Scientists with Fisheries and Oceans Canada (DFO) are working with the Nova Scotia Swordfish Harpoon Association in a first-ever Canadian high-tech tagging study of swordfish to determine their migration patterns in the Atlantic Ocean. The three-year study is funded under DFO''s International Governance of High Seas Fisheries Program.
Swordfish tagging studies using traditional "spaghetti" tags have been conducted from DFO's St. Andrews Biological Station for many years. Results from these studies have been limited as they rely on the fish recapture and information submitted by fishers. While conventional tags tell us the recapture point and how long it took to get there, they tell researchers nothing about the route taken between release and recapture, or the environmental conditions experienced by the fish during its journey. However, the conventional tagging data have indicated that, while the swordfish move north and south through the Atlantic Ocean, there is less movement from west to east than previously thought.
According to lead scientist Dr. John Neilson at the Biological Station, "while these high-tech tags have been used for other species such as Atlantic bluefin tuna, it is very unusual to see them used with swordfish. Previous studies of this nature using longline-caught fish indicated poor survival of released fish, but we think survival will improve using harpoon-caught fish. These tags will provide much more detailed information on their migration patterns and help to validate these previous findings."
The pop-up satellite tags are basically tiny waterproof computers, programmed to record the depth of swimming, temperature of the water, and daylight length, while enduring dives to more than 3000 feet. All of this information is relayed to an ARGOS satellite when the tag "pops up" to the surface in the summer of 2006. The information is then downloaded to a computer where scientists use programs to analyse the data to determine migration patterns of the fish.
Larry Sears of Shag Harbour worked with Sean Smith from the Biological Station to successfully tag 11 large female swordfish between the northeast peak of George's Bank and the western edge of Brown's Bank. The tags were harpooned into the dorsal area of the fish so as to not interfere with swimming ability. The total satellite tag assembly measures approximately 12 inches long and they have been painted fluorescent orange for improved visibility.
Scientists are asking fishers who may encounter a swordfish carrying a tag to not capture the fish but to report its location (contact information below). If a swordfish carrying such a tag is unintentionally captured, fishers are asked to retain the tag and contact the department so the tag may be redeployed on another swordfish. A $100 reward is being offered for the return of these tags from captured fish.
Swordfish are a highly migratory species managed under the International Commission for the Conservation of Atlantic Tunas (ICCAT). This commission is made up of 41 countries of which Canada is a member. There are currently 960 licensed swordfish harpoon fishers in the Maritimes Region.
