Editor's Note: Marine biologist William Gilly is on an expedition to study Humboldt squid on the University-National Oceanographic Laboratory System research vessel New Horizon in the Gulf of California. He and other scientists are learning about the giant squid, their biology and ecology on this National Science Foundation-funded expedition. This is his fifth blog post about the trip.

GULF OF CALIFORNIA—Days 7-9 Bahia San Rafael: We spent a total of four days in the Bahia San Rafael area carrying out of Oregon State University's Kelly Benoit-Bird's acoustic surveys to determine the numbers of squid present and to define their horizontal and vertical daily movements. One can even see the behavior of individual squid with this system; it is remarkable. And we continue the midwater trawls to confirm the size and species of what the acoustic sampling reveals. This will allow us to develop a more complete picture of what the predator squid and their prey are doing in this ecosystem. Next year, we will hopefully be able to carry out this cruise with the same methods in the Santa Rosalia area, assuming big squid will return there when conditions return to normal. That will reveal a lot about how Humboldt squid respond to environmental changes, a subject that I believe is at the heart of the cause for their recent range expansion into Canadian and even Alaskan waters.

We also attempted to deploy an underwater video logger on a squid here, but that turned out to be a long, sad story. The abridged version is that two deployment attempts failed. The first time we took too long with an overly complicated method of getting the squid into a cooler, into a small support boat, into the sea with the ship's crane, and finally into the water with two divers to release the squid. This process took way too long, and the squid was moribund by the time we got it back into the water. The second time we avoided the crane, small boat and divers by placing the squid directly in a cooler in the small boat. Everything went fine (except for the fact that the squid bit me), but the camera pack never reported back to us by radio like it should have after detaching and floating to the surface. Despite two days of visual searching we failed to find it. We don't know if there was a technical glitch or whether the squid (and it was a lively one!) swam out of radio range. We visited the commercial fishing boats, showed them photos of the package and distributed posters offering a reward for its return. We wait and hope, but it could be a long time before someone finds it on a beach. There are a lot of beach miles here and few people walking them. Science, like everything else, can have really bad days. This is an important lesson for young researchers like Lauren, the student who was doing the camera project. It's the real world.

Tonight is the end of our exploration in the land of big squid. What have we learned? First, the big squid here are of mixed sizes and maturity states, with only the largest being fully mature. The same is true in a "normal" year in Santa Rosalia. Second, the squid move into shallow water on the shelf at night, just as they do in Santa Rosalia, but they spend more time in shallow water here in the daytime. Temperatures are cooler here than in the south, and that is probably important. Third, the big squid are eating a variety of organisms, but mostly krill, other small shrimp, anchovies and other small fish. But there are essentially no myctophid lanternfish in the stomach content or in the trawl catches—nor in the acoustic profiles. Fourth, there are many fin whales here, versus sperm whales that typically haunt big-squid country in the Guaymas Basin.

So what we see here in the north is many big squid utilizing a krill-dominated ecosystem (with baleen whales) during and after an El Nino-like event this winter. The waters in the midriff Islands region are always cooler, because of tidal upwelling, and that makes them highly productive. These are probably the same squid that would normally be off Santa Rosalia this time of year where they utilize a myctophid-dominated ecoystem (with toothed whales). If so, the big squid have shifted their base of operation to the cooler waters and have adapted to a different set of prey organisms. This adaptability is nothing new, but the suite of evidence that we have collected on this cruise will provide a more rigorous framework for a consideration of environmental fluctuation, and by analogy climate change, as a main driver of changes in squid distribution.

And the other surprising thing to find was that all of the small squid in the north (and there were many on the surface) were sexually immature. That's the pattern we normally see in the Guaymas Basin. This year, the small squid in that area are much more mature, and that anomaly is probably also associated with the El Nino-like winter. Those small squid may have simply grown up in a warm environment and matured earlier or came in from tropical oceanic water to the south. Either way, we need to figure out how old the small squid are at all of our sampling sites. We'll do this in the lab at home by counting statolith rings. Unai Markaida, of Colegio de la Frontera Sur, Campeche, tells me that it is not really known if the small mature squid are younger than big mature squid—he only looked at a few animals after the 1997-98 El Nino. We need to answer this important question.

Although we hoped to get a final good day of sampling both large and small squid in our northern area, we had difficulty finding a hot spot to fish on our last night here. We had come south during the day, making an acoustic transect, and after a deep trawl after sunset, we found ourselves at least five miles away from the fishing fleet. We caught only a single large squid and no small ones, so we moved closer to shore over the shelf. Again, no luck. Despite all of the technology at our disposal, at the end of the day it is still fishing.

So we secured everything onboard the ship for a predicted wind and set a full-speed-ahead course for Isla San Pedro Martir, a small, lonely island in the northern end of the Guaymas Basin. With mixed feelings we leave behind the big squid and look ahead to the second half of our cruise.

Image of sorting the catch from a midwater trawl courtesy of W. Gilly; image of squid in cooler to be fitted with camera courtesy of Capt. D. Murline; image of a squid fishing boat courtesy of L. Bell; image of  search for the missing camera from sea along a deserted beach courtesy of L. Bell; image of Ashley sampling big squid courtesy of L. Bell