Abstract

Primary production in water bodies corresponds to their fish production capacity. Aquaculture planning for water resources is conducted based on specific geographical conditions and their internal and external factors. Understanding the fish production capacity of lakes enables predictions for exploitation (fishing) and restoration of reserves. This research aims to estimate the primary production of the Salman Farsi Reservoir, Fars Province, on the Ghare Aghaj River, to evaluate fish production capacity and plan aquaculture development. Sampling was conducted to measure dissolved oxygen, water temperature, pH, conductivity, transparency, total phosphorus, total nitrogen, and chlorophyll-a in three transversal sections along the side, surface, and deep areas of the open water, with three repetitions in four seasons during 2023 – 2024. Trophic conditions were estimated using Trophic Status Index (TSI) models. Total production of the lake was calculated using the Brämick-Lemke and Koeschel models, while fish production was calculated using the Brämick-Lemke and Downing models. The annual average of dissolved oxygen, transparency, electrical conductivity, pH, total phosphorus, total nitrogen, and chlorophyll-a concentration in the lake was 8.2 ppm, 4.1 meters, 1387 μS/cm, 8.3, 0.174 ppm, 4.50 ppm, and 1.38 ppm, respectively. The average TSI based on transparency, phosphorus, chlorophyll-a, and Carlson’s index was 40, 78, 33, and 50. The initial production size in the lake was estimated 292 gC.m-²y-1. Fish production capacity was calculated based on primary production at 39 Kg.ha-1.y-1 and based on phosphorus at 33 Kg.ha-1.y-1, with an average of 36 Kg.ha-1.y-1. Considering the 2000-hectare livable area for fish in the lake, the total fish production this year was estimated at 71.8 tons. Under current lake conditions, the allowable fishing size was estimated to be 7 to 11 tons of fish per year. Determining the production capacity and trophic level can help maximize exploitation while minimizing ecological impacts and potential risks associated with restocking and fishing, such as the introduction of excessive juvenile fish into the lake.

Keywords: Primary production, Chlorophyll, Total phosphorus, Fish production, Fars Province