Research on the primary production required (PPR) supporting China’s freshwater aquaculture system—from the perspective of producing edible crude protein

• China’s freshwater aquaculture PPR surged 59.35% from 2003 to 2023. • PPR per unit edible protein rose 32.65%, indicating efficiency decline. • 2023 PPR was 262.54% of China’s freshwater NPP, a huge ecological deficit. • Shift towards high-trophic species like bass and crayfish drove PPR up. • Policy must prioritize low-PPR species for sustainable blue transformation. As the world’s largest producer, China’s aquaculture plays a pivotal role in global aquatic food systems. The primary production required (PPR) metric is crucial for evaluating the ecological efficiency of protein production. This study presents the first comprehensive account of PPR for China’s freshwater aquaculture animals (FAA) from 2003 to 2023, focusing on edible crude protein (ECP) output. We introduced two novel efficiency parameters: PPR per unit wet weight and, more importantly, PPR per unit ECP. Results reveal a 59.35 % surge in total PPR, reaching 1.432 × 10 8 t-C in 2023. Strikingly, this PPR represented 262.54 % of the net primary production (NPP) of all Chinese lakes, reservoirs, and ponds, indicating a massive ’ecological deficit’. Nationally, it accounted for 4.475 % of terrestrial NPP, and globally, for 0.235 % of combined agricultural and marine NPP. Concurrently, the PPR intensity per ECP unit grew by 32.65 % (1.55 % annually), signaling a decline in ecological efficiency driven by a shift towards high-trophic species (e.g., bass, crayfish). Despite this, China’s FAA systems maintained a lower mean trophic level (3.13) than global wild fisheries (4.12), highlighting a comparative efficiency within the PPR framework. Our findings underscore that China’s aquaculture growth is increasingly reliant on external feed inputs, displacing environmental pressure onto global ecosystems. The study provides critical insights and strategic pathways for China’s blue transformation, emphasizing the need to prioritize low-PPR/ECP species for sustainable development.