Understanding what constitutes structure (hint: it's more than just wrecks and rocks), and how fish relate to it, will help boost your success rate.
Whether you fish for bass in a lake or billfish in the ocean, you probably know that fish relate to anomalies in the environment that we call structure. A tree in the lake, an oyster bar in the bay, and a wreck lying on the bottom of the ocean are all forms of fish-attracting structure. But to an angler, the term "structure" doesn't relate only to physical items; it also refers to things like temperature and salinity barriers in the water, difference in water color, and other changes in the environment.
Just how should an angler think about structure if he or she wants to be as effective as possible when hunting for fish? And how can you use a deep knowledge of structure to catch more of those finned critters?
Virtually every fish on the planet relates to some form of structure at one time or another. There are a variety of reasons, often beginning with the fact that physical structure creates habitat for the basic building blocks of the food chain. Submerged tree branches in a lake provide cover that attracts minnow, which in turn attract small predators like crappie, which are then hunted by larger fish like bass or pike. In the case of an oyster bar, the piles of jagged shells are inhabited by tiny crabs and shrimp, which are preyed on by fish like croakers and pinfish, which then get eaten by species ranging from stripers to snook. In the ocean, wrecks are colonized by mussels, barnacles, and corals, which also jump-start the food chain. Similarly, barriers between different offshore water masses can have color changes known as "breaks," which often have different concentrations of plankton (as well as temperature changes) in the bodies of water.
The physical cover provided to prey species by structure can play a huge role in attracting fish, but comfort is often a factor, too. Those tree branches provide shade when the sun beams down into the water and makes it uncomfortably hot. Those saltwater structures provide a respite from strong currents, which the fish can rest behind. And comfort explains why structure — as related to fish — can take the temperate form as well. A thermal barrier, known as a thermocline, may have water of an ideal temperature for the fish at one depth, but water that's too hot or too cold for those very same fish just a few feet away. Salinity differences between two masses of water can have a similar effect, as can oxygen levels.
The often-referenced Maslow's Hierarchy of Basic Needs begins with physical survival and denotes five things needed for a human's physical survival: food, drink, shelter, sleep, and oxygen. This explains why you don't often find people living in the middle of the desert, where there's a distinct lack of food, water, and shelter. And don't forget, it's often — and accurately — said that the ocean is like a great desert, with pockets of life like an oasis in the desert.
Intelligent anglers will think of fish and their relationship with structure in exactly the same way as Maslow's Hierarchy relates to people. We can eliminate drink from the list — fish do, after all, live in water — and perhaps substitute "rest" for "sleep" but otherwise the hierarchy rings just as true for our aquatic quarry as it does for humankind. Find an area with structure that provides food, shelter, rest, and sufficient oxygen levels, and you'll likely find fish. Go to an area that has none of the above, and generally speaking, your bait won't get bit.
When it comes to how to best plan your angling efforts at any one type of structure, sweeping statements like those we've been making about structure in general end, and specific details become incredibly important. In the case of that submerged tree, you may need to cast a 3-inch blue-and-white tube jig within inches of those branches if you want to get a bite. When it comes to that wreck, a top-and-bottom rig baited with squid might be the ticket to a bent rod. In every scenario and with every species, while the structure will tell you where you may find fish, it won't necessarily dictate the best way to catch them.
Savvy anglers look at fishing like a puzzle. Put some of the pieces together and you'll catch a fish or two; put them all together and your cooler will be filled to the brim. And while structure alone doesn't complete that puzzle, it's an incredibly important piece. Wrap your head around its role, and you've made a huge step toward becoming a better angler.