MITIGATING RIGHT WHALE-VESSEL COLLISIONS
VHF-Radio Tracking of a North Atlantic Right Whale (Eublaena glacialis) Female and Calf in the Calving Ground: Preliminary Results
Christopher K. Slay1, Steven L. Swartz2, Amy R. Knowlton1, Robert D. Kenney3,
Stephanie Martin1, Joseph Roman1, Anthony Martinez2, and James Tobias2
1. Edgerton Research Laboratory, New England Aquarium, Central Wharf, Boston, Massachusetts 02110.
2. U.S. National Marine Fisheries Service, Southeast Fisheries Science Center, Miami, Florida 33149.
3. University of Rhode Island, Narragansett, Rhode Island 02882.
North Atlantic right whale (#1612) with calf
ABSTRACT
A VHF transmitter was attached to a North Atlantic right whale cow on January 20, 1999, approximately 30 NM (nautical miles) east of Fernandina Beach, Florida. The whale and her calf were tracked continuously for 44 hours, when tracking was abandoned due to bad weather. The pair was relocated on January 25, 1999 and tracked continuously for an additional 96 hours. This poster presents data from those two tracking episodes, giving fine-scale movement, swim speed and comparing day and night surface/dive intervals. Information on the duration of the whales� time at the surface and behavior is relevant to right whales� vulnerability to collisions with ships and sightability by aerial surveys designed to reduce the potential for ship/whale collisions.
INTRODUCTION
The North Atlantic right whale (Eubalaena glacialis) population, less than 300 individuals, has declined throughout the 1990�s while southern hemisphere right whale populations appear to be growing about 6%-7% per year. Failure to show signs of recovery, despite international protection since 1937, has been attributed to a variety of factors, including the effects of human activity on mortality rates. Ship collisions kill more right whales than do any other documented causes of mortality. Of the 17 anthropogenic right whale mortalities documented since 1970, 15 were due to collisions with vessels.
North Atlantic right whales give birth and overwinter in the near shore coastal waters between Savannah, Georgia, and West Palm Beach, Florida, with an area of high-density occurring along sixty miles of coastline between Brunswick, Georgia, and St. Augustine, Florida. Three major ship channels, serving three commercial shipping ports and two military bases, transect this high density area. Since 1988, a total of 7 ship/whale collisions, including 4 mortalities, are known to have occurred in this region.
To better understand the vulnerability of calving right whales and the effectiveness of current mitigation strategies, the New England Aquarium, the National Marine Fisheries Service Southeast Fisheries Science Center, and the Gray�s Reef National Marine Sanctuary implanted a VHF-radio transmitter into the blubber layer of a right whale cow during the 1999 calving season. By tracking this animal and continuously monitoring signals from the transmitter the whale�s surface/dive behavior, fine-scale movement and swimming speed were documented. This provided information on the duration of time the whale remained on the surface and vulnerable to collisions with ships, its availability to be sighted by aerial surveys, and how far it might move in a 24-hour period. Of additional interest were certain temporal and spatial variables which are associated with increased vulnerability.
A right whale cow, #1612, was tagged with a VHF transmitter on January 20, 1999 approximately 30 NM east of Fernandina Beach, Florida. She and her calf were then tracked continuously for 44 hours, when tracking was abandoned due to bad weather. The right whale pair was relocated on January 25, 1999 and tracked continuously for an additional 96 hours. This poster presents data from those two tracking episodes, giving fine-scale movement, swim speed and comparing day and night surface dive intervals.
RESULTS
The mean length of the surface intervals was 3.26 minutes (CV 1.60, N= 839) with a 95% confidence interval from 2.91 minutes to 3.62 minutes and a maximum surface interval of 65.75 minutes. The mean length of dives was 5.58 minutes (CV 0.90, N= 819) with a 95% confidence interval from 5.23 minutes to 5.92 minutes and a maximum dive of 22.30 minutes. Visual observations during daylight hours confirmed that patterns of surfacings and dives less than approximately 1 minute were the result of whale #1612 bobbing at the water�s surface and submerging the radio tag�s antenna. An analysis of surface and dive intervals > 1 minute gave a mean surface interval of 4.69 minutes (CV 1.27, N= 552) with a 95% confidence interval from 4.20 minutes to 5.19 minutes with a maximum surface interval of 65.75 minutes. The mean for dives > 1 minute was 7.03 minutes (CV 0.68, N= 637) with a 95% confidence interval from 6.66 minutes to 7.41 minutes with a maximum dive of 22.30 minutes.
Total time at the surface (TTS) is estimated by combining the means for surface and dives <1 minute long with the mean for surface intervals > 1 minute. The mean for surface intervals < 1 minute is 0.50 minutes, the mean for dives < 1 minute is 0.47 minutes, and the mean for surface intervals > 1 minute is 4.69 minutes, for a TTS of 5.64 minutes compared to the mean for dive intervals > 1 minute of 7.03 minutes. This suggests that right whale #1612 spent approximately 45% of the time at the surface and approximately 55% below the surface on dives longer than 1 minute.
Surface-dive data were sub-sampled into daylight (0700-1800) hours and nighttime (1900-0600) hours. The mean daytime surfacing interval was 2.94 minutes (CV 1.42, N= 370) with a 95% confidence interval from 2.51 minutes to 3.37 minutes. The mean nighttime surface interval was 3.52 minutes (CV 1.67, N= 469) with a 95% confidence interval from 2.98 minutes to 4.05 minutes. The mean daytime dive interval was 5.62 minutes (CV 0.97, N= 358) with a 95% confidence interval from 5.06 minutes to 6.19 minutes. The mean nighttime dive interval was 5.54 minutes (CV 0.85, N= 461) with a 95% confidence interval from 5.11 minutes to 5.97 minutes. Surface intervals during 20-22 January were significantly larger (P < 0.001) than during 25-29 January.
Whale #1612 moved at approximately 1 knot (NM/hr) throughout the periods of tracking. Her greatest rate of movement was 2.1 knots, averaged over a 12-hour period. The total distance traveled during the first tracking episode was 46 NM, and during the second tracking episode was 99 NM. The distance traveled during daylight hours (approximately 12 hours) ranged from 7 NM to 16 NM, and the distance traveled during nighttime hours ranged from 8 NM to 16 NM.
SWIM SPEED
SEA SURFACE TEMPERATURE (0C)
