Bomb Radiocarbon

Small pelagics of the Baltic Sea

Funded 2022-2023 - BalticWaters2030.org

Understanding the life histories of small pelagic fishes for knowledge-based management decisions and a healthier 

Baltic Sea environment 


Accurate life history information for fishes of the Baltic Sea (BS) is lacking for numerous key species, including small pelagic fishes like strömming (Clupea harengus) and skarpsill (Sprattus sprattus). Knowing age, vital rates, and lifespan of these fishes is essential for proper understanding of population dynamics and informed management decisions. Inaccurate life history information is a global problem that has led to population depletions, ecosystem shifts, and extirpation of ecologically important species. Baltic strömming are assessed as 70% depleted since 1970s and while skarpsill may be sustainably exploited since 1990s, both may live >20 years. At present, age and growth are validated for only the first few years and it is assumed that otolith age reading is accurate through ontogeny. Hence, we must evaluate the methods used to age these fishes to properly model and manage population age structure and productivity with accurate biological traits.


Figure 1. Plot of bomb-produced radiocarbon (14C) — shown as a change relative to a pre-bomb standard (14C) over time — for the atmosphere (Zone NH1 covering latitudes greater than 40°N; Hua et al. 2021) with other applicable marine and freshwater chronologies. Recent findings for the Baltic Sea (juvenile Baltic cod otoliths) are similar in magnitude to the Arctic lakes of North America (otoliths; Campana et al. 2016) and phase lagged toward more recent years, as shown by an Arctica icelandica shell from the North Sea (Scourse et al. 2012) and the tropical North Atlantic (coral and otoliths; Andrews et al. 2013, 2020). The attenuated signal from the Northwestern Atlantic (otoliths) is a reference for the effects of mixing with deep-water (Campana et al. 2008). The prebomb values for Baltic Sea bivalves indicate the potential effect of radiocarbon-depleted geological sources (karst; Lougheed et al. 2013). Preliminary results for Baltic pike aged 3 and 7 years indicate the post-peak 14C alignment method works to validate age estimates of Baltic fishes.