| schnabel {fishmethods} | R Documentation |
Population Size Estimates from Repeated Mark-Recapture Experiments
Description
Estimates of population abundance from Schnabel (1938) and Schumacher and Eschmeyer (1943) are calculated from repeated mark-recapture experiments following Krebs (1989).
Usage
schnabel(catch = NULL, recaps = NULL, newmarks = NULL,
alpha = 0.05)
Arguments
catch |
A vector containing the number of animal caught in each mark-recapture experiment. |
recaps |
A vector containing the number of animal recaptured in each mark-recapture experiment. |
newmarks |
A vector containing the newly marked animals in each mark-recapture experiment. |
alpha |
the alpha level for confidence intervals. Default = 0.05 |
Details
All computations follow Krebs (1989: p. 30-34). For the Schnabel method, the poisson distribution is used to set confidence intervals if the sum of all recaptures is <50,and the t distribution is used if the sum of all recaptures is >=50. For the Schumacher-Eschmeyer method, the t distribution is used to set confidence intervals.
Value
Dataframe containing the population estimates for the Schnabel and Schumacher & Eschmeyer methods (N), the inverse standard errors (invSE), lower (LCI) and upper (UCI) confidence intervals, and the type of distribution used to set confidence intervals (CI Distribution).
Author(s)
Gary A. Nelson, Massachusetts Division of Marine Fisheries gary.nelson@mass.gov
References
Krebs, C. J. 1989. Ecological Methodologies. Harper and Row, New York, NY. 654 p.
Examples
data(Gerking)
schnabel(catch=Gerking$C,recaps=Gerking$R, newmarks=Gerking$nM,
alpha=0.10)