together on the same frame. Vertical hauls were performed from200m
to surface at 1 m/s for both types of nets. Large mesozooplankton
(1000–2000 μm) and macrozooplankton (N2000 μm) were collected
with a double Bongo net (500 μm mesh, 80 cm Ø), equipped with a
Scanmar net monitoring system and a flowmeter, in oblique tows
from 500 m to the surface at a speed of 2 knots. Most of the
mesozooplankton concentrates in the epipelagic zone, whereas some
macrozooplankton taxa may remain below that layer even during
nighttime (e.g. Andersen and Sardou, 1992; Stemmann et al., 2000). Accordingly,
the hauling depthswere chosen to sample the layer in which
the whole community was represented during the night, when
migrants go up. Thus, the 200 and 500 m depths mark the barrier of
migrants of 53–1000 and N1000 μmsizes, respectively (i.e. those organisms
that did not cross the 200 m or 500 m depth were not considered
migrants in this study).