OTN technicians boarded the DFO research vessel, The Perley, travelling to the Cabot Strait from headquarters in Halifax to offload and redeploy 58 tracking stations between Nova Scotia and Newfoundland.
The Cabot Strait line (CBS) is the second longest acoustic receiver line in the world. CBS extends 172 stations over 200 kilometres to track animal migrations in and out of the Gulf of St. Lawrence. Detections include tagged American eel, Atlantic bluefin tuna, Atlantic cod, Atlantic salmon, Atlantic sturgeon, and grey seal.
The section of the line around St. Paul Island—located 24 km north of Nova Scotia—juts west to cover an area of Atlantic cod aggregation. Stations are offloaded twice a year in increments due to limits on the number of station anchors vessels are able to transport.
Three stations were recovered significantly further away from their original deployment sites. Stations, which consist of acoustic receiver (tracking unit, which picks up and stores the unique “pings” from individual animal tags), 200 lb. anchor, and acoustic release (detaches receiver from anchor) are sometimes moved by strong currents or dragged by commercial trawlers.
St. Paul Island is an area of high commercial fishing activity with the shallower, warmer waters attracting bottom-feeding fish like cod and halibut. Station locations are broadcast by Canada’s Department of Fisheries and Oceans Notice to Mariners. These notices broadcast locations of science moorings and other hazards to fishing gear, though despite readily available information, tracking and monitoring stations are regularly ‘bycatch’ in fishing gear costing fishers hundreds of dollars in damaged nets and equipment. Unrecovered tracking instruments are not only expensive in the monetary sense, their data is valuable and provide important information on habitat use and migratory pathways to ensure that commercial fishing stocks remain sustainable and that threatened species are adequately protected.
Steps towards better informing fishers include issuing station locations as part of fishers’ licences in the region, posting line maps and general information in public areas, and face-to-face talks with fishers at events like the Fishermen Scientists Research Society.
Communication with fishing groups in the region is ongoing to position lines away from dragging sites and preserve fishing gear and tracking equipment.