Standard Presentation 2024 Australian Marine Sciences Association Annual Meeting combined with NZMSS

A comparison of ecosystems on five continental shelves influenced by western boundary currents (#465)

Iain M Suthers 1 , Hayden T Schilling 2 , Chris Chapman 3 , Neil Malan 1 , Jason Everett 4
  1. Ecology & Evolutionary Research Centre,, University of New South Wales (UNSW), Sydney, NSW, Australia
  2. NSW Department of Primary Industries, Port Stephens Fisheries Institute, Nelson Bay, NSW, Australia
  3. Environment, CSIRO, Hobart, Tas, Australia
  4. University of Queensland, St Lucia , QLD, Australia

The five main Western Boundary Currents (WBC) inherit similar tropical oligotrophic waters and distribute them polewards over the sub-tropical continental shelves of Japan, eastern USA, eastern South Africa, Australia, and Brazil. Their volume transports vary from <10 Sv (Brazil) to over 100 Sv (Agulhas and Florida), depending on season and latitude. To examine the ecosystem outcomes, we extracted fisheries landings data from the Sea Around Us project in a narrow 20 degree latitudinal band and <200 m depth, where the current interacts with the shelf.  Distinctive landed fisheries communities were evident for the three southern WBC compared to the two northern WBC. The landings of pelagic fishes per km2 of shelf (as effort data is not recorded) were greater for the Kuroshio and similar for Agulhas, Brazil and Florida currents, and the least for the East Australian Current. The Agulhas Current is in close proximity to upwelling and migratory fish from the west African coast, but the other oceanographic attributes of temperature, salinity, chlorophyll, and zooplankton do not explain all of these patterns in fisheries landings. The “Kuroshio paradox” remains an enigma where high fisheries production from clear indigo-blue waters is evident.