Dining hall at sea: feeding migrations of nektonic predators to the eastern Patagonian Shelf

Abstract

Seasonal changes in relative abundance and biomass of nektonic predators were analysed on the eastern Patagonian Shelf and continental slope; one of the most productive large marine ecosystems of the southern hemisphere. Several migratory types were revealed for species belonging to either temperate or sub‐Antarctic faunas. Despite high productivity, only a few large nektonic predators spend their entire life cycle on the eastern Patagonian Shelf and use only a small proportion of the meso‐nektonic resource. Most of the resource is exploited by non‐resident nektonic migrants, which move to the area from distant spawning grounds. Pelagic and demersal sharks and skates, the squid Illex argentinus, tunas and gadoids migrate to the eastern part of the Patagonian Shelf to feed at different times of the year; arriving in seasonal waves according to their life cycle and spawning seasonality. Some deepwater fishes and squid migrate onto the shelf as juveniles to harvest the resource, and then return to deepwater habitat as adults. It is hypothesized that the large biomass of meso‐planktonic and meso‐nektonic consumers prevents most higher‐trophic level predators from establishing spawning populations in this area, as their larvae and fry would be overwhelmed by predation. Instead, the higher‐trophic level predators establish spawning and nursery grounds elsewhere and arrive to feed on the meso‐planktonic and meso‐nektonic resources after they have outgrown their own stages of predation vulnerability.

Interannual variability in the skate assemblage on the South Patagonian shelf and slope

“…All four of the predominant species are relatively large‐sized within the Falkland Islands skate assemblage (Arkhipkin et al , 2012 a ), suggesting that large skate species in the same environment can respond differently to the same fishing pressures. Results of this study contrast with Agnew et al 's () prediction that B. albomaculata and B. brachyurops should sustain higher fishing pressures than B. griseocauda and Z. chilensis , which Agnew et al () found to have higher age at maturity.…”

Variability of higher trophic level stable isotope data in space and time - a case study in a marine ecosystem

“…On the Falkland Islands Shelf, two marine ecosystems, the southern temperate ecosystem and the sub‐Antarctic ecosystem, are separated by an ecotone running from the south‐west to the north‐east of the Patagonian Shelf through the Falkland Islands archipelago. This situation is essentially created by the varying strengths of the two Falkland Islands currents (east and west) and the influence of the Argentine Drift to the west . A number of oceanographic fronts exist on the Falkland Islands shelf itself, mainly in areas to the south and east of the Falkland Islands.…”

Predicting the distribution of a threatened albatross: The importance of competition, fisheries and annual variability

“…Here we developed models to predict the distribution of blackbrowed albatrosses foraging over the southern Patagonian shelf, part of the Patagonian large marine ecosystem and one of the most productive areas in the world (Arkhipkin et al, 2012). This area is made up of a temperate ecosystem in the north and a sub-Antarctic system in the south which is partitioned by a boundary running from south-west to north-east through the Falkland Islands (Boltovskoy, 1999).…”