Estructura poblacional, crecimiento y producción de la coquina Donax trunculus en la zona intermareal del litoral of Huelva

Abstract

Population structure, growth and production of the wedge clam Donax trunclus, inhabiting highly exposed sandy beaches of the littoral of Huelva (SW Spain) were investigated between January 2014 and July 2015. Growth rates were estimated comparing two different methods in the intertidal zones of beaches: (i) length-frequency distributions (LFD) analysis in two separated beaches (Doñana and Isla Canela) (ii) internal shell growth bands by thin shell cross sections (TS). For the TS methodology, valves were embedded in methyl-methacrylate, and sequential sections were grounded and polished to a thickness of 80-100 µm. This technique allowed the identification of annual ring depositions and the shell length-age keys were performed. In addition, several deformities (related to environmental stress or damages probably caused by fishing gears) as well as signs or recovery were observed. Both methodologies were equally appropriate to estimate growth of D. trunculus. Von Bertalanffy growth functions were established from LFD and TS using an asymptotic length (L∞) of 44.8 mm and the growth constants (K) of 0.5 (LF) and 0.44 yr-1 (TS). The intertidal biomass of D. trunculus ranged between 3.03-3.31 g ash-free dry mass (AFDW) m-2 yr-1. Individual production revealed the highest value at 27 mm length (0.117 g AFDW m-2 yr-1) and annual production ranged between 3.40 and 4.91g, resulting in renewal rate values (P/B) between 1.03 y 1.61. Differences between beaches in terms of annual production and P/B seem to be partially related to human activities.