Current Featured Articles
The Featured Article for the March 2008 issue of L&O is:
Ciancio, J. E., M. A. Pascual, F. Botto, E. Frere, and O. Iribarne. 2008. Trophic relationships of exotic anadromous salmonids in the southern Patagonian Shelf as inferred from stable isotopes. Limnol. Oceanogr. 53(2): 788-798.
This article can be read by clicking here.
Introductory comments by Stephen Hamilton (L&O Associate Editor)
The global dispersion of salmonid fishes into new environments has been underway for a long time, and there is a plethora of studies of how these fishes affect ecological relationships in the waters to which they are introduced. People introduce these fishes for a variety of reasons, generally involving recreational and commercial fisheries, but all too often the costs of these introductions to native species and ecosystems only become evident in retrospect. In fresh waters, the profound effects of introduced salmonids on food webs and on native fishes have been well documented.
Salmonids native to the North Pacific and to the North Atlantic have now been widely introduced in southern South America, both for recreational fisheries and increasingly for marine net-pen aquaculture. Indeed, Chile now produces much of the "farmed" salmon that has flooded western markets. These introduced salmonids can sustain their populations where their thermal ranges are adequate. Somewhat surprisingly given experience in other regions, introduced salmonids in Patagonia appear to be establishing anadromous populations. During their residence in the marine environment they potentially compete for resources with native species, and may prey upon commercially important species such as crabs and sprats.
This featured article by a team of Argentine scientists presents evidence for how the establishment of anadromous populations of Oncorhynchus and Salmo species along the southern Patagonian Shelf may affect endemic marine food webs. The vast extent of potential marine habitat was inferred from water temperature ranges. The authors examined the feeding habits of several species of exotic salmonids using stable carbon and nitrogen isotope ratios as tracers, together with stomach content analyses. The feeding habits of the newcomers are compared to their known habits in their native ranges, with some species appearing similar and others showing marked differences. Most importantly, comparison of the diets of introduced populations to those of native fishes, cephalopods, sea birds, and marine mammals identified several native species whose diets overlap enough to be in potential competition with the salmonids, including two species of penguins of conservation concern.
This paper adds to the very small number of studies on how exotic salmonids can affect marine ecosystems, and underscores the need for more research in this area. Introduced anadromous species represent another indirect environmental effect of salmonid aquaculture, which has come under increased scrutiny as it has grown in global importance.