Blue whales
Project Leader: Dr Diane Gendron
Background
The blue whale (Balaenoptera musculus) is the largest animal on earth and yet remains one of its least known and most endangered species. Still recovering from the effects of whaling, there has been some evidence of increasing numbers in Northeastern Pacific, though planned developments in the Gulf of California potentially present a major setback for the blue whale population.
Part of this population summers off the coast of California and migrates south in winter, along the coast of Baja California, Mexico. Less than half this population, around 500 whales, spend the winter in the Gulf of California, with female blue whales nursing their young, while feeding themselves on euphausids (krill) that form dense aggregations there. With this habitat now under threat, it is vital to build a clearer picture of their population structure.
Part of this population summers off the coast of California and migrates south in winter, along the coast of Baja California, Mexico. Less than half this population, around 500 whales, spend the winter in the Gulf of California, with female blue whales nursing their young, while feeding themselves on euphausids (krill) that form dense aggregations there. With this habitat now under threat, it is vital to build a clearer picture of their population structure.
In the field
Dr Diane Gendron
Dr Diane Gendron of the Marine Mammal Ecology Interdisciplinary Marine Science Center (CICIMAR) has been instrumental in establishing a unique database of 460 blue whale sighting histories, based on photo-identification and tissue sampling since 1993. The blubber and skin are then used to look for biotracers that could help to discriminate the whales into group/age categories. However, no information exists on the size or age structure of the population, since until now there has been no method of measuring whales at sea.
A pioneering method has been designed by a student in the CICIMAR doctoral program (Christian Ortega Ortiz, in process) which consists of taking photographic sequences of the whale’s flank, now easily accomplished using digital cameras, while simultaneously measuring the distance between the whale and the camera using a laser range finder. The estimated total lengths for the blue whales obtained with the photo-sequences method, were compared with an alternative and independent method: aerial photogrammetry.
A pioneering method has been designed by a student in the CICIMAR doctoral program (Christian Ortega Ortiz, in process) which consists of taking photographic sequences of the whale’s flank, now easily accomplished using digital cameras, while simultaneously measuring the distance between the whale and the camera using a laser range finder. The estimated total lengths for the blue whales obtained with the photo-sequences method, were compared with an alternative and independent method: aerial photogrammetry.
Aims & objectives
This SOSF supported research aims to investigate the population structure of blue whales in the Northeastern Pacific through the continued development of novel measurement techniques.
Preliminary results have suggested that the new photographic technique mentioned above provides accurate size measurements, and so far the team has measured 60 different blue whales, whose sizes have provided an average of 22.3 meters, with a minimum and maximum of 7.9 meters (a calf) and 29.9 meters respectively.
Comparisons of the total length between sexes and locations will be done in order to better describe the population structure; the measured whale will then be compared with the age group categories estimated from the life history database of the individuals. Continued SOSF funding of fieldwork and analyses will determine and validate the precision of this method, hopefully providing an urgently needed window into the population structure of this little understood giant.
Preliminary results have suggested that the new photographic technique mentioned above provides accurate size measurements, and so far the team has measured 60 different blue whales, whose sizes have provided an average of 22.3 meters, with a minimum and maximum of 7.9 meters (a calf) and 29.9 meters respectively.
Comparisons of the total length between sexes and locations will be done in order to better describe the population structure; the measured whale will then be compared with the age group categories estimated from the life history database of the individuals. Continued SOSF funding of fieldwork and analyses will determine and validate the precision of this method, hopefully providing an urgently needed window into the population structure of this little understood giant.