Influence of spear guns, dive gear and observers on estimating fish flight initiation distance on coral reefs
Januchowski-Hartley, FA and Nash, KL and Lawton, RJ, Influence of spear guns, dive gear and observers on estimating fish flight initiation distance on coral reefs, Marine Ecology - Progress Series, 469 pp. 113-119. ISSN 0171-8630 (2012) [Refereed Article]
Fish flight initiation distance (FID) is emerging as a useful metric of the response of
fishes to fishing, with significant differences in FID demonstrated between fished and no-take
marine reserves. However, studies investigating FID vary in methodology, and many of the potential
confounding effects inherent to in-water estimation of FID have yet to be investigated. Here
we examined relative effects of spear guns, dive gear, observer bias and protection status on FID
estimates. Three observers estimated FID of parrotfishes in both a fished area and a no-take marine
reserve, via both SCUBA and free-diving, and with and without a simulated spear gun (8 treatments).
We found that FID was significantly influenced by protection status, increasing by 141 cm
on average in the fished area compared to the no-take marine reserve, but not by dive type or
spear gun presence. While there were some differences between observersí mean estimate of FID,
there was no evidence of observer bias, nor were there any significant differences in the precision
of FID estimates between observers. Overall, management status explained almost 60% of the
variation in FID estimates, while observers accounted for only 4%.