Application of the extractable lipofuscin aging method to estimate mortality and population dynamics of the burrowing shrimp, Neotrypaea californiensis

Authors: BOSLEY, KATELYN - Oregon State University; WAINWRIGHT, THOMAS - National Marine Fish Services; Dumbauld, Brett

Submitted to: Estuarine, Coastal and Shelf Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/18/2019
Publication Date: 4/5/2019
Citation: Bosley, K.M., Wainwright, T., Dumbauld, B.R. 2019. Application of the extractable lipofuscin aging method to estimate mortality and population dynamics of the burrowing shrimp, Neotrypaea californiensis. Estuarine, Coastal and Shelf Science. 219:33-44. https://doi.org/10.1016/j.ecss.2019.01.015.
DOI: https://doi.org/10.1016/j.ecss.2019.01.015

Interpretive Summary: A lack of robust techniques for determining the age of crustaceans has inhibited the use of age-structured population models for these animals. Instead these models are often based on body size measurements, but size groups cannot be distinguished for older animals and differences in growth rates can bias parameter estimates in these models. In this study an ageing method based on accumulation of the pigment lipofuscin in the neural system which has been shown to be more robust for the burrowing ghost shrimp, Neotrypaea californiensis was combined with analysis of change in age frequency over time to estimate mortality rate and model population dynamics of this shrimp. These shrimp are important members of the estuarine community and are also economically important pests of oyster production along the US West Coast. Randomized surveys were conducted from 2011-2014 to estimate population abundance, average density, and age structure of shrimp in Yaquina Bay, Oregon. Mortality rate was estimated to be 0.719 yr-1 (95% CI; 0.633-0.793 yr-1) and did not vary significantly across cohorts. The spatial extent of the survey revealed spatial patterns in shrimp density that could be explained by variation in mortality and recruitment of small shrimp in to the population. This is the first study to apply lipofuscin ageing to estimate population parameters of a crustacean and the methods presented should inform managers seeking to incorporate population ecology into management plans for N. californiensis and other crustacean species worldwide.

Technical Abstract: Lack of robust aging methods for crustaceans has inhibited the use of age-structured population models. Individuals are often classified based on body size, but differences in growth can bias parameter estimates. Our study applied the lipofuscin aging method combined with catch-curve analysis to estimate mortality rate for the burrowing shrimp, Neotrypaea californiensis. This species is an important member of the estuarine community with an impact on oyster production along the US West Coast. Randomized surveys were conducted from 2011-2014 to estimate population abundance, average density, and age structure in Yaquina Bay, Oregon. Mortality rate was estimated to be 0.719 yr-1 (95% CI; 0.633-0.793 yr-1) and did not vary significantly across cohorts. The spatial extent of the survey revealed spatial patterns in shrimp density that could be explained by variation in mortality and recruitment rates. This is the first study to apply lipofuscin aging to estimate population parameters of a crustacean and the methods we present can inform managers seeking to incorporate population ecology into management plans for N. californiensis and other crustacean species worldwide.