A humpback whale calf found dead on the southeast shore of Oʻahu on Feb. 6 died of a traumatic brain injury likely caused by a vessel strike, NOAA Fisheries said Monday.
The 12-foot-long whale was removed from a reef flat near the Wailupe peninsula. A University of Hawaiʻi team from the Hawaiʻi Institute of Marine Biology transported it for a postmortem exam.
They determined the calf was a male, less than one week old, and had evidence of nursing.
"The most significant postmortem finding was clear evidence of traumatic brain injury, which may have been caused by an impact of concussive force. While the calf may have been injured by another whale, the concussive force was more likely caused by a vessel strike," NOAA said in a statement.
NOAA said boats hit whales every year in Hawaiʻi, and collisions are a serious risk to both boaters and whales.
Thousands of humpback whales migrate to Hawaiʻi to breed, give birth and nurse their young. The whale season usually runs from November through May, with a peak from January through March.
"Humpback whales, particularly calves, are challenging for vessel operators to see. They spend most or all of their time underwater and generally have a low profile when surfacing to breathe," NOAA said.
To avoid striking a whale, NOAA said boaters should stay vigilant and travel at safe speeds. If you see a whale, stay more than 100 yards away. Federal regulations prohibit approaching within 100 yards of humpback whales in Hawaiʻi waters.
Separately on Monday, the Department of Land and Natural Resources announced new guidelines for boaters: Transit speed around whales should be 15 knots or less — reduced to 6 knots when within 400 yards.
If you observe, or are involved in, a collision with a whale or see a whale in distress, call the statewide NOAA Marine Wildlife Hotline: (888) 256-9840.
