Calculate the Ryther index

The Ryther index is composed of total catch presented on a unit area basis for an ecosystem. Theoretical estimates (Link & Watson, 2019), imply the index "should probably be on the order of 0.3 - 1.1 mt km^-2 y^-1 with an extreme limit of 3 mt km^-2 y^-1. Empirically derived tipping points typically occur in fished ecosystems with total catches greater that 3 to 5 mt km^-2 y^-1 with expected system-wide MSYs on the order of 1 to 3 mt km^-2 y^-1"

calc_ryther_index(catch, area, yearField = "YEAR", catchField = "totLand")

Arguments

catch	Data frame. n x anything. Data containing the total catch in each year. Can be broken down by species. catch must be in metric tonnes
area	Numeric scalar. Area of the region (km^2) in which catch comes from.
yearField	Character string. The name of the field in catch which contains the Yearly data.
catchField	Character string. The name of the field in catch which contains the catch data.

Value

Data frame:

YEAR

Year of the index

INDEX

Value of the index

Details

The units of the index: metric tonnes km^-2 year^-1

Sources

J. S. Link, R. A. Watson, Global ecosystem overfishing: Clear delineation within real limits to production. Sci. Adv. 5, eaav0474 (2019). DOI: 10.1126/sciadv.aav0474

See also

Other Link Indices: calc_fogarty_index()