1 
Evaluation of the In Situ Ichthyoplankton 
Imaging System (ISIIS): comparison with 
the traditional (bongo net) sampler 
Email address for contact author rcowen@rsmas.miami edu 
1 Rosenstiel School of Marine and Atmospheric Science 
University of Miami 
4600 Rickenbacker Causeway 
Miami, Florida 33149 
Abstract — Plankton and larval fish 
sampling programs often are limited 
by a balance between sampling fre- 
quency (for precision) and costs. Ad- 
vancements in sampling techniques 
hold the potential to add consider- 
able efficiency and, therefore, add 
sampling frequency to improve preci- 
sion. We compare a newly developed 
plankton imaging system, In Situ 
Ichthyoplankton Imaging System 
(ISIIS), with a bongo sampler, which 
is a traditional plankton sampling 
gear developed in the 1960s. Com- 
parative sampling was conducted 
along 2 transects -30-40 km long. 
Over 2 days, we completed 36 ISIIS 
tow-yo undulations and 11 bongo 
oblique tows, each from the surface 
to within 10 m of the seafloor. Over- 
all, the 2 gears detected comparable 
numbers of larval fishes, represent- 
ing similar taxonomic compositions, 
although larvae captured with the 
bongo were capable of being identi- 
fied to lower taxonomic levels, espe- 
cially larvae in the small (<5 mm), 
preflexion stages. Size distributions 
of the sampled larval fishes differed 
considerably between these 2 sam- 
pling methods, with the size range 
and mean size of larval fishes larger 
with ISIIS than with the bongo sam- 
pler. The high frequency and fine 
spatial scale of ISIIS allow it to add 
considerable sampling precision (i.e., 
more vertical sections) to plankton 
surveys. Improvements in the ISIIS 
technology (including greater depth 
of field and image resolution) should 
also increase taxonomic resolution 
and decrease processing time. When 
coupled with appropriate net sam- 
pling (for the purpose of collecting 
and verifying the identification of 
biological samples), the use of ISIIS 
could improve overall survey design 
and simultaneously provide detailed, 
process-oriented information for fish- 
eries scientists and oceanographers. 
Manuscript submitted 8 December 2011. 
Manuscript accepted 21 September 2012. 
Fish. Bull. 111(1): 1—12 (2013). 
doi:10.7755/FB. 11 1.1.1 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessar- 
ily reflect the position of the National 
Marine Fisheries Service, NOAA. 
Robert K. Cowen (contact author)' 
Adam T. Greer' 
Cedric M. Guigand' 
Jonathan A. Hare 2 
David E. Richardson 2 
Harvey J. Walsh 2 
2 Northeast Fisheries Science Center 
National Marine Fisheries Service 
Narragansett Laboratory 
28 Tarzwell Drive 
Narragansett, Rhode Island 02882 
Regular surveys of early life stages 
of fishes provide a wealth of informa- 
tion for fisheries managers and fish- 
ery oceanographers. Indices of larval 
abundance are used quantitatively 
as fishery-independent measures of 
population abundance in stock as- 
sessments (Scott et al., 1993; Gledhill 
and Lyczkowski-Shultz, 2000; Sim- 
monds, 2009). Larval fish abundance 
also is used qualitatively, as evidence 
for change in stock status (Smith 
and Morse, 1993; Lo et al., 2010; 
Richardson et al., 2010). Spawning 
areas and times are inferred from 
early-life-stage abundance and dis- 
tribution, and they contribute to the 
definition of essential fish habitat 
(Brodziak, 2005; Levin and Stunz, 
2005) and stock identification (Begg 
et al., 1999; Hare, 2005). Larval 
fish surveys combined with process- 
oriented research also help forecast- 
ing capability of year-class strength 
(e.g., Megrey et al., 1996; Lough and 
O’Brien, 2012). 
Although larval fish studies make 
substantial contributions to the as- 
sessment of fish stocks, 3 factors 
currently limit their applicability. 
First, larval fishes are relatively rare 
within the plankton and estimates 
of variance in larval abundance can 
be large, limiting the power of sta- 
tistical comparisons of abundance 
between years or locations (Cyr et 
al., 1992). Second, larval fishes are 
patchily distributed (e.g., Davis et 
al., 1990; Cowen et al., 1993; Pe- 
pin, 2004) but not randomly distrib- 
uted; patches often are associated 
with fronts, thermoclines, or specific 
water masses (Cowen et al., 1993; 
Kingsford and Suthers, 1994). Most 
larval surveys, however, are conduct- 
ed along fixed grids or as random 
stratified designs; significant differ- 
ences in larval abundance between 
sampling times may simply reflect a 
varying intersection of sampling with 
dynamic larval habitat. Third, the 
cost of ichthyoplankton surveys is 
an important consideration and most 
programs are cost-limited in terms of 
ship time or the number of samples 
that can be processed (Tanaka, 1973; 
Lo et al., 2001; Simmonds, 2009). 
In the United States, there are 
numerous federally supported ich- 
thyoplankton programs that provide 
