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

5.0 Benthic and Epibenthic Invertebrates
5.4.1.3 Number of Species
A total of 61 unique species
were collected from the 19
stations sampled over the three
surveys (Table 5.4-2; Appendix
E). The average number of
species caught per trawl ranged
from 2 to 9. The number of
species caught during day and
night combined ranged from 6 to
15. Generally, twice as many
species were collected at night
than during the day. The
stations with the greatest variety
of species across day-night
sampling were in the outer harbor (Stations LA1, LA3, LA4, LA6, LB3). The fewest species
were caught in outer harbor shallow water (Stations LA2, LA7, and LB2). There were no other
obvious patterns in macroinvertebrate biomass with depth or location.
5.4.1.4 Diversity Indices and Dominance
In general, the diversity of macroinvertebrates in trawl catches was low (Table 5.4-3). Mean
Shannon-Wiener diversity ranged from 0 to 1.03 in day samples, 0.34 to 1.02 in night samples,
and 0.57 to 1.37 combined across sampling periods. Margalef diversity ranged from 0 to 0.8 in
day samples, 0.31 to 0.51 in night samples, and 0.47 to 1.19 combined across day-night
sampling. Dominance values also were relatively low, with 1 to 5 species accounting for 75% of
the trawl catch at all stations for day, night, and combined samples.
5.4.2 Species Composition
The most abundant species tended to be found at all stations, although in varying abundances
(Table 5.4-4). The black-spotted shrimp, Xantus’ swimming crab, and Heptacarpus shrimp were
caught at all stations, the ridgeback prawn and black-tailed bay shrimp were caught at most
stations, and the tuberculate pear crab was collected at more than half the stations. Other
species were caught in low numbers and contributed unequally to species composition. The
Xantus’ swimming crab generally was more abundant in shallow-water habitats, but patterns for
other taxa were not evident.
5.4.3 Dominant and Special Interest Species
Crustaceans (prawns, shrimps, and crabs) dominated the trawl catches. Over 6,000 individuals
representing 87% of the total catch over the three surveys was accounted for by the five most
abundant species (black-spotted shrimp, black-tailed bay shrimp, ridgeback prawn,
Heptocarpus shrimps, and Xantus’ swimming crab) (Table 5.4-1).
Other relatively abundant taxa, with 82 to 236 individuals caught in all samples, were also
crustaceans: tuberculate pear crab (Pyromaia tuberculata), Northern crangon shrimp (Crangon
alaskensis), and spotted ridgeback prawn (Sicyonia penicillata).
Several of the invertebrates found in the harbors have economic importance for the commercial
and sport fishing industry, although commercial fishing does not occur within the Ports. The
harbors provide nursery and adult habitat for many species, which contributes to the
maintenance of these resources within and offshore San Pedro Bay. Species of commercial or
2008 Biological Surveys of Los Angeles and Long Beach Harbors 5–9
April 2010