Recursos Marinos y Pesquerías

II International Symposium in Marine Science, Vigo-Spain. 27-30 April 2009

24/04/09 ,

G. Cambiè, P. Pita, D. Fernández Márquez & R. Muiño (2009). Preliminary results on Sargassum muticum (Phaeophyta) distribution in the Marine Reserve of Fishing Interest “Lira-Os Miñarzos” (Galicia, NW Spain)

Abstract: In Spain, the invasion of S. muticum has been documented in different studies, but its presence in many segment of the coastline is still doubtful. Consequently, the principal aim of our study was to describe the degree of S. muticum in the Marine Reserve of Fishing Interest “Lira-Os Miñarzos” (Galicia, NW Spain). This region is the first protected area for fishing interest instituted along the Iberian Atlantic coast. A regimen of partial or total protection from fishing can determine a different incursion level of S. muticum in the reserve.In this paper, we present preliminary results from surveys in the Lira-Os Miñarzos area from March 2008 to November 2008. To begin with, the general distribution of the invasive brown seaweed was visually detected by SCUBA diving, covering the entire rockery coastline of the Marine Reserve with Torpedo Underwater Scooter.The second aim of our study was to identify the level of the seaweed distribution in four different areas: Unprotected Zone (UZ), outside the Marine Reserve; Marine Reserve (MR) with restrictions on the number of fishing boats; Marine Reserve “Forcados” (MRf), with the same protection level of MR but less waves-exposed; and Integral Reserve (IR), with total fishing prohibition. In the above four areas were then carried out twenty-eight transects (seven for each season) over two different depth ranges (1-4 m, 4-11 m), to assess the variability of density and length of the S. muticum plants with season and zone. Temporal and spatial changes in density and length were tested by two-ways ANOVA. The statistical analysis highlighted significant variation in mean density of seaweed between the MR and the others three areas, and a significant inter-seasonal change in plants length was identified. The impact of colonizing S. muticum on the indigenous algal community was then estimated from variation in species diversity, by using the species accumulation curves and the multidimensional scaling plot. These preliminary data will be compared with subsequent data obtained in future surveys.