Discussion
Ecologists working on a number of species in a variety
of systems have realized that movement is a critical,
but poorly understood aspect of the ecology of populations
(Hulme, 2005; Chetkiewicz et al., 2006; Moffitt et
al., 2009). For species that may be vulnerable to spatially
heterogeneous human pressures, such as fishing or
pollution, understanding movement is essential for understanding
1) the level of threat a particular human
activity poses, and 2) the potential efficacy of proposed
solutions. In this paper, we investigated the movement
ecology of an at-risk apex predator, and by melding
daily-scale active tracking with seasonal-scale passive
monitoring, we were able to develop an empiricallybased
model of sixgill shark movement that adequately
described shark movement over a 150-day period. Our
work revealed that diel changes in behavior resulted in
restricted movement on a daily basis. Additionally, extrapolation
of daily movement behavior over several
months failed to predict seasonal-scale patterns. This
failure ostensibly arises from a seasonal shift in distribution
(see also Andrews et al., 2010), and the presence
of rare, long moves that were unobserved in our daily
tracking.