Rivers come in many sizes and flow through different gradients. Narrow rivers on a steep gradient will fish much differently than wide rivers on a flat gradient. The rivers will fish differently because of differences in species, food sources, structure and flows.
The size of the river has a direct influence on the fishing. Large rivers have more water for fish to navigate while small rivers have limited holding areas. In small rivers and streams fish are found under cut banks, in soft pockets and in deep pools. In large rivers, fish will also hold in deep pools and under cut banks but they will also hold in mid-river channels.
Fish are relatively easy to locate in small rivers, but anglers must make a stealthy approach to avoid spooking the fish. In large rivers, anglers can create distance by making long casts, but more effort is required to locate the fish in the broad waters.
Fishing in rivers can be done with conventional or fly fishing tackle. Conventional anglers can cover ground in large rivers by casting and retrieving spoons and spinners, or they can focus on a single deep area by bouncing bait on the bottom. Fly anglers can also cover ground by casting and retrieving streamers, or they can fish deep runs by fishing nymphs beneath an indicator. Fly anglers also have the ability to imitate specific food sources and target fish feeding on the surface.
Water temperature is an important factor when fishing in rivers. Knowing the optimum temperature for the species being targeted will increase success. As a general rule, warm water species are most active during the summer months and cold water species are active from the fall through the spring.