Climate change and decadal shifts in the phenology of larval fishes in the California Current ecosystem

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 30; pp. E4065 - E4074
• Main Author: Asch, Rebecca G
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 28.07.2015; National Acad Sciences
• Series: PNAS Plus
• Subjects: Animals; Biological Sciences; California; California Current; Climate Change; Climate change models; Climate models; Climate variability; Correlation analysis; Databases, Factual; Ecosystem; Ecosystems; El Nino; El Nino-Southern Oscillation; Fish; fish larvae; fisheries; Fishes - embryology; Fishes - physiology; Geography; global change biology; global warming; Habitats; hatcheries; Intergovernmental Panel on Climate Change; larvae; Models, Theoretical; Nonnative species; Normal Distribution; Ocean currents; Ordination; Pacific Ocean; Phenology; Physical Sciences; Pisces; PNAS Plus; Sea surface temperature; Seasons; Southern Oscillation; Spawning; Species Specificity; Surface water; Temperature; terrestrial ecosystems; Upwelling; upwelling ecosystem; zooplankton; Pacific Ocean; California; United States > US; INE, Pacific, California Current; INE, USA, California; IN, North Pacific, North Pacific Gyre; California Current; global change biology; fish larvae; upwelling ecosystem; phenology
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1421946112

In terrestrial ecosystems, earlier phenology (i.e., seasonal timing) is a hallmark organismal response to global warming. Less is known about marine phenological responses to climate change, especially in Eastern Boundary Current Upwelling (EBCU) ecosystems that generate >20% of fish catch. The phenology of 43 EBCU fish species was examined over 58 years; 39% of phenological events occurred earlier in recent decades, with faster changes than many terrestrial ecosystems. Zooplankton did not shift their phenology synchronously with most fishes. Fishes that aren’t changing their phenology synchronously with zooplankton may be subject to mismatches with prey, potentially leading to reduced recruitment to fisheries. Adjusting the timing of seasonal management tactics (e.g., fishery closures, hatchery releases) may help ensure that management remains effective. Climate change has prompted an earlier arrival of spring in numerous ecosystems. It is uncertain whether such changes are occurring in Eastern Boundary Current Upwelling ecosystems, because these regions are subject to natural decadal climate variability, and regional climate models predict seasonal delays in upwelling. To answer this question, the phenology of 43 species of larval fishes was investigated between 1951 and 2008 off southern California. Ordination of the fish community showed earlier phenological progression in more recent years. Thirty-nine percent of seasonal peaks in larval abundance occurred earlier in the year, whereas 18% were delayed. The species whose phenology became earlier were characterized by an offshore, pelagic distribution, whereas species with delayed phenology were more likely to reside in coastal, demersal habitats. Phenological changes were more closely associated with a trend toward earlier warming of surface waters rather than decadal climate cycles, such as the Pacific Decadal Oscillation and North Pacific Gyre Oscillation. Species with long-term advances and delays in phenology reacted similarly to warming at the interannual time scale as demonstrated by responses to the El Niño Southern Oscillation. The trend toward earlier spawning was correlated with changes in sea surface temperature (SST) and mesozooplankton displacement volume, but not coastal upwelling. SST and upwelling were correlated with delays in fish phenology. For species with 20th century advances in phenology, future projections indicate that current trends will continue unabated. The fate of species with delayed phenology is less clear due to differences between Intergovernmental Panel on Climate Change models in projected upwelling trends.