How should fishing mortality be distributed under balanced harvesting?

TL;DR

This paper explores a new method for distributing fishing mortality across trophic levels, showing that proportional to total production better preserves biodiversity and ecological structure than previous approaches.

Contribution

It introduces a quantitative implementation of balanced harvesting based on total production rates, enhancing biodiversity conservation in multi-species fisheries management.

Findings

Proportional to total production better preserves trophic structure.

This method safeguards rare and threatened ecological groups.

It improves biodiversity outcomes in balanced harvesting.

Abstract

Zhou and Smith (2017) investigate different multi-species harvesting scenarios using a simple Holling-Tanner model. Among these scenarios are two methods for implementing balanced harvesting, where fishing is distributed across trophic levels in accordance with their productivity. This note examines the effects of a different quantitative implementation of balanced harvesting, where the fishing mortality rate is proportional to the total production rate of each trophic level. The results show that setting fishing mortality rate to be proportional to total production rate, rather than to productivity per unit biomass, better preserves trophic structure and provides a crucial safeguard for rare and threatened ecological groups. This is a key ingredient of balanced harvesting if it is to meet its objective of preserving biodiversity.