First Quantitative Comparison of Atlantic Bluefin Tuna Spawning Grounds

Using satellite data, shipboard plankton surveys and in situ data, U.S. and Spanish scientists have provided the first quantitative comparison of the environmental characteristics of the only two known spawning habitats of Atlantic bluefin tuna (Thunnus thynnus). Collaborators included academic (the Cooperative Institute for Marine and Atmospheric Studies and Oregon State University), government (National Marine Fisheries Service and the Spanish Institute for Oceanography) and private industry (Roffers Ocean Fishing Forecasting) scientists.  Results from their collaborative study were published in Marine Ecology Progress Series.  

Background: Bluefin tuna in the north Atlantic are divided into two stocks: a western stock, which spawns in the Gulf of Mexico, and an eastern stock, which spawns in the Mediterranean Sea. Using larval catches from plankton surveys, and environmental variables from in situ measurements and remotely sensed satellite data, the characteristics of the two spawning habitats were compared.   Results highlighted the importance of warm (23-28°C), low chlorophyll areas with moderate current velocities.  Bluefin tuna spawning in the Gulf of Mexico do so in offshore waters just outside of the Loop Current, while in the western Mediterranean, they spawn at a confluence of inflowing Atlantic waters and saltier resident Mediterranean surface water. 

Significance: Atlantic bluefin tuna stocks are at historically low levels, and both eastern and western stocks are currently managed under stock rebuilding plans.  Simply limiting catch may not be sufficient for stocks to recover. A quantitative assessment of the characteristics of the natural spawning habitats is essential to understand the actual constraints upon larval growth, larval survival, and ultimately recruitment into the fishery. This research project was undertaken and funded in support of the National Oceanic and Atmospheric Administration mission goal to sustain marine fisheries and fisheries habitats within healthy oceans.

Contact Information: Barbara Muhling, bmuhling@rsmas.miami.edu