Testing of rare-earth metals as a shark deterrent in the Northwest Atlantic pelagic longline fishery
Aurelie Godin (Ph.D. student) - Principal Investigator
Boris Worm (Dalhousie University) - Supervisor
Tonya Wimmer (WWF-Canada) - Principal Investigator
Frankie Reyno (captain) and crew
Fisheries and Oceans Canada
Troy Atkinson - Nova Scotia Swordfishermen's Association
Field Trials Complete
Report In Prep
Type of Initiative:
Research - Experimental Field Trial
For which Shark Species:
Sharks species encountered in the northwest Atlantic swordfish longline fishery.
Species must commonly seen include: blue (Prionace glauca), shortfin mako (Isurus oxyrinchus), porbeagle (Lamna nasus), thresher (Alopias vulpinus).
The anterior electrosensory pores (ampullae of Lorenzini) allow sharks to detect very weak electrical and electromagnetic fields. Some rare-earth metals can either create stationary permanent magnetic fields (i.e. magnetic repellent) or generate large oxidation in seawater, (i.e. electrochemical repellent). Both processes have been shown to alter the swimming and feeding behaviour of several shark species. Neodymium/Praseodymium (Nd/Pr) alloys are a strong electropositive metal with promising deterrent results. The technology has not yet been tested in a large-scale fishing experiment.
The goal of this initiative is to examine the effects of Nd/Pr alloys on shark species encountered in the northwest Atlantic Canadian longline swordfish fishery in a field trial. In this experiment, we are seeking to answer the following questions. Do Nd/Pr alloys: (1) reduce longline bycatch rates of sharks; (2) change target species catch rates; and (3) are economically and practically viable for the pelagic longline industry?
Experimental design and analyses
A longline fishing vessel will conduct the field experiment with the locations chosen on the basis of the captain’s (Franky Reyno, Sambro) local knowledge. A total of 10 sets will be equipped with Nd/Pr alloys during a trip in September 2011. Crewmembers will attach equal numbers of Nd/Pr alloys, lead control weights, and hooks with no weight in an alternate fashion every half section (1.4km) of the mainline (total of 30 subsections per set, 840 hooks in total). Alloys will be employed for two sets before being replaced with new ones for subsequent sets. To avoid additional induced variability, fishing gear and bait will remain the same among the sets. Trained scientific observers, contracted by DFO (Javitech Limited) will monitor experimental protocols and collect data. Observers will collect date, set number, subsection treatment, set time, species name, number caught, approximate weight, and any hook bite-offs. Generalized Linear Models (GLMs) will be fit to explicitly model the underlying processes in the catch rate (catch-per-unit-of-effort CPUE) per longline set and to estimate the effect of the alloys on shark catchability. For each species, we will predict mean catch as the number of individuals while accounting for the effect of hook type, location (latitude, longitude of the set), Nd/Pr alloys power, and number of hooks. If worth pursuing, costs and revenue analyses will be evaluated. We will limit our analysis of operating costs to the unit price of the Nd/Pr hooks and species catch values.
Ph. D, Candidate
Dalhousie University, Department of Biology
Graduate Fellow, WWF-Canada
Halifax, Nova Scotia
tel: (902) 494-2478
fax: (902) 494-3736
Species Conservation Manager
Halifax, Nova Scotia
tel: (902) 482-1105 ext.32
fax: (902) 482-1107
Dr. John H. Wang, Associate Researcher at the Joint Institute of Marine and Atmospheric Research, University of Hawaii at Manoa for the Nd/Pr alloys and his scientific advises on the project. We also would like to thank our observer David Spallin of Javitech Limited. We would like to acknowledge the Natural Sciences and Engineering Research Council of Canada for supporting this work.