Small fishes in a big ocean

Image of the Month - February 2015

Trajectories of king penguins tracked during the MYCTO campaign overlayed on a weekly image of chlorophyll concentration (in mg/m3) (left) and altimetry (mean absolute dynamic topography, in cm) (Credits LOcean)

 

Interdisciplinary campaign MYCTO: to the left, ship trajectory overlaid on turbulent mixing circulation obtained from Lagrangian satellite data reanalysis in the area to the est of Kerguelen plateau; to the bottom right, pelagic trawl used during the campaign; to the middle right, king penguin (Aptenodytes patagonicus) from Kerguelen; to the up right: sampling of myctophid (Electrona carlsbergi). (Credits LOcean)

Kerguelen Islands have one of the largest populations of marine mammals and seabirds in the Southern Ocean. However, the pelagic ecosystem that sustains those populations is still poorly known. In this area, myctophids (small lantern fish) are suggested to play a major role as they constitute the main prey item for numerous top predators.
The MYCTO campaign was carried out in January 2014 in the area East of Kerguelen to elucidate the characteristics of this complex ecosystem, working at the frontier between ecology and physical oceanography. Myctophids were sampled through trawling, and also active hydroacoustic techniques for the first time in this area, to estimate the relative abundance over the study area. The cruise used an adaptive sampling strategy based on Lagrangian multisatellite data analysis ("filaments") and capable of resolving the very dynamical mesoscale (~10-100km) environment of this region.
Preliminary analyses already suggest that the physical environment, particularly the marine circulation (Polar Front,  mesoscale circulation and the thermocline), has a pivotal role in the distribution of myctophids and the behavior of penguins, which feed on them, simultaneously tracked during the cruise.

 

Acoustic echogram (depth vs time figure) displaying a fish school feeding on a zooplankton layer. The colorbar to the left indicates the target strength, in decibel.

 

See also:

Other web sites on this subject:

References:

  • Cotté C., d’Ovidio F., Dragon A.C., Guinet C., Lévy M. (in press) Flexible preference of southern elephant seals for distinct mesoscale features within the Antarctic Circumpolar Current. Progress in Oceanography (doi:10.1016/j.pocean.2014.11.011)
  • D'Ovidio F., De Monte S., Della Penna A., Cotté C. & Guinet C. (2013) Ecological implications of oceanic eddy retention in the open ocean: a Lagrangian approach. J. Phys. A: Math. Theor. 46: 254023 (doi:10.1088/1751-8113/46/25/254023)
  • see a more detailed description of the Mycto cruise