Sampling Method?

[Robert Brock]

Dry Tortugas National Park (DRTO) has received a proposal to develop a base-line
study of cryptic fish, species normally missed or underestimated in a visual
census survey. In brief, (1) a 25-sq.meter patch reef study area will be marked
by stainless steel I-bolts and a very fine mesh net will be attached to PVC
frame that is connected to the I-bolts; (2) divers will apply an ichthyocide
rotenone solution using squeeze bottles in the various inaccessible reef
habitats; (3) divers will recover all fish initially killed by the toxicant; (4)
leaving the block net in place, the procedure will be repeated 2 hours later,
and all remaining dead fish collected.

My question is simple: Does a method(s) exist where the objective of accurately
inventorying cryptic fish can be fulfilled WITHOUT killing them? I would greatly
appreciate anyone's comments and suggestions and please feel free to send them
directly to me ASAP. Thanks!

***********************************************
Robert J. Brock
Supervisory Marine Biologist
Everglades/Dry Tortugas National Parks
Homestead, Florida       33034-6733
305-242-7848 (P)
305-242-7836 (F)
robert_brock at nps.gov