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

4.0 Ichthyoplankton
Annual mean abundance of fish eggs per station (all three surveys combined) is presented in
Table 4.3-4. As noted above, the vast majority of eggs was categorized as undeveloped and
could not be identified to a lower taxonomic level. The highest weighted mean abundance of
eggs at any station over all survey data was combined was Station LA4 (13,797/100m 2 ),
followed by stations LA10 (12,071/100m 2 ) and LB7 (10,217/100m 2 ). Stations LB2
(1,362/100m 2 ) and LA3 (1,737/100m 2 ) had the lowest weighted mean abundance of eggs.
Abundances of the most common taxa at each station varied (Table 4.3-5) For gobies, CIQ
gobies were most abundant at Station LA7 followed by Station LA14, while bay gobies were
most abundant at stations LB4 and LA14, and yellowfin gobies were most abundant at stations
LA14 and LA7. Combtooth blennies were most abundant at stations LB7 and LB12, while
clingfish were most abundant at stations LB6 and LB12. The abundance of clingfish at all other
stations was generally very low.
The three most abundant taxa of larvae (CIQ gobies, combtooth blennies and bay gobies) were
found at all nineteen stations (Table 4.3-5). It is interesting to note that during the current study,
Station LA3 had the lowest abundance of larvae and one of the lowest abundance of fish eggs
compared to the other stations. Station LA3 is geographically close to LA2, yet during the
current study, LA2 had more than triple the abundance of eggs and a much higher abundance
of larval fish. Thus, egg and larval densities can differ even at geographically similar station.
Table 4.3-6 presents the weighted mean abundance (#/100 m 2 ) per survey of the ten overall
most abundant larval fishes. The total abundance of all larvae combined was similar during the
first two surveys but much higher during the July survey. This pattern was due to dramatic
increases in the abundance of three taxa (CIQ gobies, combtooth blennies, and clingfishes)
during the summer (July) survey. Three taxa, yellowfin goby, white croaker, and roughcheek
sculpin, were found during the first two surveys but not during the third, while northern anchovy
was only found during the last two surveys. The differences among surveys are due to the
seasonal reproductive patterns of these fish along the California coast (Moser 1996).
Results of the multidimensional scaling (MDS) analysis of the Bray-Curtis distances among
stations (Figure 4.3-1) show that similarities among the Long Beach Harbor stations are higher
(stations are closer together) than the similarities among Los Angeles Harbor stations, which
are more scattered in the figure. The distances among the LA stations almost mirrors the
physical locations of the stations. For example, Stations LA14, LA6, LA05, and LA15 at the top
of the figure represent an inner harbor grouping and the locations of Stations LA4, LA3, LA2,
and LA1 represent an outer harbor grouping. The relationship of the LB stations to their
physical locations is not as clear, which is due to the greater similarity in the larval data among
those stations. PRIMER SIMPER tests confirmed that the average similarity among the Long
Beach Harbor stations (65 %) was greater than the average similarity among the Los Angeles
Harbor stations (52%).
Although the MDS analysis suggests potential relationships and similarities among stations
based on larval fish, the differences that were observed could be due to differences in adult fish
composition among sites. The adult fish assemblages, in turn, are dependent to some extent
on the habitats available at each site. Sediment grain size data were used to determine if a
significant relationship exists between sediment grain size and larval fish composition. Although
sediment grain size would not be expected to affect larval fish composition directly, it might be
indicative of habitat differences that could affect adult fish composition. For example, California
halibut and other flatfishes might be more abundant in sandy areas with larger grain size than in
areas with higher percentages of clay that might support higher numbers of gobies that dwell in
burrows in the mud.
2008 Biological Surveys of Los Angeles and Long Beach Harbors 4–5
April 2010