A Novel Index of the Performance of Mytilus galloprovincialis to Improve Commercial Exploitation in Aquaculture

17 pages, 7 figures, 5 tables.-- This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY)Estuarine environments are highly heterogeneous habitats where numerous organisms interact with each other. Aquaculture systems encompass such interactions, and the eventual yields depend on how the cultivated species respond to the environmental heterogeneity. Marine mussels are calcifying organisms that rely on calcium carbonate shell and byssus filaments secreted during their lifetime to protect soft vital tissues against aggressive (abiotic and biotic) environments. Nevertheless, these protective structures can be energetically costly, depending on the environment, thus affecting the energy allocation patterns in the organism. Consequently, other important fitness parameters for the aquaculture industry, such as soft tissue condition and market value, may also be affected. Here, we present a spatial and temporal analysis of the protective and soft tissues responses in the mussel Mytilus galloprovincialis with the aim of obtaining a better understanding of the inter-location variability in individual’s performance and the corresponding main environmental drivers. Local environment with regard to food availability and hydrodynamics impact very distinctly mussel tenacity and shell thickening, e.g., higher-energy environments at the outer exposed zones caused individuals secreted stronger byssus and thicker shells. By contrast, the state of soft tissues (condition index) was similar between very distinct and distant outer exposed and inner sheltered zones due to differences in both environmental drivers. A novel, intuitive ecological index that measures the impact of both protective and soft tissues was developed and is discussed in relation to cultivation timing. The data presented provides the basis for understanding the natural variability in energetic requirements for different vital tissues in bivalve mollusk that support survival and growth. We report the scientific basis for management actions aimed to shortening the cultivation cycle in the aquaculture sector. These actions are based on the combined use of the PROFIT index and other aquaculture practices (e.g., modifying density). PROFIT helps to identify when the quality of the product, understood as PROtection and FITness strategies, would be best suited for the marketThis study was funded by the Spanish Government through the Ministerio de Economía y Competitividad through European FEDER funds (projects Ref. AGL-2013-45945-R, CTM2016-76146-C3-2-R/CTM2016-76146-C3-1-R)Peer reviewe