Spatial distribution and seasonal variation in Undaria pinnatifida ...

3.2. Seasonal monitoring of Undaria populationsTo investigate the phenology of Undaria populations in the Hauraki Gulf monitoring sites were set up in June 2011 onmussel farms in the Coromandel Harbour (Figure 2) and on the pontoons at Westhaven Marina in Auckland (Figure 3).Due to the different nature of these habitats the sampling methods used varied between these sites.3.2.1. Coromandel monitoringThe monitoring site within Coromandel Harbour is located on two adjacent mussel farms (Figure 2). Mussels grown at thissite are on the lines for approximately nine to twelve months, until mussels reach a size of 95-100mm when they areprocessed. After harvesting the floats are cleaned before re-deploying them – and they usually go back to the same site(Peter James, pers comm., 11/7/2011). Monitoring consists of boat based snorkelling along mussel lines. At both of thedesignated mussel farms, two mussel lines were chosen at random for inspection in June 2011. These lines weresurveyed each month until the mussels were harvested. The harvesting process removes Undaria from the floats. So,when lines surveyed the previous month have been harvested, surveillance shifts to the nearest parallel lines with musselspresent. Inspection occurs along the first ten mussel floats along the four designated mussel lines. All Undaria present onthe mussel floats is counted and measured. Measurements are taken of the total length of the plants and the length andwidth of the reproductive tissue at the base of the plant, the sporophyll (if present). The submerged area of the float isapproximately 1m by 1.2m. Consequently, densities are expressed on a mˉ2 basis. Data from both sites will be combinedin this report. Representative photographs of Undaria are taken at each visit.Figure 2: Coromandel Harbour monitoring sites8