Juvenile geoduck (Panopea generosa) predator protection with tubes: Assessing effects of tube diameter, length, and mesh size on growth and survivorship

Abstract

Intertidal culture of the Pacific geoduck clam (Panopea generosa) involves planting juveniles in the sediment in tubes covered with mesh for predator protection. We examined the interactive effects of tube diameter (10.2 and 15.2 cm), tube length (25.4 and 30.5 cm), and mesh size (6 and 12 mm) on percent shell-length increase, percent wet-weight increase, and percent survivorship of cultured juvenile geoducks (mean shell length ± SD = 29.6 ± 4.8 mm) over 12 months. Percent increase in shell length and wet weight were both significantly affected by the main effects of tube diameter and mesh size, as well as the interaction between the two factors. Shell length was also significantly affected by the main effect of tube length. Geoducks were significantly shorter and lighter in the 10-cm/6-mm (diameter/mesh) treatment than in the 10-cm/12-mm, 15-cm/6-mm, and 15-cm/12-mm treatments. The 25-cm-long tubes were associated with significantly longer (but not heavier) individuals than the 30-cm ones. Average survivorship (±SE) ranged from 38.3 ± 7.1% to 55.0 ± 6.5% (mean ± SD: 47.7 ± 2.5%) in the eight treatments and was not significantly affected by any main effects or interaction terms. The results have implications for commercial intertidal geoduck culture in British Columbia (Canada) and Washington (USA) where clams are protected with solid plastic tubes. Keywords: Geoduck clam, Intertidal culture, Panopea generosa, Predator protection, Tubes