fishmethods (version 1.12-1)

mature: Estimation of proportion mature at age when immature fish are unavailable

Description

Calculates proportion mature-at-age based on Maki et al. (2001).

Usage

mature(cap_age=NULL, mature_age=NULL, age_all_immature=NULL,
age_all_mature=NULL, initial=NULL, nrandoms=1000)

Value

a list object containing the estimated proportions-at-age and standard errors, the original data and expected values

Arguments

cap_age

vector of ages representing age when fish was capture. One record per individual.

mature_age

vector of ages representing age at which individual mature.One record per individual.

age_all_immature

age at which all fish are deemed immature. All ages below this age are assumed immature also.

age_all_mature

age at which all fish are deemed mature. All ages above this age are also assumed mature.

initial

starting values for proportion estimates. There should be age_all_mature - age_all_immature-2 values. If not, the last value is used for missing values or if the vector is too large, the vector is truncated.

nrandoms

the number of randomizations used to estimate standard errors.

Author

Gary A. Nelson, Massachusetts Division of Marine Fisheries

Details

Estimation of probability follows Maki et al. (2001).The standard errors of parameters are estimated via Monte Carlos methods where the number of each maturing age for each capture age are randomly draw from a multinomial distribution parameterized with probabilities and total sample size of the original data. The methods of Maki et al. (2001) are applied to the randomized data and the randomization is repeated nrandoms times. The mean and standard deviation of all runs are treated as the parameter estimates and standard errors.

References

Maki, K. L., J. M. Hoenig and J. E. Olney. 2001. Estimating proportion mature at age when immature fish are unavailable for study, with applications to American shad in the York River, Virginia. North Am. J. Fish. Manage. 21: 703-716.

Examples

  if (FALSE) {
   ## Maki data for 3 years combined
   data(maki)
    mature(cap_age=maki$capture_age,mature_age=maki$age_mature,age_all_immature=2,
                 age_all_mature=8,initial=c(0.1,0.05,0.05,0.05),nrandoms=1000)
  }