A synthesis of the early life history of the anglerfish, Lophius ...

A synthesis of the early life history of the anglerfish
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Additional information on the size and distribution of
post-larvae and pelagic juveniles (hereafter referred to as
pelagic stages) was obtained from the International
0-group Gadoid Survey in the North Sea (IOGS). The
IOGS took place in June/early July in the years 1974–
1983. The sampling gear, the International Young
Gadoid Pelagic Trawl, has a mouth opening 10 m
10 m and a 10-mm (stretched) hexagonal mesh
codend. Stratified hauls (20 min near the sea bed, 20 min
at the thermocline and 20 min within 5–10 m of the
surface) were made at or near the centre of each ICES
statistical rectangle. The total lengths of all specimens
caught in the years 1977–1983 were measured to the
0.5 cm below. (For details of catches in the IOGS see
ICES Annales Biologiques, Copenhagen, Vols 34–40.)
Although we are confident that all the pelagic
specimens 30 mm were L. piscatorius the possibility
cannot be ruled out that some of the smallest individuals
were L. budegassa.
Daily otolith increment analysis
Initial preparation and examination of two otolith
pairs (sagittae and lapilli) indicated that the latter were
generally easier to interpret because of their more clearly
defined increments and, for fish >35 mm TL, their ease
of preparation. Preparation of a readable increment
sequence in sagittae from large fish was made dificult by
multiple planes of growth, associated with the presence
of accessory primordia. Further, it was necessary to
grind both sides of sagittae from fish >35 mm TL. For
these reasons, primary increments in the lapilli were used
to estimate age, assuming that these structures were
formed daily. Lapilli were removed by means of a dorsal
incision through to the otic capsule. They were mounted
on glass slides with a methacrylate adhesive (Loctite
glass bond) which was cured using ultraviolet light.
Otoliths from fish >36 mm TL were ground with a 2500
grit metallographic grinding paper disc lubricated with
1 μm alumina slurry, using a lapping wheel. Otoliths
from larvae 600 m). Seabed
topography, initial temperature and salinity data, air
temperature, humidity, precipitation and river run-off
data were used to configure and force the models.
Hainbucher and Backhaus (1999) described results of
simulations forced by a range of wind scenarios. We
have used data from a run in which the models were
forced with March–May seasonally averaged but
spatially varying wind stress derived from the Hellerman
dataset (Hellerman and Rosenstein, 1983). The models
were run to quasi-steady state with this wind forcing
pattern, and the results from the fine scale model
were taken to represent the climatological average
hydrographic and circulation conditions for the spring
period.
Particle tracking model
The stationary hydrodynamic data from the HAMSOM
were used to drive a particle tracking model (Bryant