Green Algae Control Lake Management

PSD and Relative Weight

Record keeping is essential to maintaining a healthy and balanced pond. Below you will find an interactive table that helps you calculate PSD and Relative Weights. These are tools that professional biologists use to evaluate a lake or pond.
PSD or Proportional Stock Density is the measure of fish in a certain size category as compared to a different size category.  In order to use PSD you must first breakdown your largemouth bass into three distinct size groups. Bass that range in size from 8-12" will be referred to as Stock, 12-15" Quality and 15"+ as Preferred (categories Memorable and Trophy are also used but have been excluded for now). PSD represents the percentage of bass over 12" with the exclusion of bass under 8". A healthly pond will have a PSD of around 40-70. While PSD includes Bass in the Quality and Preferred size ranges RSD or Relative Stock Density keys only on one group. RSD of Preferred fish is included in our charts below, RSD of Preferred fish should be 10-20. Catch Per Unit Effort is also used to determine trends in fisheries. This is simply the number of fish captured for each unit of effort. For most of us this will be fish per Angler/hour or the number of fish captured for each hour that each angler fished. In the fisheries industry this could be fish per Electrofishing/hour and that data should not be compared to fish per Angler/hour.
    The last portion of this chart is Relative Weight. Standard weights have be determined for Largemouth Bass based on their length in inches. The Relative weight is Actual weight divided by Standard weight and is expressed as a percentage. A healthy fishery will have relative weights of 90 upto 120%. This is a simple yet effective method of evaluating the health of a fishery.
The key to using this tool sucessfully is good record keeping combined with as many data points as possible. Management decisions should never be made based upon a single fishing trip or a single set of data points. The more data entered the more accurate your results will be. This Feature is being replaced by DataBass.