by Julie Stewart, MARINE curriculum intern
The NOAA research vessel MacArthur II recently journeyed to the Davidson Seamount, an extinct underwater volcano about 80 miles offshore from the Monterey Peninsula. Our mission was to conduct surveys of the marine mammals and seabirds in the area. The seamount is about 26 miles long by 8 miles wide, and comes as shallow as 1.5 kilometers below the surface (the seafloor otherwise sits around 3.5 kilometers deep). This is a very productive area: as deep currents hit the seamount, they are redirected up towards the surface, so there are high concentrations of krill and other plankton that provide food for higher predators.
While remotely operated vehicles (ROVs) have documented some of the seafloor (discovering amazing soft corals, among other things), little was known about the marine mammal and seabird populations so far from shore. Our cruise spotted and documented an incredibly dense population of fin whales, as well as thousands of storm petrels (no sperm whales or albatrosses, however). I led the nighttime operations: searching for Humboldt squid in the offshore environment. The seamount would seemingly also be a nice area for Humboldt squid to be, and they have been seen there in past years. This year, however, has been different. We did not find a single Humboldt squid on the Davidson Seamount.
This has been a strange year, oceanographically speaking. It started off with El Niño: higher sea surface heights and warmer sea surface temperatures, which also leads to depressed upwelling. In June, conditions switched and now we are in a La Niña period: colder ocean conditions. Since 2002, Humboldt squid have arrived by the summertime: we see smaller ones offshore and we think they are making a northward migration from waters off Mexico to waters off Washington and Canada, where they will feed and grow throughout the fall.
In the late fall and winter, we see larger Humboldt squid in greater numbers closer to the coast: they are much more noticeable at that time in Monterey Bay in MBARI’s ROV surveys, scientific surveys, recreational fishing catch, and in the diets of marine mammals and sharks. At that point it seems that they are migrating back south, most likely to reproduce. But it is nearly August, and Humboldt squid are still absent from waters off California at the Davidson Seamount. Perhaps they will come later this year, when conditions settle back to normal? This is research: we’ll have to go back out on the water to find out.