Entanglement rates in fin whales and blue whales

"The drone project" 

 

Sub-lethal and lethal entanglement of cetaceans in fishing gear is now a major and widespread conservation concern, identified as the main impediment to recovery for certain species, such as the northern right whale (Eubalaena glacialis). Until now, the risk of entanglement in rorqual whales, like the two SARA (Species at Risk Act) listed species blue (Balaenoptera musculus) and fin whales (B. physalus), has been considered low based on the number of scarred animals in photo-ID studies. However, preliminary scarring rate analysis using additional photo data of Northwest Atlantic blue and fin whales demonstrates that prior entanglement rate estimates were severely underestimated. The primary attachment points of fishing gear on whales are the mouth area, the flippers, and the tail region in particular (peduncle and fluke). Previous attempts to estimate scarring rates have likely been underestimated for two reasons: 1) Fin whales do not raise their flukes out of the water on their final breath before a dive, and very few blue whales do so; and 2) standard photo-ID pictures do not focus on the peduncle or head/mouth region, but rather the flank of the animal. By only analyzing standard photo-ID pictures, the estimated entanglement rate is below 10% for both fin and blue whales. When selecting animals that have more complete photographic coverage of the body (flank, tail, peduncle, and fluke leading edge), the proportion of blue whales with entanglement scars increases to between 50% (n=12) and 75% (n=14), depending on the side. In fin whales, only 95 animals show large part of the peduncle above the water surface and 41% of these show signs of previous entanglement, even though this does not include the tail. In conclusion, we suspect that over 50% of blue and fin whales in the Northwest Atlantic have been entangled at one point, and that the risk of sub-lethal or lethal effects on these two SARA-listed species has been grossly miscalculated.

 

Currently conducted boat-based research techniques cannot answer the questions, thus we recommend to obtain aerial pictures of individual fin and blue whales. Using an unmanned aerial vehicle (UAV), we will obtain high-resolution aerial video and photos, with the aim of capturing images of the entire body (head to fluke) of every encountered individual. The advantage of aerial images is that scarring can be detected on body parts just below the water surface due to the more perpendicular angle between camera and subject. This aerial imagery will be used to identify individuals and to determine if they carry scars from entanglements.

 

The primary aim would be to estimate the total number of fin and blue whales carrying marks from previous entanglements. Multiple year studies are required to estimate an annual entanglement rate, thus quantifying how many animals gained new scars over the past year. This is vital to quantify the currently existing problem. To achieve this goal, a larger sample size is needed in two or more subsequent years, to study the same individuals over time. Conducted over a series of years, further aspects include the study of healing process of scars and eventually the estimation of the mortality rate due to entanglement as it has been done for humpback whales in Gulf of Maine (Robbins 2009).