Ecological stoichiometric pattern and biochemical composition analysis of Coilia species

Abstract

Ecological stoichiometry is a scientific discipline that studies the balance of energy and multiple chemical elements in biological systems, and it has been widely applied in fish research. However, there are few studies on fishes with different reproductive modes, such as Coilia, which experience habitat shifts during their life history and serve as important ecological links between marine and freshwater ecosystems. To address this gap, we compared the ecological chemical elements of four Coilia species (C. nasus, C. brachygnathus, C. mystus and C. grayii) to understand their organismal stoichiometry pattern in terms of changes in C, N, and P. The result shows, 1) The C content of Coilia had a wide range and was higher than the general fish, ranging from 40% -70%, while N% and P% were 4%-12% and 0.5%-3%, respectively. 2) Diadromous populations showed wider variations of elemental stoichiometry during migration than non-migration populations, with a higher coefficient of variation of elements and C:N:P than other Coilia species. In particular, the C content of diadromous Coilia nasus was the highest (>60% in the East China Sea) when the fish was ready for spawning migration, while N and P were opposites. Diadromous fish might have evolved a mechanism to store as much lipid as possible in their bodies to meet the energy demand during their long migration journey; 3) There were certain similarities between the biochemical composition and elemental changes. The trends of total fat and C content curves were consistent, with anadromous Coilia nasus storing a large amount of fat before migration to meet their energy needs during long-distance migration. The variation trends of crude protein and N content curve were similar to some degree, with crude protein and total fat having opposite trends, meaning that increased with a decrease in total fat, and vice versa