2 Attachment(s)
Arkansas Crappie Assessments
I finally rounded up most of the crappie assessment scores. Some biologists are still working up their 2013 data and this is not included (sorry). This is a long post but that was needed to fully explain the proccess. Thanks for your interest!
TheAGFC crappie assessment is ran on data obtained from trap net samples. One thing to remember is that trap net efficiency is different from lake to lake. In orderfor trap nets to sample efficiently the bathymetry of the lake needs to be right. A lake that only has steep sided banks or is very large (and deep) do not sample as well as lakes with gently sloping banks and are more shallow. Trap nets only effectively sample water that is 6 foot or less (where the net is placed). A fish will just swim over the lead line on a trap net set in deeper water. This is a confounding factor that can contribute to lower scores in some of these lakes. So keep that in mind when looking at these scores. This is why we (AGFC)do not really use trap nets to evaluate crappie populations in the mountainous Corps reservoirs.
The AGFC crappie assessment is based on 5 metrics: density, growth rate, age structure,size structure, and recruitment. Here are some definitions that are needed to interpret this assessment.
YOY= young of year (a fish that was born that spring)
Net night = the unit of measurement used to standard effort
Good Growth = the mean length of a 2.5 year old crappie is greater than 10-in
Poor Growth = the mean length of a 2.5 year old crappie is less than 8-in
Good Density = 20 or more crappie that are at least 1.5 years old per net night
Poor Density = less than 20 crappie that are at least 1.5 years old per net night
Density
Densityis the number of crappie (excluding YOY) per net night. The density goal for a lake with good grow this 20 or more crappie per net night (excluding YOY). The density goal for a lake with poor grow this 10 to 30 crappie per net night (excluding YOY).
Growth Rate
Growthrate is calculated as the mean length of crappie that are 2.5 years old. The goal for this metric is 9-in or more for a lake with good crappie density. Thegoal for this metric is 9 to 10-in for a lake with poor crappie density.
Age Structure
Age structure is the percent of 3 year old crappie and older in the population(excluding YOY) per net night. The goal for this metric is 15 to 25% for a lake with good growth and 15 to 19% for a lake with poor growth.
Size Structure
Size structure is the percent of crappie in the population greater than 10-in (excludingYOY) per net night. The goal for this assessment is 30 to 59% of the population being 10-in or greater for a lake with good density and 40 to 49% for a lake with poor density.
Recruitment
Recruitmentis calculated as the number of YOY crappie into the population, or the density of crappie less than a year old per net night. The goal for this metric is 4 to 29 crappie per net night for a lake with good growth and 10 to 19 crappie per net night for a lake with poor growth. However, trap nets do not sample this size crappie as effectively as larger crappie (size selective gear). So the abundance collected in the nets does not represent the true production of a lake. It is an underestimated.
Crappie Assessment Score
These five metrics are scored and weighted and a cumulative score is calculated. This score ranges from 0 to 100, with 100 being a perfect score. The following form is used for this calculation.
Attachment 147905
Based on this evaluation, here are all of the past year results that I could get my hands on.
Attachment 147906
As usual, feel free to ask me any questions. I will do my best to answer them. Thanks and Enjoy!
Matt
