Searching for Atlantic bluefin tuna larvae in the Slope Sea

More from the Gunter cruise blog:

• Atlantic bluefin tuna are one of the iconic marine fish species.  Over the course of their seasonal migrations, individual bluefin tuna can occupy both nearshore and oceanic waters, swim across the ocean, and cross through international waters and the exclusive economic zones of multiple nations.  These migrations expose bluefin tuna to a wide variety of fisheries, a factor that presents a notable challenge to managing this species.
• In recent decades, the common view of Atlantic bluefin tuna was that they spawned only in two places, the Mediterranean Sea in the Eastern Atlantic and the Gulf of Mexico in the western Atlantic.  However, in the summer of 2013 two cruises sampled the Slope Sea, both of them achieving noteworthy catch rates of early-stage bluefin tuna larvae. These collections were consistent with a hypothesis first put forward in the 1950s that the Slope Sea was a third spawning ground for this species.  Follow up sampling in 2016 again achieved notable catch rates of bluefin tuna larvae.
• Researchers aboard the NOAA Ship Gunter are evaluating the distribution and abundance of bluefin tuna larvae in the Slope Sea spawning ground.  This cruise is sampling earlier in the season than previous Slope Sea cruises to provide us information on the regional start of the spawning season for this species.
• While the focus of this cruise is on Atlantic bluefin tuna, one other exciting aspect of the project is that we are not certain of the full suite of other species we might collect or observe during visual surveys.  The Slope Sea has long been hypothesized to be important in the life history of other species, besides Atlantic bluefin tuna, that support economically valuable fisheries off the northeast United States.

So in July, aboard the R/V Henry Bigelow they went, joining the turtle tagging team. They set out to address several research questions by towing neuston and bongo nets that are sampling at varying parts of the water column: “First, what plankton are found in these regions and under these environmental conditions, specifically, in the frontal zones between warm and cold waters? Second, are there any particular fish larvae found in the plankton that would help us improve understanding of the spawning locations? Third, can we use video recording to measure the presence of gelatinous zooplankton in the water, a major food source for leatherback turtles and, occasionally, loggerhead turtles as well?” The second question is what Chrissy’s focus was on.