4 
Fishery Bulletin 1 1 1 (1) 
an ocular micrometer. Larvae observed in ISIIS im- 
ages were measured digitally with Imaged software 
after each image was calibrated to standard pixel size. 
Fishes were measured for notochord or standard length 
(the position of the posterior end of the hypural plate 
was estimated if the pigmentation on a fish was too 
dense for the internal caudal fin structure to be vis- 
ible). A subset (6 out of 409) of the fish images was 
discarded because orientation of the fish precluded ac- 
curate measurement. Despite our effort to remove such 
images from measurement, some fish sizes likely were 
underestimated when the observer was not able to dis- 
cern the offset that may have occurred where the orien- 
tation was not exactly parallel to field of view. Lengths 
of all larvae were compared between the 2 gears and 
the 2 transects. To avoid pseudoreplication, the average 
length of all larvae, family-level larvae, and species- 
level larvae from a bongo tow or ISIIS undulation was 
used for comparison. Size distributions were all highly 
skewed, and therefore a Kruskal-Wallis test was used 
to compare sizes within and between gear types. Statis- 
tical analyses were performed in R software, vers. 2.14 
(R Development Core Team, 2011) with the package 
“plyr” (Wickham, 2011) as well as visualization tech- 
niques with the package “ggplot2” (Wickham, 2009). 
Results 
Along 2 transects, we completed 24 and 12 ISIIS un- 
dulations and 6 and 5 bongo tows, respectively. ISIIS 
sampled an estimated 297 m 3 h 1 (or an average of 63 
m 3 per tow-yo (i.e., down and up undulation), for a total 
sampled volume of 2281 m 3 . The actual volume sam- 
pled was lower than the maximum possible because 
of a slight misalignment in the mirrors that occluded 
1 b b 
: 14.5 
Transect 1 
Transect 2 
Latitude (°N) 
Figure 2 
Fluorescence (voltage), temperature (°C), and salinity (ppt) measured from ISIIS along the western (transect 1) 
and eastern (transect 2) transects during 23—24 October 2008. Dotted lines in the fiuorometry panels represent the 
undulations of the In the Situ Ichthyoplankton Imaging System (ISIIS). The vertical solid lines represent the ap- 
proximate tow positions for the bongo sampler which was deployed along the length of the same transect once the 
ISIIS tow was completed. 
40.7 
40.8 
40 9 
40.7 
40.8 
40.9 
14.5 
-101 
- 20 : 
-30 
-40 
-50: 
40.7 40.8 40.9 
i J33 
| 
i! 
|32.5 
