Macroinvertebrate sampling Macroinvertebrate samples were collected using both quantitative and qualitative
survey methods to allow an assessment of macroinvertebrate density at selected
stations and to compile a list of suitable taxa as potential bioindicators for future
monitoring. The quantitative and qualitative sampling methods were adapted from
Stark et al. (2001) and modified to suit the time constraints and objectives of this
particular survey. They are described as follows:
Quantitative assessment – This is a quantitative method that provides a measure of
macroinvertebrate density is adapted and modified from Protocol C3 (Stark et al. 2001). Two replicate Surber samples (area 0.1m², 0.5 mm mesh) were collected from
riffle habitats at stony streambed sites. A riffle is a shallow area (water depth ≤0.5m)
where water flows swiftly over stones, creating surface turbulence. Surber samples
were collected from the Nasa Creek and its tributary, Wainirovurovu stream in
Tovatova catchment and Waikarakarawa Creek in Waikarakarawa catchment.
Samples were collected by placing the Surber sampler over a defined area of
streambed in riffle habitat and disturbing the habitat by washing the particles with
the water flowing through the net to collect dislodged macroinvertebrates. A sample
was also quantitatively collected using a kick-net sampler in Wainasoba Creek
(WSLQT), collecting from same surface area as that of Surber sampler. Qualitative assessment – a single sample was collected from each sampling station
either via kick-net or visually inspecting slow flowing edge habitats for taxa that
prefer these habitats (e.g. snails and damselflies). Typical habitats sampled included
runs, riffles, chutes, pool edges, trifles, woody debris, leaf litter, stream edges, and
tree roots along banks, streambank vegetation and sand/silt substrates.
Macroinvertebrate samples collected from the Surber sampler, kick-net or hand
collection were placed into 250ml specimen jars with 70% ethanol for sorting and
identification by the author. New taxa were verified by Dr. Haynes. The guides
referenced in the identification process included; Haynes (2009), Haynes (in prep.),
Haase et al. (2006), Williams (1980) Winterbourn et al. (2006), and Nandlal (unpub).
Identified macroinvertebrates were placed for preservation in small vials containing
70% ethanol for long term storage.
Data analysis Community composition and structure: the combined Surber and opportunistic data
set was used to calculate the relative abundance of the main taxonomic groups.
Macroinvertebrate density: an assessment was made of macroinvertebrate density in
riffle habitats at selected stony streambed sites based on quantitative Surber sample
data by multiplying the mean Surber sample abundance data (per 0.1m
) by a factor
of ten to give abundance/m
Status and distribution of taxa: taxa were classified as either endemic to Fiji, native to
other regions (e.g. Pacific, South Pacific, Indo-Pacific, Fiji-Australia and South East
Asia), introduced tropical species or other (i.e. marine, worldwide).
Focal species/ taxa of interest: macroinvertebrate taxa of potential interest for being
key indicators of environmental change in the catchment were selected. 7.4 Results Water physiochemistry The water physicochemistry parametres measured at the different stations are
summarised in Appendix 16. Waterways sampled ranged from almost neutral to
slightly acidic. The freshwater macroinvertebrate communities described in this
study are unlikely to be significantly affected by pH values within this range.
Conductivity is a measure of the total ions in water and ranged between 0.084 mS/cm
in the mid Mavuvu (MLVQT) and 0.047 mS/cm in the upper Nasa (NU1QT).
Turbidity (NTU) is a measurement of particles in the water column and provides an
indication of water clarity. Turbidity values ranged between 0 NTU in the
Wainirovurovu Creek sites (WRD2QT & WRU3QT) and Mavuvu catchment streams
(WKQT, WSLQT & QB1QL) to 5.8 NTU in the Nasa Creek (NU1QT). Turbidity in
Nasa Creek was higher due to heavy rainfall the night prior to surveying. Though
turbidity above 5 NTU signifies poor water quality; this was a temporary impact and
water clarity had returned to normal by late afternoon with NTU of less than 5. In
Wainirovurovu Creek (WRD2QT & WRU3QT), turbidity values were 0 NTU, which
signifies excellent water quality for macroinvertebrate survival as well as the absence
of sediment-raising activities in the catchment.
Dissolved oxygen concentrations ranged between 8.27g/m
in Waikarakarawa Stream
(WKQT) and 8.99 g/m
in Nasa Stream (NU1QT) All dissolved oxygen concentrations
were above the level considered sufficient for macroinvertebrate survival (i.e. >5 /m
This was due to unaltered waterway hydrology allowing suitable water flow coupled
with sufficient canopy cover to reduce excess temperature and highly stable bank
reducing any sedimentation impacts. Salinity measurements at the survey stations
demonstrated levels that are expected in the headwaters of any tropical inland
Habitat Characteristics The aquatic habitat and riparian characteristics of the stations surveyed are
summarised and presented in Appendix 17. The streambed of waterways surveyed
was dominated by cobble/gravel and sand and provided a diverse stable habitat for
the macroinvertebrate community (Graph 1).
Graph 1. Streambed composition at sampling stations.
Periphyton Thin light/dark brown films (<0.5mm) (i.e., 40-80% cover) was the most common
form of periphyton recorded at sampling stations with stony streambeds. This
periphyton type is a source of food directly or indirectly for macroinvertebrates and
fishes in streams.
Macroinvertebrate density A summary of the freshwater macroinvertebrates collected and their abundance is
presented in Appendix 18 (Surber sampling) and Appendix 19 (opportunistic
collections). The abundance is given as numbers of individuals, and is also grouped
into abundance categories as follows: very abundant (>100), abundant (20-99),
common (5-19), few (2-4) and very few (1). The overall (all taxa) abundance ranged
from 2049 individuals/m
at Waikarakarawa Creek downstream (WKQT) to 3686
in Nasa Creek upstream (NU1QT).
Insect larvae/nymphs were the most dominant taxa at all three sites (Graph 2). This
was strongly represented by caddisfly, mayfly and dipteran larvae. This result is
typical of the headwaters of tropical inland streams with intact or pristine
S tr e a m b e d c o m p o s ti o n (% ) Stations Silt/sand
catchments. Insect larvae are well adapted to fast flowing waters of stream/river
headwaters, compared to crustaceans and molluscs which are found in higher
numbers in lower reaches of streams/rivers with swifter flows. The small Fluviopupa (<4 mm) snails were also recorded as abundant at two sites and very abundant at one
site. These particular gastropods are usually catchment endemic and found in higher
densities in headwaters with narrow channels, swift flows and very clean water.
They have been found to be only present in streams undisturbed from cattle/horse
grazing. Hence they were abundant in the intact waterways surveyed. The moth
larvae (Nymphula spp.) also ranged from abundant to very abundant at two stations.
They are known to be found in higher densities in streams with adequate algal film
covering stream substrata and open-partial canopy shading and good water quality;
hence there abundance in these streams.
Graph 2. Community composition by major taxonomic group.
The macroinvertebrate communities documented were typical of pristine/intact
inland tropical stream headwaters. The waterways sampled provided suitable
habitats for diverse taxa composition. The sites surveyed had coarse stony streambed
substrates and a high proportion of turbulent riffle/chute habitats, which resulted in
caddisflies (Trichoptera) being the most dominant group at the majority of stations,
followed by mayflies (Ephemeroptera) and flies (Diptera). These groups combined to
give 95% (NU1QT), 98% (WRD2QT), 85% (WRU3QT) and 98% (WKQT) of the total
species recorded (Graph 2). An exception to this pattern is at site MVLQT whereby
the Mollusca group was more abundant than the Diptera, and togther with the
Trichoptera and Ephemeroptera comprised 80% of species composition.
NU1QT WRD2QT WRU3QT WKQT MVLQT
Co m m uni ty C om po si tio n ( % ) Sampling stations Mollusca
Graph 3. Community composition by taxa.
The most abundant caddisfly taxon recorded was the net-spinning filter-feeder
Abacaria fijiana. This species were most abundant in riffle habitats at Mid Mavuvu
tributary, Wainasoba Creek (WSLQT) and Wainirovurovu downstream (WRD3QT)
where they represented between 40 and 43% of total abundance respectively. Other
caddisfly larvae such as A. ruficeps, Odontoceridae, Hydroptilidae and Chimarra sp.
were also common or abundant but represented less than 9% of total abundance.
Chimarra sp. was recorded in highest proportions in the Nasa Creek (NU1QT) and
Wainasoba Creek, in the downstream Mavuvu (WSLQT).
Mayflies were also a dominant taxonomic group recorded at survey sites and
represented 69% of the community in the Waikarakawa Creek and 30% in the Nasa
Creek (NU1QT). The most abundant mayfly taxon was Pseudocloeon sp. This is
because Pseudocloeon sp.has a dorso-ventrally flattened body that allows it to graze
on thin algal films covering the surfaces of large boulder/cobble substrates in
turbulent riffle/chute habitats. In contrast, Cloeon spp. mayflies which are mostly
associated with gentle flowing habitats and are more common along stream margins
and runs were recorded in much lower proportions across the sites. Therefore many
Cloeon spp.were part of the opportunistic collection.
NU1QT WRD2QT WRU3QT WKQT
Co m m un ity Co m po sit io n (% ) Sampling stations Abacaria fijiana
Nesobasis sp. A
Conservation status and distribution of taxa A total of 57 of the macroinvertebrate taxa recorded as part of the survey were
endemic to Fiji and represented 75% of the total number of taxa recorded (Graph 4).
Graph 4. Status and distribution of taxa across all sites.
Apart from a few unique specimens (~15), many of the endemic taxa recorded are
common throughout the headwaters of Fiji Island streams. The remaining 15% of
taxa were either native to Fiji, the Pacific or the Indo-Pacific region, or introduced
tropical species or unknown species.
Graph 5 shows the total number of taxa recorded at each sampling station and their
status/distribution shown as a proportion of total taxa richness within each
community. The number of endemic/native taxa recorded at sampling stations as
part of quantitative survey ranged between 14 endemic/native taxa at
Waikarakarawa stream (WKQT) to 27 at Wainirovurovu upstream (WRU3QT). This
amounted to 88% and 90% of the total taxa per sites respectively; highlighting that
endemic species are the dominant taxa at all sites. The majority of endemic/native
taxa recorded were insects; inclusive of both qualitative and quantitative collection
(53 taxa in total). Other endemic taxa recorded were the small (<4mm) snail
Fluviopupa spp. and nereid and nematode worms. A single juvenile specimen of the
introduced tropical snail Melanoides tuberculata was also found in riffle habitat at
Nasa stream (NU1QT) of Tovatova catchment, although no adults were observed
around the edges of streams during the qualitative survey. This could possibly be an
inadvertent introduction into the stream via footwear worn by villagers/surveyors.
This tropical snail was however present in adult and juvenile sizes along the sides of
stream channel at Waikarakarawa stream and Wainasoba Creek. The common
introduced mosquitoe larvae (Culicidae) was found at Wainirovurovu stream. These
species are usually limited to stagnant waters (pools) in streams but due to the
previous night’s rainfall they might have been washed into the riffles.
Percentage of total taxa St at us & di st ribut io n
Graph 5. Status and distribution of taxa across individual sites.
A lower number of endemic taxa were observed as part of the quantitative survey at
Waikarakarawa Creek (WKQT) (14 taxa) and Wainasoba Creek (WSLQT) (17 taxa).
The qualitative survey at both stations (WKQL & WSLQL) showed a high increase in
endemic/native taxa. This is probably due to species becoming habitat specific with
changing physical parameters such as an increase in flow with increasing elevation
and steepness coupled with a decrease in channel width. Damselflies, shrimps and
some caddisfly species were more abundant on the sides of the streams which
supported slow flows, compared to riffles with swift flows. The sides of the streams
also had mass fibrous roots extended into the channel that provided habitats for
damselflies, shrimps, whirligig beetles and some caddisfly species.
Focal species / taxa of interest Certain macroinvertebrate taxa that were recorded during the surveys and that may
be of potential ecological interest are shown in Fig. 45 - Fig. 61. These highly sensitive
species are typical of pristine streams draining intact watersheds. Furthermore, some
of these taxa, such as Fluviopupa spp., Nesobasis “orangish”, the unknown moth
larvae and the nematode worm, have a very high chance of being catchment endemic
or localised endemic.
7.5 Discussion Dense forest cover, intact riparian zone and highly stable banks along these rivers
and their tributaries provide suitable conditions for a thriving freshwater
macroinvertebrate community. Dense forests ensure enough volume and clear water
entering the creeks and tributaries; maintaining a natural state of waterway
hydrology to provide different habitats such as runs, riffles, pools and chutes
coupled with appropriate streambed substrates and good water quality. Intact
riparian vegetation acted as an excellent buffer zone for any sediment intrusion from
land, thereby maintaining water quality. Adequate canopy cover along waterway
22 27 22
N um be r o f T ax a Sampling stations Endemic/Native
edges provide for shade to control water temperature, leaf litter for nutrient cycle,
sufficient light for algal cover (food for macroinvertebrates) on stream substrata,
while native tree roots, shrubs, ferns and big boulders ensured bank stability. At
Waikarakarawa Creek a few cases of natural landslides were observed, while
Qalibovitu upstream had more than six cases of landslides. These landslides caused
large trees to fall in the waterways which altered the waterway hydrology but also
provided additional habitats via branches, leaf litter and twigs. The landslides also
caused abrasion of stream banks resulting in the addition of sediment to the
streambed. However, this impact is a temporary one. The freshwater macroinvertebrate community of Emalu (in total 76 taxa) showed that
the endemic taxa were the most dominant with insects making up the majority of the
taxa. This is typical of pristine inland tropical riverine system headwaters. In
comparison with other studies in pristine headwater catchments (by the author), 27
taxa were identified from Wainavadu Creek and the headwaters of the Waidina
River in Namosi and Naitasiri Provinces, and 32 taxa were identified from the
Wainibuka River headwaters in the Nakauvadra Range. Waterways in the Emalu
area therefore supports much higher taxa richness (almost threefold more) than other
creek/river headwaters that have been surveyed in Viti Levu. A total of fourteen macroinvertebrate taxa collected as part of the survey may be of
potential ecological interest. These include four species of mayfly nymphs
(Ephemeroptera: two Pseudocloeon spp. and two Cloeon spp.), two species of
damselfly nymphs (Odonata: Nesobasis “orangish”& Nesobasis “dark green”), four
species of caddisfly larvae (Trichoptera: Apsilochorema “light green”, Hydrobiosis “pinkish”sp., Hydrobiosis sp. “green” and Chimarra sp.), one Cranefly larvae
(Tipulidae: Tipula sp.), one snail (Fluviopupa spp. (< 4mm), one nematode worm
(Unknown 1 sp.) and one moth larvae (Lepidoptera: Unknown 2 sp.). These highly
sensitive species are very good bioindicators. They are also typical of pristine streams
draining intact watersheds. In addition special taxa such as rissooidean snails
(Fluviopupa spp.), Nesobasis “orangish”, the unknown moth larvae and the nematode
worm are very likely to be catchment endemic or area endemic species. Fluviopupa snails, ten species of which are already known to be endemic to Fiji, have restricted
distribution and are usually catchment endemic, inhabiting springs and small creeks
or riffles (Haase et al., 2006). The slender red headed (Pseudocloeon sp. A) and the dark brown (Cloeon sp. A)
mayfly nymphs also have a high chance of being catchment endemic species. The
nematode worm has only been found in the Wainrovurovu tributary and not in Nasa
Creek, possibly due to the narrower stream channel and the difference in water
depth. Since the catchment is unimpacted by cattle grazing, these worms have
naturally been part of the freshwater macroinvertebrate community or may have
been introduced by birds etc. The orangish damselfly nymph and the moth larvae
(Black with orangish spots and prolegs) have been encountered for the first time.
These two taxa have not been observed in any streams surveyed prior to this survey.
However, these are only the larval stage and have not been matched with the adult
stage as yet. Therefore it cannot be confirmed if they are new species or not. In
addition, the amphipod and the caridean shrimps (Caridina sp. B-F) found in
Qalibovitu Creek QB1QL and QB2QL have a very great chance of being new species
as they do not resemble the crustaceans described so far from Fiji or Asia.
CHAPTER 8: INVASIVE SPECIES Isaac Rounds and Sarah Pene
8.1 Summary Trapping and opportunistic surveys were used to record the presence and
abundance of invasive plants and animals in the Nasa, Mavuvu and Waikarakarawa
catchments of the mataqali Emalu forests, Viti Levu. The checklist of 26 invasive
plants and eleven invasive animals recorded as present in the area includes thirteen
species which are listed in the 100 most invasive species in the world, namely;
Plants: Spathodea campanulata, Mikania micrantha, Leucaena leucocephala, Lantana camara, Imperata cylindrica, Arundo donax and Clidemia hirta.
Animals: Rattus rattus, Sus scrofa, Felis cattus, Pycnonotus cafer, Bufo marinus and
In general the occurrence and abundance of invasive species in the Emalu boundary
was associated with proximity to human habitation and to disturbed areas such as
tracks, temporary campsites and cultivated areas. The invasive plant species were
generally low in abundance, with the exception of Piper aduncum which was locally
common, and Clidemia hirta and Mikania micrantha which were both widespread.
The faunal component of the invasive species was comprised primarily of the most
common (and most serious) global invasives such as rats, mongooses, mynah birds
and cane toads, as well as feral animals of domesticated species, such as cats, dogs
and pigs. Some invasive animal species such as the Polynesian rat (Rattus exulans),
the Norwegian rat (Rattus norvegicus) and the house mouse (Mus musculus) were not
observed directly in the field but they were reported by the guides to be present in
and around the villages in the area.