Apply hyperstability or hyperdepletion to an abundance index

Modifies an abundance index to exhibit hyperstability (apparent abundance remains high even as true abundance declines) or hyperdepletion (apparent abundance drops faster than true abundance) relative to a reference level. The transformation applied is \(I^* = I_{\rm ref} \cdot (I / I_{\rm ref})^\omega\), where \(\omega < 1\) produces hyperstability and \(\omega > 1\) produces hyperdepletion.

Usage

hyperstability(object, omega = 1, ref = yearMeans(object))

Arguments

object

An FLQuant abundance index to transform.

omega

Numeric scalar; exponent controlling the degree of hyperstability (\(\omega < 1\)) or hyperdepletion (\(\omega > 1\)). Defaults to 1 (no transformation).

ref

Reference level of the index; defaults to the year means of object.

Value

An FLQuant of the same dimensions as object with the hyperstability/hyperdepletion transformation applied.

See also

survey, cpue

Author

The FLR Team