Few methods:

1. Probit Analysis: Probit analysis is a statistical method used to estimate the length at first maturity based on the proportion of mature individuals at different length intervals. It fits a probit regression model to the data and estimates the length at which 50% of individuals are mature (P50). The R package `drc` provides functions for conducting probit analysis, such as `drm()`.

2. Logistic Regression: Logistic regression is another statistical approach used to estimate the length at first maturity. It models the probability of maturity as a function of fish length using a logistic function. The R function `glm()` can be used to fit a logistic regression model to the data.

3. LFA (Length Frequency Analysis): LFA is a graphical method that estimates the length at first maturity based on the length-frequency distribution of a fish population. It involves plotting the proportion of mature individuals against fish length and estimating the length at which 50% of individuals are mature. The R package `FSA` provides functions like `LFA()` for conducting length frequency analysis.

Simple R code:

Certainly! Here's an example R script using the probit analysis method to estimate the length at first maturity in fishes:

```R

# Load required packages

library(drc)

# Example data

length_data

Estimating the length at first maturity in fishes often involves fitting growth models to length-at-age data and identifying the length at which a certain proportion of individuals become mature. Several advanced methods can be used for this purpose. One commonly used approach is the use of von Bertalanffy growth models and the estimation of the length at 50% maturity (L50). Here's a basic example using R with simulated data:

RCopy code# Install and load necessary libraries install.packages("grofit") library(grofit) # Simulate length-at-age data set.seed(123) age

It's not my field, but there are a few R package specific for fisheries that may help. fishmethods, FSA, FLR . Also the book Introductory Fisheries Analyses with R by Derek Ogle.

Thank you Dr Sal,

Can you send me the book link please.

Thank you very much for your information.

The website for the IFAR book is here: https://derekogle.com/IFAR/ . It has some materials there.

There's also the fishR site ( https://fishr-core-team.github.io/fishR/ ), that has links to additional books, R packages, and related materials.

Many thanks all of your help.

I got very crucial links.