Effects of environmental factors on the abundances of the basket stars Astrocaneum spinosum and Astrodictyum panamense (Ophiuroidea: Gorgonocephalidae) in the northern Gulf of California, Mexico

Abstract

ABSTRACTGorgonocephalid ophiuroids, or basket stars, reside in diverse ecosystems of all oceans, but there is limited information on their basic ecology worldwide; therefore, this study provides the first detailed numerical analysis published to date of the abundances and spatial distributions of gorgonocephalids from the eastern Pacific Ocean. We analysed the relevance of geography (latitude, longitude), oceanographic factors (temperature, chlorophyll a concentration) and bottom type (coral, rock, sand, fleshy algae, coralline algae and turf) on the abundances of Astrocaneum spinosum and Astrodictyum panamense in Los Angeles Bay, Mexico (29°N, 113°W), in 2006–2007. Depth did not influence the number of individuals per census, but an elevated chlorophyll a concentration resulted in a higher abundance during the autumn (possibly the reproductive season of Astrodictyum panamense and Astrocaneum spinosum). The abundances of both species were positively linked to the presence of rocky bottoms and decreased in sandy areas. Additionally, the presence of live coral favoured the occurrence of Astrodictyum panamense, while high macroalgal cover decreased its abundance. The spatial distributions of both ophiuroids were aggregated at most sites, and they were always associated with different species of octocorals, which are abundant in the area. Astrocaneum spinosum is considered among the 30 most important invertebrates in the aquarium trade in Mexico; therefore, its permanence in the study area could be affected by excessive extractions.