Spatial patterns in the population structure of the whelk Stramonita haemastoma (Linnaeus, 1766) in an Atlantic oceanic Archipelago: comparison with continental areas

The goal of this study was to determine the consistency of the vertical distribution patterns of the predatory whelk, Stramonita haemastoma, in the rocky intertidal zone of the Canarian Archipelago (eastern Atlantic) across a hierarchy of five orders of magnitude of horizontal spatial variability (from tens of m to hundreds of km). In general, this species showed a consistent vertical zonation pattern across islands, with the majority of the specimens (74.65%) found in the mid intertidal zone. This result most likely reflects the whelk’s preference for a habitat with a large amount of potential prey but minimal stress induced by swells and desiccation. The mean abundance (0 to 1.73 ± 0.40 ind m-2, mean ± SE) and size structure (7 to 45 mm in shell length) of S. haemastoma in the Canarian Archipelago was considerably lower compared to those from continental areas in the Atlantic Ocean, which suggests that there are some differences between these populations. Natural mechanisms (e.g. isolation or poor recruitment events) and human perturbations (e.g. exploitation of intertidal resources) might influence the spatial distribution patterns