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Fishery Bulletin 1 1 1 (1) 
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SST (°C) SST (°C) 
Figure 3 
Probability of finding paralarval purplebaek squid ( Sthenoteuthis oualaniensis ) and jumbo squid ( Dosidicus 
gigas ) as a function of sea-surface temperature in samples from (A) manta (surface) and (B) bongo (oblique) 
tows conducted in 1998-2006 in the eastern tropical Pacifc. All other variables were set to their median val- 
ues. Dashed lines indicate standard error of the regression. Tick marks indicate raw binomial data. 
both), abundance of paralarvae was much greater in 
surface tows. High abundance in surface tows also has 
been reported for other ommastrephids (Ueynagi and 
Nonaka, 1993), and extremely high numbers of SD- 
complex paralarvae have been captured in single sur- 
face tows: 819 off Jalisco, Mexico 4 and >10,000 in the 
4 Palomares-Garci'a, R., R. De Silva-Davila, and R. Avendano- 
Ibarra. 2007. Predation of the copepod Oncaea mediter- 
ranea upon ommastrephid paralarvae in the mouth of the 
Gulf of California. Abstract in Proceedings of the 1st inter- 
national CLIOTOP symposium; La Paz, Mexico, 3-7 December. 
Table 2 
Generalized linear models used to relate nonzero abundance of ommastrephid paralarvae in manta (surface) 
and bongo (oblique) tows conducted in the eastern tropical Pacific in 1998-2006 to 5 in situ oceanographic 
variables: sea-surface temperature (SST), sea-surface salinity (SSS), mixed-layer depth (MLD), temperature 
at thermocline (TT), and surface-concentration of chlorophyll-a (CHL). A stepwise approach selected SST, 
MLD, TT, and CHL for the final manta model and SST, MLD, and CHL for the final bongo model. The re- 
sulting percentage of explained deviance and the Akaike’s information criteria (AIC) value for these models 
indicate that none of the oceanographic variables is a strong predictor of nonzero abundance. 
Manta Bongo 
Model 
Deviance (%) 
AIC 
Model 
Deviance (%) 
AIC 
Null 
1341 
Null 
782 
SST x MLD xTTx CHL 
12.1 
1303.8 
SST x MLD x CHL 
7.5 
764.6 
MLD x TT x CHL 
11.3 
1305 
SST x CHL 
6.9 
764.8 
SST x MLD x TT 
11.1 
1306 
MLD x CHL 
6.6 
765.6 
SST x TT x CHL 
9.8 
1310.9 
SST x MLD 
4.5 
772.2 
SST x MLD x CHL 
9.5 
1312.2 
Vertical distribution of paralarvae 
We found no difference in the size of paralarvae be- 
tween surface (manta) and oblique (bongo) tows, in 
agreement with Yatsu. 3 These observations are not 
consistent with an ontogenetic vertical migration to in- 
creasing depths within the paralarval stage of develop- 
ment, as proposed for Todarodes pacificus (Yamamoto 
et al., 2002; 2007). This feature, therefore, may not be 
common to all ommastrephids. 
Although incidence of capture in surface and oblique 
tows was nearly identical (54% positive samples in 
