Cambridge Gulf Research Articles

Regional Assessment of the Conservation Status of Snubfin Dolphins (Orcaella heinsohni) in the Kimberley Region, Western Australia

Implementing conservation measures for data-limited species is a fundamental challenge for wildlife managers and policy-makers, and proves difficult for cryptic marine animals occurring in naturally low numbers across remote seascapes. There is currently scant information on the abundance and habitat preferences of Australian snubfin dolphins (Orcaella heinsohni) throughout much of their geographical range, and especially within the Kimberley region of northern Western Australia. Such knowledge gaps curtail rigorous threat assessments on both local and regional scales. To address this and assist future conservation listings, we built the first comprehensive catalog of snubfin dolphin sightings for the Kimberley. We used these data to estimate the species’ extent of occurrence (EOO) and area of occupancy (AOO) along the region’s 7,000 km coastline, following a simple Bootstrap bivariate kernel approach to combine datasets of varying quality and quantify uncertainty. Our catalog consists of 1,597 visual detections of snubfin dolphins made over a period of 17 years (2004–2020) and collated from multiple sources, including online biodiversity repositories, peer-reviewed scientific articles, citizen science programs, as well as dedicated marine wildlife surveys with local Indigenous communities and Ranger groups. Snubfin dolphins were consistently encountered in shallow waters (<21 m depth) close to (<15 km) freshwater inputs, with high detection rates in known hotspots (e.g., Roebuck Bay, Cygnet Bay) as well as in coastal habitats suspected to be suitable (e.g., Prince Regent River and surrounds, King Sound, Doubtful Bay, Napier Broome Bay and the upper Cambridge Gulf). Bootstrap estimates of EOO and AOO were 38,300 (95% CI: 25,451–42,437) km2 and 700 (656–736) km2 respectively, suggesting that snubfin dolphins in the Kimberley are likely Vulnerable under IUCN criteria B2 at a regional scale, in keeping with their global classification. Our study offers insights into the distribution of a vulnerable coastal cetacean species and demonstrates the value of integrating multiple data sources for informing conservation assessments in the face of uncertainty.

Urogymnus acanthobothrium sp. nov., a new euryhaline whipray (Myliobatiformes: Dasyatidae) from Australia and Papua New Guinea.

The Mumburarr Whipray, Urogymnus acanthobothrium sp. nov. is described from a single specimen taken from the Cambridge Gulf, Western Australia, and from images of 10 other specimens from northern Australia and Papua New Guinea (all observed but not collected). It is a very large ray that attains at least 161 cm disc width, making it amongst the largest of the whiprays. The ventral tail below the caudal sting has a low, short-based fold. A ventral tail fold (or a dorsal fold) has not been recorded for any other himanturin stingray in the Indo-West Pacific. Molecular data suggest it is most closely related to a similar but more widely distributed cognate, U. granulatus. Both of these species share a suboval disc shape, similar squamation patterns, and the tail posterior to the sting is entirely white (at least in small individuals). U. acanthobothrium sp. nov. differs from U. granulatus in having a longer and more angular snout, longer tail, more posteriorly inserted caudal sting, lacks white flecks on the dorsal surface, and the ventral disc is uniformly white (rather than white with a broad black margin). It co-occurs with two other morphologically distinct Urogymnus in the region (U. asperrimus and U. dalyensis). Like U. dalyensis it occurs in both brackish and marine waters. A key is proved to the members of the genus Urogymnus.

Sources of organic matter in sediments from the Ord River in tropical northern Australia

The sources of organic matter in the sediments from the Ord River and estuary were assessed using stable carbon isotope values (δ 13C), lipid biomarkers and distributions of chlorophylls and carotenoids as part of a larger multidisciplinary study examining the biogeochemistry of this tropical, macrotidal and large scale estuary. Two field trips were undertaken to obtain samples from both the dry (September, 2002) and wet (February, 2003) seasons. Both biomarker and stable isotope data indicate predominant contributions of organic material from the surrounding vegetation. However, the character of the terrestrial organic matter changes from the freshwater to the marine sections of the river. The sterol profiles in the freshwater sediments are relatively simple and dominated by the C 29 sterols 24-ethylcholest-5-en-3β-ol (sitosterol) and 24-ethylcholesta-5,22E-dien-3β-ol (stigmasterol) with small quantities of 24-methylcholest-5-en-3β-ol (campesterol), all of which are common sterols in higher plants. In the dry season survey, triterpenoid alcohols were generally absent from the freshwater sediments, but in the wet season there was a small contribution from compounds such as α- and β-amyrin and lupeol, indicating additional higher plant input, possibly from further inland in the catchment. Within Cambridge Gulf and the Ord estuary, the waterways are fringed with mangroves which contribute substantial quantities of organic matter as shown by distinctive distributions of triterpenoid alcohols dominated by taraxerol. However, this is not the major triterpenoid in the mangrove trees studied, but seems to be considerably more stable to biodegradation and so dominates the triterpenoids found. Isotope, biomarker (fatty acids, phytol and sterols) and pigment data suggest that only a small part of the sedimentary organic matter is derived from microalgae. Contributions from diatoms (24-methylcholesta-5,22E-dien-3β-ol; fucoxanthin), green algae (Δ 7-sterols), cyanobacteria (C 32 hopanol; zeaxanthin) and dinoflagellates (dinosterol; peridinin) could be recognized. In this environment the high turbidity of the water column severely limits phytoplankton production, although productivity of microphytobenthos on the banks of the river can potentially be high.

Allopatric distribution of juvenile red-legged banana prawns ( Penaeus indicus H. Milne Edwards, 1837) and juvenile white banana prawns ( Penaeus merguiensis De Man, 1888), and inferred extensive migration, in the Joseph Bonaparte Gulf, northwest Australia

During October to December 1997, we trawled estuarine habitats in the Joseph Bonaparte Gulf (JBG) to determine the distribution of juvenile red-legged banana prawns, Penaeus indicus (H. Milne Edwards, 1837) and white banana prawns, Penaeus merguiensis (de Man, 1888). We made 229 beam-trawls at 185 sites, mostly over a 100-m path (3-min duration). A Global Positioning System (GPS) receiver was used to verify our location. During October to December 1998, we intensively resampled three of the rivers that were sampled in 1997 to confirm the gulf-wide distribution of P. indicus and P. merguiensis and to investigate the microhabitat use of P. indicus. We chose previously sampled and new sites in Forsyth Creek (eastern JBG), the Lyne River (Cambridge Gulf), and the Berkeley River (western JBG). We made 249 trawls at 21 sites, mostly over 100 m. Juvenile banana prawns were abundant in eastern JBG, Cambridge Gulf and western JBG. They were not abundant in southern JBG, although fewer trawls were made there, due to its inaccessibility. In eastern JBG and Cambridge Gulf, over 96% and 73% (respectively) of juvenile banana prawns were P. indicus and they were more abundant there than in the western JBG. Conversely, in the western JBG over 93% of the juvenile banana prawns were P. merguiensis and they were more abundant than in the eastern JBG and Cambridge Gulf. The Lyne River in the northwestern Cambridge Gulf seems to be the transition zone; both P. indicus and P. merguiensis are equally abundant. P. indicus are most abundant on the mangrove-lined muddy banks of waterways within mangrove forests, similar habitats to P. merguiensis. Within these habitats, they were most abundant in gutters and small creeks, rather than rivers and large creeks. Few P. indicus or P. merguiensis were caught in 100 m 2 trawls undertaken midriver (on the channel bottom and on emergent banks), although these habitats may be only 100 m from the mangrove-lined habitats. In all creek and river habitats, both species are most catchable at low tide (irrespective of daylight or darkness) when they move out of the mangrove forests and accumulate in the remnant water bodies. The offshore fishery for P. indicus is in northwestern JBG in waters 50–80 m deep, about 300 and 200 km, respectively, from where juveniles are abundant in their extensive inshore habitats in east JBG and in Cambridge Gulf, demonstrating a geographical separation of the juvenile and adult phases. Postlarval P. indicus, spawned offshore, must use tides and currents to travel south and east to reach nursery habitats. Emigrant subadults must migrate north and west, across relatively shallow inshore sand substrates (30–40 m deep) to reach their offshore habitats.

The Impact of Damming the Ord River on the Fine Sediment Budget in Cambridge Gulf, Northwestern Australia

Abstract Cambridge Gulf is a turbid embayment about 50 km long, with a mean water depth of about 12 m. The spring tidal range is 8 m. At its apex, the gulf divides into two estuaries, namely the West Arm that drains the mostly undisturbed Durack and Pentecost rivers, and the East Arm that drains the Ord River. As a result of a dam constructed in 1970 on the Ord River, the river flood regime has been greatly affected within the East Arm, having silted by an average of 3 m. By contrast the West Arm bathymetry has remained practically unchanged for the last 100 years. Oceanographic studies suggest that the West Arm exports fine sediment at a rate of about 40,000 ton d−1, and that most of that sediment is now imported into the East Arm and does not reach Cambridge Gulf. Negligible net sediment flow was measured at the mouth of the gulf. This suggests that the pre-dam Cambridge Gulf received a total sediment inflow of about 100,000 ton d−1, and about zero at present. Sediment is currently being redistributed w...

Movements and home ranges of radio-tracked Crocodylus porosus in the Cambridge Gulf region of Western Australia

VHF radio-tags were attached to 16 estuarine crocodiles that were tracked between October 2001 and May 2003. Male (n = 12) and female (n = 4) crocodiles exhibited distinctly different patterns of movement. Females occupied a small core linear range (1.3 ± 0.9 km) on the main river channel during the dry season and moved up to 62 km to nesting habitat during the wet season, returning to the same core area the following dry season. They occasionally made excursions away from their core areas during the dry season. Males moved considerable distances along the Ord River throughout the year. The largest range recorded was 87 km for a 2.5-m juvenile male. However, ranges of males did not appear to be related to body size, with the largest two ranges being recorded for the smallest (2.5 m) and largest (4.3 m) males tagged. Rates of movement of males did not differ significantly between three size classes of males but there were significant seasonal differences, with the highest mean rates of movement occurring during the summer wet season (4.0 ± 5.4 km day–1). However, males were quite mobile during the dry season and the highest rate of movement detected was 23.3 km day–1 for a 4.3-m male at the end of July. The highest rate of sustained movement was 9.8 km day–1 for a translocated 2.6-m juvenile male, which travelled 118 km in 12 days to return to the area of its capture. Neither males nor females showed exclusive habitat preferences for any of four broad riverine habitats identified on the Ord River. However, the three largest males had activity centres that they returned to frequently despite numerous excursions throughout the year, both up- and downriver. Males had substantial range overlaps with no obvious spatial partitioning, suggesting that territoriality is not an important behavioural characteristic of free-ranging male crocodiles along the Ord River.

Rapid, Human-Induced Siltation of the Macro-Tidal Ord River Estuary, Western Australia

Field studies on the sediment dynamics of the two arms of Cambridge Gulf, tropical Western Australia, were undertaken. The system is macro-tidal with 8m tides. The West Arm is the estuary of the Durack and Pentecost rivers, which are largely untouched by human activities. The East Arm is the estuary of the Ord River affected by land clearing which started 100 years ago, and by two river dams constructed 30 years ago. Prior to damming of the Ord River, the natural flow in all rivers was highly seasonal, characterized by small, at times negligible, flow during the dry season, which lasts eight months, and occasional river floods during the wet season, which lasts four months. The river flow has been regulated in the East Arm as a result of damming; this resulted in suppressing large river floods. The salinity intrusion length has decreased by about 50% in the East Arm following river damming. The East Arm has silted measurably over the last 30 years, with the stream cross-sectional area decreasing by about 50%. Field and numerical studies suggest that this is due to the dam-induced suppression of large river floods, which has in turn allowed a greater amount of tidal pumping of sediment into the East Arm from Cambridge Gulf. Since tidal pumping is increasing as the system is silting, the East Arm appears to now be geomorphologically unstable as a result of human activities. Numerical studies suggest it may take as little as 100 years for the Ord River to reach a new equilibrium. Modelling suggests that this equilibrium may be characterized by a salinity intrusion length half that before damming, a channel width and depth reduced by 70%, and a much stronger tidal asymmetry characterized by an increasing size of the tidal bore. The West Arm appears to be at equilibrium since there has been no net loss or gain of sediment for the last 111 years. Tidal dynamics and river floods appear responsible for self-scouring this channel.

Catalogue of world wide diamond and kimberlite occurrences: a selective and annotative approach

Catalogue of world wide diamond and kimberlite occurrences: a selective and annotative approach

Parapolynemus, a New Genus for the Polynemid Fish Previously Known as Polynemus verekeri

The generic name Parapolynemus is proposed for the polynemid fish originally identified as Polynemus verekeri Saville-Kent. An osteological examination of the species of Polynemus Linnaeus revealed striking and unique characters in Polynemus verekeri Saville-Kent. Parapolynemus verekeri is redescribed. This is the smallest species in Polynemidae. Polynemus intermedius Nichols is a junior synonym of P. verekeri. Parapolynemus verekeri occurs along part of the north coast of Australia and south coast of New Guinea. IN his genus Polynemus, Linnaeus (1758) named three divergent species that are today recognized as Polynemus paradiseus, Pentanemus quinquarius, and Polydactylus virginicus. Feltes (1991) noted that there are two major lineages in the Polynemidae. Polynemus is representative of those polynemids that have a marked reduction in the size of the orbit, with a corresponding modification of the associated bones, and insertion of the pectoral fin relatively high on the body. The species previously recognized as Polynemus verekeri Saville-Kent shares these characters; however, based on a suite of conspicuous differences, it is placed in a new genus, Parapolynemus. The species of Polynemus occur from the Ganges Delta to Borneo, whereas Parapolynemus verekeri has been taken in Australia from the Cambridge Gulf in northern Western Australia to Arnhem Land, Northern Terri

New camaenid land snails from the northeast Kimberley, Western Australia

Abstract Seven new species and subspecies of camaenid land snails from northeastern Western Australia are described or discussed. The species all have very restricted ranges, and are found near the Northern Territory border in the area from both sides of the Cambridge Gulf in the north, to the hills lying southeast of Turkey Creek. The six described species and subspecies are: Amplirhagada cambridgensis from the Lyne River on the west side of Cambridge Gulf; Amplirhagada osmond’ from the Osmond Range-Palms Yard area southeast of Turkey Creek; Ordtrachia elegans from an isolated outlier of the Jeremiahi Hills northeast of Kununurra; Ningbingia australis elongata and Crisfilabrum rectum from the Ningbing Ranges north of Kununurra; and Mesodontrachia cockbumensis from the Cockburn Range southwest of Wyndham. Another probable new species of Cristilabrum from the Ningbing Ranges currently is represented by very limited material. It is not described at this time, but is illustrated for future-reference.

Schooling at Oombulgurri as Part of the Development of a Community

In October 1973, a small group of about 30 Aboriginal people moved from Wyndham, Western Australia, forty miles across the Cambridge Gulf, to establish the community of Oombulgurri on the site of the now closed Forrest River Mission.The move was from the ‘futurelessness’ of existence on the Wyndham Reserve to a chance to build their own future as an autonomous community living on tribal land. A Mawaba (Executive) was elected. The Oombulgurri Association employs an auxiliary staff whose role is to advise the community. The Auxiliary has no decision-making power.Just twelve months later, Oombulgurri has grown to 200 people, of whom 60 are school-age children, with an additional 30 below school age. From the outset those moving back to Oombulgurri – most of whom made little real attempt to ensure their children attended school regularly in Wyndham – insisted that a school must be included in the community plan. The school functions as a community school. Two qualified teachers are employed by the Oombulgurri Association. They work in the school with four Aboriginal teaching assistants selected from the community. Each of these assistants is involved fully in planning and decision making, and is totally responsible for the day to day teaching and disciplining of various groups within the school. It has become yery clear that the students gain a great deal by having some of their own people involved in actual teaching and curriculum building. The school has become much more than an institution imposed on the community. Women from the community are also involved in the pre-school and child care centre. Working with a member of the Auxiliary, the women plan the curriculum and carry out the daily program.

Anniversary Address - Western Australia and its goldfields

In presenting to your notice the following brief description of the Goldfields of Western Australia, I desire to convey to this Society my thanks for the honour you have done me in inviting me to be present before you this evening, and thus enabling me to deal with a subject in which I take such a deep interest, viz.:—the Goldfields of Western Australia. Little has been printed about this vast colony which I have not read; and I have likewise endeavoured in a humble way, within the last few years, to see for myself some evidences of her future greatness. Three times I have explored the North-Western district. On the first occasion I started from London early in April 1890, and made an expedition lasting three months. Again, in April 1891, I was engaged to make further investigations over the same line of country; and lastly, I visited the North-West in the present year. Then, from time to time, I have made a point of sailing to every port from Cambridge Gulf to King George's Sound, sometimes in regular coasting-vessels, and sometimes in small vessels which I hired for the purpose. From each of these ports I made journeys inland of varied duration, and with various objects in view. Western Australia has at present three great obstacles to her progress. The first is physical—her lack of water, which can only be combated by science. The second, her scantiness of population, is being slowly removed. The third can readily be surmounted,

Preliminary observations on a natural history collection made in connection with the surveying cruise of H.M.S. Myrmidon, at Port Darwin and Cambridge Gulf -- Sept. to Nov., 1888

Preliminary observations on a natural history collection made in connection with the surveying cruise of H.M.S. Myrmidon, at Port Darwin and Cambridge Gulf -- Sept. to Nov., 1888