Bluefin tuna

Question 1

What are bluefin tuna

Answer 1

Large commercially exploited apex predators
Endothermic = broad environmental niche
Stock assessment and TACs = effective conservation
Extensive knowledge of spatial ecology throughout range and life-cycle required
Complex spatial dynamics - fishing pressure, climate, recruitment

Question 2

Bluefin tuna disappeared, returned 10 yr ago, Where do they go when they leave?

Answer 2

Western migrants
Eastern migrants
Med visitation

Question 3

Specific behaviours of spawning

Answer 3

1. 00:00h - sunrise
2. Shallow (<25m)
3. Warm (~25deg C)
4. > δ T° & > δ D
   Putative spawning
   δ Depth + δ Temp spikes

Question 4

Bluefin tuna summary

Answer 4

Since 2014 Atlantic bluefin tuna have returned to
waters off the UK and Ireland.
Primary period of occupancy is August to
November (sightings and tracking)
Fish then leave UK waters and spend most
time in the High Seas and French and Spanish EEZs
Links to numerous Mediterranean spawning sites