Science on Tunas and Tuna-Like Species

International Research

International co-operative scientific research is a key feature of many tuna regional fisheries management organizations (RFMOs), including those to which Canada belongs. For example, in the International Commission for the Conservation of Atlantic Tunas (ICCAT), scientists from member countries work together to compile relevant catch and scientific data for regulated tuna species in the Atlantic. Canadian fishery scientists participated in the first meeting of the Scientific Committee of the Western and Central Pacific Fisheries Commission in August 2005, and every meeting held since then. Participants discuss the state of the region’s fisheries and provide scientific advice to the Commission on the status of tuna stocks and bycatch species.

Find out more about the Standing Committee on Research and Statistics

The Role of Science in Canada’s Sustainable Bluefin Tuna Fishery

Canada’s bluefin tuna fishery is based on rigorous, up-to-date, and relevant science.

The total allowable catch of bluefin tuna in Canada’s fishery is determined by an assessment of the Western Atlantic Ocean stock by scientists from ICCAT member countries. The assessment considers the number of spawning tuna that are 8-10 years of age, and older. It also reviews ‘indicators of abundance’ that are derived from commercial fishery observations and logbook data. For example, in 2008, bluefin tuna were abundant in Canada’s Southern Gulf of St. Lawrence fishery and at stable levels elsewhere in Canadian waters. Abundance indicators were mixed in other Atlantic Ocean locations. For example, the absence of larger older fish in US waters was a particular concern.

In recent years, Canada and its research partners in other countries have completed a number of studies pertaining to bluefin tuna stock assessment that take into consideration scientific research conducted by ICCAT members:

Otolith Microchemistry
Otoliths are calcium carbonate balance organs found in the inner ear of bony fishes. They are continuously deposited through the lifecycle of a fish, so studies can determine age and growth information. Otoliths also carry certain trace elements that are in proportion to water chemistry, allowing researchers to determine their water locations.

Studies of otolith microchemistry reveal the origin of birth of fish caught in Canadian fisheries, and allow scientists to assess the extent of mixing between eastern and western bluefin stocks. This is important because the overfishing and under-reporting of catches that have been taking place in the eastern Atlantic and Mediterranean Sea might have impeded the health of western bluefin. Results to date indicate that Canadian fisheries almost exclusively rely upon bluefin tuna that were born in the Gulf of Mexico.

Bluefin Tuna Growth
Age-structured studies of bluefin tuna’s growth and mortality provide critical information for stock assessments. With an accurate measure of the age of bluefin tuna, related to size, fisheries managers and scientists can understand growth rate, better assess the abundance and productivity of adult stocks, and predict future numbers. Canadian research has shown that the growth of bluefin tuna is slower than expected using the growth model used by ICCAT.

Satellite Tagging
Canadian scientists and tuna harvesters have participated in satellite archival tagging studies for many years, often with American researchers. Satellite tags are tiny waterproof computers which are attached to tuna to record light levels, salinity and depth.  After a pre-programmed time, the tags detach from the fish and float to the surface, where they relay their data to passing satellites. The data allow scientists to reconstruct the paths of the fish; the results of which support strong linkages of Canada’s bluefin tuna to the Gulf of Mexico.