Seasonal niche overlap and shifts: Implications for coexisting Larimichthys species in the East China Sea

Abstract

The large yellow croaker (Larimichthys crocea), a critically endangered marine fish of high economic value in China, suffered severe wild population declines in the 1980s due to overfishing and habitat degradation. Since 2000, habitat protection and large-scale restocking programs have sought to recover this ecologically important species. However, these efforts face ecological challenges, as L. crocea shares habitat and environmental preferences (temperature, salinity, depth) with its sister species, the small yellow croaker (Larimichthys polyactis), raising concerns about interspecific competition. This study quantified their climatic niche overlap using principal component analysis and generalized boosting models, integrating occurrence records and key environmental variables (temperature, salinity, depth, mixed layer thickness) across seasons. Results revealed significant niche overlap, with Schoener’s D values ranging from 0.55 (summer) to 0.66 (winter), indicating heightened competition risks during overwintering periods. L. polyactis exhibited broader niche breadth and greater salinity adaptability, whereas L. crocea displayed niche conservatism, relying on stable coastal habitats (40–70 m depths). Seasonal drivers differed: mixed layer thickness shaped summer distributions, while temperature and sea surface height dominated winter patterns. Overlap zones (4.73 % of the study area) concentrated in Zhejiang’s coastal waters, coinciding with key fishing grounds. Vertical stratification and dietary differences likely reduced direct competition, but L. crocea’s narrow niche breadth increases its vulnerability to environmental change. This study advocates for spatially explicit management, including decreased seasonal fishing effort in high-overlap zones and prioritizing restocking in non-overlapping areas. These findings advance understanding of niche-mediated coexistence in marine ecosystems and provide science-based strategies to balance species recovery with sustainable fisheries.