Summary of Reported Whale-Vessel Collisions in Alaskan Waters

Table 1

Ship strike confidence categories.

Confidence category	Definition
Definite strike	There is evidence that a strike occurred beyond a reasonable doubt. For example:
	Strike was witnessed by the vessel operator/crew or by the operator/crew of a nearby vessel
	or
	Strike was not witnessed but whale has massive blunt impact trauma (defined by disarticulated vertebrae or fractures of one or more heavy bones including skull, mandible, scapula, vertebra or adult rib, and a focal area of severe hemorrhaging)
	or
	Strike was not witnessed but carcass has apparent propeller wounds^1 (i.e., deep parallel slashes or cuts into the blubber) on the dorsal aspect
	or
	Strike was not witnessed but carcass has propeller wounds on the ventral and/or lateral aspect which a necropsy confirms were produced ante mortem
	or
	Strike was not witnessed but carcass has an amputated appendage (e.g., fluke or flipper) which a necropsy confirms occurred ante mortem due to a sudden and traumatic laceration (versus an entanglement injury causing a slow, ischemic loss of the appendage)
	or
	Strike was not witnessed but evidence of a collision was found on the vessel (e.g., whale skin or tissue)
	or
	Whale was found on the bow of a ship
	………………………………………………………………
	>Subcategory: Whale struck stationary vessel
	Vessel was stationary at the time of the collision (i.e., anchored or drifting)^2
Probable strike	The report is likely to be true; having more evidence for than against, but some
	evidence is lacking. For example:
	Vessel operator/crew or operator/crew of a nearby vessel believes that a strike
	occurred but cannot confirm the strike with absolute certainty
	or
	Strike was not witnessed, and the whale is a calf with smaller broken bones (e.g.,
	ribs) that could have been fractured by another animal rather than by a vessel
	or
	Strike was not witnessed and the whale shows partial evidence of a collision other
	than as defined under definite strike. For example:
	(i) Whale has a focal area of severe hemorrhaging but no known broken bones;
	therefore, it is possible the trauma was caused by another animal rather than by a vessel;
	(ii) Carcass has propeller wounds on the ventral and/or lateral aspect; however, the necropsy is not able to determine if they were produced ante mortem
Possible strike	The report may be true; however, a majority of evidence is lacking. For example:
	Vessel operator/crew or operator/crew of a nearby vessel believes that a strike may
	have occurred but there is significant uncertainty
	or
	Vessel operator/crew or operator/crew of a nearby vessel believes that a strike
	occurred, while the vessel operator/crew or operator/crew of a nearby vessel believes
	that a strike did not occur
	or
	Strike was not witnessed, and the whale shows partial evidence of a collision other
	than as defined under definite or probable strike, such as damage to an appendage or skin, but the necropsy is incomplete or there is no close examination of the whale (e.g., whale is viewed from a distance only)
Rejected report	The report is not credible. For example:
	Third-hand report
	or
	No credible eyewitnesses^3
	or
	Lacking sufficient detail or documentation to be credible
	or
	Necropsy determines an alternate cause of death

¹We only included whales with propeller wounds where there was evidence that the strike occurred in Alaska (i.e., the propeller wounds had to be from a strike that was witnessed and/or the propeller wounds had to be fresh (bleeding) or assessed to be fresh by a trained observer.)
²We counted collisions involving kayaks and canoes under this subcategory unless the kayak/canoe was known to be traveling at >0 kn.
³The credibility of the eyewitness(es) was assessed on a case-by-case basis. The most credible eyewitness is someone who had “something to lose” in reporting the collision (e.g., the captain and/or the crew of the vessel that struck the whale) because it is presumed they would not risk reporting the collision if it had not occurred. The least credible eyewitness is a passenger on a commercial vessel (e.g., whale watch vessel, cruise ship, etc.) who reports a collision, but there is no supporting evidence (photos, observation of wound, blood, etc.) or other eyewitnesses. In these cases, the report was rejected unless the passenger was an experienced observer and/or additional eyewitnesses were available to corroborate the report (assessed on a case-by-case basis).