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Understanding connectivity is crucial for the effective conservation and management of biota. However, measuring connectivity directly is challenging and it is often inferred based on assumptions surrounding dispersal potential, such as environmental history and species life history traits. Genetic tools are often underutilised, yet can infer connectivity reliably. Here, we characterise and compare the genetic connectivity and genetic diversity of three diadromous Australian fish species: common galaxias (Galaxias maculatus), tupong (Pseudaphritis urvillii) and Australian grayling (Prototroctes maraena). For each species, we investigate the extent of genetic connectivity across a study region in south-eastern Australia (~700 km). We further determine the potential roles of contemporary ocean currents in shaping the patterns of genetic connectivity observed. Individuals across multiple rivers were sampled and >3000 single nucleotide polymorphisms were genotyped for each species. We found differences in genetic connectivity for the three species: common galaxias were highly connected, and Australian grayling and tupong exhibited patterns of isolation by distance. The degree of genetic connectivity for tupong and Australian grayling appeared unrelated to oceanic currents. This study indicates that the degree of connectivity for different diadromous species can vary greatly despite broadly similar life history strategies, highlighting the potential value of genetic tools for informing species-specific management plans.

This study analysed the spatial–temporal abundance and distribution of exotic Chinook salmon (Onchorynchus tsawytscha) along the shore zone of the Lapataia River in relationship with the presence of non-native brook trout (Salvelinus fontinalis) and brown trout (Salmo trutta), and native small puyen (Galaxias maculatus) during the four seasons of the year. These data were used to detect fish patchiness and spatial overlap and related to environmental characteristics to determine the habitat used by each species. Juvenile Chinook salmon was recorded only in spring and summer, showing a highly aggregated spatial distribution pattern. The native small puyen dominated fish assemblages all over the year, except in winter when brook trout showed the highest abundance. The highest overlap was detected between small puyen and Chinook salmon. Chinook salmon distribution was mainly explained by the occurrence of flood plains. Brown trout distribution was highly related to the presence of woody debris, while small puyen and brook trout showed no preferences for any environment. These results provide little evidence for habitat competition between Chinook salmon and the other native and non-native fish species. In contrast, species habitat preferences are likely shaping the current fish distribution.

The visual capacity of aquatic organisms is, in general, related to light penetration in the water. Therefore, aquatic environments that differ in color can potentially contribute to species polymorphism, especially in fish. In this study, we explore the relationship between light quality and intensity in water bodies and the eye and mouth size in Galaxias maculatus, one of the most widespread fish. Fish morphology was studied photographically, and the vertical attenuation coefficient of light (Kd) was measured in five aquatic systems: two humic lakes, two estuaries, and one river. Water color was also estimated as absorbance at 440 nm. In those environments with less light penetration and darker water color, we observed bigger eyes and, additionally, larger mouths. The darkness of water bodies was mainly related to water color associated with humic substances. As G. maculatus is known to be a visual predator, our results suggest that bigger eyes increase visual capacity in darker environments, which would result in improved feeding rates, also supported by larger mouth length.

This study reports the phenotypic and genetic differences between individuals of puyen Galaxias maculatus from two sites in the same river basin in Tierra del Fuego National Park, southern South America. Individuals from the two sampling sites presented morphometric and genetic differences. The morphometric differences indicated that individuals from Laguna Negra (LN) were short and more robust and had large eyes, whereas those from Arroyo Negro (AN) were thin and elongated and had small eyes. Genetic differences showed that AN individuals had a greater genetic structuration and an older demographic history than LN individuals. The results of this study affirmed that the individuals from the two sampling sites belong to different populations with a high degree of isolation. The demographic history could indicate that the individuals of G. maculatus which migrated to northern areas during the last glaciation settled in the Beagle Channel after its formation. The LN population could have originated after the retreat of the glaciers, migrating from AN.

Amphidromy is the most prevalent type of diadromous migration. Despite this, the conservation and management of amphidromous species is exceptionally challenging because this life history type, with larval development in a pelagic habitat (usually marine) and adult development in fresh water, is poorly resolved. The chronological properties of otoliths, together with a spatial and temporal analysis of post‐larval migration traits and adult reproductive traits, were used to reconstruct the life history of a widespread, yet declining amphidromous galaxiid, Galaxias maculatus, and to explore relationships between marine and freshwater life phases. A wide range of post‐larval migration traits were observed over the peak migratory period. Post‐larvae were smaller and younger at inward migration late in the migration season (November) and were derived from winter spawning events. Earlier migrants (September) were larger, older and derived from autumn spawning events. Age estimates confirmed that G. maculatus is largely an annual species, but back‐calculated hatch dates showed that spawning times are more extensive than previously known. Growth reconstructions revealed that winter‐hatched larvae were faster growing during marine and freshwater life and attained sexual maturity at a younger age than autumn‐hatched fish. However, no differences in body size or reproductive investment were detected between autumn‐ and winter‐hatched larvae. The first 50 days of marine growth were inter‐dependent, indicating that early larval growth may be the critical link to understanding intra‐ and inter‐annual recruitment variations of inward migrating post‐larvae. Furthermore, growth after 60 days of larval life propagated through to adult freshwater development, highlighting linkages between late marine and adult freshwater life. This study highlights the value of studying the marine and freshwater life phases of amphidromous species in tandem. This interconnected understanding must ultimately be achieved for the conservation and management of species with this poorly understood life history type.

Anthropogenic alterations to river flow regimes threaten freshwater biodiversity globally, with potentially disproportionate impacts on species that rely on flow cues to trigger critical life history processes, such as migration for diadromous fishes. This study investigates the influence of river discharge on the abundance of juvenile fish moving into rivers by four temperate catadromous or amphidromous species (common galaxias Galaxias maculatus, spotted galaxias Galaxias truttaceus, climbing galaxias Galaxias brevipinnis and the threatened Australian grayling Prototroctes maraena). Fyke netting or fishway trapping was used to catch juvenile fish moving from estuaries into freshwater in five coastal waterways in south-eastern Australia during the spring migratory period. There was a positive relationship between the probability of high catch rates and mean discharge in September. We also found a positive relationship between discharge and the number of recruits captured 22-30 days later in a flow stressed system. In addition, day-of-year had a strong influence on catch rates, with the peak abundance of juveniles for three species most likely to occur midway through the sampling period (spotted galaxias in October, climbing galaxias in late October and Australian grayling in late October and early November). Our study shows that higher magnitudes of river discharge were associated with increased catches of juvenile catadromous and amphidromous fishes. With a limited supply of environmental water, environmental flows used to enhance immigration of these fishes may be best targeted to maintain small amounts of immigration into freshwater populations in waterways or years when discharges are low and stable. When there are natural, large discharge volumes, relatively large numbers of juvenile fish can be expected to enter coastal waterways and during these times environmental flows may not be required to promote immigration.

River regulation has degraded aquatic biodiversity globally, and the effects can be pronounced for diadromous species, whose life history processes can depend on flow conditions, such as cues for adult migration, spawning, attracting recruits into coastal rivers and promoting upstream dispersal. Environmental flows are being used to mitigate the effects of river regulation, and understanding their effectiveness is required to improve management practices. This study examined the effects of targeted environmental flows on the upstream dispersal of three temperate catadromous fish species, namely common galaxias Galaxias maculatus, tupong Pseudaphritis urvillii and short-finned eel Anguilla australis. Fyke netting was used to capture fish moving upstream before and during environmental flows in summer and autumn in two coastal rivers. We found significant increases in the catch of young-of-the-year (YOY) common galaxias (6-fold higher) and juvenile short-finned eel (26-fold higher), relative to control sites, during environmental flow pulses compared with stable, regulated base-flow conditions. A significant response was not detected for YOY tupong, despite a 39% increase in the catch. These results demonstrate that environmental flows enhance the upstream movement of juvenile diadromous fishes, a critical process governing population persistence or recovery. The findings provide managers with confidence in the use of environmental flows to support populations.

The population of Galaxias maculatus studied here, Arroyo Negro (54° S), is located at the southern extreme of the species distribution. This is the first work on growth and other life history traits of a Fueguian diadromous population based on otoliths study. This species is part of the native fish fauna of Patagonia. Furthermore, studies on the growth and reproduction of G. maculatus in South America mostly refer to freshwater populations of Andean-Patagonian lakes and rivers (about 41° S). Size cohorts were studied; age and growth parameters were estimated, the latter using the VBGM. Four size cohorts were established, and 3+ was determined as maximum age class. No differences were found in growth curves between males and females. The 1+ age class was by far not only the most numerous in the population but also the most represented in the reproductive population. The relation between mean TL and latitude was positive (r = 0.62) for South American populations; however, further studies are needed to determine whether it is this population’s life strategy, the local adaptation of a peripheral population or countergradient growth. The results are interpreted in the context of the information available for other populations, and provide important information about the plasticity in life history traits of this species. Fil: Rojo, Javier Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Figueroa, Daniel Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; Argentina Fil: Boy, Claudia Clementina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

Here, we describe a methodology for quantifying the spawning habitat of īnanga (Galaxias maculatus), a protected native fish species. Our approach is demonstrated with a survey of the Heathcote/Ōpāwaho following the Canterbury earthquakes that produced unexpected findings. Spawning habitat was detected over a 2.5 km reach and the area occupied by spawning sites (75m2) was much larger than in previous records (ca. 21m2). Sites dominated by the invasive Phalaris arundinaceae were found to support high egg numbers. Spawning has not previously been recorded on this species and it is identified in the literature as a threat to spawning habitat. Considerable spatio-temporal variation was also detected in the location of spawning sites and pattern of egg production. Together, these aspects illustrate the need for a comprehensive survey methodology to reliably quantify spawning habitat. The Heathcote/Ōpāwaho example shows the utility of our census approach for achieving this, and supporting habitat conser...

Galaxias maculatus (Jenyns, 1842) is a widespread freshwater fish and an important component of the economically important whitebait fisheries across the Southern Hemisphere. We report a new myxosporean parasite (Cnidaria: Myxozoa) infecting the kidney of G. maculatus from northwestern Patagonia (Argentina). Ortholinea lauquen sp. nov. was characterized using myxospore morphology, morphometrics and small subunit rDNA (ssrDNA) sequence data. Our ssrDNA phylogenetic analyses showed that O. lauquen sp. nov. is a member of the oligochaete-freshwater urinary tract clade and basal to a clade containing 4 different spore morphotypes (Chloromyxum, Myxidium, Zschokkella, Hoferellus). We explored host-parasite relationships at the macro- and microscale by analyzing the distribution, tissue tropism and pathology of O. lauquen sp. nov. Prevalence was relatively low (7%) by microscopy, but PCR detection revealed hidden levels of infection (49%), with the highest detection in lakes Morenito and Moreno (63-90%, Río Negro Province). The only locality negative by both microscopy and PCR was the Caleufu River (Neuquén Province), suggesting differences in fish life history traits (landlocked vs. potamodromous) or preference of the putative obligate invertebrate host for lentic habitats. O. lauquen sp. nov. sporulates in the renal tubules and occasionally in the glomerular space. The plasmodia frequently occluded the tubule lumina, and cellular necrosis and disintegration of the epithelium were observed. O. lauquen sp. nov. could represent a potential threat to G. maculatus culture under intensive farming conditions. Fil: Alama Bermejo, Gema. Universidad Nacional del Comahue. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". - Provincia de Río Negro. Ministerio de Agricultura, Ganadería y Pesca. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni". Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet Centro Nacional Patagónico. Centro de Investigación Aplicada y Transferencia Tecnológica en Recursos Marinos "Almirante Storni"; Argentina. Czech Academy of Sciences; República Checa Fil: Viozzi, Gustavo Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Waicheim, María Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Flores, Verónica Roxana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Atkinson, S. D.. State University of Oregon; Estados Unidos

Body mass and temperature are primary determinants of metabolic rate in ectothermic animals. Oxygen consumption of post-larval Galaxias maculatus was measured in respirometry trials under different temperatures (5–21 °C) and varying body masses (0.1–>1.5 g) spanning a relevant range of thermal conditions and sizes. Specific respiration rates (R in g O2 g−1 d−1) declined as a power function of body mass and increased exponentially with temperature and was expressed as: R = 0.0007 * W −0.31 * e 0.13 * T. The ability of this model to predict specific respiration rate was evaluated by comparing observed values with those predicted by the model. Our findings suggest that the respiration rate of G. maculatus is the result of multiple interactive processes (intrinsic and extrinsic factors) that modulate each other in ‘meta-mechanistic’ ways; this would help to explain the species’ ability to undergo the complex ontogenetic habitat shifts observed in the lakes of the Andean Patagonic range. Fil: Milano, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Laboratorio de Fotobiologia; Argentina Fil: Vigliano, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Beauchamp, David. U.S. Geological Survey. Western Fisheries Research Center; Estados Unidos

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.

This study aims to evaluate the effect of pH on embryonic survival of Galaxias maculatus. Embryos were incubated at 6 different pH levels in the water. One-way ANOVA was used to compare averages between treatments and Tukey test to determine post hoc differences. The Probit regression was used to estimate the embryonic and the hatching period. Embryos survive pH from 5 to 11 and die at pH extremes 3 and 13. The best average survival rates were obtained at neutral pH (78.7 ± 1.2) and as the pH decreases away from embryonic survival 7 embryonic survival decreases. In conclusion, pH is an important factor to consider for the production of larval G. maculatus.

Inanga (Galaxias maculatus) is an amphidromous fish, capable of moving freely between waters of different salinities. The impact of environmental salinity on inanga physiology was investigated by examining ionic and osmotic regulation, nitrogen excretion, oxygen metabolism and energy expenditure. After 16 days of acclimation to salinities ranging from freshwater to 43, inanga showed only minor changes in plasma osmolality and no significant changes in metabolic rate or calculated energy expenditure, underlining their high salinity tolerance. Decreases in ammonia excretion at salinities close to the isosmotic point, and variation in oxygen to nitrogen ratios did, however, suggest changes in fuel use. Partitioning studies isolating the head from the body indicated that there was no trade-off between oxygen consumption and nitrogen excretion functions in the gills of inanga with salinity. Although extra-branchial epithelia (i.e. skin and/or kidney) were significant contributors to both gas exchange and ammonia excretion (e.g. ~ 35% of ammonia excretion was extra-branchial), these contributions were independent of salinity. These data suggest that inanga do not incur significant physiological costs following acclimation to a wide range of environmental salinities, but that there may be subtle physiological advantages to inhabiting salinities close to their isosmotic point.

The objective of this study was to assess the frequency of use of marine resources in recruitment of Southern Hemisphere native riverine fish Galaxias maculatus from rivers across a latitudinal gradient. To do this, we analysed the concentrations of δ34S in vertebral column tissues from fish collected in ten Chilean river systems across latitudes 36°–47°S. The analyses of δ34S signatures in these rivers suggest that the use of marine resources by riverine populations of G. maculatus in large river systems in Chile is variable, with marine resources playing a limited role in more northern large rivers, characterised by warmer temperatures and predictable flow regimes and floodplain inundations. This is in contrast to life histories described for G. maculatus in rivers from New Zealand and Australia, where riverine populations are believed to be characterised by an obligatory recruitment phase in marine environments. Recruitment of G. maculatus in Chilean large rivers appears to depend on their freshwater productivity driven by climate as well as both longitudinal (headwaters lakes-estuary) and lateral (main channel-floodplains) hydrologic connectivities.

Se evaluo e l efecto de la salinidad en la supervivencia embrionaria, periodo embrionario y periodo de eclosion de puye, Galaxias maculatus . Se utilizaron ocho tratamientos, con salinidades de 0, 4, 8, 12, 16 y 20 obteniendose supervivencias embrionarias promedios respectivas de 84,9; 84,0; 85,5; 86,1; 82,6 y 75,8%, sin diferencias significativas entre ellas, mientras que con salinidad de 24 se obtuvo sobrevivencia de 10,4%, significativamente diferente al resto de los tratamientos y con salinidad de 28 causo 100% de mortalidad. A diferencia del estado juvenil y adulto, el embrion es incapaz de resistir la salinidad marina y su umbral de tolerancia se encuentra entre salinidades de 24 y 28. Las mayores supervivencias promedios larvales a 10 dias de vida fueron con salinidades intermedias de 8, 12 y 16 de 79,3; 80,3 y 74,6% respectivamente, sin diferencias significativas entre ellas, demostrando alta viabilidad del embrion post-eclosion. Los periodos embrionarios promedios (50%) mas breves fueron a bajas salinidades 0, 4, 8, 12 con 28,7; 28,0; 29,7 y 29,7 dias y los mas extensos en los tratamientos con salinidades de 16 y 20, con 34,0 y 34,3 dias, sin diferencias significativas entre ellos. Los periodos de eclosion promedio (50%) con salinidades de 0, 4, 8, 12, 16, 20 y 24 fueron de 5,0; 5,5; 7,5; 8,8; 13,0; 14,3 y 15,8 dias respectivamente, sin diferencias significativas entre ellos.

The freshwater fish Galaxias maculatus (inanga) is a widespread Southern hemisphere species, but despite its habitation of lowland near-coastal waters with a high potential for cadmium contamination, nothing is known regarding its sensitivity to this toxic trace metal. Acute (96h) exposures were therefore performed to determine sublethal responses of inanga to waterborne cadmium at a regulatory trigger value (nominally 0.2μgL-1; measured 1μgL-1), an environmental level (measured at 2.5μgL-1), and an effect level (measured at 10μgL-1). Whole body (tissue remaining following excision of kidney and liver) cadmium burden remained constant up until an exposure concentration of 10μgL-1, at which point cadmium concentration increased significantly. A transient effect of cadmium on metabolic rate was observed, with an impaired oxygen consumption noted at 2.5, but not 1 or 10, μg L-1. Cadmium did not impair influx rates of either sodium or calcium, and no effects of cadmium on oxidative stress parameters (catalase activity, lipid peroxidation) were noted in the kidney. However, at cadmium concentrations of 2.5 and 10μgL-1, lipid peroxidation in the liver increased, concomitant with a decline in hepatic catalase activity. These data indicate that there are significant differences in the mechanisms of cadmium toxicity in inanga, relative to better-studied Northern hemisphere species, especially with respect to ionoregulatory impacts. However, effects were induced at cadmium concentrations unlikely to be encountered in any but the most highly contaminated waterways, and thus our data suggest that current trigger values for cadmium concentrations in Australian and New Zealand waters are likely to be protective of inanga.

The puyen Galaxias maculatus is a fast-growing species, and the studied population at the southernmost extreme of the species’ distribution (54°S) has the shortest growing season among the South American populations (least daylight hours and lowest temperatures), as well as the largest size. Thus, it offers an opportunity to study the effects of strong seasonal variation. The energy allocation pattern on a diadromous population of the species and the influence of ‘Winter’ (4 °C, light:dark photoperiod of 7:17) and ‘Summer’ (10 °C, light:dark photoperiod of 17:7) experimental conditions on the bioenergetics of the species were studied using both physiological and biochemical indicators. Somatic growth, energy density, food consumption, oxidative metabolism and oxygen consumption were measured. In wild conditions, summer and winter were the more ‘energy demanding’ seasons, leading to the lowest energy density of individuals. Same levels of food consumption were found both in wild and ‘Summer’ and ‘Winter’ experimental conditions. Moreover, basal metabolism did not differ under experimental conditions, however, under ‘Winter’ experimental conditions individuals did not grow and diminished their somatic condition and energy reserves. Therefore, during winter this population would not lower energy demands (as expected by temperature) with no changes in metabolic rates, but with the consequent lower gross conversion efficiency, the complete absence of growth in length, mass and muscle, and the depletion of energy reserves. These findings suggest a mechanism for metabolic demands, i.e. postprandial increase in O2 consumption (SDA) independent of the amount of ingested food, relocating energy reserves to fuel winter costs in G. maculatus. These results provide evidence of different energy allocation strategies for winter and summer. A higher proportion of energy could be directed to growth and reproduction in summer, and to activity support in winter. Fil: Boy, Claudia Clementina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Pérez, Analía Fernanda. Universidad Maimónides. Área de Investigaciones Biomédicas y Biotecnológicas. Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y de Diagnóstico; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Tagliaferro, Marina Beatriz. Universidad Nacional de Luján. Instituto de Ecología y Desarrollo Sustentable. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Ecología y Desarrollo Sustentable; Argentina Fil: Lattuca, María Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Gutierrez, Marcelo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Vanella, Fabián Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina

A series of 14 day experiments was conducted on five common New Zealand fish species (redfin bully Gobiomorphus huttoni, inanga Galaxias maculatus, brown trout Salmo trutta, longfin eel Anguilla dieffenbachii and koaro Galaxias brevipinnis) to assess the effect of pH on survival and changes in body mass. No species survived in water of pH

Estuaries are natural sinks for a wide range of urban, industrial and agricultural contaminants that accumulate at potentially toxic but non-lethal concentrations, yet we know relatively little about the long-term impacts of toxicants at these levels on aquatic organisms. In this study, we present an integrated, multi-pronged approach to detect and assess the impacts to estuarine fish of exposure to sublethal concentrations of metal mixtures. Our aims were to (1) examine the effects of sublethal metal exposure on the embryonic development of Galaxias maculatus, an estuarine spawning fish native to southeastern Australia, (2) determine whether sublethal exposure during development has knock-on effects on larval behaviour, and (3) establish whether a signature of metal exposure during embryogenesis can be detected in larval otoliths ("ear bones"). G. maculatus eggs are fertilised in water but develop aerially, in direct contact with estuarine sediments. We were thus also able to explore the relative importance of two exposure pathways, water and sediment. Embryos were exposed to two concentrations of a metal mixture containing Cu, Zn and Pb in water (during fertilisation) and on spiked sediments (during development), using a fully crossed experimental design. Overall, we found that exposure to the metal mixture reduced embryo survival and slowed embryonic development, resulting in poorer quality larvae that exhibited a reduced phototactic response. Differences in exposure to metals between treatment and control embryos were also permanently recorded in the developing otoliths. Combined these three approaches have the potential to be a powerful novel bioassessment tool as they provide a means of identifying a history of metal exposure during the embryonic period and linking it to suboptimal early growth and performance traits which could have long term fitness consequences.

The Canterbury mudfish Neochanna burrowsius was found to be a pseudo-aestivating galaxiid with a low metabolic rate and significant cutaneous oxygen uptake (c. 43%) in both air and water. Another galaxiid, inanga Galaxias maculatus, had a higher metabolic rate in both media but the proportion of oxygen uptake met by cutaneous respiration rose significantly from 38 to 63% when the fish were exposed to air. Besides its important role in oxygen uptake, the skin of both species also contributed significantly to excretion of carbon dioxide in air, indicating the critical role of the integument as a respiratory tissue. In air, G. maculatus may increase cutaneous gas exchange to meet metabolic demands owing to the reduced utility of the gills, but as emersed G. maculatus were only able to maintain metabolic rates at c. 67% of that measured in water, this strategy probably only permits short-term survival. By contrast, the low and unchanging metabolic rate in water and air in N. burrowsius is a feature that may facilitate tolerance of long periods of emersion in the desiccating environments they inhabit.

This study evaluated the effect of ramp length and slope on fish passage over baffled ramps with 15° and 30° gradients. Three fish species indigenous to New Zealand were tested: the redfin bully Gobiomorphus huttoni, the common bully Gobiomorphus cotidianus and the inanga Galaxias maculatus with ramp lengths of 3, 4·5 and 6 m. As slope and ramp length increased, passage success rate decreased for G. maculatus and G. cotidianus. At a slope of 15°, both G. maculatus and G. cotidianus could pass all ramp lengths tested with the highest success rate on the 3 m ramp. As the gradient increased to 30°, G. maculatus could only pass the 3 m ramp, and G. cotidianus were incapable of passing any ramp. Gobiomorphus huttoni were the only test species capable of climbing the wetted margin of the ramps. Increasing ramp slope significantly reduced passage success for G. huttoni, but ramp length, up to the maximum used in this study, had no significant influence on successful passage.

Despite the well known importance of ω-3 polyunsaturated fatty acids (PUFA) in marine and freshwater fish larvae, there are few studies on how essential fatty acid requirements and composition on whole body can be altered by changes in water salinity. The present study aimed to determine the effect of salinity on ω-3 PUFA requirements, larval growth survival and fatty acid composition of G. maculatus larvae cultured at two different salinities (0 and 15 g∙L-1) for 20 days while fed rotifers containing two different levels of ω-3 PUFA (1.87 and 3.16%). The results denoted a marked difference in ω-3 PUFA requirements and in the pattern of fatty acid deposition in the whole body of larvae reared at different salinities, depending of ω-3 PUFA in diets. Thus, to improve growth and survival larvae of G. maculatus reared at 0 g∙L-1 require higher levels of ω-3 PUFA, principally 18: 3ω-3. Larvae reared at salinities of 15 g∙L-1 require low levels of ω-3 PUFA for optimal survival, especially 18: 3ω-3. Eicosapentaenoic acid and docosahexaenoic acid content in the whole body of larvae was also affected by water salinity.

Fil: Boy, Claudia Clementina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Austral de Investigaciones Cientificas; Argentina

Se evaluó el uso de antifúngicos para mejorar la supervivencia embrionaria de Galaxias maculatus. Se diseñaron tres tratamientos utilizando formalina en dosis de 250 ppm; yodo en dosis de 100 ppm y sal de mar en dosis de 30 ups y un tratamiento control. Para cada tratamiento y el control se utilizaron 15 réplicas con 100 embriones por réplica. El tratamiento correspondió a sumergir los embriones en un baño profiláctico por una hora cada dos días y el control sólo en agua de salinidad 10. Posteriormente se evaluó la supervivencia larval de cada tratamiento y control a los 15 días de vida. En el tratamiento con sal se obtuvo la mayor supervivencia embrionaria y larval, mejorando en un 27,4 y 11,6% (P < 0,05) por sobre el control. En el tratamiento con formalina se obtuvo supervivencia embrionaria y larval de 9,8 y 4,0% respectivamente sobre el control (P < 0,05) y en el caso del yodo se obtuvo una supervivencia embrionaria de 2,6% por sobre el control (P > 0,05) y supervivencia larval de un 16,4% menor al control (P < 0,05). En conclusión la sal muestra mayor efectividad como tratamiento profiláctico para mejorar la supervivencia embrionaria de G. maculatus. The use of antifungals was assessed to improve embryo survival of Galaxias maculatus. Three treatments using formalin dose of 250 ppm, iodine dose of 100 ppm, and sea salt in doses of 30 ups were designed, and a control treatment under 10 of salinity water. For each treatment and control, 15 replicates were used, with 100 embryos in each replicate. Embryos were immersed into each treatment solution for one hour every two days. Larval survival after 15 days old was assessed. Higher embryonic and larval survival was obtained in sea salt treatment improving by 27.4 and 11.6% (P < 0.05) respectively over control results. Formalin treatment resulted in embryonic and larval survival of 9.8 and 4.0% respectively more than control (P < 0.05) and in the case of iodine embryonic survival, 2.6% more than control (P > 0.05) and larval survival of 16.4% lower than the control (P < 0.05). In conclusion, sea salt shows greater effectiveness as a prophylactic treatment to improve the embryonic survival of G. maculatus.

Fil: Carrea, Cecilia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Patagonia Norte. Instituto de Investigacion En Biodiversidad y Medioambiente; Argentina

The mitigating effects of fish passes to aid fish dispersal are well recognised; however, non-sports fish species, juveniles and weak swimmers have mostly been neglected when developing solutions to fish passage issues. We studied the juvenile (fork length, FL

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

Restoring longitudinal connectivity is a key river restoration goal. This study tested the efficacy of a fish ramp and spoiler baffles for restoring indigenous fish communities upstream of a culvert. Before–after monitoring showed that installation of the ramp and spoiler baffles increased species richness (mean increase 80%) and total fish density (mean increase 45%) upstream of the culvert. Passage trials on the ramp and baffled culvert were carried out using inanga, Galaxias maculatus (Jenyns), a commonly occurring weak-swimming migratory fish. The trials showed that inanga were capable of successfully ascending both the ramp (overall 27.1% success) and culvert with baffles (overall 6.2% success) under the conditions tested (cf. 0% success for this species before retrofitting), but passage efficiency was still relatively low in both cases. Retrofitting of culverts can therefore be effective for restoring upstream fish passage. However, to maximize effectiveness it is essential that restoration goals are well defined and retrofitting solutions are designed appropriately for the target species. Copyright © 2012 John Wiley & Sons, Ltd.

Food availability and predation risk have been shown to affect phenotypes during early life history of fishes. Galaxias maculatus, a small fish widely distributed around the southern hemisphere, clearly exhibits a complex trade-off between feeding and predation avoidance during growth over the larval period. We studied the effect of different environmental variables on diet, growth, mortality, and morphology through field surveys and data revision in the literature for limnetic G. maculatus larvae in five oligotrophic lakes of Patagonia. Both number of food categories and prey ingested by larvae were directly related to zooplankton density. Larval growth rate was related with zooplankton density and temperature. Lakes with high zooplankton densities and low predation risk had larvae with deeper bodies and shorter caudal peduncles, while in lakes with less food and high predation risk larvae were slender with shallower bodies and longer peduncles. Food availability and predation risk seem to operate on the swimming performance of G. maculatus larvae through the slenderness of the body and the length of the caudal peduncle. The observed phenotypic variation in growth and morphology could be a key feature that has allowed this species to successfully colonize a wide variety of environments in the southern hemisphere.

We analysed 344 juvenile Galaxias maculatus (length 35–59mm) collected from two sites in the lower Waikato River, North Island, New Zealand, to determine diet during the period of upstream migration (August–November). In total, 53% of guts contained invertebrate food items comprising 16 taxa, with Cladocera numerically most abundant overall (32% of items), followed by Chironomidae, Saldidae and unidentified Insecta (18–24%). Cladocera heavily dominated G. maculatus diet in October (74–97%), particularly at the upper site, which was downstream of a lake- and wetland-fed tributary inflow. There were greater proportions of the cladocerans Bosmina and Daphnia and fewer Copepoda or Rotifera in guts compared with relative abundances in river water at locations where fish were caught during the day. These results highlight the potential importance of a range of foods items, in particular large zooplankton, to the diet of migratory juvenile G. maculatus, and implicate off-channel habitats as potential sources of cladoceran food following spring high flow events.

Galaxias maculatus is an osmeriform native ¢sh of the Southern Hemisphere, in which the crystalline larvae is considered as a luxury delicacy, for this reason, it has been commercially exploited in Chile, Argentina and New Zealand. However, the ¢sheries have been rapidly decreasing due to the overexploitation and the predation of introduced species. Because of these events, there is a need to determine a carrying capacity for an intensive ¢sh culture. In order to optimize stocking densities for ¢sh culture, this paper proposes objectives to determine oxygen consumption (OC) rates, dissolved oxygen concentrations that produce signs of hypoxia and the average time elapsed between food intake and peak OC in G. maculatus. In the oxygen experiments under routine metabolism conditions, we found that G. maculatus adults and whitebait showed signs of asphyxia at dissolved oxygen concentrations between 1.3 and 2.2 mg L � 1 and that adults tolerated dissolved oxygen levels as low as1.3 mg L � 1 . The results showed that G. maculatus individuals with an average weight of 0.04 g consumed 0.048 mg O2 h � 1 , whereas individuals with an average weight of 1.4 g consumed 0.345 mg O2 h � 1 . Galaxias maculatus increased the OC rate by 31%, from 0.39 to 0.51mg O2 h � 1 g � 1 , occurring 14 min after food intake. The carrying capacities for industrial cultures of G. maculatus, were estimated using an allometric equation (OC 50.2363 � W 0.612 ), a water £ow rate of 1m 3 h � 1 and an input oxygen concentration of 10 mg L � 1 at 12 1C. The density culture of whitebait (4 g) can be allowed to reach 8^11kg m � 3 ; therefore, these stocking densities reduce the risk of hypoxia and mortality, ensuring the appropriate growth and feed conversion rates.

An increasing number of studies are uncovering considerable flexibility in migration patterns of diadromous fishes. The development of otolith microchemical techniques has largely driven this research and led to an appreciation of the significance of facultative diadromy in the life history of numerous species. However, validation experiments need to be undertaken for each species and life stage of interest before diadromous migrations can be confidently reconstructed. These validation experiments are required to establish a salinity calibration series against which the otolith microchemistry of unknown individuals can be compared. To facilitate research on facultative amphidromy in galaxiids, we reared the larvae of two species, Galaxias maculatus and G. argenteus, in five different salinities (2, 5, 10, 20, 34). We tested whether trace element signatures of fish reflected their salinity treatment, and hence whether otolith microchemistry could reconstruct diadromous migrations. Distinguishing low salinity (2 and 5) from high salinity (20 and 34) treatments was straightforward using otolith Sr:Ca alone. The five salinity treatments resulted in five distinct multi-trace element signatures for both species (DFA classification success of 85% and 92% for G. maculatus and G. argenteus, respectively). Otolith lithium showed a similar trend to otolith Sr:Ca (ie. higher in saltwater), and otolith Rb:Ca showed a surprising negative trend with salinity despite higher ambient Rb concentrations in saltwater. Our results suggest otolith Li:Ca and Rb:Ca should be considered as part of a multi-trace element approach when investigating diadromous migrations, particularly when non-marine Sr levels may be high.

Despite the importance of certain highly unsaturated fatty acids in osmotic regulation, few studies have been addressed to determine the essential fatty acid requirements for a given species cultured under different salinities. As Galaxias maculatus is a diadromic species, the present study aimed to determine the effect of salinity on the optimum dietary EPA/docosahexaenoic (DHA) ratio for survival and growth during the larval stages. Larvae were fed for 20 days with rotifers containing two different EPA/DHA ratios (low: 0.64 and high: 2.18) at three different salinities (0, 10 and 15 g L−1). The results of this study showed a marked effect of water salinity on larval dietary lipid utilization in G. maculatus larvae. These results suggested that G. maculatus larvae reared at higher salinities may have a higher dietary requirement for DHA, whereas larvae reared at 0‰ showed higher requirements for EPA. The overall results of the present study indicate that even small changes in salinity can determine the optimum dietary EPA/DHA ratio and the quantitative essential fatty requirements of fish. This may have important repercussions and affect the rearing performance of G. maculatus cultured under different salinities.

Mortality from predation during the early life-stages of most teleost fishes can be extreme, and many species have developed specialized spawning strategies to reduce predation. In the diadromous fish Galaxias maculatus there is terrestrial development of eggs which restricts aquatic predation, but exposes them to terrestrial predators and a more extreme physical environment. We hypothesised that exotic slugs (Milax gagates, Deroceras panormitanum and D. reticulatum) and mice (Mus musculus) reduce the survival of developing eggs and tested this using laboratory and field predation experiments and sampling. We also tested the effects of riparian vegetation composition and density on egg survival. We found that exotic slugs (M. gagates and D. panormitanum) reduced the survival of eggs in laboratory experiments, but that neither slugs nor mice affected egg survival in field experiments. Egg densities were positively associated with the stem density of riparian vegetation and the thickness of the aerial root-mat. Egg survival was also positively associated with stem density and aerial root-mat thickness, but was not density-dependent. Although predation by mice and slugs did not appear to be a major cause of egg mortality in our study locations, mortality dynamics could be different in areas with greater densities of predators. Abiotic factors are important in egg survival and these are heavily modified by the height and density of riparian vegetation. It is likely that G. maculatus egg survival, therefore, co-varies with the composition of riparian vegetation.

Anti-predator behaviour often represents a trade-off between the benefits of reducing predation risk and the drawbacks of limiting access to resources (e.g. food availability, mating and nesting sites). The effectiveness of avoidance behaviour relies on the ability to detect predator cues, which may provide reliable information on predation risk. Using controlled laboratory experiments, we studied the relative importance of visual and chemical cues in the triggering of anti-predator responses in Galaxias maculatus, where Oncorhyncus mykiss was used as the predator. Metabolic cost was also estimated, measured as oxygen consumption. Exposure to different types of predator cue induced diverse behavioural responses in G. maculatus. Detection of the exotic predator, using both visual and chemical stimuli, resulted in reduced G. maculatus swimming activity and changes in respiratory rate.

Summary This study establishes the reproductive cycle, batch fecundity and oocyte diameter of a diadromic population of the puyen, Galaxias maculatus, in the Rio Ovando, Tierra del Fuego, (54°S), at the southernmost limit of its distribution. Given the short ‘favourable season’ in relation to other populations of the species (in terms of temperature, photoperiod and food availability), the study also explores the trade-offs between feeding and oocyte production and between phases of growth and reproduction. The reproductive cycle was analyzed by the monthly evolution of the proportion of gonadal maturity stages (determined from microscopic examination of the gonads). Oocytes were measured using a micrometric ocular scale and classified by diameter and morphological characteristics; absolute fecundity was established as the total number of hydrated oocytes per ovary. The studied population exhibits a repetitive spawning strategy, given the coexistence of post-ovullatory follicles and hydrated oocytes in histological sections and the presence in ripe ovaries of an intermediate cohort of yolked oocytes ready for hydration. Individual fecundity is lower (1422 ± 422 oocytes/ovary) than in other puyen populations, but the egg production increases through individual repetitive spawnings during the protracted spawning period (from October to February). Females attain larger sizes than those of other South American populations (the largest female reaching 115 mm total length), maximizing its potential fecundity. The present paper contributes to the knowledge of the variability of reproductive traits of G. maculatus in relation to diadromic populations, given that the bulk of information in South America refers to landlocked populations.

Exotic rainbow trout Oncorhynchus mykiss support an economically valuable recreational fishery in Patagonia but also create concern for impacts on native organisms. These concerns are intensified by the possibility of hatchery release programs in this region. We estimated losses of different prey from predation by rainbow trout in Lake Moreno, Río Negro Province, Argentina, using a bioenergetics model combined with input data from directed sampling on growth, seasonal diet, distribution, and thermal experience. The fish community was sampled seasonally using gill nets, hydroacoustics, and ichthyoplankton nets. Pelagic galaxiid larvae and benthic juvenile and adult small puyen Galaxias maculatus were the most important components of the diet. Bioenergetics simulations showed that over a 6-year life span in the lake (ages 1-7), rainbow trout attained a body mass of 2.3 kg and consumed 74.7 kg of food, of which 20% consisted of galaxiid larvae and 16% consisted of adult small puyen. Based on an estimated abundance of 29,000 rainbow trout of ages 1-7, this predator exerted significant but sustainable mortality on the native prey populations, consuming 44 metric tons or an estimated 23% of the annual larval galaxiid production and 35 metric tons of adult small puyen, which represented an unknown fraction of the postlarval population. Galaxiids supported the estimated predation demand under current conditions. However, simulations of stocking strategies normally proposed for this region showed that consumption demands on prey would increase to unsustainable levels, reducing native fish populations and likely reducing growth of rainbow trout. It is also probable that the fish community composition would shift further in response to the increased demand for prey by stocked predators. This implies that in some cases, stocking could jeopardize sport fisheries; stocking strategies should be evaluated on a case-by-case basis to be consistent with specific objectives for native fish conservation and sustainable food web interactions. Fil: Vigliano, Pablo Horacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Beauchamp, David. University of Washington; Estados Unidos Fil: Milano, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Macchi, Patricio Jorge. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Alonso, Marcelo Fabián. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Garcia Asorey, Martin Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Denegri, Maria Amalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina Fil: Ciancio Blanc, Javier Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; Argentina Fil: Lippolt, Gustavo. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Rechencq, Magali. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Grupo de Evaluación y Manejo de Recursos Ícticos; Argentina Fil: Barriga, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones en Biodiversidad y Medioambiente. Universidad Nacional del Comahue. Centro Regional Universidad Bariloche. Instituto de Investigaciones en Biodiversidad y Medioambiente; Argentina

The effects of riparian manipulation in New Zealand are described for two case studies, one a short‐term study of the effects of the removal of riparian vegetation on fish, and the second, a long‐term study of the effect of re‐establishment of riparian vegetation on fish and benthic macro invertebrates. The first case study was an experiment carried out between November 2001 and May 2002. Overhanging bank vegetation and in‐stream wood were removed from short reaches of a small pastoral stream that had intact riparian margins, resulting in a change in stream structure with the formation of shallow uniform runs rather than pool and riffle structures as in unmodified reaches. The removal of bank cover and consequential instream habitat changes reduced inanga (Galaxias maculatus) densities by a factor of four within months of vegetation removal, showing the importance of instream cover and habitat to inanga. Adult longfin eel (Anguilla dieffenbachii) also became less abundant in the cleared reaches, ...

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.

Introduced rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta fario are the most abundant fishes in the northern Chilean Patagonia, and their effect on native fishes is not well known. We tested for interactive segregation between trout and native fishes by using a before-after, control-impact design in which we deliberately reduced the density of trout and observed the response of the native fishes in their mesohabitat use (pool, run, riffle). Three native fish species, Brachygalaxias bullocki, Galaxias maculatus (inanga), and Trichomycterus areolatus, apparently had niche overlap with introduced trout and changed their mesohabitat use after trout reduction. The expansion of the three species into a wider range of mesohabitats after trout reduction suggests that these fishes occupy a broader spatial area when trout are reduced or possibly absent. However, some native fish species, such as Geotria australis, did not respond to the trout reductions. To protect Chilean native fishes, po...

The larvae and larval development of Galaxias maculatus are described from a freshwater lake and a saline river in southwestern Western Australia. The size at hatching (7.0 mm total length) was similar to that recorded elsewhere for G. maculatus and the sequence of fin development (i.e., caudal, dorsal, anal, pectoral, and pelvic fins) was identical to that recorded for galaxiids generally. There were relative increases in the proportions of head length and body depth with larval growth and a decrease in proportion of pre‐anal length. Larvae from river habitats were smaller throughout larval stages of development than those from the lake. Fins of riverine fish began and completed development at a smaller size of fish than the lacustrine population, presumably as a response to the need for great motility at a smaller fish size in lotic environments.

Life-history studies comparing landlocked versus diadromous populations reveal factors associated with life-history evolution under different scenarios. We describe several aspects of spawning and development of landlocked Aplochiton zebra in Patagonia (Argentina) based on the presence of eggs, the gonadal development, the analysis of otolith daily growth increments validated by tetracycline marking experiments, and the analysis of standard length frequencies. Among Patagonian galaxiids, A. zebra showed intermediate size and age at first maturity and high fecundity, with vitellogenic oocytes covered with short chorionic filaments. Free embryos of A. zebra were larger than those of Galaxias maculatus and Galaxias platei. This information is particularly significant for conservational purposes when we consider the reduced distribution of landlocked populations of the species and the risks imposed by salmonid introduction.

The growth of commercial aquaculture in Chile generated an income of $2.300 million USD in exports in 2005. Currently, 15 different species are cultivated commercially, of which seven are native; these had returns of 185 million USD. Among these native species is Galaxias maculatus (whitebait), which is endemic to Chile and figures significantly in Chilean fishing statistics. Since the 1990s, the School of Aquaculture of the Universidad Catolica de Temuco has been developing cultivation of this native species. This work presents the state of the art of the cultivation of this fish.

The presence of a settlement mark in the otoliths of the common galaxid Galaxias maculatus was validated by examining the relationship between changes in otolith microstructure and otolith microchemistry. Two methods were used to examine the microchemistry of otoliths: (1) laser-ablation multi-collector inductively-coupled plasma mass spectrometry (LA-MC-ICPMS) to examine changes in Sr isotope ratios, and (2) laser-ablation inductively-coupled-plasma mass spectrometry (LA-ICPMS) to examine changes in Ba/Ca and Sr/Ca. Both analytical techniques detected changes in otolith microchemistry consistent with movement from oceans into rivers (settlement). There was a strong correlation between the timing of settlement as indicated by otolith microstructure and both Sr-based methods; however, Ba/Ca was a less reliable marker of settlement for this species. These results support the use of this settlement mark for further otolith based studies of age, growth and the reconstruction of settlement histories in G. maculatus and demonstrate the potential utility of otolith microchemistry as a method for validating settlement marks in other diadromous fish. © Inter-Research 2008.

Summary Laboratory tank studies were used to identify the outcome of behavioural interactions between Gambusia affinis (gambusia) and Galaxias maculatus (inanga), whereas field data on spatial distribution were used to determine whether gambusia could be affecting inanga populations in the wild. Mortality rates for juvenile inanga (mean length 42 mm) exposed to gambusia (mean length 32 mm) for 15 days at 10°C were low (

Summary Reproductive aspects of a peripheral population of Galaxias maculatus are described and the relationship with the physiology and handling of energetic reserves under marginal environmental conditions is investigated. The G. maculatus population of Tierra del Fuego has an extended reproductive season, with differences in timing and duration compared to other populations of continental Patagonia, New Zealand and Australia. Elevated gonadosomatic indexes (IG) were observed during this period in both sexes (maximum IG ¼ 33.49% males; 35.94% females). The high abundance of mature males (with high IG values) on the spawning grounds during the reproductive season suggests that they were waiting for the return of the mature females. Larger females reached total maturation at the beginning of the reproductive season, whereas the size of maturing females diminished toward the end (mean TL ¼ 96 mm, October; 70 mm, February). Both sexes showed an extremely high investment in reproduction, reaching a maximum IG of about 35% for both sexes. At the beginning of the reproductive season females reached the maximum median IH (3.37%) and males the minimum (0.96%), suggesting differences in the role of the liver in the management of energetic reserves during sexual maturation. The variation in the fat index (IF) suggests that fat reserves were used to survive winter (maximum median IF > 1%, autumn; minimum about 0.2%, spring).