Predator and prey relationships are not just something you see when the lion is chasing the gazelle on Animal Planet or National Geographic. They are all across the landscape. In fact, predator and prey relationships impact our fishing every time we are on the water. Today, we’ll discuss the dynamics of predator/prey relationships and how they impact our fishing.
When you say the word “predator” to an angler, they’ll often think of species like northern pike, muskie, lake trout, walleye and probably bass as well. However, they aren’t the only predators in the water. In fact, yellow perch, bluegill and crappie are all predators as well. All species of fish are predators. To understand this, let’s breakdown how the food chain works in the standard Midwest lake.
Understanding the Food Chain
Phytoplankton sit at the bottom of the food chain. These microscopic organisms drift on their own and rely on sunlight to produce their own food for themselves via photosynthesis. Zooplankton are slightly larger invertebrates that feed on these phytoplankton. These zooplankton play a major role in the lives of all fish species.
Whether we are talking walleye, yellow perch, largemouth and smallmouth bass, and even northern pike and muskie, zooplankton are a critical part of their diet when they are still in the fry stage. As these fish grow, their diets will continue to change, but early on in their lives these zooplankton are critical.
As fish grow larger, their diet will begin to shift to larger invertebrates, called macroinvertebrates. These are the “aquatic bugs” we are used to referring to, especially when we are talking ice fishing in the Dakotas. Depending on the species, their diet may also begin to incorporate minnows, fry and other juvenile aquatic life.
Once they reach adult sizes, this is when the stereotypical predator/prey relationships we often discuss will begin to take hold. However, it’s very important we acknowledge how they got to these sizes. Every fish species mentioned, even the zooplankton, were or are a predator to something smaller than them. The zooplankton ate the phytoplankton. The fry ate the zooplankton. Then diets began to shift to larger aquatic bugs, minnows and more as their life cycle continues. All of these relationships involved an organism being a predator to another.
How These Relationships Impact Angling
Now, let’s focus on how this impacts angling. obviously, regardless of what species they are targeting, anglers are looking to catch adult fish. many of these species targeted are piscivorous, meaning they eat other fish. However, the same small aquatic bugs stated above can still be an important part of a fish’s diet. Other species such as frogs, salamanders, and other juvenile aquatic organisms can all be part of a fish’s diet as well.
The specific relationships are going to vary based on the aquatic community within each lake. Generally, walleye and yellow perch will have a predator/prey relationship. Largemouth bass and bluegill are one of the most famous predator/prey relationships in the fisheries world. When you’re trying to use these relationships to your advantage, you need to consider all aspects involved.
Example: Walleye and Yellow Perch
For our example, let’s take a look at a fishery that features a strong walleye and yellow perch fishery. The walleye are generally going to be keying on those small perch. These small perch they are keying on will often be a predator to aquatic bugs. This means to find the walleye, you need to find where the bugs are. Why is that?
At first look, it seems that the walleye have the most control of these situations. This isn’t the case though. In fact, predators are at the mercy of their prey. The predators must follow the prey where they go, because if they are not near the prey they will have nothing to eat! In this particular situation, the walleye are looking for the perch are looking for the bugs.
Let’s say this lake features mud flats that are full of aquatic bugs. You can expect the perch are going to be out on these flats, rooting around in the mud to find these bugs. The walleye will also be on these flats, because they’re looking for perch and will find them out on the mud flats. The lake might feature some spectacular rock structures, but if the prey isn’t there you can’t expect to consistently find good numbers of walleye on these rock features.
Now we have to take in the specifics of the species involved. Yellow perch are light feeders, they see very well and are active when light levels are high. Walleyes’ eyes are accustomed to low light feeding, including featuring a tapetum lucidum, the organ in the eye that captures available light and allows the walleyes to use it to their advantage. This is why the evening bite may be spectacular, because the walleye are using their low light advantage on perch.
Use Your Resources to your Advantage
With so many factors that go into predator/prey relationships, let’s take a look at some of the key pieces of information you can use to your advantage to understand what kind of dynamics are going on in the lake you are fishing.
Yellow perch are a perfect example of this. The yellow perch of the Dakotas are known for their small mouths, but brick like body and shoulders. Why do these fish have such small mouths in comparison to their bodies? The main food source of these fish are small, aquatic bugs. These tiny, high protein snack packs do not need a large mouth to effectively feed on them. Because of this, the perch bodies grow large, but their mouth does not have to.
By contrast, yellow perch that may be feeding on minnows, shiners or other fish species will need larger mouths so they can capture and effectively feed on this food source. A small perch may have a larger mouth than the mouth of a trophy caliber fish feeding on aquatic bugs.
You can learn a lot about the fish in the vicinity just by looking at your flasher screen. Often times, small perch, bluegill and other species may be found all over you screen, but not taking your bait. However, when these marks disappear, it could mean a larger species that may prey on them is in the area.
Many people get frustrated when they are only finding these small fish, but this may not be a bad thing. Often times, larger fish waiting to feed are often not far away.
You can often quite easily find lake survey reports on many of the lakes you are looking to fish. The South Dakota Fisheries Report Viewer is an excellent place for anglers looking to fish South Dakota to start. You can get a sense of what type of predator/prey relationships will be going on just by looking at this report, long before you get to the lake.
If you see an abundance of small perch in the survey, you can expect this is what walleyes will be keying on. The same can be said for bluegill and largemouth bass. Now, keep in mind what type of gear is being used for these surveys. An abundance of small fish may be able to swim in and out of a larger meshed net, that would capture a larger adult species. Though they should not be considered gospel, reading and understanding these reports can really help you have a successful day on the water.
Successful Predators Make for Tough Fishing
While a large population of small fish can mean happy predators, this means the predators are very well fed. Walleye that have been gorging on an abundance of small perch often don’t need to feed regularly. This means the angler really has to catch these fish at the right time.
The argument could be made that you would want to fish away from where the prey is, but this isn’t necessarily true. If the predators can’t find prey, they continue to search until they find it. Once they have found it, they often will be keeping close tabs on it. Yes, a fish away from the primary prey source may be hungry, but it won’t be sticking around long.
Once you’ve found where the prey are, you’ll find the greatest concentration of predators. The more of the species you’re targeting, the higher the chances are you can get one or several to bite. Find the lowest relevant element of the food chain and you’ll often be able to work your way up to the species you are targeting.
Don’t fall into the belief that northern pike, lake trout or other large fish are the only predators in the water. At a certain level, even zooplankton is a predator. Whether you’re fishing for walleye, northern pike or even bluegill and perch don’t be afraid to treat them like a predator. Fish aggressively, play the cat-and-mouse game and treat every fish as a critter looking to eat another critter for their own survival. In reality, it’s how every fish in the water survives. Good fishing!