Optimal harvesting of farmed Atlantic salmon at two cohort management strategies and different harvest operation restrictions

Abstract

The main harvest planning problem in commercial fish farms is to determine the best time‐sequence of harvesting different fish cohorts in order to maximize the overall farm profit. Due to both annual and fish‐size variations in market prices, future forecasts of fish growth and size distribution are required to optimize harvest plans. Two management strategies for harvesting size‐structured fish cohorts are considered. The first strategy allows the fish farmer, at any time, to size‐grade, harvest and sell the most profitable fish sizes from the standing stock. The second strategy allows the fish farmer to harvest and sell a fish batch with similar size distribution as that of the standing stock. In this paper, two size‐structured fish growth models have been built to fit the two management strategies. The growth models are integrated in a multiperiod linear programming model that optimizes the harvest outputs for each of the two management strategies. Model outputs demonstrate clearly that it is more profitable to size‐grade fish prior to harvest compared to harvesting a batch of fish with similar size distribution to that of the standing stock. Five different harvest operations constraints have been identified for commercial salmon farming. The decrease in profitability of fish farming is shown for a variety of harvest operation constraints.

Keywords:

• Atlantic salmon
• harvest planning
• linear programming
• mixed‐integer programming
• size‐structured growth models