schnabel: Population Size Estimates from Repeated Mark-Recapture...

In fishmethods: Fishery Science Methods and Models

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 [e-mail]

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)

fishmethods documentation built on April 27, 2023, 9:10 a.m.