meanLengthCommunity: Calculates the Mean Length of the Community weighted by...
In marindicators: Marine Ecosystem and Fishing Pressure Indicators

Description Usage Arguments Details Value Author(s) References Examples

This function calculates the Mean Length of the Community weighted by biomass or abundance for j areas and i years.

1	meanLengthCommunity(X_length, metric, years)

`X_length`	A dataframe of fishery independent data derived from research vessel survey data or model output, with columns `YEAR`, `ID`, `SPECIES`, `LENGTH`, and `BIOMASS`. `YEAR` indicates the year the observation was recorded, `ID` is an area code indicating where the observation was recorded, and `SPECIES` is a numeric code indicating the species sampled. `LENGTH` is the length class (cm) and `BIOMASS` is the corresponding abundance at length (stratified and corrected for catchability as required). Species for which there are no length data should be assigned `LENGTH = -99`. These observations are removed by the function.
`metric`	A character string indicating which column in `X` to use to calculate indicator.
`years`	A vector of years for which to calculate indicator.

MeanLength = Σ(Length_m * metric_i)/Σ metric_j

where Length_m is the length (cm) of an individual in size class m, metric_i is the biomass or abundance of species i and metric_j is the total biomass or abundance of the community (Shin et al., 2010).

Returns a dataframe with 3 columns. ID, YEAR, and MeanLength_metric.

If there is no data for spatial scale j in year i, indicator value is assigned NA.

Danielle Dempsey Danielle.Dempsey@dfo-mpo.gc.ca, Adam Cook, Catalina Gomez, Alida Bundy

Bundy A, Gomez C, Cook AM. 2017. Guidance framework for the selection and evaluation of ecological indicators. Can. Tech. Rep. Fish. Aquat. Sci. 3232: xii + 212 p.

Shin, YJ, Shannon LJ, Bundy A, Coll M, Aydin K, Bez N, Blanchard JL, Borges, MF, Diallo I, Diaz E, Heymans JJ, Hill L, Johannesen E, Jouffre D, Kifani S, Labrosse P, Link JS, Mackinson S, Masski H, Möllmann C, Neira S, Ojaveer H, Abdallahi KM, Perry I, Thiao D, Yemane D, and Cury PM. 2010. Using indicators for evaluating, comparing and communicating the ecological status of exploited marine ecosystems. Part 2: Setting the scene. ICES Journal of Marine Science, 67: 692-716

data(X_length)
# Weighted by abundance
meanLengthCommunity(X_length, metric = "ABUNDANCE", years = c(2014:2019))
# Weighted by biomass
meanLengthCommunity(X_length, metric = "BIOMASS", years = c(2014:2019))