Parks Victoria Standard Operating Procedure

Parks Victoria Technical Series No. 9Subtidal Reef Monitoring SOP5.2 LOCATION OF SAMPLING SITEThe central position of sampling sites is located with differential GPS to maintain accuracy of± 5 m. The position is marked with a weighted buoy line and the boat is anchored nearby.Where large diving support vessels are used, such as at Wilsons Promontory, a small tenderwith portable GPS is launched prior to the dive and used to position the marker buoy. Allcoordinates are recorded using the Australian Geodetic Datum 1994.The accuracy of the current GPS system varies (albeit infrequently) according to theconfiguration and the operational limitations of satellites. Sites that can only be locatedaccurately with the GPS are not sampled on days when the GPS is unreliable. Many sitesare positioned immediately adjacent to distinctive natural features (such as underwaterbombies or rocky outcrops on the shoreline). These features are used to accurately positionthe marker when the use of the GPS system is inappropriate.5.3 UNDERWATER VISUAL CENSUS PROCEDURE1. Divers gear-up on the boat, methods and transects are assigned to each observer andthe direction of the first transect section (T1) is clarified;2. Two divers descend to the marker weight with the transect reels, clip the ends off andswim off in opposite directions along the same isobath, unreeling the 100 m transect linesas they go. The divers swim above the kelp canopy (where present), navigating using adepth gauge, compass and familiar underwater features. Care is taken to ensure thetransect line will be at the desired depth once it settles beneath the kelp canopy;3. The resulting 200 m of transect line (with the marker in the centre) is divided into four50 m contiguous sections, labelled T1 (i.e. Transect 1), T2, T3 and T4 (Figure 5.1). Thetransect line is numbered every metre (colour coded for each 10 m section), has a leadweight every 5 m and two lead weights at 50 m. The direction of T1 is fixed, being thesame for each survey at each site. The direction of T1 to T4 is in a clockwise directionaround the coast (i.e. generally from east to west);4. To minimise diver disturbance, fish surveys are always completed first, and divermovements are organised so that no diver moves through an area being surveyed byanother diver;5. Once the transect line is set, the two outer divers commence the fish census (Method 1,described below) of T1 and T4;6. If there are only two divers, they then survey fish on T2 and T3 (Figure 5.2);7. If there are three or four divers, they descend down the marker line once the transect isset (5-7 min) and commence the fish census of T2 and/or T3 (Figure 5.3);15