Dataset: dogfish_alloys
Deployment: NEC-ST2006-1

In total, six dogfish research trips were undertaken, during August and September of 2007. The
commercial lobster vessel, FV Survivor (13 m), was utilized as the research platform, which afforded
extensive deck space and winch gear for efficient operation of the longline and jig gear.

To prepare for deployment on fishing gear, industry standard trapezoidal mischmetal ingots (HEFA
Rare Earth Canada Ltd., Richmond, BC, Canada) measuring ~45 mm x ~45 mm x ~45 mm x ~130 mm
were sliced into pieces measuring ~45 mm on each side, by ~5 mm thickness. For attachment to
fishing gear, ~2 mm holes were drilled at ~5 mm up from the bottom edge and ~5 mm down from
the top corner of each mischmetal slice; the slices were then attached to jigging gear using 2 mm zip
ties, and to the longline gear by threading the twine leaders through the drilled holes. On both
jigging gear and longline gear, the mischmetal was secured ~10 cm up from the hook and bait.

A total of four (100 hook) longlines were built, each consisting of 50 control hooks (just hook and
bait) and 50 treatment hooks (hook, bait and mischmetal). The hooks were arranged along the
longline in alternating groups of 10 (i.e. 10 control, 10 treatment, etc.)as a means of efficiently
verifying that equal numbers of treatment and control hooks were attached to each longline; this
approach also enabled effective gear maintenance in the field where deck space is limited. Four
longlines with 100 hooks were set on trips 1-3; at this time one longline was lost overboard. On trips
4-6, three longlines were set, two with 100 hooks each and one with 140 hooks. The additional
hooks were added to make up for the lost longline, but mischmetal availability limited this increase
to 40 hooks. In total, during six sampling days 21 longlines were set, totaling 2080 hooks (50%
control and 50% treatment). All longlines were set at similar depths on each day (~60-100 m), in
close proximity to one another to ensure similar fishing conditions between each set. Soak times
ranged from 1-2 hours.

Jigging using rod and reel took place on each of the six vessel days, to test the effectiveness of
mischmetal at deterring dogfish from recreational hook gear. Jigging was undertaken during the
soak-time for each longline. Each rod and reel (n=3) was set up with two hooks (2-4 hooks is typical
while fishing for groundfish), with one treatment and one control hook; 73 jig-lines were set,
comprising a total of 146 baited hooks (50% control (C) and 50% treatment (T)).

All animals caught by both jig and longline gear were noted for: hook type (i.e. treatment or
control), bait presence, species, size (total length, TL) and sex where possible. The catch was then
released.

In addition, wire lobster gear was deployed on two days. Two strings were set for 24 hour soak
times, each string comprising 16 traps in total. Control (n=8) and treatment (n=8) traps were
alternated along each string. All traps were baited, and the treatment traps had three pieces of
mischmetal attached around the trap entries. The total catch was counted and quantified by
species; only fish species were measured, and where possible, such as in the case with
elasmobranchs, sexed. (from final report)

In situ video footage was obtained through collaboration with the University of New Hampshire's
Atlantic Marine Aquaculture Center (Durham, NH).