Wedge clam (Donax trunculus Linnaeus, 1758) reproduction: reproductive traits and environmental influence in the NW Iberian coast and contrast across Atlantic and Mediterranean waters

Abstract

Production of wedge clam (Donax trunculus) has experienced a widespread decrease. Environmental conditions have been postulated as an important agent though the effects on reproduction are poorly understood. We here review the reproductive cycle and evaluate the influence of environmental conditions in Galicia (NW Iberian coast). We further contrast the variability of reproductive traits across the distribution range. Reproductive individuals dominate size classes between 20 and 30\xa0mm, and spawning spans from April to July with a subsequent inactive period from September onwards. Length at first maturity (L50) was established at 19\xa0mm. Oocyte size was unrelated to shell size or gonad occupancy, and realized fecundity averaged 8\u2009×\u2009105 eggs per female. Environmental conditions had significant effects on the gonadosomatic index and flesh yield which were lower in less productive waters. Furthermore, the interannual proportion of fully mature individuals during the spawning period maximized at high and low levels of coastal upwelling and continental runoff, respectively. Across the distribution range, water temperature and chlorophyll concentration defined the geographical differences on reproductive traits with lower L50 and longer spawning period occurring in warmer waters and the central month of spawning taking place earlier in the year in more productive waters.