Zampatti B.P.,SARDI Aquatic Sciences Center |
Zampatti B.P.,University of Adelaide |
Leigh S.J.,SARDI Aquatic Sciences Center
Marine and Freshwater Research | Year: 2013
Restoring fish populations in regulated rivers requires an understanding of relationships between hydrology and population dynamics. In the present study, spawning and recruitment of golden perch, Macquaria ambigua ambigua, were investigated in relation to flow in the regulated lower River Murray. All life stages were sampled in three successive years, with peak flows of 8500 (2004-05), 15000 (2005-06) and 7000MLday-1 (2006-07). Larvae occurred only in November/December 2005, and young-of-year fish only in early 2006. Counts of daily increments in otolith microstructure indicated spawning in late October/early November 2005. Back-calculated birth years for adults, derived from otoliths and compared with the hydrograph for the preceding 25 years, revealed the dominance of three year classes spawned in association with increased discharge in 2000, 1998 and 1996. In 2007, an additional year class of 1-year-old fish appeared, following spawning in 2005. In each case, strong recruitment followed spring-summer spawning, when peak flows were >14000MLday-1 and water temperatures would have exceeded 20°C. Restoration of within-channel flows of 15-25000MLday-1 from late spring through summer would promote spawning and recruitment and improve the resilience of golden perch populations in the lower Murray. Journal compilation © CSIRO 2013.
Wedderburn S.D.,University of Adelaide |
Hammer M.P.,South Australian Museum |
Bice C.M.,SARDI Aquatic Sciences Center
Hydrobiologia | Year: 2012
Over-abstraction of water places unsustainable pressures on river ecosystems, with the impacts amplified under drought conditions. Freshwater fishes are particularly vulnerable due to associated changes in water quality, and habitat availability, condition and connectivity. Accordingly, fish assemblages are ideal indicators of the impacts of drought and over-abstraction. The Murray-Darling Basin (MDB), south-eastern Australia, terminates at the Ramsar listed Coorong and Lower Lakes, which comprise Lake Alexandrina and Lake Albert. Over-abstraction and extreme drought during the last decade has placed these lakes under severe environmental stress. The purpose of this study was to investigate shifts in fish assemblages caused by substantial water level recession and salinization in the Lower Lakes. Small-bodied fish assemblages were sampled at the beginning and several years into the drought. Off-lake habitats held diverse fish assemblages in 2003, but most sites were dry by 2009. Remaining habitats were disconnected, salinities increased substantially, and aquatic vegetation shifted from freshwater to salt-tolerant species. There was a substantial decline in the proportion of specialist species, especially diadromous and threatened species, and an emerging dominance of generalist freshwater and estuarine species. The findings warn of the inevitable ecological impact of over-allocating water for human use in drought-prone regions, and highlight the need for adequate environmental water allocations. This study also emphasises that understanding the ecological attributes of a fish species, and the subsequent assignment to a functional group, will help predict vulnerability to decline and extirpation. © 2012 Springer Science+Business Media B.V.
Tanner J.E.,SARDI Aquatic Sciences Center |
Tanner J.E.,University of Adelaide
Estuaries and Coasts | Year: 2014
The loss of seagrass meadows is an increasing problem worldwide. The important role that these meadows play in coastal ecosystems has resulted in substantial attention to the development of seagrass restoration techniques. Here, I present long-term (up to 5 years) results of seagrass restoration off the coast of Adelaide, South Australia, where >5,000 ha of seagrass has been lost and where trials of traditional restoration techniques using seeds and transplants have failed due to high levels of sand and water movement. Hessian (burlap) sandbags were deployed bimonthly (with some interruptions) from November 2007 to November 2012 (a total of 24 deployments), with a mix of single- and double-layered bags, to provide a stable substrate for naturally occurring Amphibolis seedlings to recruit to. At the end of the study (January 2013), bags deployed in August 2009 had similar stem densities to those found in adjacent natural meadows (15.2 ± 1.4 (SE) vs 18.6 ± 2.5). Bags deployed in May 2008 and August 2011 had 12.8 ± 2.3 and 13.2 ± 2.2 stems, respectively. Furthermore, stem lengths on older bags were greater than those on natural meadows (42.1 ± 4.2 after 62 months vs 30.2 ± 1.5 cm). While there was some interannual variation in recruitment success, the strongest predictor of success was deployment month. Bags deployed outside the austral winter recruitment season did not retain the ability to catch a large number of recruits, indicating that any restoration using this technique will have to be undertaken between approximately May and August to maximize chances of success. © 2014, Coastal and Estuarine Research Federation.
Zhang S.,Northwest University, China |
Sadras V.,SARDI Aquatic Sciences Center |
Chen X.,China Agricultural University |
Zhang F.,China Agricultural University
Field Crops Research | Year: 2013
Improvement of wheat water use efficiency (WUE = grain yield per unit seasonal evapotranspiration) in the dryland area of Loess Plateau of China is an imperative imposed by the critical situation of water resources, as well as by the demographic pressure. The aims of this study were (i) assessing WUE of dryland wheat in the Loess Plateau, and (ii) identifying management practices returning higher efficiencies. We compiled a data base of 39 sets of experiments spanning 20 years, where conventional practice was compared with alternatives including NT, no tillage without straw mulching; RT, reduced tillage without straw mulching; NTS, no tillage with straw mulching; SS, subsoiling with straw mulching; CTS, conventional tillage with straw mulching; PM, plastic film mulching 100%; RM, ridge mulched with plastic film + bare furrow; RMS, ridge mulched with plastic film + furrow mulched with crop straw.Yield ranged from 818 to 7900kgha-1 and WUE from 3.4 to 23.4kgha-1mm-1; the maximum yield and WUE were achieved under RM and RMS and the minimum under NT/RT. Practices had small and inconsistent effect on seasonal evapotranspiration, hence variation in both yield and WUE were attributable to changes in the contribution of soil evaporation to total evapotranspiration, and the partitioning of seasonal water use before and after anthesis. The yield-evapotranspiration relationship indicated that present yields are limited by environmental (e.g. seasonal distribution of rainfall) and management factors. The range of WUE is very large for the same or various practices, and thus offers tremendous opportunities for maintaining or increasing WUE. Implications for crop management and further improvement in yield and WUE are discussed. © 2013 Elsevier B.V.
Zampatti B.P.,SARDI Aquatic Sciences Center |
Bice C.M.,SARDI Aquatic Sciences Center |
Jennings P.R.,SARDI Aquatic Sciences Center
Marine and Freshwater Research | Year: 2010
River regulation can diminish freshwater flows to estuaries and compromise estuarine functionality. Understanding biotic responses to altered flow regimes is imperative to effectively manage aquatic ecosystems. The present study investigated temporal variation in fish assemblage structure and the recruitment of catadromous fish in the Coorong estuary at the terminus of the Murray River, in south-eastern Australia. Over the three-year study period, freshwater inflows to the estuary diminished and ultimately ceased, disconnecting freshwater and estuarine environments. It was hypothesised that these conditions would lead to (1) increases in estuarine salinities and concomitant changes in fish assemblage structure and abundance, and (2) decreased recruitment of catadromous fish. As freshwater inflow decreased, salinities immediately downstream of a series of tidal barrages increased from brackish to marinehypersaline, species richness and diversity decreased, freshwater and diadromous species became less abundant and assemblages were increasingly characterised by marine species. Furthermore, the abundance of young-of-year catadromous fish decreased dramatically. Excessive regulation of freshwater inflows is resulting in the Coorong estuary resembling a marine embayment, leading to a loss in species diversity. We suggest, however, that even small volumes of freshwater may promote diversity in estuarine fish assemblages and some recruitment of catadromous species. © CSIRO 2010.
Humphries A.W.,SARDI Aquatic Sciences Center
Crop and Pasture Science | Year: 2012
Lucerne is a deep-rooted herbaceous perennial legume with high levels of summer production and adaptation to a broad range of agro-ecological environments in southern Australia. The ability of lucerne to extend the growing season of winter-based pasture and respond quickly to rainfall after periods of drought makes it one of the most valuable plants in our feed base. However, for all the advantages of lucerne, it remains underutilised. Lucerne is often considered to be a speciality fodder crop, requiring careful management to achieve high levels of production and persistence. This paper investigates the opportunity of whole-farm integration of lucerne; from speciality fodder crop to traditional pasture. The future trends of lucerne production in temperate grazing and intensive dairy systems are discussed in relation to breeding objectives identified to meet these demands. If lucerne is to be used more commonly as a pasture, the plant and systems must adapt. This paper investigates the plant traits and management principles that are important for growing lucerne in mixtures with other plants and improving the integration of lucerne into the whole-farm plan. Journal compilation © CSIRO 2012.
Zampatti B.,SARDI Aquatic Sciences Center |
Leigh S.,SARDI Aquatic Sciences Center
Ecological Management and Restoration | Year: 2013
Flooding is often considered a stimulus for production of fish in floodplain rivers. In the southern Murray-Darling Basin (MDB), Australia, however, few native fish species have been shown to use the floodplain for spawning, and recruitment has been positively and negatively associated with flooding. In 2010/11, extensive flooding in the lower River Murray provided an opportunity to investigate the recruitment response of Golden Perch (Macquaria ambigua ambigua) following 10 years of drought and floodplain isolation. Annual variation in Golden Perch abundance and recruitment were investigated in anabranch and main channel habitats at Chowilla in the floodplain geomorphic region of the lower River Murray over a 7-year period incorporating the flood and 6 years of in-channel flow. Spatial variation in recruitment in the lower River Murray was also investigated by comparing the age structure of Golden Perch in the swamplands/lakes, gorge and floodplain geomorphic regions. Golden Perch abundance in the Chowilla region increased significantly postflooding compared with drought years. Age structures indicated that increased abundance was due predominantly to fish spawned during the flood (2010/11) and the previous year (2009/10), which was characterised by in-channel flows. Age structure was similar in the nearby Katarapko Anabranch system indicating a uniform postflood recruitment response in the floodplain geomorphic region. Juvenile Golden Perch from the 2010/11 and 2009/10 cohorts were less apparent in the gorge and swamplands/lakes regions. Golden Perch have flexible life histories and will spawn and recruit in association with in-channel rises in flow and overbank flows, but significant increases in abundance in the lower River Murray may result from overbank flooding. Contemporary approaches to flow restoration in the MDB emphasise overbank flows and floodplain processes. We suggest, however, that environmental flow management that incorporates floodplain and in-channel processes, at appropriate spatio-temporal scales, will result in more robust populations of Golden Perch. © 2013 Ecological Society of Australia.
Tanner J.E.,SARDI Aquatic Sciences Center
Estuaries and Coasts | Year: 2011
The epifaunal and infaunal assemblages associated with Caulerpa taxifolia in the Port River/Barker Inlet estuary of Adelaide, South Australia were compared to those associated with the co-occurring seagrass Zostera muelleri. Both taxa contained an abundant and diverse fauna, but with substantial differences between them. In particular, ophiuroids (brittle stars) were abundant in Caulerpa, but almost absent from Zostera. Crustaceans, mostly amphipods, and annelids, mostly polychaetes, were abundant in both Caulerpa and Zostera, but the families present differed substantially. Taxa that dominated in Caulerpa include the amphipods: Amphithoidae, Corophiidae, and Talitridae; and the polychaetes: Cirratulidae, Nephtyidae, and Nereididae. Zostera was dominated by the polychaetes: Capitellidae; amphipods: Caprellidae; isopods: Sphaeromatidae; and Neballidae. Some taxa (arthropods, nemerteans, and echinoderms) had their peak abundance during summer, when Caulerpa biomass was highest, while others did not seem to respond to changes in Caulerpa biomass. Overall, epifauna were 4-9 times more abundant in Caulerpa than Zostera, while infauna were slightly more abundant in Zostera, indicating that at least in South Australia, Caulerpa provides a functional habitat for a diverse array of taxa. © 2011 Coastal and Estuarine Research Federation.
Soede N.M.,Wageningen University |
Langendijk P.,SARDI Aquatic Sciences Center |
Kemp B.,Wageningen University
Animal Reproduction Science | Year: 2011
The oestrous cycle in pigs spans a period of 18-24 days. It consists of a follicular phase of 5-7 days and a luteal phase of 13-15 days. During the follicular phase, small antral follicles develop into large, pre-ovulatory follicles. Being a polytocous species, the pig may ovulate from 15 to 30 follicles, depending on age, nutritional status and other factors. During the luteal phase, follicle development is less pronounced, although there is probably a considerable turnover of primordial to early antral follicles that fail to further develop due to progesterone inhibition of gonadotrophic hormones. Nevertheless, formation of the early antral follicle pool during this stage probably has a major impact on follicle dynamics in the follicular phase in terms of number and quality of follicles. Generally, gilts are mated at their second or third estrous cycle after puberty. After farrowing, pigs experience a lactational anoestrus period, until they are weaned and the follicular phase is initiated, resulting in oestrus and ovulation 4-7 days after weaning. This paper describes the major endocrine processes during the follicular and luteal phases that precede and follow ovulation. The role of nutrition and metabolic status on these processes are briefly discussed. © 2011 Elsevier B.V.
Riffkin P.,DPI Victoria |
Potter T.,SARDI Aquatic Sciences Center |
Kearney G.,36 Paynes Road
Crop and Pasture Science | Year: 2012
Area and production of canola (Brassica napus L.) in the High Rainfall Zone (HRZ) of southern Australia has increased significantly over the past decade. Varieties available to growers have not been bred specifically for the HRZ and are generally adapted to the drier regions of the cropping belt. Field experiments were conducted at Hamilton in south-west Victoria in 2005, 2006 and 2008 to identify canola traits and management suited to the HRZ of southern Australia. Nine varieties with different reported maturities (winter and spring types) were sown at either two times of sowing and/or under different nitrogen (N) fertiliser regimes. Dates of key phenological development were recorded, dry matter was determined at bud, flowering and maturity and grain yield and yield components were determined at harvest. Plant traits and climate data were assessed in relation to grain yield. Yields of the winter types were either significantly (P0.05) greater or not significantly less than the spring types in all 3 years and similar to those reported under experimental conditions in Europe. This was despite the winter types flowering up to 35 days later than the spring types and spring rainfall being approximately half that of the long-term average. In general, the winter types had greater early vigour, greater dry matter production at the bud, flowering and maturity stages and were taller than the spring types. Regression analysis showed positive relationships between grain yield and pod density and plant size (dry matter and plant height). Plant size was influenced by variety, time of sowing and N fertiliser application rates. Crops in the HRZ were able to sustain more seeds per pod at larger canopy sizes and pod densities than those achieved in the northern hemisphere. Despite the number of pods per g of dry matter at flowering being nearly double that reported in the UK, there was little apparent reduction in the number of seeds per pod. It is possible that higher solar radiation and warmer minimum temperatures in the HRZ of Australia provide conditions more favourable for growth before, and during grainfill. This indicates that different dry matter production and yield component targets may be appropriate for canola in this environment especially in more typical seasons. It is likely that growers will need to sow new, later maturing varieties earlier and with higher rates of N fertiliser than is current practice in Australia. This study indicates that winter types may have the potential to provide improvements to the yield of canola in the HRZ either through the direct importation of varieties from overseas or through the identification and incorporation of desired traits into existing material. It is recommended that a wider range of germplasm be assessed over a greater geographical area to identify traits and management practices to optimise phenology and canopy structure. This information can be used to help inform breeders on crop improvement priorities as well providing tailored management practices to maximise grain yields for this environment. © 2012 CSIRO.