Lol, I love crankbaits in rivers!
So, rivers...
And we'll forget seasonal patterns, and just focus on the where and why.
These are all general rules, and there are some pretty specific exceptions. Also, bigger and more complex river systems can shake this stuff up, but this is how I've grown to understand how rivers work. I've found the same rules hold up with most species of predatory fish and how to look at prime holds or prime lies. I'm sure i'll look back at this want to edit it the next time i can't figure fish out, and totally consider it a work in progress, but I kinda want to put this out there to see what you guys think.
- Current is the food delivery system. It carries drifting baitfish, crayfish, nymphs, leeches, and every imaginable food item in between. Faster current, especially with riffles, will also be more oxygenated. The most aggressive and active fish will hang out here because there will be the greatest access to feeding opportunities and the oxygen to fuel their fast metabolism.
- The thing about holding in current, is that fast current requires way more energy to hang out in. This means a few things. Predators will only hang out directly in the current when they're feeding actively, but will often hold at the closest possible current break or piece of structure. Think about boulders, fallen trees, ledges, wing dams, inside bends, undercut banks, weed beds, or in pockets along the bottom (current almost always flows fastest at the surface). These places will almost always concentrate active fish.
- Some fish are likely to feed more actively, more often. Smaller fish are generally going to be feeding almost exclusively on larva/nymphs/press bugs/etc. These are the base of your food chain and will be super abundant in and around riffles and most fast current (can be quite shallow). This is where you'll also find lots of smaller bass, chubs, sculpins, madtoms, smaller trout (where applicable), etc feeding on the real little stuff. Because of this, riffles and immediate current breaks along them can load up with small smallmouth in the summer/fall because they need to eat tons and tons of nymphs to grow. Areas like these are the places where fish will strike almost recklessly and eat almost anything. "Oh, you bought the novelty spoon that looks like a twig and berries? Yeah, it'll catch fish here."
- If there are small fish, you'll find very big fish close by. So, this is the topic of "prime holds". Some eddies, current breaks, weed lines, boulders, bridge pilings, etc make for the best hang out spots for predators because of their proximity to fast current, complex structure, or just ability to ambush without taking the full brunt of the water. These are the places most likely to hold the most dominant actively feeding fish in the area. The above ugh... "Silver Johnson rule" also sometimes applies here if these holds are breaks in or IMMEDIATELY adjacent to fast current.
Prime holds will usually have a few common things. First, look for access to deep water. This literally means anything from a change of 6" or 6' so long as it offers slower current (think rest and digestion), protection from predators (birds, bigger fish, us, etc), and a comfortable combination of temperature and oxygenation (this is why deep buckets below or adjacent to riffles can be killer).
Second, you want immediate access to a food source. This could mean fry, frogs, bugs, and baitfish in grass/weed beds (if they're green), schools of alewives or perch chilling behind bridge pilings or downed trees, or even the bottom of a run during a mayfly hatch. I cannot stress enough the importance of knowing what smallmouth are feeding on (even when they aren't being picky) if you're serious about consistently finding them. A good example... The Susquehanna is a smallmouth factory because it's a bug factory. It's common to see all kinds of hatches from giant dobsonfly/helgramites (bodies over 4") to mayflies and midges ranging from size 6-12 (white flies) to 14-18 (sulphurs and cahills) all the way down to 22 and 24 (midges, BWO). It's common to see runs of slow current in 3-6' of otherwise featureless water just explode before dusk. Why? It's below riffles (hatches happen where the bugs are in riffles and runs) and loaded with bugs, has comfortable current, and has everything from baitfish through small bass through huge pike and musky feeding in it. Once you figure this out, you'll realize you can fish using anything from dry flies through poppers or floating jerkbaits (to imitate the baitfish feeding on the flies/emergers) and catch fish. Understanding events like this is huge because they happen in the same types of places on most nights from spring through late fall. This type of event can effect the quality of holds because the massive abundance of food can mean almost featureless or seemingly uninteresting water for 20 hours of the day can become the place to be for two hours in the am and two hours at night.
Third is the sciencey part. These holds need to provide water that is the appropriate temperature and oxygen level for the fish's activity level. Big, jarring changes are rough on fish, and fish will seek comfort in every season. Fish are cold blooded, so water temperature drives their EVERYTHING. Eating, being almost comatose, being super aggressive, making sexy time, digesting food - all of these things are driven by or at least timed around water temperature. Oxygen content can make the difference between a killer hold and the dead sea. Generally, more oxygen means happier, healthier, more comfortable fish. Riffles/fast current, wind, springs, and most green healthy vegetation will add oxygen to the water while decaying anything will remove oxygen. This is why active predators hang out around faster current or along green weed beds and tend to avoid brown, stagnant pools (most of the time).
The 4th factor in determining the quality of a hold is security/safety. Is the fish easily spotted by eagles, ospreys, or herons over head? Is the hold leaving the bass exposed to larger predator fish? Does the hold offer camouflage/cover? Is the water clear and forcing fish to hold deeper or stained enough to protect them from overhead? These things will all effect how safe a fish feels in a particular lie.
The trick to finding consistent patterns, even in rough conditions is find the spots that provide the best combination of those 4 things possible.
A good example of a good mid-day 90+ degree, high sun, clear water, low flows. A lot of fish may be unwilling to even hang out in/around the fastest most oxygenated water because of high water temperatures or exposure to predators (poor lie) unless there are springs and a ledge immediately below the fast water to offer protection and comfort (prime lie). Another philosophy might be to fish deeper current breaks. This might be really slow fishing if those points/islands/whatever don't have a lot of food around them and will likely hold mostly resting/neutral-negative active fish. A better hold might actually be in shallow water even in the mid day heat if there's overhead cover/shade and structure/cover to allow ambush. Extra points if there are springs close by. I've caught a lot of surprisingly large mid-day smallmouth pitching 1/8-3/4oz jiggs into shade lines, laydowns, grass edges, submerged trees, and once even below an old sofa in these types of conditions. Basically, current + typically largemouth flipping spots + jig = fat smallies even mid day in the right conditions.
Presenting in current is probably the next important thing after finding fish.
Seasons are another big topic, but I'm focusing on the warmer months when most are on the water.
Flow and water clarity are also too big to cover in this rant lol.
If this is helpful for anyone as much as putting it out there is cathartic for me, awesome. Also, if this helps anyone, i'll gladly put out some thoughts on the other stuff.