Size structure and reproduction of Gefidium robusturn (Rhodophyta) in the central part of the Baja California peninsula, Mexico

The size structure and reproduction of Gelidium robustum were studied at Punta San Hipólito at 6 m depth, and at Isla Natividad at 8 and I5 m depth. Both sites are located on the Pacific coast of Baja California Sur, Mexico. Vegetative reproduction was greater, but average frond size was smaller at the two shallow sites than at 15 m. The degree of reproduction by sporophytes was directly related to frond size and occurred year-round. Tetrasporic fronds outnumbered carposporic ones. Carposporic fronds were less abundant at 15 m depth than at 6 and 8 m, and were shorter, on average, than tetrasporic fronds at all sites. The minimum reproductive size was also smaller for carposporic fronds than for tetrasporic fronds. The minimum reproductive size of tetrasporic fronds was smaller at Punta San Hipolito (7.4 cm), followed by Isla Natividad 8-m fronds (16.5 cm) and Isla Natividad 15-m fronds (22.8 cm). It is thought that maintaining the rhizoidal part of a plant with the associated juvenile fronds (less than IO cm in length) is very important for the recovery of a bed after harvesting.