How to Estimate Exploitation With Baranov Catch Equation

Clarify your variables. This is central. Many of them, such as total fish population, are estimates. In fact, the only variable that is not an estimate is total catch, or ̶0;C̶1; as written in the equation. In general, these will only be used in fisheries, rather than oceans, where an educated estimate is easier.

Write out the equation. In the simplest terms, it is C = F*N. ̶0;F̶1; here is the general fishing deaths given the total population. ̶0;N̶1; is the survival rate. ̶0;N̶1; in this equation often has a bar over it. This bar means that you are averaging the survival rate over a period of time, say five years. This might give a more accurate picture.

Estimate your variables. In a small fish hatchery, this might not be too hard. Fishing deaths and the total catch are easy. The survival rate is not. "N(bar)" is very difficult to estimate in larger fisheries and lakes. In essence, you are taking away the normal average catch in a specific year (exploitation) and estimates of deaths from other causes such as old age and nonhuman predators.

Estimate "N(bar)" with special care. "N(bar)" is a complex of several variables and can be written with the equation (F*N*A)/Z. "A" is the total number of deaths in a specific time frame, and "Z" is the annual rate of total mortality.

Use the basic C = F*N equation. Sine you are trying to estimate exploitation, or "F," you know the values for "C" and "N(bar)." For the sake of simplicity, use an easy example. The values are 15 = 3*F. It is then a simple matter of solving it. Remove the "F" from the equation and divide both sides of the equals sign by 3. The value of "F" (exploitation) is 5.

Interpret your results. Five is your exploitation estimate, because the average survival rate -- N(bar) -- is always an estimated figure, and an average of an estimate over time. What 5 means here is that, given the simple numbers used, the average fishing deaths in a specific season is 5. In a small hatchery, it's probably an accurate figure. Exploitation can then be used to estimate total mortality given estimates on the survival rate of fish. Biologists studying a certain lake, for example, have fairly accurate estimates of total population and deaths from nonfishing causes. When abstracting out the 5, biologists can now get a better figure for total population, deaths and conditional deaths. Figuring out "F" over time will give an even more accurate figure, since you are not relying on one year.