Apologies if you have already considered this and discounted it, but I use a camera with a customisable multi-shot timer. The problem with remotes is the need for a third hand to press the button while holding the fish, although some have mastered the art of pressing a button with a knee.
My camera can be set to take up to 10 shots about 2 seconds apart (longer if the flash has to recharge). If the fish makes an escape attempt, it doesn't matter, you just miss 2 or 3 shots while yuo control it. Once you think you've got a couple of decent takes, you can half turn or move the fish to one side for an alternative shot.
I have a 2nd-hand Canon S5 (a popular camera on here) which has a hinged display so you can frame the shot while in position and see what you are taking as you go along. The Canon G6 is similar with more features but a smaller zoom. Both compact cameras though but not too compact

You can pick them up on ebay for £100-£150. There are newer ones on the market with similar facilities but I'm not up-to-date with the latest models.