Fossil fish otoliths reveal how ocean warming has affected fish populations

The Biodiversity Research Center and Institute of Oceanography at National Taiwan University conducted a study linking ocean temperatures to intermediate-depth fish populations. Their research, titled “Ocean temperature drove changes in the mesopelagic fish community at the edge of the Pacific Warm Pool over the past 460,000 years,” was published in Science Advances. By analyzing well-preserved fish otoliths found in sediment cores, they reconstructed the history of mesopelagic ocean ecosystems.

The findings suggest that anthropogenic ocean warming could lead to marine ecosystem degradation, affecting mesopelagic fish populations. These fish reside at depths between 650 and 3,300 feet and play a crucial role in linking surface and deep-ocean ecosystems through diurnal vertical migration.

Over the past 460,000 years, fish production and diversity have been influenced by temperature changes. The study revealed that even small temperature shifts of about 1.5° to 2.0°C can negatively impact diversity. Warm interglacial periods experienced significant declines in both production and diversity, with peak warmth being the primary cause.

The fluctuations in fish production and diversity over glacial-interglacial timescales correlated with temperature gradients, highlighting the importance of temperature in shaping these patterns. Interestingly, the study observed a consistent decrease in fish population and an increase in species diversity over the past four glacial cycles. However, the reasons behind this observation remain unclear.

The research provides vital ecological data for fishery management and highlights the potential impacts of anthropogenic ocean warming on marine ecosystems. It’s essential to consider that the fluctuations in temperature observed in the study occurred over tens of thousands of years, unlike the rapid rate at which anthropogenic warming is taking place today.

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