Cowen et al.: Evaluation of the In Situ Ichthyoplankton Imaging System and comparison with the bongo-net sampler 
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Volume sampled (m 3 ) 
Number of larvae 
c 
Concentration (number rrr 3 ) 
Figure 5 
Vertically discrete (by depth) larval fish (A) sampling 
effort and (B) counts measured with the In Situ Ich- 
thyoplankton Imaging System (ISIIS) in this study 
conducted south of Woods Hole, Massachusetts, in Oc- 
tober 2008. (C) Larval concentration was calculated 
from data in A and B, and a linear regression was fit- 
ted to the data (coefficient of determination |r 2 ]=0.96). 
The star denotes the mean water-column concentra- 
tion value (0.22). 
Discussion 
Design of larval fish surveys requires a balance of ship 
time, sample-processing time, and adequate sampling 
effort for resolution of the spatial (and temporal) varia- 
tion to provide a robust measure of spatial distribution 
and abundance of this life-history stage. In essence, 
survey design is a cost-benefit issue. Greater sampling 
frequency will improve precision of estimates (e.g., Cyr 
et al., 1992), but it does so at a cost of greater ship 
time and laboratory sample processing. Consequently, 
surveys are limited, in part, by the sampling tool of 
choice (and its inherent limitations and benefits). 
Results indicate that data collected with this proto- 
type version of ISIIS are comparable to data collected 
with a bongo sampler. Measurements of larval concen- 
trations were similar, although identifications of larvae 
fish were possible with ISIIS only at a coarser level of 
taxonomic resolution compared to that with the bongo 
sampler. In waters with relatively low species diversity 
of ichthyoplankton, like the shelf of the northeastern 
United States, the taxonomic resolution possible with 
ISIIS is adequate for conducting an array of studies, 
particularly when data are verified with net samples. 
However, in species-rich waters, the taxonomic resolu- 
tion possible with ISIIS may limit the applications of 
