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Project Update: Billfish and Baitfish

*This post was originally uploaded on April 18th, 2019 on a website that has since been deleted. Posts from that website will be re-uploaded here at a later date.

In addition to deploying six satellite tags on sailfish and blue marlin, the DynaMAR team launched the OpenROV Trident on its maiden voyage during the March 2019 trip! During this trip, we spent four days far from the shallows (125 miles offshore, to be exact) of Quepos, Costa Rica. Fishing effort was concentrated on a fish aggregating device, or FAD, which is anchored to an offshore seamount. The FAD (or fast-food restaurant) aggregates baitfish which then attract blue marlin and sailfish. During our first ROV deployments, we were already able to look below the surface of the ocean to survey the composition and size of the baitfish aggregations found near the FAD. From the underwater video, we were able to identify several species hanging out around the FAD including skipjack tuna, yellowfin tuna, and rainbow runners (see our last blog post!). The team also tested the ROV after dark and were able to see other critters that appear more often at night including squid, flying fish, and juvenile African pompano (coming soon!). We now have a better idea of which species of baitfish might be important for sustaining the billfish populations in this region.

The most challenging part so far is getting used to driving the Trident! Currents and open blue water make it difficult to keep the ROV on a steady path and figure out what direction you’re driving. The good news is that we’ve already improved! By the end of the trip, we got the trick of simultaneously turning and ascending/descending. The baitfish even started to get curious and would follow the ROV around as it moved about the FAD. We can’t wait to continue to learn about the species composition on the FAD and hope to catch a glimpse of a sailfish or blue marlin with our ROV on the next trip!

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