Shark Predation on Hawaiian Monk Seals - Pacific Islands Fisheries ...

(2) Concise information about pup movement patterns could inform deterrent or removal
tactics and deterrent/device placement. The distance pups swim from shore, their
coordination with their mothers, the frequency with which they enter the water, and the
times of day they are attacked all need to be substantiated by mining previous data,
collecting additional nocturnal data and cataloging shark incidents in a standardized
way. Preweaned pups could be fitted with sonic tags in order to track their movements
and any coincident swimming with tagged sharks.
(3) The use of the array of deterrents and devices and the application of a “suite of devices”
were viewed with skepticism, with the exception of the use of the anchored boat and
boat noise. It was suggested that each device be tested in isolate on free-ranging
Galapagos sharks during the off-season or at another location (not when preweaned pup
safety was at risk). Another approach discussed was the application of a suite of devices
initially; and if shown to be effective, one device type (visual, auditory,
electromagnetic) at a time would be removed. A stratified approach was also discussed,
whereby different deterrent types would be applied to different pupping sites. Low
sample size (few pups born at some sites and low numbers of incidents) was mentioned
as a confounding factor to such analysis. It was suggested that each deterrent and device
be tested individually to determine its effectiveness and feasibility in influencing shark
behavior; this research could be gone on free-ranging Galapagos sharks in MHI waters.
(4) Removal methods were discussed and HIMB’s methods (depths, bait, gear) for tagging
were endorsed as likely to be adequate for HMSRP’s removal efforts in shallow waters.
Longer soak times and deeper sets would lead to greater catch rates; even HIMB’s
methods are expected to lead to few returns in shallow waters. For this method, the
gear, the timing, and location of fishing would lead to minimal bycatch. The following
concerns were also expressed: (a) lethal take of offending sharks near pups is likely to
be small and insufficient to provide much protection for pups, (b) the opportunity cost
of pursuing permits and the actions necessary for lethal removal are large; these
resources may well be better spent for the recovery of HMS elsewhere, and (c) shark
experts and HMS experts differ in their thinking, experience and/or grasp of the issues.
(5) Placing field staff camp on island to guard pups and harass sharks was discussed. The
fact that shark predation has not historically been a problem at Tern Island, where
human presence is common, was mentioned as possible evidence that sharks will avoid
areas with human activity.
(6) Constructing a physical barrier that would protect pups at their natal sites received
support. A semipermeable design with “guarded” openings that allowed seals and
turtles to transit to beaches but prevented sharks from entering nearshore areas was also
discussed. Electromagnetic deterrents (e.g. <strong>Shark</strong> Shields) placed at the openings may
deter sharks from passing. Concerns were raised about employing engineering strategies
to accommodate for wave surge and a possible negative influence on the normal
movement patterns of seals and turtles.
(7) Moving mothers and pups together to 'safer' islands (e.g., from Trig to East or Tern)
was mentioned but not recommended to be a priority. General support was withheld
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