Assessing the sources of the fishing down marine food web process in the Argentinean-Uruguayan Common Fishing Zone
Andrés J. Jaureguizar and Andrés C. Milessi

The temporal trend in the mean trophic level (mTL), fisheries-in-balance index (FIB), trophic categories landing (TrC) and landing profile (LP) of the exploited marine community (82 species) in the Argentinean-Uruguayan Common Fishing Zone (AUCFZ) were examined from 1989 to 2003. The total landings (Yt) (rs=-0.561; P<0.05) and the Yt of carnivores and top predators has declined, while the Yt of herbivores, detritivores and omnivores has increased. Consequently, the mTL significantly decreased (rs =-0.88; P<0.01) at a rate of 0.41 from 1991 (mTL =3.81) to 2003 (mTL =3.4), and the FIB index has declined in the last 6 years. The LP temporal pattern showed four periods with significant differences in their species composition and Primary Production Required, which shows a strong decline in the traditional fishery resources (i.e. Merluccius hubbsi, Micropogonias furnieri), and increases in crustacean (Chaceon notilis), molluscs (Zygochlamys patagonica) and some fishes (Macrodon ancylodon, Macruronus magallanicus, Rajidae). The mTL trend reflects the changes in the AUCFZ landing structure. This was characterized by large, slow-growing and late-maturing species during the early 1990s, while during recent years, early 2000s, it was mainly characterized by medium-sized fishes, crustaceans and molluscs. The examination of the mTL, FBI, TrC trajectories and LP temporal pattern suggests that new fishery resources are developing or that the fishing effort has been redistributed from overexploited resources to lightly exploited resources. In addition, the examination of discriminator and common species, and the fact that traditional resources are being over-fished support the hypothesis that the mTL trend has been influenced more by the impacts of new fishing technologies than the changes in market-driven exploitation and environmental fluctuation. These results provide evidence of the fishing down process along AUCFZ.

Keywords: trophic structure, landing profiles, overfishing, ecosystem management, Argentina, Uruguay
Contents of this volume Sci. Mar. 72(1) : 25-36 Back PDF
Please, send comments to
ICM (CSIC) - Passeig Marítim de la Barceloneta, 37-49. E-08003 Barcelona (Spain)