Trophological calendar for salmon in the Okhotsk Sea

Abstract

Feeding habits of salmon are examined on the data from “Trophology” and “Zooplankton” databases for 1988–2023, taking into account calendar dates and spatial localiza tion of the salmon size classes. The dominant zooplankton species and groups in salmon food are defined and their availability in terms of time and depth of habitat is determined. Daily rhythm of salmon feeding is found uniform for all size groups. The areas and time (months) of maximum concentrations of salmon are determined, by size groups, and those ones are considered as the areas and periods of their most active consumption. A trophological calendar is constructed to show where, when, and what type of food is consumed by certain species and size group of salmon. Daily food rations are calculated for all salmon species and size groups. The rations are similar with those in the Bering Sea, with small differences possibly caused by different structure of the plankton communities. The application tables are compiled for operational calculations of total food consumption by size groups of salmon species with a predominant zooplankton prey (pink, chum and sockeye). According to the forecast published at VNIRO website vniro.ru, the salmon catch in the Far Eastern basin will decrease by more than 2 times in 2024, primarily due to pink salmon. In this case, significant reduction in salmon pressure on plankton community can be expected.

Keywords

• okhotsk sea
• database “trophology”
• salmon
• pink salmon
• chum salmon
• sockeye salmon
• zooplankton
• stomach feeling
• daily food ration
• daily rhythm
• gastric fullness index (gfi)