Abstract
AbstractGreat whales have been detected using very‐high‐resolution satellite imagery, suggesting this technology could be used to monitor whales in remote areas. However, the application of this method to whale studies is at an early developmental stage and several technical factors need to be addressed, including capacity for species differentiation and the maximum depth of detection in the water column. Both require knowledge of the spectral reflectance of the various whale species just above the sea surface, as when whales bodies break the surface of the water to breath, log or breach, there is, at times, no sea water between the whale's skin and the satellite sensor. Here we tested whether such reflectance could be measured on dead whale tissue. We measured the spectral reflectance of fresh integument collected during the bowhead subsistence harvest, and of thawed integument samples from various species obtained following strandings and stored at −20°C. We show that fresh and thawed samples of whale integument have different spectral properties. The reflectance of fresh samples was higher than the reflectance of thawed samples, as integument appears to darken after death and with time, even under frozen conditions. In this study, we present the first whale reflectance estimates (without the influence of sea water and for dead tissue). These provide a baseline for additional work, needed to advance the use of satellite imagery to monitor whales and facilitate their conservation.
Highlights
Whales can be detected from 600 km above the ocean using very-high-resolution (VHR) satellite imagery, that is,
The permutational multivariate ANOVA performed here, showed that the time spent in a freezer was the only variable to significantly (P < 0.05) explain the variation observed among the spectral reflectance averaged per animal (Table 1); and the clustering
Our results led to two interesting biological outcomes: (1) whale integument darkened the longer it stayed in a freezer, and (2) spectral reflectance of thawed samples showed no difference among species, potentially due to (1) above
Summary
Whales can be detected from 600 km above the ocean using very-high-resolution (VHR) satellite imagery, that is,
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