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

3.0 Adult and Juvenile Fishes
Dominance is defined as the number of species accounting for 75% of the total abundance at a
specific station. Dominance values during all surveys ranged between 1 (one species
accounted for 75% of the total abundance) and 3 (three species accounted for 75% of the total
abundance), with most stations averaging 1 (Table 3.3-3). In general, higher dominance values
(2 and 3) were found at shallow-water stations.
3.3.2 Dominant and Selected Species
Four of the 20 species collected over all surveys and stations in 2008 comprised over 98% of
the total catch: northern anchovy, topsmelt, California grunion, and Pacific sardine (Table 3.3-1).
All of these species are schooling fishes that spend most of their lives in the harbor
environment.
As described above, northern anchovy was the most abundant species collected, and
represented 87% of the total lampara catch and nearly 57% of the total biomass (Table 3.3-1).
This species was collected at every sampling station and during every survey quarter (day and
night samples). Average size for all measured northern anchovy ranged between 3 and 14 cm,
with most individuals between 7 and 11 cm (Figure 3.3-3). No spatial trends in fish sizes were
evident.
Topsmelt were the second most abundant fish species collected during lampara surveys and
represented over 7% of the total catch and 9% of the total biomass (Table 3.3-1). Similar to
northern anchovy, this species was collected during all survey quarters and at every sampling
location (day and night samples). Sizes ranged between 4 and 32 cm, with most individuals
between 6 and 12 cm (Figure 3.3-3). Average size for all measured topsmelt ranged between 8
and 13 cm, with most fishes falling into the 10 or 11 cm size class. No spatial trends in fish
sizes were evident.
Other dominant pelagic species in terms of abundance included California grunion and Pacific
sardine, each representing approximately 1.9% of the total lampara catch and 1.2% and 3% of
the total biomass, respectively (Table 3.3-1). California grunion had a bimodal size distribution,
with peaks at 6-7 cm and 13-14 cm (Figure 3.3-3). Although there was a peak in 10 cm size
class Pacific sardine, their size distribution was also generally bimodal, with both small (4-8 cm)
and large (9-15 cm) represented.
3.3.3 Summary of Spatial and Temporal Variations
A total of 20 species represented by 81,084 individuals, with a combined weight of 656 kg, was
collected at 19 stations over 3 sampling quarters (seasons) in Los Angeles and Long Beach
harbors.
In contrast to typical seasonal patterns for pelagic harbor fishes where summer is the peak of
abundance (MEC 2002), the total number of individuals collected in this study using the lampara
net was higher in winter (January) than in summer (August) (Figure 3.3-2). Significant
differences were observed between night and day samples, with nearly ten times more fish
collected at night.
Differences in diurnal catch were primarily due to large night catches of northern anchovy (Table
3.3-1). No spatial patterns of abundance were apparent. This is likely due to the mobile habits
of most common pelagic fishes, which spend most of their lives moving in and around various
locations in and outside the harbors.
Temporal biomass patterns were similar to the abundance trends described above, with
significant day-night differences in biomass. Seasonal patterns in biomass were also observed,
with values lowest in winter (January) and highest in summer (July) for both day and night
3–6 2008 Biological Surveys of Los Angeles and Long Beach Harbors
April 2010