Lab Exam 2 Flashcards
Frequently used to estimate fish, aquatic inverts, and occasionally small mammal populations
delury method (removal sampling)
Estimates derived are of number present at the beginning of study
Delury method (removal sampling)
This method can be used only when uniform capture efforts are possible
Delury Method (removal sampling)
what does the DeLury or Removal method rely on?
- successive removal of members of a population
- the catch per unit effort (Ct) decreasing linearly as the total catch (Kt) increases
- should be a negative linear correlation between catch per unit effort and cumulative catch
Assumptions for removal method
- a constant proportion of N is captured with each unit of effort
- catchability stays the same during the sampling period
- the population is closed
- the investigator’s removal of animals is the only major source of mortality in the population during the entire study
Ct
(catch/unit effort) (y)
Kt
(Cumulative catch) (x)
takes advantage of the fact that as a population of finite size is harvested, the number of animals captured per unit effort in successive attempts will decrease in proportion to the number of animals previously harvested
delury’s method (removal)
examines the potential relationship between two variables in nature - the dependent variable and the independent variable
regression analysis
if one wants to see if there is any relationship between catch per unit effort and cumulative catch (after a series of catch attempts)
regression analysis
catch/unit effort
dependent variable
cumulative catch
independent variable
the mathematical equation for a straight line
Y = bX - a
Y
dependent variable
X
independent variable
b
slope of the line
a
Y-intercept (value of Y when X=0)
the value of the slope (b) may be positive, which represents a ________ between two variables
positive correlation
when the slope is negative
there is a negative relationship between the dependent and independent variables
uniquely defined by its y-intercept (a) and its slope (b)
regression line
such a line may be fitted through existing data points showing the strength of the relationship between the dependent and independent variables
regression line
SP
sum of the cross products of the deviations of X and Y from their means
SSx
Sum of the squares of the X (independent) data points
Y-intercept =
mean of y data - slope (mean x data)
this method is more applicable to game populations in which one sex is being exclusively removed
Ratio/Dichotomy Method
relies on being able to recognize distinct subgroups within the population
Lincoln-Peterson index and Ratio/Dichotomy Method
Reliance is generally on natural vs. artificial recognition features
ratio/dichotomy method