54 
PACIFIC SCIENCE, VoL XVII, January 1963 
TABLE 3 
Results of Co-Variance Tests on Differences in Morphology of Gillichthys mirabilis 
(Hypothesis tested is equal means after adjustment for standard length. 
Key: F, F ratio; d.f., degrees of freedom; F. 05 , 5% critical value.) 
F 
d.f. 
F .95 
DECISION 
Head length 
Gulf/Pacific/Salton Sea 
80.3 
2,299 
3.03 
reject 
Gulf/Pacific 
8.87 
1,201 
3.89 
reject 
Pacific (5 populations) 
14.8 
4,128 
2.44 
reject 
Salton Sea ( 1953-55) 
10.1 
2,97 
3.09 
reject 
Salton Sea (1954-55) 
336 
1,66 
3.99 
accept 
Upper jaw length 
> 90 mm 
Gulf/Pacific/Salton Sea 
10.6 
2,87 
3.10 
reject 
< 90 mm 
Gulf/Pacific/Salton Sea 
41.6 
2,208 
3.04 
reject 
Salton Sea (1953-55) 
7.99 
2,84 
3.10 
reject 
Salton Sea (1954-55) 
<0.58 
1,66 
3.99 
accept 
Anal fin height 
Gulf/Pacific/Salton Sea 
37.8 
2,291 
3.03 
reject 
Pacific ( 6 populations ) 
19.1 
5,129 
2.29 
reject 
Salton Sea (1953-55) 
3.13 
2,95 
3.10 
reject 
in those from the Salton Sea. The jaw is 81, 74, 
and 7 1 % of head length for Gulf, Pacific Coast 
and Salton Sea fish, respectively. Thus, the jaw 
of the Salton Sea fish is shorter in regard to 
head length as well as standard length. 
Median Fin Height 
The soft dorsal and the anal fins are higher 
in fish from the Gulf than in those from Cali- 
fornia and the Salton Sea (Barlow, 1961*, table 
1 ) . Only the variation in anal fin height is re- 
ported in detail. 
The anal fin height varies significantly from 
population to population along the Pacific Coast 
(Fig. 4, Table 3). San Francisco fish, for in- 
stance, often fall below the fitted regression; 
Newport Bay and Estero Punta Bunda speci- 
mens usually are above it. The data are too few 
to make an unequivocal statement about trends, 
but the fins of northern fish tend to be lower 
than those from the south. 
Gilbert and Scofield (1898: 498) mentioned 
the higher anal fin of detrusus ( = mirabilis 
Cooper) when they described it as a new species. 
The type locality is the tidal region of the Colo- 
rado River delta, but high anal fins are also 
typical of the populations to the south in the 
Gulf (Fig. 4). The regression of fin length 
on standard length for Gulf forms is higher and 
steeper than those for the populations from the 
Pacific Coast and the Salton Sea. The variation 
between Gulf populations is assumed to be 
significant. No trend with latitude is apparent. 
One sample from the northwestern region of 
the Gulf (an isolated salt pond 25 km north of 
San Felipe) has remarkably low median fins, 
and the dorsal fin profile is less rounded than in 
the typical Gulf form (Fig. 5) - The height of 
the anal fin averages 8.8% (8. 3-9.5%) of the 
standard length (based on 10 specimens, 61- 
102 mm in length). Thus the anal fin height 
and the dorsal fin shape resemble those of fish 
from the Pacific Coast. These data were not in- 
cluded in the regression of fin height versus 
standard length because the specimens had not 
been examined at the time the calculations were 
carried out and the figure was prepared. The fish 
of this population are thought to be not repre- 
sentative of the usual Gulf condition. 
