Humpbacks Make a Splash!

Humpback whale. Photo: MojosCoast

by Mary Jane Schramm

Sought after for their oil, baleen and other byproducts, humpback whales were hunted intensively in the North Pacific until 1966 when they gained international protection. At the time, the population estimate for the North Pacific stocks numbered a mere 1,400.

Today, humpbacks still remain on the endangered species list. It has been a challenge to determine to what extent they have recovered from historic whaling due to the lack of accurate abundance estimates for this wide-ranging species. However, in a report released in May 2008, there are encouraging indications that several humpback whale stocks in the North Pacific are recovering.

The report, SPLASH (Structure of Populations, Levels of Abundance and Status of Humpbacks), reflects the collaborative efforts of over 50 research groups and more than 400 researchers in 10 countries. It was supported by a number of agencies and organizations including the Office of National Marine Sanctuaries, National Marine Fisheries Service, and many other national and international research groups. The report represents one of the largest international collaborative studies of any whale population ever conducted.

SPLASH was designed to determine the abundance, trends, movements, and population structure of humpback whales, and to examine human impacts on this population. This study combined existing data and incorporated new data from throughout the North Pacific Basin into a unified, integrated database.

The resulting SPLASH 2008 estimate of nearly 20,000 whales is consistent with a moderate rate of recovery for a depleted population. While the overall humpback whale abundance and trends in the North Pacific are encouraging, some areas give cause for concern, especially Asia. Abundance estimates in this area are low (below historical levels based on the number taken in this region), and whales along the Asian coast appear to be subject to a high level of incidental mortality.

In the Eastern Pacific, in 1986, the Gulf of the Farallones National Marine Sanctuary initiated research on humpback whales in the Gulf region by funding the first three critical years of research by Cascadia Research Collective. This "seed grant" laid the foundation for a decades-long, ongoing study.

Systematic photo-identification and other research gradually evolved a picture of local populations, which John Calambokidis, Cascadia's Principal Investigator for this study, later expanded to central and southern California and beyond to Central America. This is one of the populations showing a healthy rate of increase.

Despite this encouraging news, a caution: the ocean is changing, and these changes will be reflected throughout all levels of the food web. Krill – found in greatest quantity offshore at the Continental Shelf break – has long been a staple food of humpbacks in the Gulf of the Farallones region. Starting in 2005, for three consecutive years, because of unfavorable upwelling, krill was scarce in the Gulf, although small schooling fish were abundant.

Calambokidis notes that “ … over the last 10 years we have seen several dramatic shifts in both blue and humpback whale distribution and feeding that we suspect reflect changes in krill occurrence. Humpback whales off California have shifted from feeding primarily on krill in the 1990s to feeding primarily on fish in more recent years. This has also tended to bring them closer to shore and into shallower waters.”

Closer to shore in the Gulf of the Farallones means closer to the Golden Gate’s busy shipping lanes, where ship strike is a threat. Closer to shore is also where the greatest danger of entanglement in fishing gear lurks. But sometimes closer to shore means that hikers on our coastal trails and beaches may look out to sea and spot the smoke-like blows of humpbacks as they feast on swirling shoals of silvery anchovies and sardines.

To learn more about Cascadia Research click here.

 

All photos: MojosCoast