The Volokh Conspiracy
Mostly law professors | Sometimes contrarian | Often libertarian | Always independent
So holds the 9th Circuit, in today's decision in Makah Indian Tribe v. Quileute Indian Tribe:
At the time of signing, "fish" had multiple connotations of varying breadth. For example, Webster's Dictionary  simultaneously defined "fish" broadly as "[a]n animal that lives in water" (which would include whales and probably seals) and narrowly as a "name for a class of animals subsisting in water" that "breathe by means of gills, swim by the aid of fins, and are oviparous" (which would exclude whales and seals). Other sources also acknowledged the popular understanding that the word "fish" could cover sea mammals; for example, the Supreme Court wrote that "For all the purposes of common life, the whale is called a fish, though natural history tells us that he belongs to another order of animals." In re Fossat, 69 U.S. 649, 692 (1864). …
Recognizing the ambiguity in the Treaty … brings us to the Indian canon of construction. As a general rule, treaties "are to be construed, so far as possible, in the sense in which the Indians understood them," and "ambiguous provisions [should be] interpreted to [the signatory Indian tribe's] benefit." …
One linguistic clue provides powerful evidence that the Quileute and Quinault assigned a broad meaning to the use of "fish." The district court found, based on linguist Professor Hoard's testimony, that "[t]he negotiators most likely used the Chinook word 'pish,'" which translates into English as "fish." The court credited Professor Hoard's explanation that the negotiators would have opted for a broad cover term because Chinook language had general terms referring to large groups (like "fish") and specific terms referring to individual species (like "whales," "seals," and "salmon") but no intermediate terms referring to taxonomies (like "finfish" and "sea mammals").
The Quileute's and Quinault's corresponding words for "pish" have even wider sweep. Like Chinook jargon, the Quileute and Quinault languages have no intermediate terms for taxonomies. As Professor Hoard explained, the Quileute would likely have used "?aàlita?," which translates as "fish, food, salmon." Similarly, the Quinault's term "Kémken" is defined alternatively as "salmon," "fish," and "food." Because the Quileute and Quinault traditionally harvested whales and seals for food at and before treaty time, these pieces of linguistic evidence strongly support the district court's finding that the tribes "would have understood that the treaty reserved to them the right to take aquatic animals, including … sea mammals, as they had customarily done." …
Evidence of post-treaty activities further supports the view that the Quileute and Quinault (and possibly even the commissioners) understood the Treaty to protect whaling and sealing. No party contests the district court's finding that "[d]uring the post-treaty period, the tribes continued to harvest whales and seals from the Pacific Ocean" with active encouragement from government agents. Although the government's acquiescence does not definitively show that the parties believed the right was preserved by the Treaty, the district court rightly noted that this important fact tends to suggest that "both sides believed the right to harvest sea mammals to have been reserved to the tribes."
By the way, whales and porpoises—as well as sturgeon—were labeled "royal fish" by English law, and belonged to the king (or, in Cornwall, to the prince of Wales); but the 9th Circuit rightly didn't rely on this.
Thanks to Howard Bashman (How Appealing) for the pointer.