Deployment: NEC-ST2006-1

Catches of spiny dogfish, Squalus acanthias, are considered to be unacceptably high by many
inshore fishermen (commercial and recreational) during the summer and fall months in the Gulf of
Maine. However, biologically, these species are considered vulnerable to overexploitation. Despite
the range of views and opinions about dogfish, there is a strong common interest for finding a
practical and economic dogfish deterrent for application in various fishing gears. Through an
industry-science collaboration, a total of six research trips were executed during August and
September 2007. Triangular slices of the rare-earth metal cerium/lanthanide alloy (or 'mischmetal')
were incorporated into three commercial gear types (longlines, rod and reel gear and lobster gear)
to assess the material's effectiveness at reducing dogfish catches. For each gear type, catches with
mischmetal (treatment) were compared with a 'control' (i.e. no mischmetal present). In situ
underwater video footage was captured to aid the interpretation of data. Field observations were
inconclusive for the lobster gear since the traps caught no dogfish, regardless of treatment. For both
hook gears, a slight reduction in dogfish catch was recorded (~6% for rod and reel, and ~5-10% for
longline), but these results were not statistically significant. One complicating factor for the study
was the high rate of mischmetal dissolution, which led to the rapid disintegration of the mischmetal
slices in all gears. In situ video footage verified persistent dogfish feeding behavior on bait regardless
of mischmetal presence and when one dogfish pursued the bait, the scene would generally escalate
to frenzied feeding by multiple dogfish. Overall, there is little evidence to suggest that mischmetal
has the potential to reduce the catch of dogfish in either commercial or recreational gear types in
the Gulf of Maine.

Contract # PZ07087; Contracted Gulf of Maine Research Institute