Temporal Changes in the Harvest of the Brown Algae Macrocystis pyrifera (Giant Kelp) along the Mexican Pacific Coast
MARIA MARGARITA CASAS VALDEZ
Elisa Serviere Zaragoza
DANIEL LLUCH BELDA
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"Macrocystis pyrifera (L.) C. Agardh “Sargazo gigante” is distributed along the west coast of Baja California Peninsula, from the border with the USA to Punta Prieta, Baja California Sur. This kelp forms dense submarine prairies that emerge from the sea covering areas of several hectares or square kilometers. Macrocystis has been harvested from Islas Coronado (32° 15´ N) to Bahía del Rosario (30° 30´ N) in 15 beds for 49 years, from 1956 to 2004. It was exported raw for alginate production. Recently, it has been harvested in smaller quantities to obtain extracts to be used as fertilizer (Casas-Valdez et al., 2003). The Macrocystis seaweed was harvested by specially designed ships that cut the algae at a depth about of 1.2 m and then transported it. The ships “El Capitán” harvested from 1956 to 1966 (storage capacity of 300 t) and “El Sargacero” from 1967 to 2004 (storage capacity of 400 t). The ship operations were the same at all beds and did not change over the study period. The biomass and standing crop of Macrocystis was evaluated in summer 1982 and in an annual cycle in 1985-1986 in their natural distribution (Casas-Valdez et al., 1985; Hernández- Carmona et al., 1989a, 1989b, 1991). The recruitment and effect of nutrient availability during the ENSO event of 1997-1998 at the southern limit of distribution of Macrocystis were studied by Lada et al. (1999), Hernández-Carmona et al. (2001) and Edwards & Hernández (2005). The relationship between environmental variables as temperature, upwelling, sea level and wind speed and the catch per unit effort (CPUE) of Macrocystis were analyzed by Casas-Valdez et al. (2003). They found an inverse correlation between temperature and harvest and concluded that temperature is the variable that best explained the variations in the Macrocystis harvest. This is the first time that the temporal variability of harvest, effort, and harvest per unit effort (CPUE) as an indicator of the abundance in each of 15 harvested beds of Macrocystis has been analyzed."
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