The data review process involves assessment of existing databases to determine the adequacy of existing site-based biological data for use in subsequent analyses. The outputs of the review can be used to identify priority areas and data gaps to be filled through future survey work. The data review relies on expert knowledge and professional judgment.
The distribution of survey sites where adequate data on fish and aquatic macroinvertebrates is shown in Map 11.
Intensive inventory surveys of fish assemblages in the Central Highlands have been primarily conducted by the Department of Natural Resources and Environment (NRE). Some investigations which incidentally recorded fish species, were conducted by other government agencies, universities or private individuals.
Pre - 1990 fish surveys
Very few historical records (pre - 1970) exist for the Central Highlands region, and prior to 1970, records were sporadic, consisting of observations of individual species from only a few locations. The first survey of fish assemblages was undertaken in 1973 at seven sites on the La Trobe River (Tunbridge 1974). Between 1973 and 1990, a total of 11 recognised major surveys occurred in the area contributing 164 new sites (Table 7.4), exclusive of resampled sites.
Five of these surveys were fisheries orientated, targeting larger, recreational species and using techniques (e.g. netting with large mesh sizes) not designed to capture all fish species. These types of surveys are referred to in this report as “partial surveys”. Consequently, smaller fish species were not sampled by these surveys, and they were generally conducted in the larger reaches of the main rivers in lowland to foothill areas only.
Table 7.4: Major surveys conducted for freshwater fish in the Central Highlands prior to 1989.
Note: * indicates fisheries surveys.
All sampling of fish in the region has been sporadic pre-1990 and non-systematic. Information obtained from successive surveys has not necessarily been complementary, resulting in significant gaps in the knowledge of species distributions in the region, and within particular river systems.
Post - 1990 fish surveys
Since 1990, survey intensity and coordination has improved for the region, mainly due to intensive sampling of specific areas, with 282 new sites (exclusive of resampled sites) being assessed in major surveys. Further, the majority of surveys used techniques which potentially sampled the entire community rather than just selected species (e.g. electrofishing - termed “full” surveys), and were also conducted in foothill to upland areas in many of the smaller streams. Much useful information was collected by Peter Unmack from 70 sites across the region (Table 7.5) though unfortunately nearly all of these collections are rated as a partial survey as the equipment used would generally not have sampled all species present (eg. seine net, dipnet, and angling).
Both Raadik (unpublished data) and Saddlier (unpublished data) have intensively surveyed a total of 144 sites across the region (Table 7.5), concentrating on the smaller fish species and sampling in foothill and upland areas for specific projects, some of which is reported in Koehn et al (1991). Many of these sites were surveyed for the nationally threatened Barred Galaxias (Galaxias fuscus), as were the 13 sites sampled by Shirley (1991). Koehn et al. (1991) also details various miscellaneous surveys conducted in the region. No systematic survey of the aquatic habitat across this region has been undertaken, with most information being derived from specific intensive surveys for specific projects.
Table 7.5: Major surveys conducted for freshwater fish in the Central Highlands since 1990.
Goulburn, Thomson, Latrobe, Bunyip and Yarra catchments
Goulburn, Thomson, La Trobe, Bunyip and Yarra catchments
Goulburn, La Trobe and Yarra catchments
Koehn et al. 1991
Goulburn and Yarra catchments
Note: * indicates fisheries surveys.
The number of freshwater survey sites in the Central Highlands is 572, with 264 located north of the divide in the Goulburn River catchment and 308 in the four catchments to the south (Table 7.6). Of these, 400 sites are considered to be fully surveyed (full coverage of species diversity) which provide adequate data quality, 145 north of the GDR and 255 in the south.
There is generally wide spatial coverage of the aquatic habitat across the Region, though many survey sites fall into `hot spot’ areas where survey intensity has been very high in a few areas due to specific projects such as the Barred Galaxias project (see earlier). Consequently, there is a very extensive knowledge of fish from only a few areas within the Region.
Table 7.6: Summary of information on fish survey sites in the Central Highlands from 1973-1994.
Notes: Full - all fish species recorded; Partial - only larger, recreational species collected.
By comparison, Jackson and Davies (1983) surveyed 115 sites in the Grampians region, in an area approximately 15% the size of the Central Highlands, and Cadwallader (1979) surveyed 60 sites in one river system (Seven Creeks). It is considered that these scales of intensity are required to give excellent survey coverage. If the Central Highlands were to be surveyed with the same intensity to that conducted in the Grampians, approximately another 360 sites would be required, and more importantly, these sites would need to be more spatially orientated than previous ones to provide better coverage. Table 7.6 shows that survey sites have been concentrated in State forest, other public land and private land, with significantly less sites sampled in conservation reserves The current number of quality sites (400) comprises some 52% of the coverage required if survey intensity in this region were to match the two surveys described above.
Some 92 sites (16.1%) have been located in areas set aside for conservation purposes, 237 (41.4%) were located in private land and other areas of public land (eg. licensed stream frontages). Two hundred and forty three sites (42.5%) have been located in State Forest and many of these have been surveyed since 1990, or were surveyed approximately 15 to 25 years ago.
7.2.2 Aquatic macroinvertebrate fauna
Inventory surveys of aquatic macroinvertebrates in the Central Highlands have been primarily conducted by a number of Government Departments and Monash University. Some investigations which incidentally recorded invertebrate species (e.g. as part of taxonomic studies) have been conducted by universities or private individuals.
Pre-1990 macroinvertebrate surveys
Department of Water Resources (1989) recorded 131 sites where aquatic macroinvertebrate surveys have been conducted in the Central Highlands prior to 1990 (Table 7.7). These were sampled as part of several studies, primarily investigating the impact of human disturbance on stream systems, but included 13 graduate and post-graduate projects at Monash University. Studies associated with the construction of the Thomson Dam (Malipatil and Blyth 1982; Doeg et al. 1987; Marchant 1989), eductor dredging in the Goulburn Rivers (Doeg 1987) and the release of the former State Electricity Commission cooling waters into the Latrobe River (Metzeling et al. 1984; Marchant et al. 1984) were all conducted by the Museum of Victoria. The impact of the construction of Blue Rock Dam was conducted by the EPA (Chessman et al. 1982) and the effect of mercury contamination was studied in the upper Goulburn River through Rusden College (Ealey et al. 1983).
The Yarra catchment has been the most extensively surveyed with 45 sites sampled prior to 1990. Of these, 12 sites were part of Monash University graduate and post-graduate projects, but the remaining 33 sites were part of a more extensive monitoring program (Campbell et al. 1982; Pettigrove 1985).
Unfortunately, a variety of different survey techniques was employed in each of these studies. As these often used different sampling methods and regimes, data comparisons between these surveys should be treated with caution.
Table 7.7: Major surveys conducted for aquatic macroinvertebrates in the Central Highlands prior to 1990.
Monash University, Rusden College, Dandenong Valley Authority
Ministry for Conservation, Monash University, Rural Water Commission
Post-1990 macroinvertebrate surveys
Since 1990, various surveys have continued in some catchments. A number of graduate and post-graduate projects at Monash University have continued, primarily in the upper Goulburn River catchment (Taggerty, Steavensons and Acheron Rivers), while a few studies have been conducted in the Yarra catchment (Saddlier and Doeg 1996). No new major surveys have been conducted in the Latrobe, Thomson or Bunyip catchments.
As part of the Monitoring River Health Initiative (MRHI), 40 sites are currently being monitored in the Central Highlands region (L. Metzeling, EPA, pers. comm. - Table 7.8). An additional 47 sites have also been sampled in the urban sections of the Yarra River. Melbourne Water also conducts an extensive community based monitoring program for aquatic macroinvertebrates in the Yarra River.
Table 7.8: Number of sites sampled as part of the MRHI after 1990 in each catchment in the Central Highlands.
There has been no comprehensive or systematic study of the aquatic macroinvertebrate fauna of the entire Central Highlands Region. Numerous individual studies have been conducted for specific purposes. The recent introduction of 40 sites surveyed under the MRHI program will provide some baseline data for the region. The data from these are being used to construct a national predictive model, allowing the invertebrate fauna to be predicted on the basis of the river characteristics (e.g. water quality, altitude, bed structure). However, an overall survey intensity at a greater density than 40 sites in the Central Highlands will be required. The number of additional sites required for accurate localised modelling cannot be estimated, but a further 50 sites in the Central Highlands would contribute significantly to the input of suitable models.