Calculate the equilibrium Beverton-Holt estimator of instantaneous total mortality (Z) from length data with bootstrapped standard errors or the same using the Ehrhardt and Ault(1992) bias-correction

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`len` |
the vector of length data. Each row represents one record per individual fish. |

`type` |
numeric indicate which estimation method to use. 1 = Beverton-Holt, 2 = Beverton-Holt with bias correction. Default is both, c(1,2). |

`K` |
the growth coefficient from a von Bertalanffy growth model. |

`Linf` |
the L-infinity coefficient from a von Bertalanffy growth model. |

`Lc` |
the length at first capture. |

`La` |
the largest length of the largest size class. |

`nboot` |
the number of bootstrap runs. Default=100. |

The standard Beverton-Holt equilibrium estimator of instantaneous total mortality (Z)
from length data (page 365 in Quinn and Deriso (1999)) is calculated. The mean length
for lengths >=Lc is calculated automatically. Missing data are removed prior to calculation.
Estimates of standard error are made by bootstrapping length data >=Lc using package `boot`

.

Dataframe of length 1 containing mean length>=Lc, sample size>=Lc, Z estimate and standard error.

Gary A. Nelson, Massachusetts Division of Marine Fisheries gary.nelson@state.ma.us

Ehrhardt, N. M. and J. S. Ault. 1992. Analysis of two length-based mortality models applied to bounded catch length frequencies. Trans. Am. Fish. Soc. 121:115-122.

Quinn, T. J. and R. B. Deriso. 1999. Quantitative Fish Dynamics. Oxford University Press, New York, New York. 542 pages.

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