Understanding the relationships between hydrodynamics and the spawning activities of small pelagic fishes is crucial for understanding their recruitment dynamics and for fisheries management. Here, we clarify the effects of marine environmental factors and the associated hydrodynamic processes on the spawning activities of the Japanese anchovy Engraulis japonicus in the coastal Yellow Sea using data from in situ ichthyoplankton surveys (7 recent years), a hydrodynamic model and satellite remote sensing. We confirmed the peak spawning period (May and June) and primary spawning location (Haizhou Bay). We defined the ‘spawning temperature optima’ hypothesis to identify the optimal spawning temperature (13.0–18.0°C) for the Japanese anchovy based on egg occurrence and abundance. We detected fortnightly variation in spawning behaviour, which peaked after the spring tide. Anchovy eggs showed evident aggregation in the nearshore upwelling area during May and June, while strong upwelling in July may cause a negative spawning‐site choice in upwelling zone. These findings clarify the effects of hydrodynamics on the spawning behaviour of the Japanese anchovy in the coastal Yellow Sea.

Japanese Spanish mackerel Scomberomorus niphonius and Japanese anchovy Engraulis japonicus are typical predator and prey species, respectively, with high commercial values in the China seas. However, the interspecific interaction, particularly the relationship between the two species during early life stages, is unclear. Here, based on ichthyoplankton surveys in the coastal Yellow Sea during 2013–2018, we analyzed the relationship between the two species based on egg occurrence and abundance in the context of species interaction. Spawning optimal temperature were examined for anchovy (13.0–18.0°C) and mackerel (15.0–20.0°C) based on egg occurrences and abundances in relation to sea surface temperature. We confirmed the peak spawning periods (May and June) and primary spawning areas (Haizhou Bay) for both mackerel and anchovy based on spatiotemporal distributions of two species eggs. Mackerel showed a high spawning overlap with anchovy, and anchovy egg abundance were also higher in overlap areas. Anchovy egg abundance may be more important for mackerel spawning than environmental variables, suggesting the significance of prey for predators during early recruitment. The temperature also has important effects on mackerel spawning and could be a threshold affecting mackerel spawning activity. Mackerel might have evolved a spawning strategy of short‐term spawning timed to coincide with the peak spawning of anchovy in the coastal Yellow Sea. These results highlight the effects of interspecific relationships on spawning strategy of anchovy and mackerel in the coastal Yellow Sea and may provide some insights for early recruitment studies of piscivorous fishes in the context of the match–mismatch hypothesis.