Objective: Habitat Verification (HV)
The habitat types and extent/boundary of the watercourses selected for surveying were uploaded onto a hand held Window’s CE PC with GIS software linked to GPS unit and checked against the information on the habitat map prepared for the previous Study. Field data were inputted directly into an electronic database during the survey, and the extent of the natural watercourse was marked and amended in situ. Photographs were taken to show the general condition of the habitat.
Objective: Ecological Value Assessment (EVA)
A general description was made of the survey location. Characteristics surveyed included:
• naturalness of the habitat;
• size of the habitat;
• water quality (ie turbidity, water flow rate);
• nature of the substratum (ie coarseness of particles);
• number and abundance of floral and faunal species groups observed;
• presence of "rare" species (if any);
• presence of known ecologically important areas in its vicinity (if any); and
• degree of disturbance and damage (if any).
Since a highly turbid, stagnant watercourse tends to have a lower ecological value, turbidity and water flow condition of the habitat were noted during the field visits. The nature of the substratum, ie whether it is composed of large pebbles or fine mud, was also described as it may affect the habitat value through a variation in its ability to provide shelter for stream organisms. The number of animal species groups encountered along a walking transect of the habitat was recorded with particular attention devoted to the presence of "rare" species. A sampling net was used to observe macroinvertebrates (eg dragonfly larvae) and vertebrates (eg fish). Animals living under rocks (eg mayfly nymph) were also recorded through active searching. Animals living in deep and shallow waters, and shaded and unshaded areas, as well as areas close to the river banks, and in and around emergent and submerged
vegetation where animals tend to congregate were also noted. Wherever, possible, abundance of the species groups recorded was graded as
"dominant", "abundant", "frequent", "occasional" or "scarce". In addition to the characteristics described above, degree of shade and presence of notable amount of detritus was also noted as they were regarded as important attributes of natural watercourse(1).
As indicated in Figure 4.4a, watercourse surveys would preferably be
conducted during the wet season when the habitat resources (eg insect larvae, fish) are best appraised. However, due to time constraints for this Study, field surveys for Natural Watercourse were undertaken during the period between mid December 2002 and end March 2003 which is a sub-optimal survey period for characterisation of this habitat type. Although the surveys were conducted outside the optional period, the surveyors focussed on habitat structure and the value of surrounding habitats to assign ecological value. This method is considered to be suitable and allows confidence in the survey results. The survey effort allocation for the natural watercourse is presented in the following table (Table 4.5), and the survey locations are presented in Figure
4.5e.
Table 4.5 Allocation of Survey Effort far Natural Watercourse
Survey Areas Previously Surveyed – to be surveyed (Days)
Proposed New Survey Sites (Days)
Survey Objective(s) North-east New Territories 3 3 HV; EVA North-west New Territories 4 1 HV; EVA
Central New Territories 2 1 HV; EVA
Sai Kung 1 4 HV; EVA
Lantau Island 4 1 HV; EVA
Hong Kong Island 1 0 HV; EVA
4.5.6 Mangrove
Objective: Habitat Verification (HV)
"Spot-checking" of the habitat type and boundary of mangrove stands was achieved by checking the locations and boundaries of the stands against the habitat map prepared for the previous Study using a hand held Window’s CE PC with GIS software linked to GPS unit. Field data were inputted directly into an electronic database during the survey, and the boundary of the mangrove in the map was marked and amended in situ. Photographs were taken to show the general condition of the habitat.
Objective: Ecological Value Assessment (EVA)
During site visits, the following information was recorded:
• naturalness of the mangrove stand;
• size of the habitat;
• number and abundance of mangrove plant species groups;
• number and abundance of benthic macrofaunal species groups;
• presence of "rare" species (if any);
• presence of known ecologically important areas (eg fish spawning
grounds) in its vicinity (if any); and
The distribution of the flora in each stand was measured by transect and quadrat analyses. Two transects were laid perpendicularly to the shoreline covering the extent of the mangrove community from land to sea. Along each transect, three quadrats (3m x 3m) were laid to record the type and abundance of the floral and macrofaunal species groups present, as well as the presence of plant seedlings. Special attention was also devoted to the presence of ecologically important floral and faunal species groups. Any on-going construction activities nearby or other disturbances, such as the discharge of pollutants into the habitat, were also recorded as these may cause degradation in the ecological status of the surveyed habitat. The information collected has been used to evaluate the ecological value of individual mangrove stands against the criteria delineated in Section 2 of this Report.
As shown in Figure 4.4a, there is no seasonal restriction on the survey period for mangroves, therefore surveys can be conducted at any time when the tide is low enough to expose the habitat. Surveys were undertaken during the period between mid February 2003 and early March 2003. Allocation of the survey effort over the mapped mangrove habitats and individual objectives for the selected survey locations are given in Table 4.6. The survey locations are presented in Figure 4.5f.
Table 4.6 Allocation of Survey Effort for Mangrove
Survey Areas Previously Surveyed – to be surveyed (Days)
Proposed New Survey Sites (Days)
Survey Objective(s) North-east New Territories 2 0 HV; EVA North-west New Territories 2 0 HV; EVA
Sai Kung 0 3 HV; EVA