The relationship between marine fronts and fish diversity in the Patagonian Shelf Large Marine Ecosystem

Abstract

Aim To evaluate the relationship between marine fronts and (1) fish diversity patterns, (2) fish biomass distribution, and (3) fish assemblage structure. Location Patagonian Shelf, Southwestern Atlantic Ocean. Methods Three main frontal systems and eight nearby zones (frontal vs. non‐frontal areas) were compared. An extensive fishery database, obtained during an a priori sampling scheme (spatial resolution 1 × 1) from 1978 to 1979, was employed. Analyses of 248 trawling stations were performed using a combination of diversity measures (species richness, Shannon diversity and evenness), biomass analyses and multivariate analyses [nonparametric analysis of similarity (ANOSIM), non‐metric multidimensional scaling ordination (NMDS) and similarity percentages (SIMPER)] to evaluate the effect of fronts on fish communities. Results In total, 46 fish taxa were identified. Demersal fish diversity increased at the tidal front of Península Valdés but decreased in the frontal zones of the Southern Shelf‐Break and Magellan frontal systems. The richness and biomass of pelagic fish were higher at the Península Valdés Tidal Front, while the biomass of demersal fish was higher at its non‐frontal counterpart. Fish diversity did not differ consistently along the Northern Shelf‐Break Front. However, a higher fish biomass was registered at the non‐frontal zone. Demersal and pelagic fish assemblages differed between frontal and non‐frontal zones. Main conclusions The Patagonian Shelf Large Marine Ecosystem has diverse frontal types that appear to have different effects on fish diversity and assemblage structure. Seasonal (tidal) or permanent fronts have different effects on the parameters analysed, which could be due to productivity–diversity relationships. The Península Valdés Tidal Front, a relatively short temporal scale system, demonstrates a stronger influence on fish diversity, biomass and assemblage structure than the other frontal areas studied. The seasonality of nutrient input owing to frontogenesis, which begins during the austral spring, may play an important role in determining local diversity. At permanent frontal features, diversity decreases when the nutrient availability is high. This is potentially because, when food resources increase, a few species become dominant.

Simultaneous multi-colony tracking of a pelagic seabird reveals cross-colony utilization of a shared foraging area

“…The aggregation of foraging seabirds at frontal systems, including the ISF, is well documented (Le Fèvre 1986, Stone et al 1994, Schneider 1990, Begg & Reid 1997, Durazo et al 1998, Vlietstra et al 2005. Frontal systems increase primary production (Savidge 1976, Beardall et al 1982, Le Fèvre 1986, Yoder et al 1994) and encourage aggregation (Scrope-Howe & Jones 1985) or physical retention of zooplankton and nektonic organisms (Herman et al 1981, Yoder et al 1994, attracting high densities of pelagic fish (Laurs et al 1977, Alemany et al 2009). Physical retention of coastally spawned fish larvae by associated cyclonic gyre currents (as in the WIS) can also drive stable seasonal recruitment (Hill et al 1994, Dickey-Collas et al 1997, providing a reliable prey resource for higher trophic levels, including seabirds (Durazo et al 1998).…”

Towards a model of postglacial biogeography in shallow marine species along the Patagonian Province: lessons from the limpet Nacella magellanica (Gmelin, 1791)

“…The minor Patagonian Coastal Current (PCC) influences the Atlantic Patagonia coast and moves northward up to 38°S [110-112]. Moreover, oceanographic fronts such as the Atlantic Patagonian cold estuarine front on the eastern margin of the Strait of Magellan has been described as an oceanographic barrier between Pacific Patagonia and the southern Atlantic coast [113-115]. As expected under the general circulation pattern in this region, we found asymmetrical gene flow in the species among Pacific Patagonia, Atlantic Patagonia and the Falkland/Malvinas Islands.…”

Spatio‐temporal genetic structure and the effects of long‐term fishing in two partially sympatric offshore demersal fishes

“…; Alemany et al . ). Therefore, the observed contrasting evolutionary histories of these species may have resulted from an interaction between life history traits and the stratification of the Benguela Current oceanographic features with depth (White et al .…”

“…Despite being an offshore demersal species, the spatial structure of M. capensis closely resembles that of other inshore marine taxa, where genetic breaks appear to be linked with coastal oceanographic features (Alemany et al . ; Henriques et al . , , ).…”