TAGGING: UNDERSTANDING A FISHES’ LIFE STORY

Tagging research provides important information on behaviour, growth patterns, natural mortality and population size estimates of commercial fish and invertebrate species. There are many types of tags available for use, from conventional tags that are attached to fish and removed when the fish are recaptured to high technology tags that log and report via satellite detailed information such as geo-location, swimming depth and, water temperature.

LARGE PELAGICS

Biological Station researchers are currently working with industry to tag the highly migratory Atlantic Bluefin Tuna using both conventional and electronic tags. The International Commission for the Conservation of Atlantic Tunas uses the tagging data in the assessment of stocks and to make management decisions.

Conventional (Spaghetti or Streamer) Tagging Program

Since 2015, the Prince Edward Island and Gulf of Nova Scotia Bluefin Tuna Catch and Release Charter Fishery have participated in the International Commission for the Conservation of Atlantic Tunas (ICCAT)’s Grande Bluefin Year Program (GBYP) by attaching conventional tags on Bluefin Tuna (Figure 1 & 2). This program is showing important migratory patterns of juvenile and adult tuna from the eastern and western populations, and is being used to estimate growth rates, population size and mortality rates. During the 2015/2016 fishing seasons, a total of 786 conventional tags were deployed by this fishery.

So much can be learned when tags are recovered! For example, a Bluefin Tuna tagged in the Gulf of Cádiz (South of Spain) in December 2010 was measured at 76.2 centimetres long. The tag was recovered by a Canadian fisherman 100 km east of Sable Island, approximately 4,500 km from where the fish was originally tagged in November 2016. In five years, the Bluefin Tuna had grown to 238.8 centimetres in length and weighed over 204.1 kilograms!

Figure 1: Bluefin tuna being tagged with a conventional tag

Figure 2: ICCAT Conventional Tag

Electronic Tagging (Pop-off Satellite Archival Tags)

The Biological Station Large Pelagics Group has been deploying Pop-off Satellite Archival (PSAT) tags on Swordfish and Bluefin Tuna since 2000 (Figure 3). This electronic tagging program provides very detailed migratory patterns including the daily vertical movement in the water column. Since 2000, a total of 109 Bluefin Tuna have been tagged with PSAT tags and 85 PSAT tags were attached to Swordfish.

Figure 3: Wildlife Computers’ Pop-off Satellite Archival Tag

Figure 4: Migration route of a Bluefin Tuna tagged near Shippagan, NB in September of 2015.

An example of the migratory movement of a Bluefin Tuna tagged with a PSAT in 2015 is shown in Figure 4. The tag was deployed on September 18th, 2015 near Shippagan, New Brunswick. This fish stayed in the Gulf of Saint Lawrence until late-October, before making a relatively direct migration to the Caribbean. The tag later popped off the fish on January 19th, 2016 providing 123 days of information.

Further information:

Recovery Potential Assessment for Western Atlantic Bluefin Tuna (Thunnus thynnus) in Canadian Waters