An aquatic ecology survey of Hutchinson Creek in the Daintree Lowland Rainforest has identified the presence of the critically endangered Daintree Rainbowfish. 

Daintree Rainbowfish - photo by Michael Hammer

On the 22nd November 2021 aquatic ecologists, Keith Martin and Susan Barclay voluntarily conducted an aquatic survey of Hutchinson Creek, in the vicinity of property Lot 93 Cape Tribulation Road at Diwan. The survey focused on the 375 m of the frontage of Lot 93 to the adjacent Hutchinson Creek and also 600 m upstream (including a small side creek), and about 200 m downstream of the property.

The most significant finding of the survey was the discovery of a small population of Daintree Rainbowfish (Cairnsichthys bitaeniatus) in a side creek about 500 m upstream of Lot 93. This species is on the IUCN Red List of Threatened Species, where it is classified as Critically Endangered (Martin et. al. 2019). This species is known only from some small tributary streams of Hutchinson and Cooper creeks, where it is generally uncommon. It has been observed in the main channel of Hutchinson Creek on one occasion previously, but it likely avoids this area due to increased predator pressure from larger species and unstable water conditions (Martin & Barclay 2013).

The Daintree Rainbowfish was only described as a new species in 2018 and has been listed as Critically Endangered. An important action needed to ensure their survival is creekside habitat protection. Lot 93 Cape Tribulation Road is a freehold property that can be developed for housing subject to approval by the Douglas Shire Council. The purchase of this property and others in the Cooper-Hutchinson catchment area will ensure their management for conservation and will support the ongoing conservation of the Daintree Rainbowfish.

Hutchinson Creek adjacent to Lot 93 - Photo by Steven Nowakowski

Freshwater Biota observed in Hutchinson Creek in November 2021.

Fishes

Ox-eye Herring (Megalops cyprinoides)
Wet Tropics Tandan (Tandanus tropicanus)
Eastern Rainbowfish (Melanotaenia splendida splendida)
Daintree Rainbowfish (Cairnsichthys bitaeniatus)
Pacific Blue-eye (Pseudomugil signifer)
Jungle Perch (Kuhlia rupestris)
Roman Nose Goby (Awaous acritosus)
False Celebes Goby (Glossogobius illimus)
Speckled Goby (Redigobius bikolanus)
Snakehead Gudgeon (Giurus margaritacea)
Empire Gudgeon (Hypseloetris compressa)
Mangrove Jack (Lutjanus argentimaculatus)

Crustaceans

Common River Prawn (Macrobrachium australiense)
Shrimp (Caradina spp.)

Aquatic Plants

Blyxa (Blyxa aubertii)

Additional fish species recorded in Hutchinson Creek on previous surveys

Glassfish (Ambassis myops)
Long-finned Eel (Anguilla reinhardtii)
Green back Gauvina (Bunaka gyrinoides)
Pacific Silver Biddy (Gerres argentea)
Spotted Flagtail (Kuhlia marginata)
Yellow-finned Tandan (Neosilurus hyrtlii)
Bullrout (Notesthes robusta)
Blue Stream Goby (Sycyopterus lagocephalus)
Red Stream Goby (Stiphodon rutilaureus)

Eastern Rainbowfish (Melanotaenia splendida splendida)

Jungle Perch (Kuhlia rupestris)

Pacific Blue-eye (Pseudomugil signifer)

Speckled Goby (Redigobius bikolanus)

Mangrove Jack (Lutjanus argentimaculatus)

Empire Gudgeon (Hypseloetris compressa)

False Celebes Goby (Glossogobius illimus)

Wet Tropics Tandan (Tandanus tropicanus)

Example of a Wet Tropics Tandan nest

A deep waterhole on Hutchinson Creek adjacent to Lot 93

Blyxa (Blyxa aubertii)

Photos courtesy of Keith Martin & Susan Barclay. 

Report by Keith Martin and Susan Barclay 

The objective of the survey was to assess the fish diversity of the creek and provide an overall assessment of the aquatic ecology and values of the site. The study area is within the “Daintree Rainforest”. Lot 93 Cape Tribulation Road is an 8 ha property with no permanent habitable structures and no modified access to the adjacent creek. There are no permanent watercourses on the property, but it has approximately 375 m of frontage to the adjacent Hutchinson Creek.

Hutchinson Creek is one of the larger streams of the Daintree area and has permanent water flow. The creek is sourced in high rainfall coastal rainforests on the south-eastern slopes of Thornton Peak, Queensland’s fourth highest mountain. The catchment size upstream of the property is about 14 sq km. The creek becomes tidal and enters a mangrove estuarine environment about 1 km downstream of the property, eventually debouching into the sea at the southern end of Alexandra Bay. The elevation along the creek adjacent to Lot 93 is around 22 m. The field survey was conducted on 22nd November 2021. Field methods were generally non-invasive.

Snorkel-searching was the primary search method used as conditions were suitable for this in most areas. Searching by snorkelling is a proven reliable method for rapid assessment of fish populations in the Daintree streams (Martin & Barclay 2013; Ebner & Thuesen 2010). Where depths permitted, the observers snorkel-searched the entire length (about 375 m) of the stream adjacent to Lot 93. In order to get a more complete picture of the environmental setting, we also snorkel-searched the creek for about 600 m upstream of the property (including a small side creek), and about 200 m downstream of the property. Night spotlighting was another method used in the creek adjacent to Lot 93. The observers waded along the creek with a strong head lamp and dip net, looking particularly for nocturnal species. Some fish were captured to verify identification and then released.

In addition to the field surveys, in this report we include unpublished data from the authors’ previous surveys of this and other areas of Hutchinson Creek. To our knowledge, there are no previously published data on the aquatic ecology of Hutchinson Creek. Identification of species was based on published field guides, research publications, and the authors’ long experience with the fishes of this area.

Results

A total of ten freshwater fish species were recorded along the creek adjacent to Lot 93. In the 600 m reach upstream of Lot 93, eight species were recorded, and six species were recorded in the 200 m downstream section. Overall, the upstream and downstream surveys only yielded an additional two species, bringing the total number of fish species recorded in the surveys to twelve. Only one species, Speckled Goby (Redigobius bikolanus) was observed only in the reach adjacent to Lot 93, although it is likely to be more widespread.

Our database records, dating from 2012, indicate an additional nine fish species present in the freshwater reaches of Hutchinson Creek, all of which are considered to potentially occur in the reach adjacent to Lot 93 either as residents or occasional transients (Table 2). These records combine for a total of 21 species recorded by the authors from Hutchinson Creek freshwaters. It is likely that several other species are present, especially in the lower reaches of the creek. Crustaceans observed along the creek included River Prawn (Macrobrachium australiense) and shrimp (Caridina spp.) 

All fish species are native to the area. The most commonly observed species during snorkel surveys in the creek were Jungle Perch (Kuhlia rupestris), Empire Gudgeon (Hypseleotris compressa), Pacific Blueeye (Pseudomugil signifer) and False Celebes Goby (Awaous acritosus). Night spotlighting surveys revealed additional species including Snakehead Gudgeon (Giurus margaretacea), Wet Tropics Tandan (Tandanus tropicanus) and Ox-eye Herring (Megalops cyprinoides).

Environmental conditions in the creek were good although water flows were very low at the time of the survey. Most of the area adjacent to Lot 93 comprises shallow riffle and pool structure, with some larger pools. One large pool about midway along this reach is over 3 m deep and one of the deepest pools in the system. Substrates along the creek are generally comprised of granite sands and gravels, with some larger boulders and bedrock. Water quality was good, with clear, flowing water of average pH and low conductivity (Table 3). Aquatic vegetation along the creek, as with most of the Daintree streams, was sparse. However, Blyxa aubertii was quite common in the area, being encountered as individual plants and as dense stands in some areas. An unidentified edge grass species was also observed also growing in deeper water. Some areas of still water had high levels of suspended green algae.

Discussion

Several of the fish species observed adjacent to, or just downstream of Lot 93 are estuarine vagrants. These include Mangrove Jack (Lutjanus argentimaculatus), Speckled Goby and Ox-eye Herring (Megalops cyprinoides). The presence of these species indicates that the area is something of a transitional zone between freshwater and estuarine habitats and is used by species from both ecological niches.

The creek is in a relatively undisturbed state, with no introduced fish species present, and instream conditions good. However, there are many private properties along the creek upstream of Lot 93, some of which have been cleared of the original rainforest vegetation close to the creek, and one which has been extensively cleared for cattle production. These disturbances may account for the observed algal blooms in the creek, which indicate a high nutrient load.

Water extraction is also a common activity along this creek and will contribute to lower stream levels, especially late in the year.

This survey is a snapshot in time and may not represent a comprehensive list of all species in the creek.

Photos of site habitats and sampling methods, as well as some of the fish species observed, are provided in the Appendix.

References

Allen, G.R., Midgley, S.H. & Allen, M. 2002. Field Guide to the Freshwater Fishes of Australia. Western Australian Museum: Perth. 394 pp.
Ebner, B. C. & Thuesen, P. 2010. Discovery of stream-cling-goby assemblages (Stiphodon species) in the Australian Wet Tropics. Australian Journal of Zoology 58: 331-340.
Martin, K., Hammer, M. & Ebner, B. 2019. Cairnsichthys bitaeniatus. The IUCN Red List of Threatened Species 2019: e.T129041926A129041938. http://dx.doi.org/10.2305/IUCN.UK.2019-
3.RLTS.T129041926A129041938.en
Martin, K. C. & Barclay, S. 2013. New Distribution Records for the Cairns Rainbowfish Cairnsichthys rhombosomoides: implications for conservation of a restricted northern population. Aqua International
Journal of Ichthyology 19 (3): 155–164