Energy density empirical predictor models for three coastal crab species in the southwestern atlantic ocean

Abstract

Energy density was measured for key intertidal and subtidal crab species in the Southwestern Atlantic Ocean. Empirical models were developed to link energy density to water content (expressed as dry weight) and the fit to data was compared between different taxonomic and gender aggregations. Predictive power of models with different levels of aggregation and the effect of using a model of a surrogate species or group were also evaluated. Neohelice granulate (Dana, 1851) (3728 J/g wet weight) contained the highest energy density followed by Cyrtograpsus angulatus Rathbun, 1914 (3334 J/g wet weight), and C. altimanus Dana, 1851 (3042 J/g wet weight). Females (3645 J/g wet weight) showed higher energy density compared to males (3074 J/g wet weight). Dry weight of whole individuals provided good energy density predictions, with low predictive power when using species or same genus models (6.4-9.6% for the median error). Predictive power improved when more specific levels of taxonomic aggregation were employed. Interestingly, the two congeneric Cyrtograpsus did not differ in their energy density predictor model, suggesting a unique model could be used for this genus. This paper provides valuable inputs for bioenergetic modeling in coastal ecosystems in the Southwestern Atlantic.