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Stephen E. Swearer - One of the best experts on this subject based on the ideXlab platform.
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smell no evil copper disrupts the alarm chemical response in a Diadromous Fish galaxias maculatus
Environmental Toxicology and Chemistry, 2016Co-Authors: Oliver R. B. Thomas, Nicole C. Barbee, Kathryn L. Hassell, Stephen E. SwearerAbstract:Fish, at all life stages, utilize olfactory information in the decision-making processes essential to survival. Olfaction is a sensitive sensory process, and toxicants within urban aquatic environments can have destructive or depreciating effects. In the present study, the authors exposed Galaxias maculatus, a native Fish commonly found in urban waterways throughout southeastern Australia, to 1 of 5 ecologically relevant copper (II) chloride concentrations (<1 μg/L, 1 μg/L, 6 μg/L, 8 μg/L, 18 μg/L) for 16 h. After exposure, the authors tested the response of individual Fish to 1 of 3 stimuli: a conspecific skin extract containing a stress-inducing alarm chemical odor, a conspecific odor, and distilled water as a control. Stress responses were quantified through behavioral assays. The authors found evidence for distinct changes in behavioral response with increasing copper concentration and a marked difference in response between control Fish and Fish exposed to the alarm chemical odor. Copper, even at relatively low concentrations, can have a significant effect on the stress response behavior shown by G. maculatus. Environ Toxicol Chem 2016;35:2209-2214. © 2016 SETAC.
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trade offs obscure the relationship between egg size and larval traits in the Diadromous Fish galaxias maculatus
Marine Ecology Progress Series, 2012Co-Authors: David Semmens, Stephen E. SwearerAbstract:Egg size is one of the most frequently used surrogate measures of maternal investment and is strongly related to fitness-determining traits, such as offspring size in many marine animals, but the relationship is not universal. Because the amount of yolk allocated to eggs is finite, not all fitness-determining traits can be simultaneously maximised, and trade-offs should be expected. The results of the present study show that egg size (quantified as cross-sectional area) poorly predicts the size of larval morphological traits (length, yolk sac area, oil globule area, myomere depth, and eye area) in the native Australian Fish Galaxias maculatus. Egg size was correlated with yolk sac size and larval body depth, but it explained <13% of the total variation in these traits. Moreover, egg size did not predict the time it took for larvae to hatch, nor did it predict the duration from hatching to starvation. However, when egg size and yolk sac size (i.e. yolk remaining at hatching) were both included as predictors, the fits with larval traits improved greatly (r 2 = 0.02 to 0.46 for larval length, r 2 = 0.11 to 0.17 for myomere depth, and r 2 < 0.001 to 0.14 for eye area). These findings indicate that there is a trade-off between the quantity of yolk at hatching and the size of larval morphological traits in G. maculatus. The remaining unexplained variation may be a consequence of trade-offs with other unmeasured traits, such as metabolic rate, and the potential that egg size is not a good proxy for maternal investment. © Inter-Research 2012 · www.int-res.com.
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estuarine geomorphology and low salinity requirement for fertilisation influence spawning site location in the Diadromous Fish galaxias maculatus
Marine and Freshwater Research, 2010Co-Authors: Nicole C. Barbee, Stephen E. Swearer, Andy S Hicks, Barbara J DownesAbstract:In habitats such as estuaries, which are characterised by large and fluctuating gradients in abiotic variables, finding appropriate habitat for successful spawning and egg development can be critical to a species' survival. We explored how salinity requirements for successful fertilisation may govern the distribution of estuarine spawning habitat for the Diadromous Fish, Galaxias maculatus, which spawns in inundated vegetation on estuary banks during spring tides. Artificial fertilisation experiments confirmed that successful fertilisation only occurs at low salinities (<20). Thus, we predicted that egg distributions would depend upon the extent of low-salinity surface waters in an estuary. Using estuary geomorphology classification schemes, which classify estuaries by physical and chemical characteristics such as their salinity dynamics, we hypothesised that stratified estuaries would provide a greater extent of low salinity surface water than well-mixed estuaries. This prediction was supported by surveys of egg distributions in five estuaries in Victoria, Australia. Eggs were distributed over a greater proportion of 'stratified' v. 'mixed' estuary types. We suggest that combining knowledge of the spawning requirements of a species and physical properties of the habitat, such as those encapsulated in estuary geomorphic classification schemes, can greatly facilitate efforts to identify critical habitats and thus aid in species management and conservation.
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separating natural responses from experimental artefacts habitat selection by a Diadromous Fish species using odours from conspecifics and natural stream water
Oecologia, 2009Co-Authors: Robin Hale, Stephen E. Swearer, Barbara J DownesAbstract:Animals use sensory stimuli to assess and select habitats, mates and food as well as to communicate with other individuals. One way they do this is to use olfaction, whereby they identify and respond to chemical cues. All organisms release odours, which mix with other chemical substances and ambient environmental conditions. The result is that animals are frequently immersed in a complex, highly dynamic sensory environment where they must identify and respond to only some of the potential stimuli they encounter in the face of significant levels of background noise. Understanding how organisms respond to different chemical cues is therefore dependent on knowing how these responses might be influenced by potential interactions with other stimuli. To test this, we examined whether the Diadromous Fish Galaxias maculatus was attracted to conspecific odours and whether this response differed when cues were offered in an artificial environment lacking other potential chemical stimuli (tap water) or a more natural background environment (stream water). We found that (1) Fish responded to both natural stream water odours and those from conspecifics but the response to the latter was stronger; (2) the attraction to conspecific odours was stronger in tap water than in stream water, which indicates the importance of these odours may be overestimated when they are offered in artificial media. We also conducted a brief literature review, which confirmed that artificial media are commonly used in experiments and that the background environment is often not considered. Our results show that future research testing the responses of organisms to auditory, olfactory and visual cues should carefully consider the context in which cues are presented. Without doing so, such studies may inaccurately assess the importance of sensory cues in natural situations in the wild.
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Post-settlement migratory behaviour and growth-related costs in two Diadromous Fish species, Galaxias maculatus and Galaxias brevipinnis.
Journal of fish biology, 2009Co-Authors: C.a. Jung, Nicole C. Barbee, Stephen E. SwearerAbstract:The physiological challenges incurred during the transition from sea to fresh water and the constraints they place on the rate at which the common galaxiid Galaxias maculatus and the climbing galaxiid Galaxias brevipinnis can migrate from marine to freshwater habitats were examined. The duration of the marine to freshwater transition, the relationship between post-settlement age (PSA) and standard length (L(S)) as a proxy for energetic costs incurred during settlement and the potential effects of estuary geomorphology on migratory behaviour was investigated. Rate of upstream migration after settlement was not uniform. Upstream migration rate was slowest directly after settlement and increased with increasing PSA and distance from the river mouth, indicating a delay in upstream migration by newly recruited galaxiids. L(s) did not increase with age, at least within the first 21 days post settlement. These patterns were consistent for both species, in spite of differences in their life histories, across the recruitment season, despite seasonal variation in recruit size, and among estuaries with different properties. The results suggest that the timing and speed of migratory behaviour primarily reflect physiological constraints. Given the duration of residency of these species in estuaries, this study indicates that estuaries are critical transitional habitats for Diadromous Fishes during their migration from marine to freshwater habitats.
Douglas R Tocher - One of the best experts on this subject based on the ideXlab platform.
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investigating long chain polyunsaturated fatty acid biosynthesis in teleost Fish functional characterization of fatty acyl desaturase fads2 and elovl5 elongase in the catadromous species japanese eel anguilla japonica
Aquaculture, 2014Co-Authors: Shuqi Wang, Oscar Monroig, Guoxia Tang, Liang Zhang, Cuihong You, Douglas R TocherAbstract:The capacity for endogenous production of LC-PUFA from PUFA in euryhaline or Diadromous Fish is largely unknown other than for Atlantic salmon (Salmo salar), an anadromous species, which displays a freshwater pattern. The aim of the present study was to characterize the enzymes of the LC-PUFA pathway in Japanese eel (Anguilla japonica), the most important catadromous species currently being farmed. cDNAs of two key genes were cloned and functional assays showed that they encoded a desaturase (Fads2) with Δ6 and Δ8 activity and an elongase (Elovl5) with activity towards C18 and C20 PUFA, with activities similar to marine Fish and an Δ6/Δ8 activity ratio similar to Atlantic salmon. Furthermore, tissue distribution of the mRNA showed a clear marine pattern with the highest expression in the brain and the eyes. Phylogenetic analysis placed the eel cDNAs in line with classical taxonomy. The data suggest that Diadromous species display a pattern of LC-PUFA biosynthesis capacity that likely reflects the environmental and nutritional influence of their early life stages rather than those of adult Fish. Future studies aim to establish the full range of PUFA desaturases and elongases in Japanese eel and to provide further insight into the importance and relevance of LC-PUFA biosynthesis in Fish species and the influence of diadromy.
Shuqi Wang - One of the best experts on this subject based on the ideXlab platform.
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investigating long chain polyunsaturated fatty acid biosynthesis in teleost Fish functional characterization of fatty acyl desaturase fads2 and elovl5 elongase in the catadromous species japanese eel anguilla japonica
Aquaculture, 2014Co-Authors: Shuqi Wang, Oscar Monroig, Guoxia Tang, Liang Zhang, Cuihong You, Douglas R TocherAbstract:The capacity for endogenous production of LC-PUFA from PUFA in euryhaline or Diadromous Fish is largely unknown other than for Atlantic salmon (Salmo salar), an anadromous species, which displays a freshwater pattern. The aim of the present study was to characterize the enzymes of the LC-PUFA pathway in Japanese eel (Anguilla japonica), the most important catadromous species currently being farmed. cDNAs of two key genes were cloned and functional assays showed that they encoded a desaturase (Fads2) with Δ6 and Δ8 activity and an elongase (Elovl5) with activity towards C18 and C20 PUFA, with activities similar to marine Fish and an Δ6/Δ8 activity ratio similar to Atlantic salmon. Furthermore, tissue distribution of the mRNA showed a clear marine pattern with the highest expression in the brain and the eyes. Phylogenetic analysis placed the eel cDNAs in line with classical taxonomy. The data suggest that Diadromous species display a pattern of LC-PUFA biosynthesis capacity that likely reflects the environmental and nutritional influence of their early life stages rather than those of adult Fish. Future studies aim to establish the full range of PUFA desaturases and elongases in Japanese eel and to provide further insight into the importance and relevance of LC-PUFA biosynthesis in Fish species and the influence of diadromy.
David R. Schiel - One of the best experts on this subject based on the ideXlab platform.
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Nonselective use of vegetation for spawning by the Diadromous Fish Galaxias maculatus
Restoration Ecology, 2017Co-Authors: Michael J. H. Hickford, Jessica C. B. Stevens, David R. SchielAbstract:Terrestrial egg development is advantageous for the amphidromous Fish Galaxias maculatus because it increases access to oxygen, increases incubation temperatures, and reduces aquatic predation. The characteristics of New Zealand's riparian vegetation have changed considerably since colonial times from native vegetation to exotic grasses, with potential effects on the spawning dynamics of Fish. Here, we used a series of experiments to test preferences of G. maculatus for egg laying in combinations of a native sedge and rush, and two exotic grasses. In laboratory experiments, G. maculatus spawned in all available habitats with no preference for native over exotic vegetation. Egg survival did not differ between the vegetative habitats, but in a treatment where only river stones were available, eggs were laid but they dehydrated and died. In a field experiment, there was no evidence for a preference for spawning in native vegetation, and no association between a “key” feature of vegetation—tiller density—and the number of eggs laid. The microclimate beneath dense vegetation in experimental treatments was more constant than ambient conditions with few extreme temperatures and low humidities. Given the readiness of G. maculatus to spawn in exotic vegetation, there appears to be no benefit in restoring native vegetation to enhance egg laying or survival of these taxa.
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Evidence of iteroparity in the widely distributed Diadromous Fish inanga Galaxias maculatus and potential implications for reproductive output.
Journal of fish biology, 2016Co-Authors: Jessica C. B. Stevens, Michael J. H. Hickford, David R. SchielAbstract:Gaps in understanding variability among populations of inanga Galaxias maculatus in the timing of reproduction were addressed in southern New Zealand (NZ), where G. maculatus constitutes a declining Fishery. Reproductive activity was delayed by 1 month on the west coast compared with the east coast and the west coast spawning season was prolonged into winter. The evidence for post-spawning survival of some Fish was unequivocal from histological studies. These older and larger Fish contributed disproportionately to egg production. Estimates of fecundity were considerably lower than those previously calculated for NZ populations. The importance of quality habitats being available during critical life history periods are highlighted. It was apparent that some streams supported Fish that were larger and in better condition and that this translated into greatly increased fecundity. Future research should focus on whether this is a legacy of these Fish experiencing better pre-settlement marine habitat as larvae, or higher quality instream habitat enhancing the growth and development of adults.
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Experimental Rehabilitation of Degraded Spawning Habitat of a Diadromous Fish, Galaxias maculatus (Jenyns, 1842) in Rural and Urban Streams
Restoration Ecology, 2014Co-Authors: Michael J. H. Hickford, David R. SchielAbstract:Riparian vegetation has been compromised worldwide by anthropogenic stressors, including urbanization and livestock grazing. In New Zealand, one consequence has been a reduction in the obligate riparian spawning habitat of Galaxias maculatus. This Diadromous species forms the basis of an important Fishery where juveniles are caught as they migrate into freshwater. Spawning success of G. maculatus is closely associated with the nature of available riparian habitat. We used a field experiment in a rural stream to test whether livestock grazing limits egg production and whether there is a lag in increased egg production after protection from grazing because of the recovery time of riparian vegetation. In a separate experiment in an urban stream we tested whether improved riparian management can increase egg production. Livestock exclusion produced an immediate and long-lasting increase in the height and density of riparian vegetation with reduced fluctuations in the ground-level physical environment, and positive changes to the density and survival of eggs. After 4 years, egg densities in exclosures were 400 times greater than in grazed controls and egg survival had doubled. Mowing riparian vegetation 2 months prior to spawning reduced egg densities by 75% and survival by 25%. Our experiments showed that altering grazing and mowing in spawning sites produced dense riparian vegetation, that this improved the microsite environment and resulted in greatly increased egg deposition and survival over several years. This clearly indicates that the single most effective step in rehabilitating G. maculatus spawning habitat is a simple reduction in grazing/mowing pressure.
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Artificial Spawning Habitats Improve Egg Production of a Declining Diadromous Fish, Galaxias maculatus (Jenyns, 1842)
Restoration Ecology, 2013Co-Authors: Michael J. H. Hickford, David R. SchielAbstract:Anthropogenic impacts from urbanization, deforestation, and agriculture have degraded the riparian margins of waterways worldwide. In New Zealand, such impacts have caused changes in native vegetation, enhanced invasion by exotic grasses, and altered river bank morphology. One consequence has been a great reduction in obligate spawning habitat of a Diadromous Fish, Galaxias maculatus. Juvenile G. maculatus comprise a culturally important Fishery that has been considerably reduced over recent decades. Rehabilitation of riparian vegetation needed for spawning is relatively straightforward, but slow. We hypothesized that artificial spawning habitats could accelerate restoration of Fish egg production by creating an environment that would support at least the same density and survival of eggs as non-impacted vegetation. We tested three artificial devices (straw bales, straw tubes, and moss tubes) in degraded and intact sites. Eggs were laid in all of these with numbers and survival usually exceeding that in riparian grasses. Where habitat was degraded, artificial spawning habitats yielded up to 10,000 eggs compared to none in nearby natural spawning habitat. The ground-level environment of artificial habitat was similar to that of intact vegetation in buffering ambient temperature and humidity fluctuations. Crucial properties of the artificial habitats were (1) shelter to provide shade and hold moisture; (2) accessibility to allow adult Fish to deposit and fertilize eggs; and (3) robustness to provide reliable surfaces and protection for the eggs during their development. We show that artificial spawning habitats are a viable short-term alternative to rehabilitating spawning habitat while legacy effects abate and riparian vegetation recovers.
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synergistic interactions within disturbed habitats between temperature relative humidity and uvb radiation on egg survival in a Diadromous Fish
PLOS ONE, 2011Co-Authors: Michael J. H. Hickford, David R. SchielAbstract:Anthropogenic impacts, including urbanization, deforestation, farming, and livestock grazing have altered riparian margins worldwide. One effect of changes to riparian vegetation is that the ground-level light, temperature, and humidity environment has also been altered. Galaxias maculatus, one of the most widely distributed Fishes of the southern hemisphere, lays eggs almost exclusively beneath riparian vegetation in tidally influenced reaches of rivers. We hypothesized that the survival of these eggs is greatly affected by the micro-environment afforded by vegetation, particularly relating to temperature, humidity and UVB radiation. We experimentally reduced riparian vegetation height and altered shading characteristics, tracked egg survival, and used small ground-level temperature, humidity and UVB sensors to relate survival to ground-level effects around egg masses. The ground-level physical environment was markedly different from the surrounding ambient conditions. Tall dense riparian vegetation modified ambient conditions to produce a buffered temperature regime with constant high relative humidity, generally above 90%, and negligible UVB radiation at ground-level. Where vegetation height was reduced, frequent high temperatures, low humidity, and high UVB irradiances reduced egg survival by up to 95%. Temperature effects on egg survival were probably indirect, through reduced humidity, because developing eggs are known to survive in a wide range of temperatures. In this study, it was remarkable how such small variations in relatively small sites could have such a large effect on egg survival. It appears that modifications to riparian vegetation and the associated changes in the physical conditions of egg laying sites are major mechanisms affecting egg survival. The impacts associated with vegetational changes through human-induced disturbances are complex yet potentially devastating. These effects are particularly important because they affect a very small portion of habitat that is required to complete the life history of a species, despite the wide distribution of adults and juveniles across aquatic and marine environments.
David A. Crook - One of the best experts on this subject based on the ideXlab platform.
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Migration to freshwater increases growth rates in a facultatively catadromous tropical Fish
Oecologia, 2019Co-Authors: Brien H. Roberts, John R. Morrongiello, Alison J. King, David L. Morgan, Thor M. Saunders, Jon Woodhead, David A. CrookAbstract:Diadromy is a form of migration where aquatic organisms undergo regular movements between fresh and marine waters for the purposes of feeding and reproduction. Despite having arisen in independent lineages of Fish, gastropod molluscs and crustaceans, the evolutionary drivers of Diadromous migration remain contentious. We test a key aspect of the ‘productivity hypothesis’, which proposes that diadromy arises in response to primary productivity differentials between marine and freshwater habitats. Otolith chemistry and biochronology data are analysed in a facultatively catadromous tropical Fish (barramundi, Lates calcarifer ) to determine the effect of freshwater residence on growth rates. Individuals that accessed freshwater grew ~ 25% faster on average than estuarine residents in the year following migration, suggesting that catadromy provides a potential fitness advantage over non-catadromous (marine/estuarine) life histories, as predicted by the productivity hypothesis. Although Diadromous barramundi exhibited faster growth than non-Diadromous Fish, we suggest that the relative reproductive success of Diadromous and non-Diadromous contingents is likely to be strongly influenced by local environmental variability such as temporal differences in river discharge, and that this may facilitate the persistence of diverse life history strategies within populations.
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predicting the influence of streamflow on migration and spawning of a threatened Diadromous Fish the australian grayling prototroctes maraena
Environmental Management, 2018Co-Authors: Wayne M Koster, David A. Crook, David Dawson, S Gaskill, John R. MorrongielloAbstract:The development of effective strategies to restore the biological functioning of aquatic ecosystems with altered flow regimes requires a detailed understanding of flow-ecology requirements, which is unfortunately lacking in many cases. By understanding the flow conditions required to initiate critical life history events such as migration and spawning, it is possible to mitigate the threats posed by regulated river flow by providing targeted environmental flow releases from impoundments. In this study, we examined the influence of hydrological variables (e.g., flow magnitude), temporal variables (e.g., day of year) and spatial variables (e.g., longitudinal position of Fish) on two key life history events (migration to spawning grounds and spawning activity) for a threatened Diadromous Fish (Australian grayling Prototroctes maraena) using data collected from 2008 to 2015 in the Bunyip–Tarago river system in Victoria. Our analyses revealed that flow changes act as a cue to downstream migration, but movement responses differed spatially: Fish in the upper catchment showed a more specific requirement for rising discharge to initiate migration than Fish in the lower catchment. Egg concentrations peaked in May when weekly flows increased relative to the median flow during a given spawning period. This information has recently been incorporated into the development of targeted environmental flows to facilitate migration and spawning by Australian grayling in the Bunyip–Tarago river system and other coastal systems in Victoria.
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low interbasin connectivity in a facultatively Diadromous Fish evidence from genetics and otolith chemistry
Molecular Ecology, 2014Co-Authors: Jane Hughes, David A. Crook, D R Schmidt, Jed I Macdonald, Joel A HueyAbstract:Southern smelts (Retropinna spp.) in coastal rivers of Australia are facultatively Diadromous, with populations potentially containing individuals with Diadromous or wholly freshwater life histories. The presence of Diadromous individuals is expected to reduce genetic structuring between river basins due to larval dispersal via the sea. We use otolith chemistry to distinguish between Diadromous and nonDiadromous life histories and population genetics to examine interbasin connectivity resulting from diadromy. Otolith strontium isotope (87Sr:86Sr) transects identified three main life history patterns: amphidromy, freshwater residency and estuarine/marine residency. Despite the potential for interbasin connectivity via larval mixing in the marine environment, we found unprecedented levels of genetic structure for an amphidromous species. Strong hierarchical structure along putative taxonomic boundaries was detected, along with highly structured populations within groups using microsatellites (FST = 0.046–0.181), and mtDNA (ΦST = 0.498–0.816). The presence of strong genetic subdivision, despite the fact that many individuals reside in saline water during their early life history, appears incongruous. However, analysis of multielemental signatures in the otolith cores of Diadromous Fish revealed strong discrimination between river basins, suggesting that Diadromous Fish spend their early lives within chemically distinct estuaries rather than the more homogenous marine environment, thus avoiding dispersal and maintaining genetic structure.