Academic literature on the topic 'Retropinna semoni'

The smelt genus Retropinna nominally includes three small (<150 mm) freshwater fish species endemic to south-eastern Australia and New Zealand. For the two Australian species, the broad range of R. semoni (Weber) on the mainland suggests some vulnerability to isolation and genetic divergence, whereas the apparent confinement of R. tasmanica McCulloch to Tasmania is curious if, as suspected, it is anadromous. Analyses of Australian material using allozyme electrophoresis show five genetically distinct species with contiguous ranges and no evidence of genetic exchange. Three occur along the eastern seaboard (including three instances of sympatry), another in coastal and inland south-eastern Australia and Tasmania, and a fifth species in the Lake Eyre Basin. There is no indication of a simple ‘tasmanica’ v. ‘semoni’ dichotomy, but instead a complex pattern involving discrete clusters for the Upper Murray plus Darling rivers, Lower Murray, Glenelg River and Tasmanian regions, with coastal western Victorian samples having varying affinity to these groups. The overall pattern is one of deep divergences among species and strong genetic sub-structuring within and provides a strong argument for extended studies to prepare for appropriate conservation measures.

The reproductive biology and growth of R. semoni and A. nigripinnis were studied in Brisbane, south- eastern Queensland, over a 20-month period (1981-1982). R. semoni began to breed in winter at water temperatures exceeding 15�C, reflecting its salmoniform affinities and temperate distribution. A. nigripinnis, a subtropical species of Indo-Pacific origin, required a period of rising temperature before breeding began in spring at 22�C. Both species concentrated their breeding activity into the months that precede summer storms and high, variable stream discharges, which can generate fluctuating water levels, destruction of weedbeds and instability of the stream substrate. Pre-flood spawning also occurs in three other small-bodied native species in the region, and appears to have adaptive value in the seasonally unstable environments of coastal streams. Dispersal of juvenile fish may be facilitated by rising water levels during summer months following spawning. R. semoni grew faster and to larger sizes than A. nigripinnis and growth of both species was adequately described by the von Bertalanffy equation. Male and female R. semoni and male A. nigripinnis live and breed for 2 years but female A. nigripinnis survive and may breed into their third year. These patterns of survivorship and reproduction are consistent with the contention that natural mortality is higher in open-water foragers such as R. semoni than in species like A. nigripinnis, which tends to forage amongst littoral vegetation and in mid-water. Differences in the sizes of eggs and larvae of the two species are also consistent with the probability that they experience different relative exposure to predation. These and other attributes, coupled with pre-flood spawning, enable both species to achieve large populations in suitable habitats within coastal streams, in spite of their relatively low fecundities.

Freshwater fishes often exhibit high genetic population structure due to the prevalence of dispersal barriers (e.g., waterfalls) whereas population structure in diadromous fishes tends to be weaker and driven by natal homing behaviour and/or isolation by distance. The Australian smelt (Retropinnidae:Retropinna semoni) is a native fish with a broad distribution spanning inland and coastal drainages of south-eastern Australia. Previous studies have demonstrated variability in population genetic structure and movement behaviour (potamodromy, facultative diadromy, estuarine residence) across the southern part of its geographic range. Some of this variability may be explained by the existence of multiple cryptic species. Here, we examined genetic structure of populations towards the northern extent of the species’ distribution, using ten microsatellite loci and sequences of the mitochondrial cytbgene. We tested the hypothesis that genetic connectivity among rivers should be low due to a lack of dispersal via the marine environment, but high within rivers due to dispersal. We investigated populations corresponding with two putative cryptic species, SEQ-North (SEQ-N), and SEQ-South (SEQ-S) lineages occurring in south east Queensland drainages. These two groups formed monophyletic clades in the mtDNA gene tree and among river phylogeographic structure was also evident within each clade. In agreement with our hypothesis, highly significant overallFSTvalues suggested that both groups exhibit very low dispersal among rivers (SEQ-SFST= 0.13; SEQ-NFST= 0.27). Microsatellite data indicated that connectivity among sites within rivers was also limited, suggesting dispersal may not homogenise populations at the within-river scale. Northern groups in the Australian smelt cryptic species complex exhibit comparatively higher among-river population structure and smaller geographic ranges than southern groups. These properties make northern Australian smelt populations potentially susceptible to future conservation threats, and we define eight genetically distinct management units along south east Queensland to guide future conservation management. The present findings at least can assist managers to plan for effective conservation and management of different fish species along coastal drainages of south east Queensland, Australia.

AbstractNative and exotic fishes were collected from 29 sites across coastal and inland New South Wales, Queensland and Victoria, using a range of techniques, to infer the distribution of Bothriocephalus acheilognathi (Cestoda: Pseudophyllidea) and the host species in which it occurs. The distribution of B. acheilognathi was determined by that of its principal host, carp, Cyprinuscarpio; it did not occur at sites where carp were not present. The parasite was recorded from all native fish species where the sample size exceeded 30 and which were collected sympatrically with carp: Hypseleotris klunzingeri, Hypseleotris sp. 4, Hypseleotris sp. 5, Phylipnodon grandiceps and Retropinna semoni. Bothriocephalus acheilognathi was also recorded from the exotic fishes Gambusia holbrooki and Carassiusauratus. Hypseleotris sp. 4, Hypseleotris sp. 5, P. grandiceps, R. semoni and C. auratus are new host records. The parasite was not recorded from any sites in coastal drainages. The only carp population examined from a coastal drainage (Albert River, south-east Queensland) was also free of infection; those fish had a parasite fauna distinct from that of carp in inland drainages and may represent a separate introduction event. Bothriocephalus acheilognathi has apparently spread along with its carp hosts and is so far restricted to the Murray-Darling Basin. The low host specificity of this parasite is cause for concern given the threatened or endangered nature of some Australian native freshwater fish species. A revised list of definitive hosts of B. acheilognathiis presented.

Patterns of dispersal in riverine populations of Australian smelt ( Retropinna semoni ) were examined using otolith chemistry (Mg:Ca, Mn:Ca, Sr:Ca, Ba:Ca) and genetic markers (allozymes, mtDNA, microsatellite DNA). During a period of prolonged low flows, young-of-year smelt were collected from 13 streams within three catchments of the southern Murray–Darling Basin, Australia. Spatial differences in otolith core and edge chemical signatures and high levels of genetic assignment to sampling locations were observed, suggesting that most recruits were retained in natal areas after spawning. Following a subsequent period of hydrological connection, the same cohort was sampled as 1-year-olds. Maximum likelihood estimation using otolith core chemistry data from these fish suggested that retention in natal areas was highly variable between years and a similar, though less pronounced, pattern was evident in genetic assignments. Partitioning of genetic variation among catchments was not significant (FCT < 0.004) and probably reflects disequilibrium between migration and genetic drift due to an historical population expansion (~270 000 years ago). Taken together, otolith chemistry and genetic analyses suggest that contemporary dispersal of smelt within these catchments is relatively restricted and may be mediated by changes in hydrological connectivity.

South Australia is a large Australian state (~1,000,000 km2) with diverse aquatic habitats spread across temperate to arid environments. The knowledge of freshwater fishes in this jurisdiction has advanced considerably since the last detailed catalogue of native and alien species was published in 2004 owing to significant survey and research effort, spatial analysis of museum data, and incidental records. The updated list includes 60 native and 35 alien species. New additions to the native fauna include cryptic species of Retropinna semoni s.l. (Weber) and Galaxias olidus s.l. (Günther). Two others have been rediscovered after long absences, namely Neochanna cleaveri (Scott) and Mogurnda adspersa (Castelnau). Range extensions are reported for native populations of Galaxias brevipinnis Günther, Leiopotherapon unicolour (Günther), Hypseleotris spp. (hybridogenetic forms) and Philypnodon macrostomus Hoese and Reader. There are five new alien species records (all aquarium species) including Phalloceros caudimaculatus (Hensel), Poecilia reticulata Peters, Xiphophorus hellerii Heckel, Astronotus ocellatus (Agassiz) and Paratilapia polleni Bleeker, with confirmation of Misgurnus anguillicaudatus (Cantor). Other range extensions for alien (exotic or translocated native) species in different drainage divisions (various modes of human-mediated dispersal) include Nematalosa erebi (Günther), Cyprinus carpio Linnaeus, Oncorhynchus mykiss (Walbaum), Salmo salar Linnaeus, Salvelinus fontinalis (Mitchell), Melanotaenia fluviatilis (Castelnau), Atherinosoma microstoma (Günther), Macquaria novemaculeata (Steindachner), Nannoperca australis Günther, Pseudaphritis urvillii (Valenciennes), and Hypseleotris spp. (hybridogenetic forms). New records are a combination of greater available information and new incursions, highlighting the need for ongoing detailed surveys and reporting to detect rare native and alien species.

Ecological theory and research has shown a critical link between in-stream connectivity and the ecological persistence of aquatic fauna with particular emphasis on taxa with higher commercial or recreational value such as fishes. However, limited information exists on both the dispersal levels and behaviour of fish that have no obvious economic or conservation values. The biological connectivity (or isolation) of individuals/populations across heterogeneous spatio-temporal dimensions occurs primarily via the processes of movement and dispersal. The movement of individuals affects current patterns of population dynamics over an ecological timescale whilst dispersal ultimately shapes the level of gene flow among populations and contributes to the processes that shape population dynamics over an evolutionary timescale. Despite the temporal differences in scale, both the ecological and evolutionary outcomes of connectivity are governed by the ability of individuals to freely move or disperse through all axes of space and time. This very ability for individual connectivity relies on factors both intrinsic and extrinsic to the species. In an attempt to better understand the fundamental population dynamics of aquatic fauna in the natural environment, it is vital to design and apply methodologies that can accurately estimate in-stream levels of connectivity. By utilising such techniques researchers can then determine the underlying biological principles that shape the patterns of distribution and abundance for a given species and use these key biological indicators to contribute to the information required in the long term protection and management of an often undervalued resource. The focus of the study was to estimate levels of connectivity in a model species, the ubiquitous Australian smelt (Retropinna semoni), both on an ecological and an evolutionary timescale across contrasting drainage systems from inland rivers of Australia. Contrasting patterns of connectivity from different drainage systems allowed inferences to be drawn on the effects that extrinsic factors, such as flow regimes and stream architecture, have had on population dynamics. Additionally, utilising a temporal approach provided information on the changes that have occurred to population dynamics on a small scale from annual changes in local hydrological conditions and longer term changes resulting from human induced impacts, and finally the effects that may have shaped the structure of a species over evolutionary timescales...
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment
Science, Environment, Engineering and Technology
Full Text

Generally freshwater fish exhibit higher levels of genetic structuring between spatially distinct populations than marine species due to the presence of natural and artificial barriers to dispersal in freshwater ecosystems. In addition, freshwater species are not able to move between populations that are separated by either terrestrial or marine habitat. Diadromy constrains the development of genetic structuring, even among geographically isolated populations due to potential connectivity via movement through the sea. As a result, higher levels of gene flow and lower population structuring tend to be observed in diadromous fishes than freshwater species. The Australian smelt (Retropinna semoni) is a native fish species complex widely distributed across coastal and inland drainages of south-eastern Australia. Recently, a complex of five or more cryptic species of Australian smelt has been recognized throughout their geographic range based on genetic studies. Variation in life history strategies has been observed in many cryptic fish species and multiple life history patterns were also found in southern smelt lineages (Retropinna sp.) where mainland Australian populations contain diadromous and wholly freshwater individuals and Tasmanian populations contain estuarine individuals. Despite the populations of southern smelt containing diadromous individuals, strong genetic structuring and low levels of connectivity were reported in at least some populations, which were suggested to result from apparently diadromous individuals being retained in the estuaries. It is possible that the different cryptic species may differ in life history. In the present study, I examine the genetic structure and life history variation of the South-east Queensland (SEQ) lineage of Australian smelt which was further subdivided into northern and southern lineages (SEQ-N, SEQ-S). I used both molecular and ecological approaches to understand the pattern of genetic structure and life history variation in this species to compare with other members of the species complex. Prior to this task, twenty one polymorphic microsatellite primers were developed (Chapter 2), which were then used for species delimitation and population structure analysis. In chapter 3, I used one mitochondrial gene (cyt b) and ten microsatellite loci to investigate patterns of genetic structuring in Australian smelt (R. semoni) and describe the genetic differences between these two cryptic lineages (SEQ-N and SEQ-S). These two lineages formed monophyletic clades in the mtDNA gene tree and among river phylogeographic structure was also evident within each clade. There was clear genetic divergence between the two lineages, suggesting that they have been separated historically by a hard barrier. Strong genetic structuring was observed from microsatellite analysis in both lineages (SEQ-S FST = 0.13; SEQ-N FST = 0.23) suggesting limited dispersal among rivers. Slightly lower levels of genetic structuring were observed in the SEQ-S lineage than the SEQ-N lineage. This might be the result of different microhabitat preferences between these two cryptic lineages (SEQ-N and SEQ-S), for example intolerance to water quality parameters. Another plausible explanation is that SEQ-S catchments may have been connected more recently and /or more often than those in the SEQ-N group during flood events. Contemporary movement of individuals only occurred between nearby sites within a river, but not between rivers, suggesting that if local extinctions occur in one or more of these rivers, then recolonization from elsewhere is unlikely to occur rapidly. Similarly, extinctions within a site are only likely to be recolonised from nearby sites in the same river. In chapter 4, I used otolith micro-chemistry analysis to examine the life history patterns of smelt at the northern extent of their range and to identify any differences in migratory behaviour of the two lineages (SEQ-N and SEQ-S) in this region. Based on otolith core-to-edge transects of Sr:Ca and Ba:Ca, there was no evidence of marine residence for either lineage suggesting that both are non-diadromous. This contrasts with the two southern smelt species, in which both exhibit evidence of diadromous movement of individuals within some populations. Significant differences in multi-elemental otolith chemistry signatures were observed among rivers and between paired sites within some rivers, suggesting no exchange of individuals among catchments and limited dispersal of individuals over large spatial scales within a river. This is almost certainly the result of the marine habitat conditions along the coastal drainages which isolate rivers and restrict movement of fish between them, combined with some limited dispersal within a river. In addition, movement of fish may also be precluded due to anthropogenic migration barriers within river catchments. This study has presented a holistic view of population structure using ecological and genetic markers and revealed that R. semoni is highly structured across south-east Queensland from the Mary River to Currumbin Creek. Genetic analysis delivers the general framework for applying ecological methods and substantial information regarding exchange between populations. Sensitive ecological methods such as otolith chemistry provide resolution of the fine-scale spatial separation within and between sample collection locations because movements within an individual lifetime can be inferred. The results of the present study emphasise the advantages of using complementary methods to evaluate the connectivity of fish populations. The combination of otolith chemistry and molecular markers provided insights into the role of migration in structuring smelt populations over a range of temporal and spatial scales. Overall, the current study furnished new insights into the population genetic structure and life history patterns of Australian smelt, which has significant implications for the sustainable management and conservation of this ecologically variable species along coastal drainages in south-east Queensland.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

Six rivers within the upper Mumbidgee catchment were sampled for larval and juvenile fish. The rivers represented both regulated and unregulated flow regimes and varied widely in size. There was wide variation in the larval fish communities supported by each river, both in terms of the species diversity and total abundance of fish sampled. The highly regulated reach of the Mumbidgee River sampled during this study had the highest numbers of native species and native individuals of any river sampled. In the two rivers selected for further study, the Murmmbidgee and Goodradigbee, there was a high level of inter-annual consistency in the species composition within the reaches sampled, despite considerable change in the temperature and flow regimes of both rivers. This indicates that at least some spawning of those species sampled may occur each year, regardless of environmental conditions. Estimates of the relative abundance of each species sampled changed markedly between years, and it is argued, on the basis of growth information contained in the otoliths, that differential survival of larvae and juveniles was largely responsible for this shift in relative abundance. Otolith microstructure provided information on the date of spawning and early growth patterns of all species sampled in the upper Mumumbidgee catchment. In addition to determining the age and thus 'birth-date' of an individual, the effect of a particular event or series of events has on growth, and subsequent survival, is permanently recorded in the otolith microstructure. This enables accurate back-calculation and correlation to management actions or natural events. No other research tool has this ability to retrospectively assess, on a daily basis, the impacts of management actions on condition and subsequent survival of fish larvae. Species sampled could be separated into three groups based on spawning requirements; those linked with flow, those linked with temperature and generalist species that appear to have river independent cues, such as photoperiod or moon phase. Patterns in growth rate during the early life history stages enabled quantification of the consequences of variation in environmental conditions on the survival and recruitment of various species. Growth was not always highly correlated with water temperature, in fact, for mountain galaxias, high temperatures appear to negatively affect larval condition and subsequent survival. Conversely, carp exhibited a strategy more consistent with common perceptions, with growth and survival increasing with increasing temperature. The study uncovered spawning and growth patterns that were unexpected. Age analysis of western carp gudgeon demonstrated that they had undertaken a mid-winter spawning, when the water temperature in the main channel was far lower than that at which spawning was previously recorded for this species. Redfin perch from the unregulated Goodradigbee River exhibited growth rates exceeding the published upper limits for this and other closely related species. This growth could not be correlated with either temperature or flow, indicating that there are additional factors that dominate growth rates of redfin perch in the Goodradigbee River. The proportion and abundance of native species alone is not necessarily indicative of a 'healthy' or pristine system; some native species may be positively affected by river regulation, at least as juveniles. Comparison of the current larval fish community with likely pre-European fish communities does provide an indication of change to the system. The results of this study suggest that larval fish growth rates can be strongly influenced by environmental conditions, thus providing a powerful tool for monitoring future change and the factors which cause it. This study has demonstrated the value of larval and juvenile fish age and growth information, derived from otolith microstructure techniques, for many aspects of river management. Current river management priorities for which these techniques provide unique information include the determination of environmental flow regimes and the control of undesirable exotic species such as carp.

<i>Abstract.</i>—We document a simple electrofishing-only monitoring program for assessing fish assemblages across large spatial extents. First, we demonstrate the justification for using only electrofishing for the monitoring. Second, we demonstrate the usefulness of having a well-designed surveillance-monitoring program in place to demonstrate the effect of landscape disturbances. Implementing electrofishing alone means that multiple sites can be sampled in a single day and there is no need to return to clear nets or traps within a sampling site. Whereas electrofishing alone does not return full species lists within sampled sites, we demonstrate that when data are aggregated up to the watershed or catchment extent, more than 90% of species are included. Analyses that do not require a census of species, such as bioassessment of river health can be readily carried out using electrofishing data. The Murray–Darling basin, Australia, was sampled with the recommended large-extent electrofishing program between 2004 and 2012, a period that saw the region subjected to large-scale variations in river flow levels spatially and temporally. We fit generalized additive models to the electrofishing data in conjunction with river flow data to document large-extent relationships between fish species occurrence and relative flow levels for the previous 3 d, 3 months, or 3 years. We found that several small-bodied species, Eastern Mosquitofish <i>Gambusia holbrooki</i>, Flathead Gudgeon <i>Philypnodon grandiceps</i>, and Australian Smelt <i>Retropinna semoni</i>, were more likely to be collected when conditions were drier in the past 3 d to 3 months, whereas common medium and large-bodied species were less likely to be collected when flow was lower over the previous 3 months to 3 years.