[L&O Featured Article] L&O Featured Article, Vol. 53 (2) March 2008

[L&O Feature Articles Announcements]

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 at:

http://www.aslo.org/lo/toc/vol_53/issue_2/0788.pdf

Introductory comments by the 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.