66 
Fishery Bulletin 1 1 1 (1) 
Distance in front of vehicle 
Figure 5 
Percentage of fishes that reacted at a specific distance in front 
of the manned submersible and the remotely operated vehicle 
(ROV). These percentages were used in 2007 off central Califor- 
nia in our study of the reactions of fishes to underwater vehicles. 
The total number of reactions in) is indicated for each vehicle. 
hide for target species and environmental 
conditions. Through such efforts, researchers 
will gain a better understanding of the effec- 
tiveness and limitations of potential survey 
vehicles. 
Acknowledgments 
We thank R. Starr, co-principal investigator of 
the Delta submersible cruise; J. Butler for the 
use and operation of the ROV; S. Mau for pi- 
loting the ROV; Delta Oceanographies; and the 
crews of the FV Velero IV and the David Starr 
Jordan. We thank M. Love, M. Nishimoto, 
T. O’Connell, and D. Watters for help with data 
collection. D. Watters also created the map 
of our study site. We also thank C. Rooper, 
S. Sogard, K. Stierhoff, R. Starr, and L. Wed- 
ding for their helpful comments on early 
versions of this manuscript. This study was 
funded in part by a grant from the California 
Ocean Protection Council to R. Starr and M. 
Yoklavich. 
used a working-class ROV and Starr et al. (1996) used 
the Delta submersible to estimate fish abundance; both 
studies determined that these vehicles were not re- 
liable in assessment of the abundance of fishes well 
above the seafloor. 
Conclusions 
What are the implications of the reaction of a fish to a 
survey vehicle? If the reaction occurs over a small dis- 
tance and the fish remains inside the survey transect, 
then the fish would be counted and its reaction would 
not affect the outcome of the survey. However, some 
reactions (both large and small in magnitude) could 
cause a fish to move out of the survey transect or out of 
view (e.g., into a hole or behind a rock) — behavior that 
would, thereby, bias the resultant abundance estimate. 
Similarly, overestimates of abundance could be made if 
a fish moves into a transect because of its reaction to 
a survey vehicle. 
Reactions of the target species need to be considered 
in selection of a survey vehicle, and the limitations 
of vehicles need to be evaluated relevant to the goals 
of a study. For instance, a comparative study can be 
undertaken to estimate abundance and reaction rates 
of fish species with various underwater vehicles (e.g., 
a submersible, ROV, camera sled, an autonomous 
underwater vehicle, or drop camera) within a specific 
survey area or over particular transects. From this 
type of study, the reaction of fishes and abundance es- 
timates can be ascertained for each vehicle, thereby 
aiding in the selection of an appropriate survey ve- 
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