Sleepy Cod Research Articles

Isolation and characterization of 48 SNP markers of sleepy cod, Oxyeleotris lineolata by whole-genome resequencing

Isolation and characterization of 48 SNP markers of sleepy cod, Oxyeleotris lineolata by whole-genome resequencing

Adaptive Management of Malkumba-Coongie Lakes Ramsar Site in Arid Australia—A Free Flowing River and Wetland System

The Malkumba-Coongie Lakes Ramsar Site has extensive terrestrial and freshwater ecosystems (largest Ramsar Site in Oceania, 2,178,952 ha, designated in 1987), including freshwater and salt lakes, lignum swamps and river channels in central Australia. It is supplied by Cooper Creek, a free-flowing Lake Eyre Basin river system. The area includes pastoral leases (97% of site grazed, including a regional conservation reserve (35%)) and a National Park (3%), with the largest oil and gas production field in Australia. We developed a Strategic Adaptive Management (SAM) Plan, linking science, monitoring and management of this social-ecological system, involving stakeholders and workshops. This involved developing a shared vision and hierarchy of objectives linked to management actions and identified outputs and outcomes. We exemplify this approach with explicit and measurable end-points (thresholds of potential concern) culminating from low level objectives for fish communities, particularly the alien sleepy cod Oxyeleotris lineolata. We describe this framework, highlighting the benefits in prioritizing management actions and monitoring in collaboration with a diverse range of stakeholders, driving adaptive feedback for learning. The whole approach is aimed at successfully achieving mutually agreed management objectives and the vision to maintain the ecological character of the Malkumba-Coongie Lakes Ramsar Site.

The ongoing invasion of translocated sleepy cod (Oxyeleotris lineolata) in the Lake Eyre Basin, central Australia

Context Present-day distribution records show that Oxyeleotris lineolata (sleepy cod) has colonised many ephemeral streams and refugial waterholes of the Cooper Creek catchment in the Lake Eyre Basin within a decade of the first record or capture. When introduced to new habitats outside its natural range, this species is considered to be a serious conservation risk to native fish species. Aims The present study aims to document the transport, establishment, colonisation and integration of O. lineolata in the Lake Eyre Basin, and quantify its impact on native fish assemblages. Methods Fish samples were taken annually in 21 waterholes between 2011 and 2016, by using a combination of single- and double-winged fyke nets. We collected novel diet and life-history information from 242 O. lineolata individuals across their known distribution. Key results Abundance, length distribution and life-history information suggested a ‘colonising front’ moving downstream, across state jurisdictional boundaries and into the Coongie Lakes Ramsar site. Oxyeleotris lineolata diet is most similar to that of two native generalist invertivore–piscivores and preys on several native fish species. With a derived longevity in excess of 15 years and a life-history strategy that combines batch spawning, high fecundity and parental care (i.e. high juvenile survivorship), there is real potential for O. lineolata to dominate fish assemblages in waterholes that provide refuge for native fishes during dry periods. Conclusions The present study showed that O. lineolata has the potential to negatively influence native fish assemblages through both competition and predation in refugial waterholes. Eradication of O. lineolata from the Cooper Creek catchment in central Australia is highly unlikely, given its widespread distribution, the remoteness of the receiving landscape and a current lack of resources to monitor spread and attempt eradication at the moving front of the Cooper Creek population. Implications Achieving greater awareness of the potential impacts of introducing or spreading non-native species is an important first step towards preserving the native fish fauna of the Lake Eyre Basin. Further research is warranted to fully understand the current and potential future distribution of O. lineolata in the basin, its biological and ecological requirements, and influence on native fish species and assemblages.

The complete mitochondrial genome of the sleepy cod (Oxyeleotris lineolatus)

The complete mitochondrial genome of the sleepy cod (Oxyeleotris lineolatus) is determined for the first time in this study. It is a circular molecule of 16,519 bp in length, consisting 37 genes, typically found in other vertebrates. The AT content of the overall base composition of the whole mitogenome was 53.90%, while the control region was 62.59%. The protein-coding genes and 6 CSBs were identified. The sequence information could play an important role in the study of phylogenetic relationships between the sleepy cod and its related species.

Complete mitochondrial DNA sequence and phylogenic analysis of Oxyeleotris lineolatus (Perciformes, Eleotridae)

In this study, the mitochondrial genome of Oxyeleotris lineolatus was first determined. The length of entire mtDNA sequence was 16,522 bp with (A + T) content of 53.81%, and it contained 13 protein-coding genes, two rRNAs, 22 tRNAs, and a control region. The gene order and the orientation are similar to some typical fish species. The data will provide useful molecular information for phylogenetic studies concerning O. lineolatus and its related species.

The efficacy of clove oil for anaesthesia of eight species of Australian tropical freshwater teleosts

AbstractThe efficacy of clove oil for anaesthesia was examined on eight species of Australian tropical freshwater fishes: the native Mulgrave goby (Glossogobius bellendenensis, Gobiidae), empire gudgeon (Hypseleotris compressa) and sleepy cod (Oxyeleotris lineolatus) (both Eleotrididae), Eastern rainbowfish (Melanotaenia splendida, Melanotaeniidae), Pacific blue‐eye (Pseudomugil signifer, Pseudomugilidae), and eel‐tailed catfish (Tandanus tandanus, Plotosidae), and the non‐native species spotted tilapia (Pelmatolapia mariae, Cichlidae) and guppy (Poecilia reticulata, Poecilidae). Induction to anaesthesia, recovery from anaesthesia and survival of fish were determined for five concentrations (20 mg/L, 30 mg/L, 40 mg/L, 80 mg/L, and 160 mg/L). A 20 mg/L clove oil concentration was not sufficient to induce a loss of reflex reactivity within 10 min for most individuals (> 85%) in the eight species examined. Effective clove oil concentrations for anaesthesia induction and recovery (40–80 mg/L) for seven out of the eight species examined overlap with those reported for other tropical freshwater fish species. Differences in induction and recovery times among treatments were not always independent of fish size for G. bellendenensis, M. splendida, O. lineolatus, and P. mariae, emphasizing the importance of taking biological and environmental factors into account when determining and applying effective clove oil concentrations for anaesthesia in fish. In contrast, long recovery times and mortality for T. tandanus in even relatively low concentrations suggests that clove oil may not be an appropriate anaesthetic for at least some fish species.

CARBON FROM PERIPHYTON SUPPORTS FISH BIOMASS IN WATERHOLES OF A WET–DRY TROPICAL RIVER

ABSTRACTThe identification of the dominant sources of carbon supporting consumer biomass in aquatic food webs is often difficult but essential to understanding the limits to aquatic secondary production. Stable isotope analysis (SIA) is a powerful tool to estimate the contribution of different sources to consumers, but most food web studies using this approach limit analyses to a few key consumer taxa rather than measuring biomass‐weighted contribution of sources to the entire community. Here we combined stable isotope analysis with standardized measurements of abundance and biomass of fishes and invertebrates in seven waterholes of a wet–dry tropical river sampled early and late in the dry season. We showed that periphyton (as opposed to phytoplankton and terrestrial C3 plant detritus) was responsible for most standing fish biomass (range 42%–97%), whereas benthic invertebrates were reliant on a mixture of the three sources (range 26%–100%). Furthermore, larger, older fishes at high trophic levels (catfish Neoarius spp., sleepy cod Oxyeleotris lineaolatus and barramundi Lates calcarifer) were supported almost exclusively by periphyton. Phytoplankton and detritus supported a considerable biomass of benthic and pelagic invertebrates, but only in taxa that occupied low trophic levels (e.g. snails). These measurements provide further evidence that although periphyton is relatively inconspicuous relative to other sources, it contributes disproportionately to metazoan biomass in wet–dry tropical rivers. Copyright © 2012 John Wiley & Sons, Ltd.

The effect of fructo-oligosaccharides on blood RBC count and digestive enzyme activities of oxyeleotris lineolatus

This study was designed to evaluate the effect of fructo-oligosaccharides (FOS) on blood RBC (red blood cell) count and digestive enzyme activities of oxyeleotris lineolatus. 60 oxyeleotris lineolatus were randomly divided into three groups with 20 fish in each group: control, low and high dose of FOS-treated groups. Animals in the control group consumed basic feed, animals in FOS-treated groups consumed the feed containing 1.5 and 3% FOS, respectively. After 20 days of FOS administration, growth rate, blood RBC count andhemoglobin (Hb) level of oxyeleotris lineolatus were dose-dependently significantly enhanced (P < 0.05) compared to control group, in addition, digestive enzyme activities in stomach and intestine of oxyeleotris lineolatus were dose-dependently significantly enhanced (P < 0.05) compared to control group. The present data indicated that supplementation of FOS could improve nutritive value of food through altering its digestibility and intestinal morphology. In other words, the addition of an appropriate level of digestible carbohydrates to the diet made with this raw material improved the nutritive utilization of the dietary protein and of the diet as a whole. Key words: RBC, Hb, oxyeleotris lineolatus, digestive enzyme, FOS.

Phylogenetic analysis of betanodavirus isolates from Australian finfish

In Australia, disease caused by betanodavirus has been reported in an increasing number of cultured finfish since the first report of mortalities in 1990. Partial coat protein gene sequences from the T2 or T4 regions of 8 betanodaviruses from barramundi Lates calcarifer, sleepy cod Oxyeleotris lineolata, striped trumpeter Latris lineata, barramundi cod Cromileptes altivelis, Australian bass Macquaria novemaculata and gold-spotted rockcod Epinephelus coioides from several Australian states were determined. Analysis of the 606 bp nucleotide sequences of the T2 region of 4 isolates demonstrated the close relationship with isolates from the red-spotted grouper nervous necrosis virus (RGNNV) genotype and the Cluster Ia subtype. Comparison of a smaller 289 bp sequence from the T4 region identified 2 distinct groupings of the Australian isolates within the RGNNV genotype. Isolates from barramundi from the Northern Territory, barramundi, sleepy cod, barramundi cod and gold-spotted rockcod from Queensland, and striped trumpeter from Tasmania shared a 96.2 to 99.7% nucleotide identity with each other. These isolates were most similar to the RGNNV genotype Cluster Ia. Isolates from Australian bass from New South Wales and from barramundi from South Australia shared a 98.6% sequence identity with each other. However, these isolates only shared an 85.8 to 87.9% identity with the other Australian isolates and representative RGNNV isolates. The closest nucleotide identity to sequences reported in the literature for the New South Wales and South Australian isolates was to an Australian barramundi isolate (Ba94Aus) from 1994. These 2 Australian isolates formed a new subtype within the RGNNV genotype, which is designated as Cluster Ic.

Translocation and Spread of Piscivorous Fishes in the Burdekin River, North-eastern Australia

The distribution of the biogeographically distinctive fish fauna of the Burdekin River, north-eastern Australia, is largely determined by the presence of a large waterfall located at the lower quarter of the river’s length. Downstream of the falls, assemblages are characterised by the presence of piscivorous fishes whereas such species are largely absent from upstream reaches. Sleepy cod (Oxyeleotris lineolatus), a large piscivorous gudgeon, was first introduced into the upper reaches of the Burdekin River in 1980 and other releases, both official and unofficial, have occurred subsequently. The population remained small and restricted to the site of introduction for a decade, but expanded in size and distribution after the occurrence of a large flood and entry into a prolonged period of drought. This gudgeon is now present in every tributary system of the Burdekin Basin. Despite the occurrence of substantial temporal variation in fish abundance due to a highly variable flow regime, negative impacts on one species, a small gudgeon (Mogurnda adspersa), are evident. Both deliberate and accidental releases of other species into the upper Burdekin River have also occurred, often to satisfy recreational fishing demand. Such species are typified by large size and piscivorous habit, characteristics alien and inimical to the native fish fauna. It is hypothesised that these piscivorous species may have even greater impact than O. lineolatus in some tributary systems of the upper Burdekin River.

The fishes of Lake Kununurra, a highly regulated section of the Ord River in northern Western Australia

The Ord River, situated in the east Kimberley region of Western Australia, is regulated by two darns that supply irrigation water for tropical agriculture. The regulation of water in the 55 km span of river between these dams has resulted in this section now resembling a lacustrine rather than riverine environment that is reflected in its name, Lake Kununurra. Utilising various sampling techniques we captured/observed 4157 fish from 19 species in 13 families, whilst the presence of a further three species was confirmed by reliable sources. Nematalosa erebi, Craterocephalus stramineus and Melanotaenia austrahs were the three most widespread and abundant species, being encountered throughout the lake and representing -66% of all fish recorded. Ambassis sp., Arius midgleyi, A. graeHei, Glossamia aprion, Amniataba percoides, Hephaestus jenkinsi, Glossogobius giurus and Toxotes chatareus were found throughout the lake but generally at fewer sites and in smaller numbers (-30% of all fish) than the three dominant species. The remaining species Neosilurus ater, Strongylura kreHtii, Leiopotherapon unicolor, Syncomistes but/eri, Lates calcari{er, Mogumda mogumda, Oxyeleotris lineolatus and Ambassis madeayi were generally found at few sites and in low numbers, and accounted for less than 4% of the overall catch. The regulation of the Ord River has apparently altered the species composition and abundances in Lake Kununurra. For example, marine/estuarine species, commonly encountered in the freshwaters of large northern Australian Rivers, are largely absent, while species such as L. unicolor, which is one of the most abundant species in nearby rivers and tropical Australian rivers in general, contributed to <1°/,) of the total catch.

Effects of Added Shelter and Stocking Density on Growth of Sleepy Cod Oxyeleotris lineolatus in Ponds

AbstractSleepy cod Oxyeleotris lineolatus is a species of freshwater goby in demand in Australian markets by consumers of Asian origin. It is related to marble goby Oxyeleotris marmoratus, the most expensive freshwater food fish in Asia, which is cultured throughout southeast Asia in ponds and cages. The performance of sleepy cod in culture conditions was investigated to assess the viability of farming them in northern Australia. Sleepy cod fingerlings (62.8 ± 0.8 mm total length and 2.56 ± 0.095 g) were stocked into experimental ponds at 32,857 fish/ha, and grown out for 8 mo. Shelter was provided in each of three replicate ponds and was absent in three control ponds. The provision of shelter in juvenile growout was found to be of no benefit, although fish in ponds provided with shelter weighed slightly more per unit length than fish in ponds without shelter. Cannibalism was not a problem in growout, and survival was close to 100%. After the shelter trial was completed, fish were graded into large and small classes (three replicates of each), and grown out without shelter at the same density for 158 d. Following that, fish were again graded, and the largest 30% retained from growout at a density of 8,857 fish/ha (large, 198 ± 6.44 g) or 10,000 fish/ha (small, 48.9 ± 1.27 g). These were grown out for 188 d. Growth of selected stock at low densities was slower than earlier growth rates, although smaller fish gained weight more rapidly than larger fish. Growth rates were better than the only published data for marble goby. Further investigation into high density culture and different genotypes of sleepy cod needs to be undertaken to determine the viability of pond culture.

Breeding and fecundity of the endemic Australian gudgeon, sleepy cod Oxyeleotris lineolatus (Steindachner 1867) (Eleotridae)

Sleepy cod ( Oxyeleotris lineolatus Steindachner) is a tropical species of eleotrid native to northern Australia. A related species, sand or marbled goby, is the highest priced freshwater fish in Asia, and a market for a similar fish exists in expatriate Chinese communities. Sleepy cod breed when minimum temperatures reach 24 °C for more than 3 days. During the breeding season the genital papilla is broad and flattened in females compared to the triangular papilla of males and juveniles. Spawning pairs were usually of approximately equal size. Females could spawn up to 10 times during one breeding season. Wet weather increased the frequency of spawning. Eggs were usually laid hanging from the underside of a surface. Most spawning occurred between 05:00 and 10:00 h. Females attended egg masses immediately after spawning, after which males cared for eggs until hatching, 3–5 days later. Agitation of the egg mass was essential for development. The mean number of eggs per spawning was 43 130. Larvae commenced feeding 2–5 days after hatching, on plankton from 100 to 250 μm in size. A spawning trap used to collect egg masses is described. The breeding biology of sleepy cod is considered to be an adaptation to the monsoonal tropics.

Natural-series radionuclides in traditional North Australian aboriginal foods

Activity concentrations of the radionuclides 226Ra, 210Pb, 210Po, 238U, 234U, 230Th, 232Th and 227Ac were measured in edible flesh of traditional Aboriginal food items from the Magela and Cooper Creek systems in the tropical Northern Territory of Australia. Fish, buffalo, pig, magpie goose, filesnake, goanna, turtle, freshwater shrimp and freshwater crocodile were studied. Activity concentrations in water were also measured to enable the calculation of concentration ratios (CRs). For most edible flesh samples, activity concentrations followed the approximate order: 210Po≫ 226Ra> 210Pb>[ 234U∼ 238U]>[ 230Th∼ 232Th]. The 210Po/ 210Pb activity ratio was particularly high (greater than 100) for pig flesh. CRs for fish species fall into two groups. Group 1 (bony bream and sleepy cod) had CRs about five times higher than for group 2 (eight other species). CRs for turtle flesh were similar to those for fish in group 1, while those for turtle liver were about a factor of 10 higher. CRs for magpie goose, filesnake, freshwater shrimp, goanna and crocodile flesh were also of the same order as for fish in groups 1 or 2. Calculations of dose resulting from release of wastewaters from uranium mining operations in the region show that the dominant pathway would be uptake of radionuclides, especially 226Ra, by freshwater mussels, followed by radionuclide uptake by fish.