Find further information on the Conservation of Freshwater Ecosystem Values (CFEV) Program and its data at www.dpipwe.tas.gov.au/cfev.
TitleRiver biological condition sub-index
CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment
CreatorSteve Carter, Environmental Dynamics
DescriptionAn index which rates the biological condition of rivers according to its platypus condition, native fish condition, exotic fish impact, macroinvertebrate condition and the extent of native riparian vegetation.
Input data
Lineage
A biological condition sub-index was derived by using expert rule systems whose inputs were: the condition of platypus populations; the presence and influence of exotic fish; the state of macroinvertebrate communities and native fish assemblages; the status of riparian vegetation; and the presence of willows (see ‘Assigning values to ecosystem spatial units’ below). Information on expert rules systems can be found in Appendix 3 of the CFEV Project Technical Report.
The willows data was used as a modifier for the native riparian vegetation data in a pre-processing step where the native riparian vegetation score (RS_NRIPV) decreased by 0.2 if willows present (RS_WILLOWS = 0) down to a minimum of 0.
Weightings were applied to the other inputs in order of influence to the biological condition score: macroinvertebrate condition, native riparian vegetation, and native fish condition and exotic fish impact. The latter two inputs being equally weighted.
The method for assigning a biological condition sub-index score to the river spatial units is provided below.
Date createdNovember 2004
Scale and coverage1:25 000; Statewide
Column headingRS_BIOL
Type of dataContinuous but has been converted to categorical format (see Table 3).
Number of classes5
Assigning values to ecosystem spatial units
A biological condition sub-index score (0 = poor condition – 1 = good condition) was assigned to river spatial units as RS_BIOL using the expert rule systems shown as a definition tables in Tables 1 and 2. Table 1 shows the definition table for when native fish are absent (i.e. RS_FISHCON = -9) (e.g. if native fish are absent from the river section and it has a HIGH score for macroinvertebrate condition, HIGH score for exotic fish and a LOW score for native riparian vegetation condition, then assign a score of 0.6.), while Table 2 presents the rules to apply when native fish are present (i.e. RS_FISHCON ≠ -9). A modifier was also applied to the outputs to account for variation in platypus condition (i.e. the presence of Mucormycosis), where the biological condition score was reduced by 0.1 if RS_PLATYP = 0, down to a minimum of 0. Using fuzzy logic enables input data and output results to be continuous rather than categorical as implied here (i.e. inputs and output data can range on a continuous scale between 0 and 1, and the process of executing the expert rule system will determine its membership as being HIGH or LOW) (refer to Appendix 3 of the CFEV Project Technical Report for more information on expert rules systems).
Table 1. Expert rules system definition table for the biological condition sub-index for rivers, when native fish are absent (RS_FISHCON = -9).
Macroinvertebrate condition (RS_BUGSCO) | Exotic fish impact (RS_EXOTICF) | Native riparian vegetation (RS_NRIPV) | Biological condition score (RS_BIOL)* |
H | H | H | 1 |
H | H | L | 0.6 |
H | L | H | 0.7 |
L | H | H | 0.4 |
H | L | L | 0.5 |
L | H | L | 0.2 |
L | L | H | 0.3 |
L | L | L | 0 |
Table 2. Expert rules system definition table for the biological condition sub-index for rivers, when native fish are present (RS_FISHCON ≠ -9).
Macroinvertebrate condition (RS_BUGSCO) | Exotic fish impact (RS_EXOTICF) | Native riparian vegetation (RS_NRIPV) | Native fish condition (RS_FISHCON) | Biological condition score (RS_BIOL)* |
H | H | H | H | 1 |
H | H | H | L | 0.83 |
H | H | L | H | 0.7 |
H | H | L | L | 0.57 |
H | L | H | H | 0.83 |
H | L | H | L | 0.7 |
L | H | H | H | 0.7 |
L | H | H | L | 0.57 |
H | L | L | H | 0.43 |
H | L | L | L | 0.3 |
L | H | L | H | 0.3 |
L | H | L | L | 0.2 |
L | L | H | H | 0.3 |
L | L | H | L | 0.2 |
L | L | L | H | 0.1 |
L | L | L | L | 0 |
The rivers spatial data layer has the continuous biological condition sub-index data categorised according to Table 3. The categorical data was used for reporting and mapping purposes.
Table 3. Biological condition sub-index categories for rivers.
Category | Min to max values |
1 | 0 to <0.2 |
2 | 0.2 to <0.4 |
3 | 0.4 to <0.8 |
4 | 0.8 to <1 |
5 | 1 |
CFEV assessment framework hierarchy