Quick Start Guide: Size Limit Builder

Here we’ll walk through the basic steps to get started creating size limit options with the Size Limit Builder. As a reminder a minimum size limit sets the minimum size fish must be before they are allowed to be harvested. The Size Limit Builder can help users to evaluate tradeoffs between sustainability and catch associated with different size limit options. Let’s get started!

1. Create an account

First, you’ll need to either log in or create an account with https://natureanalytics.ca/FishKit/.

2. Select inputs

Once you’re into the app, on the left hand side navigate to the “Input” section and select “Life history”.

3. Preview life histories

Here you can browse through all the available life histories available in the public repository. Once you find the life history you’d like to use, select it in the table, and then click the preview button below to view the life history.

4. Activate life histories

 When you scroll down, you should then see a window containing a summary of the life history as well as the parameters themselves. Once you’ve decided that you would like to “Activate” the life history and make it available for analysis, click the “Activate” button. After doing so, you should see a blue checkmark appear indicating that the life history is now ready for use. 

Along the top of the screen you should also see the option to create a new life history, to submit information you’ve gathered on a species of interest. This option requires that you have well documented information on the species life history as well as an intermediate understanding of fish biology. Instructions on creating a life history will be documented and posted separately on our resources page.

5. Navigate to the Size Limit Builder

Now that you have activated a life history, you can return to the navigation bar on the left hand size of your screen, and select “Size limit builder” in the Analysis section. 

Here you should see that the life history you selected is automatically displayed, with the title on the top of the screen and selected in the dropdown menu in the far right box. 

The orange slider and button indicate the size limit automatically selected, which is set just above the length at 50% maturity. Above are two dials representing the “Sustainability score” and “Catch score” associated with this size limit.

Screenshot of Size Limit Builder

The “Sustainability score” represents the population’s ability to replenish itself on a scale of 0-100%, and is also known as Spawning Potential Ratio (SPR). Optimal values for this metric vary for different species, but under sustainable harvest, values ranging from 20%-40% are generally expected. 

The “Catch score” represents the relative catch score for the entire fishery on a scale of 0-100%. This metric is also known as Yield-per-recruit (YPR). A value of 100% represents the theoretical maximum sustainable yield for the population, while a score above 80% could be considered a pretty good yield.

6. Retain size limit options

As you move the orange slider you can view different size limits and their respective scores. Once you’ve landed on a score that you’d like to retain, click on the orange “Retain option” button to save that size limit option. Once you’ve retained an option, you can scroll down to see it displayed on the graph below. 

You can repeat this process for as many species and size limits as you like, while the app retains your progress.

7. Document your progress

Once you’re satisfied with your session or ready to close out of the app, visit the upper right hand corner of the screen and click “Create report” to export a PDF detailing your session. You can continue to explore life histories, size limit options, and create as many reports as you like. 

You can repeat this process for as many species and size limits as you like, while the app retains your progress.

That concludes the overview of the Size Limit Explorer’s basic functionality! Please visit our resources page for more helpful information and tutorials.