This puzzle played more difficult for me than most Tuesdays. Perhaps it's because it's a 16x15 grid. I very much enjoyed it in any case, and I am especially impressed by some of the grid construction.
The theme is taking a species of fish that can also be used as a verb and coming up with a phrase with said verb. All the phrases are of the form: [past-participle][preposition]. The only one which doesn't feel like it quite fits is CARPEDABOUT. That is to say, the others suggest a movement of some sort, while this one doesn't. The central 16-letter answer, FLOUNDEREDAROUND, is excellent, though, and the others are fine.
The revealer is a bit odd: 59A: Classic out-of-office sign ... or what this puzzle's author has done? (GONEFISHING). It's a great first half for the clue. I imagine an old-time rural doctor's office with the sign on the door. But it doesn't quite work as a revealer for the theme. I mean, yes, there are fish in each answer. But why are they put in that form? It's a total nitpick on my part to bring it up, and I think I'm only doing it because I liked the theme overall.
More impressive to me are the four long down answers in the middle third of the grid. Each one crosses three themers as well as two other long across answers. 8D: Avoided phoniness (KEPTITREAL) is great. 30D: Noble knight who found the Holy Grail (SIRGALAHAD) will always be a favorite for this Monty Python enthusiast.
35D: Sneaky shelters (TAXDODGES) is very nice indeed. And my favorite clue-answer pair for today resides at 5D: They get the paddy started (RICESEEDS). P!nk would be very impressed.
I'm not entirely convinced by CANOEISTS, although it googles all right. I found a debate amongst aficionados of that form of transport as to whether they should be this term or "canoers". It reminds me of "detectorists", those people who use metal detectors as a hobby. And I definitely recommend the BBC series by the same name. Very sweet and lightly amusing. I've never heard of SALTDOMES, but that term googles very well, and the definition is precise.
There's a fair amount of glue, as Jeff Chen calls it, ranging from IME (which was an immediate fill for me, but which is a very strange partial) to ACAD, LCDS, APAL. But I enjoyed ETCETC and CLOUSEAU is of course wonderful. Although on rewatching some of those movies, I was struck by how out of date the humor is, and sometimes offensive.
1A: Boots, backpack, tent, etc. (GEAR): C-. Plus, that "etc." echoes 2D too exactly.