|Two whales "lunge-feeding," one showing its ventral pleats bulging with prey. Photo by Sophie Webb.|
Big humpback whales, several groups of twos and threes, were in perfect viewing range. Though we were at the end of our third straight day at sea, the fatigue of constant searching and sampling suddenly fell away. Surrounded at close quarters by about a dozen whales actively feeding, we cut the engines and drifted for over an hour on that late June day, enjoying some of the best possible views of vertical-lunge-feeding humpbacks. Half their bodies were coming straight out of the water, and the angle allowed us to look past their baleen and right down their throats!
On PRBO surveys in the Gulf of the Farallones, surprises for the crew of biologists and volunteers aboard come in many forms, from extreme scarcity of marine birds and mammals, and very little krill, to hundreds of marine birds and mammals and abundant krill. In the spring of 2008, for instance, several of our cruises encountered virtual deserts. That's one reason why, just two months later on that June expedition, I was so thrilled by the great display of life.
For the past 20 years I've been leading natural history trips and have also been involved in research surveys offshore of Central California. I have been completely drawn to the sea, and the call to be 'out there' is now stronger than ever. I have spent thousands of hours scanning the surface of the ocean, from the vessel to the horizon, for a soaring shearwater or change in the surface -- ripples, a single splash or many of them, or one big splash most likely caused by a breaching whale.
|Carol Keiper and Sophie Webb at sea. Photo by Drew Devlin/Natl Marine Sanctuary.|
My on-board duty begins when three of us climb up to the boat's flying bridge and into position to start our observations. The captain calls up to us, "Are you ready?" We say, "Yes," and he replies, "OK, you are on effort." This means that we have officially started the transect line, and I have to constantly scan for cues such as blows, splashes, or body parts. When I spot something, I say "Sighting: humpback whale" and then the number, bearing (compass direction), and distance. The recorder enters data into a portable computer. Unlike seabirds, marine mammals spend so little time at the surface that a major challenge is to be looking at a spot precisely when and where an animal surfaces.
|Black-footed Albatross. Photo by Sophie Sebb.|
As I reflect on the amazing ocean wilderness along the California coast, with its globally significant species diversity, I see the need to learn more about it scientifically. We spend hundreds of hours surveying established grids of transect lines--collecting data on physical oceanography, obtaining prey samples of zooplankton in the upper 50 meters (using "hoop nets") and of krill at various depths (using a "tucker trawl"), and identifying and counting all marine birds and mammals sighted along each transect.
Long days, sometimes physically challenging due to rough sea conditions, make us really appreciate the beauty of calm conditions. Over the years I have also learned to appreciate the ways that small- and larger-scale oceanographic processes affect the abundance and distribution of predators and prey -- how inextricably everything out there is linked!
The marine ecosystem can change quickly, as we saw during the end-of-June whale extravaganza. That three-day cruise started a bit rough, but each successive day got calmer and calmer. We saw nine species of marine mammals (with over 40 humpback whales, several hundred northern right-whale dolphins and Risso's dolphins, breaching killer whales, and very playful young northern fur seals). We sighted 16 species of seabirds (over 80 wanderers of the North Pacific -- Black-footed Albatross -- and an all-time high number of Fork-tailed Storm-petrels for me, over 140).
|Common Murre adult male followed by its chick. Photo by Sophie Webb.|
Along with the feasting whales, we also had evidence of the presence of prey in our seabird observations. Many Common Murres on their way to the Farallones or to rocky islets along the coast were carrying small fish in their beaks to provision their chicks.
Marine birds and mammals are expert navigators and oceanographers, as well as amazing hunters that seek their shifting, very patchy prey resources across a seemingly faceless ocean. Future analyses will no doubt shed light on the significance of data we collect at sea. I feel very fortunate to be working with Jaime Jahncke on PRBO's study of the dynamic marine ecosystem just off our shores.