Calculate the mean Trophic Level

mean Trophic Level is calculated from a time series of landings: It is the sum of the species Trophic levels #' weighted by their landings #'

calc_mtl_index(catch, speciesTL, speciesCode = "NESPP3")

Arguments

speciesTL

dataframe. m x anything. Species codes and trophic level for the most abundantly caught species. One column must be named NESPP3 and another Troph

speciesCode

Character string. The name of the column that holds the speciesCodes. Default = "NESPP3".

data

dataframe. n x anything. Data containing the total catch by each species in each year. A complete grid of year by species must be passed. Columns must be named YEAR,NESPP3,catch.

Value

Data frame:

YEAR

Year of the index

INDEX

Value of the index