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Marine Ecology Progress Series

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MEPS 666:135-148 (2021)  -  DOI:

Exposing changing phenology of fish larvae by modeling climate effects on temporal early life-stage shifts

Benjamin Weigel1,*, Jussi Mäkinen1,2,3, Meri Kallasvuo4, Jarno Vanhatalo1,5

1Research Centre for Ecological Change, Organismal and Evolutionary Biology Research Programme, Faculty of Biological and Environmental Sciences, University of Helsinki, PO Box 65, Helsinki 00014, Finland
2Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA
3Center for Biodiversity and Global Change, Yale University, New Haven, CT 06520, USA
4Natural Resources Institute Finland (Luke), PO Box 2, Helsinki 00791, Finland
5Department of Mathematics and Statistics, Faculty of Science, University of Helsinki, PO Box 64, Helsinki 00014, Finland
*Corresponding author:

ABSTRACT: Changing environmental conditions are influencing the seasonal timing in life history events of organisms. Such shifts in phenology are often linked to increasing temperatures that stimulate faster developments or earlier arrivals. This phenomenon has been demonstrated in terrestrial and aquatic realms, but data and knowledge are limited on how early life stages of fish are affected over long-term and broad environmental scales. Here, we analyze 2 decades (1974-1996) of size class-specific Baltic herring Clupea harengus membras L. larval data along the whole coast of Finland to expose shifts in phenology linked to changes in environmental covariates. We use a novel Bayesian hierarchical spatio-temporal hurdle model that describes larval occurrence and abundance with separate processes. Abundances are modeled with the Ricker population growth model that enables us to predict size-specific larvae groups in relation to the environment while accounting for population density dependence. We quantify shifts in phenology at multiple life stages, based on first appearances of smallest larvae (<10 mm) and by detection of higher proportions of larger larvae (>15 mm) appearing earlier than they have done historically. Our results show a strong signal in shifting phenology of the larvae toward an earlier development of 7.7 d per decade. Increasing temperature had a positive effect on the earlier development of larger larvae. Additionally, we highlight that the survival of larvae becomes more density dependent as their size increases. Our modeling framework can reveal phenological shifts of early life stages in relation to environmental change for survey data that do not necessarily cover the onset of reproduction.

KEY WORDS: Baltic Sea · Phenology · Climate change · Clupea harengus membras · Ricker model · Hurdle model · Spatio-temporal modeling · Hierarchical modeling of species communities · HMSC

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Cite this article as: Weigel B, Mäkinen J, Kallasvuo M, Vanhatalo J (2021) Exposing changing phenology of fish larvae by modeling climate effects on temporal early life-stage shifts. Mar Ecol Prog Ser 666:135-148.

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