Marianas Cetacean Surveys 2013: Updates on Our Satellite Tagged False Killer Whales (July 12 – 27)

by Marie Hill, Allan Ligon, Adam Ü, and Mark Deakos

Figure 1: False killer whale photographed off of Rota. (Photo credit: Marie Hill, collected under NMFS permit 15240).

At the beginning of July we deployed four satellite tags on false killer whales (Pseudorca crassidens) during our surveys around Rota (https://pifscblog.wordpress.com/2013/07/15/marianas-cetacean-surveys-2013-rota-summary-july-4-10/).  The first satellite tag (128903), deployed on 6 July, transmitted for four days.  During that four day period the first satellite tagged whale traveled with the second satellite tagged false killer whale (128904).  It is possible that the two whales continued to travel together beyond those four days.  On 11 July, the tagged whale 128904 was over the West Mariana Ridge, more than 280 km west of Guguan (Figure 1).  Over the next four days the tagged whale traveled south along the ridge then returned to the waters off of Rota and Guam. The whale then moved north along the Island chain never staying in one place for very long.  During the last transmission reported here the tagged false killer whale was approximately 50 km west-southwest of Farallon de Medinilla. The tag has transmitted for a total of 21 days.

Figure 2: Track of satellite tagged false killer whale 128904.

The third satellite tagged false killer whale (128906) was tagged on the same day as the first two but was in a separate subgroup.  We last reported that this tagged whale was approximately 76 km due west of Saipan on 11 July (Figure 3).  Since then, the whale has made a large counterclockwise circuit moving north along the Island chain to Guguan, west to the West Mariana Ridge, eventually making its way back to the Island chain on 21 July.  On 23 July, satellite tagged whales 128904 and 128906 joined up off the northwest side of Saipan and moved north again just beyond Anatathan (Figures 2-3).  On 27 July these two satellite tagged whales were still together, approximately 50 km west-southwest of Farallon de Medinilla.  Tag 128906 has also transmitted for a total of 21 days.

Figure 3: Track of satellite tagged false killer whale 128906.

The fourth and final satellite tagged false killer whale (128908) was tagged on 7 July, the day after the first three were tagged.  After being tagged, this whale moved to the south and spent most of its time within the Mariana Trough (Figure 4).  Between 21 and 23 July 128908 made a trip out to the West Mariana Ridge.  To date, this tagged whale has remained south of Farallon de Medinilla and has not joined up with any of the other satellite tagged false killer whales.  The satellite tag 128908 has transmitted for a total of 20 days.

Figure 4: Track of satellite tagged false killer whale 128908.

The satellite tagging operations were conducted under NMFS permit 15240 and CNMI Fish and Game License 02694. Funding was provided by the NOAA Fisheries and the U.S. Pacific Fleet. The satellite tag tracks shown are based on raw transmission data and have not been quality checked.  The final products may vary from those shown in the figures above.