calc_ryther_index.RdThe 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")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
Numeric scalar. Area of the region (km^2) in which catch comes from.
Character string. The name of the field in catch which contains the Yearly data.
Character string. The name of the field in catch which contains the catch data.
Data frame:
Year of the index
Value of the index
The units of the index: metric tonnes km^-2 year^-1
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
Other Link Indices:
calc_fogarty_index()