Semiochemicals are chemical messengers or "clues" sharks may use to orient, survive and reproduce in their specific
environments. Certain semiochemical extractions have the ability to trigger a flight reaction in sharks, but these trace chemicals present unique difficulties for isolation and detection. The possible use of
semiochemicals as shark repellents was proposed by Baldridge (1990) and by Rasmussen and Schmidt (1992). In 2001, investigation of these possibilities led Eric M. Stroud and Michael Herrmann to begin qualitative
analysis on semiochemical extractions using captive juvenile sharks. A variety of analytical instruments and techniques were employed to isolate possible candidates. The most promising semiochemical candidates were
scaled up, and during 2003, with the help of Dr. Samuel Gruber, Grant Johnson, and the Bimini Biological Field Station, the team was able to document a number of successful field tests on wild feeding sharks. The
results of these field tests were presented at the 2004 Joint Meeting
of Ichthyologists and Herpetologists 26 - 31 May, 2004, in Norman, OK
The detection of semiochemicals is
hypothesized to be via olfactory pathways. Recent (2007) electro-olfactogram studies conducted by a major US university support that semiochemical extracts (diluted to10-4L) are detected by
N. brevirostris. Dosages of 100uL (100x10-6L) directed towards the nares have been shown to terminate tonic immobility in juvenile N. brevirostris. Competitively feeding populations of C. perezi and C. acronotus
respond to surrounding cloud dosages of 350-700mL of semiochemical extract by halting feeding activities and leaving visual range. This reaction draws some similarity to a schreckreaction (von Frich 1938).
Semiochemical extractions are selective to elasmobranchs. In teleosts studied to date including T. albacares, no flight reactions were observed when fish are directly exposed to the extract. In
some instances, teleosts are observed feeding inside of the cloud of extract.
While the original semochemical extractions were made from decayed shark tissue, present work is focused on green synthesis
pathways. Our time-release longline gel has been synthesized to contain one compound which is believed to act upon the shark's olfactory system.