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length_weight

Source: R/population_dynamics.R
length_weight.Rd

The LENGTH-WEIGHT table presents the a and b values of over 5,000 length-weight relationships of the form W = a x Lb, pertaining to about over 2,000 fish species.

Usage

length_weight(
  species_list = NULL,
  fields = NULL,
  server = c("fishbase", "sealifebase"),
  version = "latest",
  db = NULL,
  ...
)

Arguments

species_list

A vector of scientific names (each element as "genus species"). If empty, a table for all fish will be returned.

fields

subset to these columns. (recommend to omit this and handle manually)

server

Either "fishbase" or "sealifebase".

version

a version string for the database. See available_releases() for details.

db

database connection, now deprecated.

...

additional arguments, currently ignored

Value

a table of length_weight information by species; see details

Details

See references for official documentation. From FishBase.org: Length-weight relationships are important in fisheries science, notably to raise length-frequency samples to total catch, or to estimate biomass from underwater length observations. The units of length and weight in FishBase are centimeter and gram, respectively. Thus when length-weight relationships are not in cm-g, the intercept 'a' is transformed as follows:

a'(cm, g) = a (mm, g)*10^b a'(cm, g) = a (cm, kg)*1000 a'(cm, g) = a (mm, mg)*10^b/1000 a'(cm, g) = a (mm, kg)10^b1000

However, published length-weight relationships are sometimes difficult to use, as they may be based on a length measurement type (e.g., fork length) different from ones length measurements (expressed e.g., as total length). Therefore, to facilitate conversion between length types, an additional LENGTH-LENGTH table, #' presented below, was devised which presents linear regressions or ratios linking length types (e.g., FL vs. TL). We included a calculated field with the weight of a 10 cm fish (which should be in the order of 10 g for normal, fusiform shaped fish), to allow identification of gross errors, given knowledge of the body form of a species.

References

http://www.fishbase.org/manual/english/fishbasethe_length_weight_table.htm

Examples

if (FALSE) { # interactive()
if (FALSE) { # \dontrun{
length_weight("Oreochromis niloticus")
} # }
}