What Is CPUE? Understanding Fishery Data

As anglers it’s helpful to understand a little about fisheries biology, especially when interpreting stocking, netting, and catch data on the lakes we fish. One of the most significant terms you’ll encounter is CPUE, or Catch Per Unit Effort.

In a nutshell, Catch Per Unit Effort (CPUE) refers to the relative measurement of the abundance of a target fish species. Total fish caught in a survey are divided by the number of nets, total net length, or other indication of effort.  Lots of fish caught with little effort expended leads to high CPUE numbers. Changes in the CPUE are inferred to signify changes to the target species’ true abundance. A decreasing CPUE can indicate population decline due to a number of culprits, from overfishing to baitfish crashes. An unchanging CPUE can indicate sustainable harvesting, and a high CPUE demonstrates large species abundance.

How CPUE Works in Fisheries Data

CPUE data is valuable to fisheries biologists because it does not interfere with routine harvesting operations, and data are easily collected. The data are also easy to analyze, even for non-biologists, in contrast to other methods. Catch refers to the number of fish caught by gill nets, traps, surveying anglers, or conducting creel surveys. It provides all great insight into the sheer abundance of species population on a certain lake. 

Why CPUE Matters for Anglers

CPUE is valuable to anglers; it gives a good idea of sheer species abundance of all sizes and is easily compared to other lakes in the same class. It can point to lakes that are ideal habitat for large population growth and have ideal conditions to foster good fishing—at least catching a lot of fish, but probably of all different sizes, often on the smaller side. 

Therefore, a lake with high CPUE is a good target to catch lots of fish, which might make it an ideal candidate if the weather on other nearby lakes isn’t as favorable or if there are water temperature issues and seasonal trends happening that make fishing more difficult elsewhere. 

CPUE data also helps anglers find those lakes where there’s obviously a balance between human fishing activity and conservation efforts and management seems to be going well – ultimately, what results in a day catching lots of fish compared to other water bodies. 

“CPUE is one of the best indicators that an angler can use to identify what species may be in relative abundance on a lake. Generally speaking, high is high and low is low. A higher CPUE means quite simply more fish being caught with less net or survey effort, meaning there’s a high number of that species in that lake to target for fishermen,” says onX’s Joel Nelson.

Things To Keep In Mind

Things to keep in mind include that when looking for overall fish abundance, CPUE is the best comparison. For example, high CPUE lakes, especially those with the designation “outlier” in onX Fish, simply have more fish of selected species in them than other lakes of similar classification. 

However, low CPUE lakes for individual species can still mean they’re good trophy lakes. For example, the best big bluegill lakes don’t typically have a large abundance of the species, yet do have disproportionately larger amounts of shifted size distribution toward truly big fish. This is something to keep in mind with all species. 

Using CPUE With onX Fish

If you’re an angler who simply wants to catch lots of fish, onX Fish has listed very simply “low,” “average,” and “above average” designations via the Species Abundance Insights feature as a slider bar on the CPUE scale. Lakes listed as “above average” or “outlier” can be places to really key in on in terms of finding vast numbers of that specific species to really enjoy a day of fishing. 

The other thing the onX Fish user can do is compare CPUE for a certain lake to other lakes in its class. If you look at the CPUE slider bar and how the pointer is represented to the blue bar, it shows how the CPUE of that individual lake compares to other lakes of a similar class. 

Ultimately, onX Fish provides CPUE-based data for smarter fishing. Unique to any fishing apps available today, onX gives anglers like you the power to leverage historical and current insights with the most current state fisheries data available—all in one place—for better fishing!