History and context
The Gulf of California is an important winter/calving and feeding area for Northeastern Pacific blue whales that feed off of the west coast of California in summer months. Of the roughly 3,000 whales in the northeast Pacific population1, approximately 300 are estimated to spend their winters in the Gulf of California2. Photo Identification studies have shown that blue whales remain in the Gulf of California for up to 70 days, and that nursing mothers and their calves show a particular preference for the coastal waters of the National Park of Loreto Bay (NPLB) 2. From 1996 onward, these blue whales became the focus of marine tourism and whale watching activities, and by 2009 roughly 50 small boats were operating in the marine park. There were indications that proposed coastal developments, marine traffic and whale-watching activities would significantly increase in the coming years.
Concerned that the level of vessel traffic and uncontrolled whale watching behaviour would have a negative impact on the whales (particularly the mothers and calves that needed time to rest, nurse and feed before undertaking the long migration back to northern feeding grounds) Dr. Diane Gendron and her research team decided to implement a study on the impacts of whale watching. By this time the team had built up a photo-identification catalogue of 750 individual blue whales3 and collaborated with the National Commission of Protected Areas (CONANP) in the design of Mexico’s Blue Whale Program of Action for Species Conservation (PACE).
In the months of February-April every year from 2009-2016, the team used a 7 m long skiff with an outboard engine to conduct continuous individual focal sampling3 adapted to blue whales. They continually recorded whales’ swimming tracks and surfacing and diving behaviour, in order to compare how these varied in the presence of whale-watching boats versus when no whale-watching boats were present. To minimize their own disturbance to the whales, the research team followed at a distance of more than 100 m (range: 100-800m) and shut down their engines as frequently as they could while still keeping sight of the whales. Over the years, they conducted follows on a total of 148 individuals (66 females, 20 females with calves, 38 males and 24 individuals of unknown sex) amassing a total of 646 hours of track and dive data (an average of five hours per day).
When the data were analyzed, the team found that the presence of whale watching vessels had a significant impact on the whales, which spent less time at the surface and had shorter dive times in the presence of whale watching boats. Perhaps just as significantly, through their research the team also discovered that their own method of conducting focal follows - maintaining a distance from the whales and turning off their engines whenever possible -resulted in whales sometimes approaching the vessel more closely than when they were approached by whale watching vessels with engines continually running. The team had naturally developed a new concept of whale watching that some of the whale watching vessel captains decided to imitate, and called “passive whale watching”. A 2014 study on tourists' impressions of whale watching revealed that their willingness to return and/or recommend trips to others were partially dependent on their perception that whales were not crowded or disturbed during whale watching activities4.