>>1983594They are extremely useful for ice fishing. Through the ice you can always see your lure/bait, any fish that comes cruising by, and get an idea of how they are reacting to your setup. If a lot of fish come by but ignore your lures, time to switch up your presentation. No fish coming by? Time to move. Whole lot of tiny marks on the bottom? Size down and get a limit of perch. The perch school suddenly disappears and there is just a giant mark sitting there? Drop down something big and flashy quick and catch a predator. You would also be surprised at how often fish come by well off the bottom and you can quickly reel up to meet them. Ignoring all that, the simple advantage of knowing when a fish is down there and being ready to set the hook is massive.
For open water, it's harder (but possible when there is nearly no wind) to spot your lure, but you can still use it for figuring out where structure is and where fish schools are. Last fall, for example, I spent a couple hours cruising around a lake slow trolling the bottom hoping for perch, but only ended up finding them after spotting a school on top of a 15 foot rocky submerged point that didn't even show up on lake maps. Ended up going back to the exact spot 4 separate days and catching all the perch I wanted. Without the sonar, I would have not realized that spot was there. The same spot also ended up being great for trout and is rarely fished.
Ideally you would get a flasher for ice fishing and an LCD fish finder for open water, but it's not required. The Striker 4 is a great, very cheap unit that can do double duty if you get the ice fishing bundle then also buy a separate open water transducer. I mounted mine on my kayak with a Scotty mount. For flashers, I think the Ice-35 is the best of the cheapest flashers. It has zoom and dual beam to help with fishing on drop-offs and deep water, but is known to have noise problems. Also, get yourself a Battery Tender Junior for charging the 12V batteries.
