appendix b final 2008 biological surveys of los angeles and long ...

4.0 Ichthyoplankton
4.0 ICHTHYOPLANKTON
4.1 INTRODUCTION
A large number of different fish species live and spawn in the various habitats in the Los
Angeles and Long Beach Harbor complex (MEC 1988 and 2002). The eggs and larval stages
of many fish (ichthyoplankton) stay in the water column for a period of time after being released
by the female and/or after hatching. The ichthyoplankton are typically sampled by pulling a
plankton net through the water column.
The first studies of the ichthyoplankton within Los Angeles and Long Beach Harbors were
conducted in 1972. Larger studies were conducted by the Harbors Environmental Project (HEP
1976, 1979), Brewer (1983), MBC (1984), MEC (1988 and 2002). The studies conducted
through 1988 generally had fewer stations but more frequent sampling than the MEC 2002
study and the current study. A variety of collection techniques were used during the earlier
studies, but recent studies have been more standardized.
4.2 METHODOLOGY
4.2.1 Sample Collection
Quarterly ichthyoplankton surveys were conducted
at night during February, April, and July 2008, at
the same nineteen stations (ten in the Port of Los
Angeles and nine in the Port of Long Beach)
sampled for adult fish (Figure 4.2-1). The water
column was sampled using three techniques and
equipment types: a manta net was used to sample
the surface water (neuston), stepped-oblique
bongo net tows sampled the midwater (from near
the bottom to the surface), and a wheeled bongo
net sampled the near bottom (epibenthic) level.
During the stepped-oblique sample collection, the
net was lowered to the bottom and during retrieval
to the surface it was kept at two midwater depths
(‘steps’) for a longer period of time that at the rest
of the depths. This equipment and these methods
were the same as those used during the 2000
biological baseline study (MEC 2002). The
neuston samples were collected using a manta
net that had an 85-cm-wide, 17-cm-high
rectangular opening. The midwater and
epibenthic samples were collected using a
wheeled bongo frame and nets. The bongo frame
has two 0.6-meter diameter openings, each with an attached net. All nets and codends (sample
collecting chamber on the end of each net) were made from 0.335 mm mesh. A calibrated
flowmeter was attached in the mouth of each net to calculate the volume of water filtered during
each deployment. Nets were towed for 10 minutes at a speed of about 1 knot at each location.
Samples were placed in labeled jars and fixed in either 70-80% ethanol or 4-5% buffered
formalin in the field. Samples that were preserved in formalin were transferred to ethanol prior
to laboratory processing. All collections were completed during the night because previous
2008 Biological Surveys of Los Angeles and Long Beach Harbors 4–1
April 2010