Distribution, growth and recruitment of Actinia equina (Cnidaria, Anthozoa) in the Cantabric Sea: crevices vs. rock pools.

A comparative study of size distribution, growth and spring recruitment in a population of the intertidal sea anemone Actinia equina dwelling in crevices and rock pools was undertaken using photogrammetric methods. Two adjacent sites in the littoral area of Sopelana (43º 23´N, 2º 59´ W in Biscay, Spain) characterized by a well represented intertidal rocky area (loamy limestone) and located at similar zonation level (tidal exposure ranging from 12 to 16 hr/day) were selected: A long crevice (4640 mm length) and a succession of shallow rock pools (4500 mm length) on a rocky platform separated by a distance of 200 m. Actinia equina appeared well represented at both sites (75 to 130 for the crevice and the rock pool at the beginning of the experiment) including mainly red and green morphs, brownish specimen occurring occasionally. These two sites were monitored in 7 occasions between February 10th and August 17th 2015 (7 sampling episodes) and physical parameters (luminosity, air and water temperature and humidity) were also recorded. Additionally a group of 20 specimens was taken to the laboratory to perform biometrical and growth determinations and evaluating individual offspring production. Simultaneous determinations of live weight (mg) and pedal area (mm2) obtained from picture examination (Image-J) in the laboratory specimens allowed scaling biomass to biometric parameters to analyze field images.

M.Mercedes Ortega & Marta Barrenetxea
Book of Abstracts of the XV International Symposium on Oceanography of the Bay of Biscay. ISOBAY15
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Servicio editorial Universidad del País Vasco
Bilbao (Spain)