To reduce the possibility of inaccurate readings, Ashe has used a “certainty score” to better estimate various population abundances. Her 2022 study published in Mammalian Biology explained it succinctly: ‘Identified individuals within an encounter were matched and a certainty score of “Certain” (100% confident), “Likely” (< 100% but ≥ 90% confident), or “Possible” (< 90% but ≥ 50% confident) was assigned to putative matches between pairs of photographs based on the degree of confidence in each match.’ The researcher then took those certainty scores and used them to determine three different population estimates with minimal human bias.

Photo-identification is just as painstaking and labour intensive as it sounds — Ashe spends hundreds of hours scouring countless photographs to match dorsal fin to dorsal fin. It can take up to a year to go through a season’s worth of photos, with the resulting data then used to come up with population estimates. Until the 1990s, this photo-identification work was done with film cameras, with renowned American-Canadian marine biologist Alexandra Morton a major contributor.

“She was shooting on film at this remote base, and so she would shoot on film, then put the film on a float plane,” Ashe explains. The film would then go to a photo lab, which would send back contact sheets compiling all of Morton’s photos. The researcher would then have to look through a loupe (a special type of magnifying glass), picking out and circling which photos she wanted to get printed. Then she’d send her choices back on the float plane and wait for the photos to be printed and returned to her. “So that was a whole other level of love!” says Ashe.