Evol Ecol Res 20: 523-535 (2019)     Full PDF if your library subscribes.

Fluctuating age distributions and sex ratio tracking in a protandrous shrimp

Eric L. Charnov1,2 & Scott D. Groth3

1Department of Biology, University of New Mexico, Albuquerque, New Mexico, USA
2School of Biological Sciences, University of Utah, Salt Lake City, Utah, USA
3Oregon Department of Fish and Wildlife, Charleston, Oregon, USA

Correspondence: Eric Charnov email: rlc@unm.edu; Scott Groth email: scott.d.groth@state.or.us


Question: Do recent sampling data (2001–2019) of the protandrous marine shrimp Pandalus jordani show that population sex ratios track population fluctuations [predicted by ESS (evolutionarily stable strategy) theory] as was shown for previous decades (1960s–2000)?

Methods: Oregon Department of Fish and Wildlife biologists sampled the commercial catch to estimate age distribution and sex ratio during each fall breeding period from 2001 through 2019. ESS modelling predicts sex ratio for each of the two breeding-age groups, first and second breeders. Geometric mean regression is used to fit the lines.

Conclusions: The sex ratios tracked population fluctuations during 2001–2019, just as in the previous decades. The theoretical predictions of adaptive (ESS) sex ratios are still strongly supported. The total data sets now cover ~ 50 years and the three locations studied span the entire Oregon coast.

Keywords: ESS, long­term data sets, Pandalid shrimp, recruitment variation, sex­change

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