possesses only about half the number of molluscan species, about one third as many fish species, and many fewer species of crabs, shrimp, and shellfish. The low biodiversity of the North Atlantic ecosystem has apparently made it more vulnerable to fishing pressure resulting in a series of population collapses. Many of the overfished populations have become so depleted that their recovery has become questionable. In the marine environment, species invasions and introductions evidently have not caused extinction of native species or loss of biodiversiry. Rather than devoting all our efforts toward the restoration of depressed populations, it is suggested that we undertake a proactive management program. Proactive management means the addition of species to low diversity ecosystems in order to decrease annual variation, to increase biodiversity, and to augment overall production.