Last night I mentioned that a large number of Harbor Porpoises (Phocoena phocoena) were visible off Bodega Head yesterday. Although the porpoises were far from shore (~1-2 km), making photographing them a challenge, I wanted to include a few photos for the record.
I estimate that more than 100 Harbor Porpoises passed by Bodega Head between 10:30-11:30 a.m. on 12 March 2022. Although there was some back-and-forth movement, they were primarily swimming south. The group sizes ranged from 2 to more than 15 individuals; groups of 6-8 individuals were common.
In my experience, it's unusual to see so many Harbor Porpoises at one time. From Marine Mammals of the World: "Most harbor porpoise groups are small, generally consisting of less than five or six individuals. They do, at times, aggregate into large, loose groups of 50 to several hundred animals, mostly for feeding or migration." (Jefferson et al. 2015)
You can click on the images for larger versions:
Hmmm... Any speculation about what might be causing this shift in behavior?
ReplyDeleteHi, Alice!
ReplyDeleteWell, there are different options. One possibility is that sometimes Harbor Porpoises are out there in these types of numbers, but we don't often see them because the conditions and timing need to be just right. Another possibility is that there's something that drew them to this area at this time -- e.g., oceanographic conditions or food, for example.
I looked at back at a post from a few years ago when I also noticed Harbor Porpoises on a very calm day and it was also in early March (see link below). So although that's just two "data points," it made me wonder if there's something going on at this time of year. Are some Harbor Porpoises migrating south past Bodega Bay in March? It'll probably remain a mystery for now.
https://bodegahead.blogspot.com/2018/03/calm-seas-and-rolling-fins.html
Jackie
Aha! I just looked at that older post, and see that I loved that one then, too!
ReplyDeleteHi, again!
ReplyDeleteYes, I remembered that the previous porpoises had caught your eye! I like being able to look back at older posts. Hard to believe this is year 11 of the NHBH!
:) Jackie