marindicators (version 1.0.0)

CVBiomass: Calculates the Coefficient of Variation of the Biomass

Description

This function calculates the Coefficient of Variation of the Biomass for \(j\) areas and \(i\) years.

Usage

CVBiomass(X, wind = 5, negative = FALSE, years)

Arguments

X

A dataframe of fishery independent data derived from research vessel survey data or model output, with columns YEAR, ID, and BIOMASS. YEAR indicates the year the observation was recorded, ID is an area code indicating where the observation was recorded, and BIOMASS is the total recorded biomass (stratified and corrected for catchability as required). (Note: if X has an additional SPECIES column, the function will automatically calculate the total biomass).

wind

Window for the moving average. The first and last floor(wind/2) values of the indicator are assigned NA to account for the moving average. Default is wind = 5 years.

negative

If negative = TRUE, the indicator will be multiplied by -1 so that the expected response is to decrease with increasing fishing pressure. Default is negative = FALSE.

years

A vector of years for which to calculate indicator.

Value

Returns a dataframe with three columns: ID, YEAR, and CVBiomass.

The first and last floor(wind/2) values of the indicator are assigned NA to account for the moving average. If there is no data for spatial scale \(j\) in year \(i\), indicator value is assigned NA.

Details

The Coefficient of Variation of the Biomass (CVBiomass) was estimated as an n-year moving average (Blanchard and Boucher, 2001):

CVBiomass = sd(total biomass for the past n years)/mean(total biomass for the past n years)

References

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.

Blanchard F, Boucher J (2001) Temporal variability of total biomass in harvested communities of demersal fishes. Fisheries Research. 49. 283<U+2013>293. 10.1016/S0165-7836(00)00203-4.

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, M<U+00F6>llmann C, Neira S, Ojaveer H, Ould Mohammed Abdallahi ., 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

See Also

Other stability and resistance indicators: IVILandings, allStability, biomassPerTL, meanMaxAge, meanMaxLength

Examples

# NOT RUN {
data(X)
CVBiomass(X, wind = 5, negative = TRUE, years = c(2014:2019))
# }