An aquatic ecology survey in a Daintree lowland rainforest stream has identified fourteen species of fish in an undisturbed ecosystem. 

The survey was conducted on a voluntary basis by Keith Martin & Susan Barclay in September 2020 on Lot 155 and Lot 157 Cape Tribulation Road. The Rainforest 4 Foundation acquired Lot 155 in November 2020 and at the time of writing a contract of sale has been exchanged for the purchase of Lot 157.

Snorkel searching in an upper rockpool on Lot 157

The study area is within the “Daintree Rainforest”. The creek which flows through the properties is an unnamed small southern tributary of Cooper Creek, which arises in the foothills of the Thornton Range and debouches into lower Cooper Creek and eventually to the sea at Alexandra Bay. The upper catchment size of the surveyed tributary is very small, only about 0.5 sq km on and upstream of the properties. In and below the lower portion of the properties, the creek enters an estuarine environment, entering the sea about 2 km downstream of Lot 155. Elevations along the survey transect ranged between 30 and 20 m. The field survey was conducted on 29th and 30th September 2020.

Field methods were generally noninvasive. 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. The observers snorkel-searched the length (about 500 m) of the stream on Lot 157 from near the main road crossing to as far upstream as was practically possible. Downstream on Lot 155, only about 150 m of the stream could be surveyed by this method, as the creek conditions became deep and murky, and the presence of some estuarine fish species indicated the potential presence of Saltwater Crocodiles.

Upstreamboulder habitat and rockpools on Lot 157

Night spotlighting was another method used on Lot 157. 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. Identification of species was based on published field guides, recent research, published checklists of Cooper Creek fishes and the authors’ long experience with the fishes of this area.

A total of fourteen freshwater fish species were recorded on the two lots. All species are native to the area. The most commonly observed fish species during snorkel surveys in the creek were Jungle Perch (Kuhlia rupestris), Empire Gudgeon (Hypseleotris compressa), Snakehead Gudgeon (Giurus margaretacea), Pacific Blue-eye (Pseudomugil signifer) and Eastern Rainbowfish (Melanotaenia splendida splendida). Night spotlighting surveys revealed additional species including Wet Tropics Tandan (Tandanus tropicanus), Long-finned Eel (Anguilla reinhardtii) and Ox-eye Herring (Megalops cyprinoides).

Eastern Rainbowfish

Other biota recorded along the creek included Saw-shelled Turtle (Wollumbinia latisternum), frogs, tadpoles and crustaceans. The creek supports very little aquatic vegetation, with just occasional specimens of Blyxa aubertii present.

Environmental conditions in the creek were good. The creek is generally in an undisturbed, natural state and is fringed by rainforest throughout its length. The main disturbance to the creek is from feral pigs, which have dug up significant areas of bankside soils, thus contributing to siltation of substrates and some turbidity in the water column. Flows in the creek were fairly slow and the deepest pools were less than 1.5 m deep. Substrates were generally sandy or silty with some cobbles, and the upper reaches of the creek were strewn with large boulders and rockpools. 

The fish variety in the creek, with fourteen species present, represents about 56% of the total known species in the entire Cooper Creek basin. Banded Rainbowfish (Melanotaenia trifasciata) was observed on two occasions in the survey, so is quite uncommon in the creek. The Wet Tropics form is known only from the Cooper Creek area in the Daintree, one creek in the Bloomfield area, and an area to the north of Cooktown, so this species reaches its southerly distribution limit in this area. Wet Tropics Tandan is endemic to the Wet Tropics Bioregion and is most abundant in the Daintree streams.

The relatively undisturbed nature of the creek, and the total lack of any introduced or translocated species means that it is a good representative example of the local aquatic environment. 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.

Jungle Perch 

Banded Rainbowfish

Wet Tropics Tandan

Nest of the Wet Tropics Tandaen on Lot 157

Freshwater Biota observed on Lots 157 & 155, September 2020.

Fishes                                   

Long-finned Eel (Anguilla reinhardtii)

Ox-eye Herring (Megalops cyprinoides)

Wet Tropics Tandan (Tandanus tropicanus)

Eastern Rainbowfish (Melanotaenia splendida splendida)

Banded Rainbowfish (Melanotaenia trifasciata)

Pacific Blue-eye (Pseudomugil signifer)

Silver Grunter (Mesopristes argenteus)

Jungle Perch (Kuhlia rupestris)

Mullet (Liza sp.)

Roman Nose Goby (Awaous acritosus)

Snakehead Gudgeon (Giurus margaritacea)

Empire Gudgeon (Hypseloetris compressa)

Greenback Gauvina (Bunaka gyrinoides)

Mangrove Jack (Lutjanus argentimaculatus)

Reptiles & Amphibians

Saw-shelled Turtle (Wollumbinia latisternum)

Water Frog (Papurana daemeli)

Jungguy Tree Frog (Litoria jungguy)

Giant Tree Frog (Litoria infrafrenata)

Thank you to everyone helping to purchase and protect land in the Daintree Lowland Rainforest. For more information please see our project page.

Ecological surveys are undertaken on the properties we propose to purchase and protect to help us prioritise acquisitions and to understand the flora and fauna we are protecting. A summary of the flora survey conducted on Lot 157 Cape Tribulation Road can be seen here. 

Photos courtesy of Keith Martin & Susan Barclay.