Optimal Harvesting in Stream Networks: Maximizing Biomass and Yield

TL;DR

This paper develops a model to determine optimal harvesting strategies in stream networks, balancing biomass and yield, and characterizes strategies for small and large growth rate regimes.

Contribution

It introduces a metapopulation model framework for stream networks and characterizes optimal harvesting strategies for both small and large growth rate scenarios.

Findings

Optimal strategies depend on growth rates and network connectivity.

A single strategy can maximize both biomass and yield when growth exceeds a threshold.

For large growth rates, strategies focus on patches with specific competition and flow characteristics.

Abstract

In this study, we develop a metapopulation model framework to identify optimal harvesting strategies for a population in a stream network. We consider two distinct optimization objectives: maximization of total biomass and maximization of total yield, under the constraint of a fixed total harvesting effort. We examine in detail the special case of a two-patch network and fully characterize the optimal strategies for each objective. We show that when the population growth rate exceeds a critical threshold, a single harvesting strategy can simultaneously maximize both objectives. For general $n$-patch networks with homogeneous growth rates across patches, we focus on the regime of large growth rates and demonstrate that the optimal harvesting strategy selects patches according to their intraspecific competition rates and an effective net flow metric determined by network connectivity parameters.