Long-Term Changes in the Seasonal and Interannual Dynamics of the Abundance of Eggs of Common Pelagophilic Fish Species in the Gdansk Deep of the Baltic Sea

The abundance of eggs of the Baltic cod Gadus morhua Linnaeus, 1758 and the Baltic sprat Sprattus sprattus (Linnaeus, 1758) in the Gdansk Deep of the Baltic Sea was estimated from data for March–August 2015–2022. The estimates were compared with historical data for 1968–1977. In the modern period, the average sprat egg abundance increased one and a half times from 134.7 to 192.6 eggs/m² and the spawning peak shifted to earlier dates, from May–July 1968–1977 to April–June 2015–2022. The average cod egg abundance decreased by half from 16.3 to 8.0 eggs/m² and the spawning shifted to 1 month later, from May–June to June–July, which is apparently related to climate change.