UC San Diego

Richly productive polar marine ecosystems are hypothesized to have evolved within the last ~30 million years through the rise of diatoms to ecological dominance and diversification of distinctive polar fish, sea birds, seals and whales. Today, short diatom-based food chains support substantial fish biomass, but whether polar fish production is high enough to sustain current industrial fishing is unknown. To this end, we compared ichthyolith accumulation rates (IAR), a proxy for fish production, across ocean ecosystems to trace the development of global fisheries stocks over the past 1.8 million years. We find that the magnitude of polar fish production, based on the flux of fish teeth to deep-sea sediments, is an order of magnitude lower than seen in subtropical and tropical sites. We suggest that polar fish production is systematically suppressed by extreme seasonality, phenological mismatch, low functional redundancy, and extreme glacial-interglacial climatic variability in the high latitude oceans. Comparisons of our Pleistocene data to similar records from the Eocene and Oligocene oceans (~42-28 Ma) show that fish production in high latitudes has been consistently low for the last 30-40 Ma relative to most of the tropical and subtropical locations. We conclude that the stock crashes observed in the polar regions over the past several decades reflect overexploitation of ecosystems that have had low fish production for tens of millions of years.