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In this study, we evaluated the isotopic niche dynamics in resident and migratory populations of facultative amphidromous fish Galaxias maculatus (Jenyns, 1842). We hypothesised that the isotopic niche space occupied by its populations differs between resident and migratory populations and among river ecosystems. To evaluate these hypotheses, we compared the isotopic niches of G. maculatus populations along the longitudinal gradient in five river systems in the central–southern Chile. Our results revealed differences among the isotopic niches of migratory and resident populations with greater diversity of carbon sources (wider isotopic niches) in amphidromous populations and narrower isotopic niche spaces in resident populations. Galaxias maculatus is a species with complex ecological characteristics that is frequently abundant in temperate river ecosystems of the Southern Hemisphere. The dynamics of its isotopic niches and carbon sources seems to strongly relate to life-history strategy employed by specific populations and mediates trophic structure and energy flow in river ecosystems where they are abundant. [ABSTRACT FROM AUTHOR]

Despite the importance of juvenile growth to lifetime fitness, high variability exists within many fish species where some individuals grow markedly faster than others. Here, we explored whether social context mediated growth performance in n = 35 Galaxias maculatus by manipulating the social environment after identifying different growth phenotypes. We found that initially fast-growing fish slowed their growth rate when pooled with similarly fast-growing individuals, whereas none of the initially slow-growing fish markedly improved their growth when pooled with other slow-growers. We examined for any metabolic underpinnings to the findings by measuring standard, routine, and maximum metabolic rates (SMR, RMR, and MMR) at two time points separated by ~4 months. SMR and RMR positively correlated with growth rates when the fish were pooled into growth phenotypes, but not when they were returned to their original (mixed) social groups. We highlight research directions to further elucidate how social context and metabolism interact to govern growth phenotype.

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Despite the demonstrated benefits of marine protected areas, there has been relatively little dialogue about freshwater protected areas (FPAs) even though some have been established to protect freshwater species from recreational and commercial fishers. After populations recover from fishing pressure, abundances and densities of formerly fished species increase, and we should therefore expect changes in demographic traits compared to those in exploited populations. To test this, we used capture-markrecapture data for 10 Galaxias maculatus populations across a density gradient mediated by different degrees of fishery closure. We examined the extent to which density-dependent (DD) and density-independent (DI) effects interact to affect specific growth rates in post-recruit populations. We found that population density, stream temperature and individual size interact to affect growth rates. When population densities were high, compensatory responses of far slower growth rates were strongest, indicating that DD growth is a key mechanism regulating post-recruit populations of G. maculatus. This study emphasizes the importance of understanding DD and DI processes, their interactions, function and effectiveness for freshwater fisheries management. For FPAs to be effective, the extent and quality of target species' habitats must serve as key criteria for protection to alleviate competition for limited resources that underpins DD processes. [ABSTRACT FROM AUTHOR]

Abstract Galaxias maculatus aquaculture objectives is to produce millions of eggs. Wild females are small (2 g), have quick sexual maturity and low mean fecundity (500 eggs/female), requiring larger fishes with higher fecundity. This study aim is to evaluate experimentally the effect of the levels of protein, lipid and dietary energy on weight increases in adults. Five independent experiments were performed at different sequential time periods at the UCT hatchery, Chile. Specimens were obtained from a) Crystalline sea return specimen catches in the Tolten estuary (4 -6 cm, 0.3-0.4 g.). b) Hatchery cultured fish. Fish were fed by hand ad libitum. In experiments 1 to 4, pelleted diets were prepared with 3 to 5 levels of protein (treatments 27 up to 57%), crumble size, three 100 L fibre ponds replicates. In experiment 5 the effect of two lipid levels (8 and 21%) was evaluated with commercial extruded Salmon Nutra Starter isoproteic crumble 1 diet at 63%, replicated in 4 ponds. The results show: A tendency to increased weight in all sizes with an increased protein level in the pelleted diet.A maximal adult growth is obtained with a diet containing a minimum of 37% crude protein, with 40% the optimal value. A higher % protein in the diet or growth in weight lower feed conversion ratio. The feed conversion ratio in the extruded diet reaches up to 0.5 and in the pelleted vary from 0.7 to 1.5. Fish 0.6 g fed with 63% protein, extruded commercial diet with two different lipid levels (8 and 21%, 20.40 and 23.84 MJ kg-1, PE/TE 0.62 and 0.71) increased weight the first month 67 and 105% each. It has been established that high-energy diets with optimal levels of protein and lipid are a good short-term solution to obtain G. maculatus of higher weight.

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. [ABSTRACT FROM AUTHOR]

Estuaries worldwide have been severely degraded and become reservoirs for many types of pollutants, such as heavy metals. This study investigated the levels of Cd, Cu, Mn, Ni, Pb, and Zn in water and whole fish. We sampled 40 juvenile silversides Odontesthes regia and 41 juvenile puye Galaxias maculatus from the Valdivia River estuary, adjacent to the urban area in southern South America (Chile). Samples were analyzed using a flame atomic absorption spectrophotometer. In water samples, metals except Zn were mostly below the detection limits and all metals were below the maximum levels established by local guidelines in this estuary. In whole fish samples, concentrations of Cu, Zn, Pb, Mn, and Cd were significantly higher in puyes than in silversides. Additionally, Zn, Pb, and Mn were correlated to body length and weight in puyes, whereas Cd was correlated to body length in silversides. The mean concentration of heavy metals in silverside and puyes were higher than those reported in the literature. In silversides, all heavy metal levels were below the limits permitted by current legislation (FAO), whereas in puyes Pb and Cd levels were above the recommended maximum level established by international guidelines, therefore putting the human population at risk. [ABSTRACT FROM AUTHOR]

Helminth infections within tissues tend to be subjected to a host response that can include encapsulation and melanization to isolate the parasite. The effectiveness of this response depends on the host species. During a survey of parasites of the native fish, Galaxias maculatus , we found conspicuous, strongly melanized exterior cysts located in the caudal peduncle of the fish. Dissection of these cysts exposed larval nematodes whose morphometrical features allowed their identification as Eustrongylides sp. Species of this genus are distributed worldwide. Galaxias maculatus was previously reported as second intermediate host to Eustrongylides sp. larvae, and the aquatic bird Podiceps major was cited as definitive host of Eustrongylides tubifex in Andean Patagonian lakes. The site of infection in the fish, and the host's response are unique among infections by larvae of Eustrongylides sp. in fishes, so the objective of this study was to describe the histological injury caused by larvae of the genus Eustrongylides parasitizing G. maculatus. Samples of fish were taken near the shore of Gutiérrez lake, in northwestern Patagonia. Some larval morphometric features were described to confirm the identity of larvae to generic level. Histopathological analysis (tissues sectioned at 5–7 μm, stained with Hematoxylin and Eosin, and Masson's Trichrome) of the caudal peduncle revealed almost complete disappearance of the epaxial musculature due to compressive atrophy and a chronic inflammatory response, associated mainly with a dense fibrotic capsule and an intense melanic deposit. This is the first description of the histopathology of an external cyst caused by Eustrongylides sp. larvae in fishes. Image 1 • The larva produces a conspicuous, melanized, external cyst in the caudal peduncle of Galaxias maculatus. • The localization and fish response are unique among infections by Eustrongylides sp. • The pathology includes an almost complete disappearance of the musculature. • The infection could compromise the survival of this prey fish. • The histopathology of an external cyst is described for the first time for Eustrongylides infection. [ABSTRACT FROM AUTHOR]

Abstract Chemical mixtures represent environmentally-realistic exposures of contaminants to aquatic biota. However, there remains a limited understanding of how toxicant mixtures may impact biological function, relative to their individual components. In the current study, oxidative stress responses of the freshwater galaxiid fish inanga (Galaxias maculatus) were examined following exposure to the pro-oxidant trace metal cadmium (2 or 9 μg L−1), and the anti-oxidant pharmaceutical drug diclofenac (770 μg L−1), individually or in simple binary mixtures. Cadmium exposure in the absence of diclofenac significantly decreased renal catalase activity, increased hepatic catalase activity, decreased renal superoxide dismutase (SOD) and decreased glutathione-S-transferase activity, effects that are suggestive of anti-oxidant defense inhibition and/or generation of increased reactive oxygen species. Diclofenac exposure in the absence of cadmium resulted in a decreased renal lipid peroxidation, consistent with its known anti-oxidant properties. The presence of waterborne diclofenac altered the effects of cadmium on catalase activity in the liver, SOD activity in the gill, and lipid peroxidation in the liver. Co-exposure with cadmium modulated diclofenac effects on lipid peroxidation in the kidney. These data indicate the capacity of each of these toxicants to offset biological effects of the other when both co-occur in urban waters at specific concentrations. This study also demonstrates the complexity of outcomes in contaminant mixtures, even when these stressors are presented as simple binary combinations. Graphical abstract Image 1 Highlights • Cadmium (Cd) promoted oxidative stress in the freshwater fish, inanga. • Diclofenac exposure resulted in a decrease in renal lipid peroxidation. • In mixtures, diclofenac modified the pro-oxidant effects of Cd. • The presence of Cd prevented diclofenac's anti-oxidant effects. Contaminant mixtures of a pro-oxidant (cadmium) and an anti-oxidant (diclofenac) produce complex and unpredictable effects on oxidative stress endpoints in the freshwater fish, inanga. [ABSTRACT FROM AUTHOR]

Estuaries worldwide have been severely degraded and become reservoirs for many types of pollutants, such as heavy metals. This study investigated the levels of Cd, Cu, Mn, Ni, Pb, and Zn in water and whole fish. We sampled 40 juvenile silversides Odontesthes regia and 41 juvenile puye Galaxias maculatus from the Valdivia River estuary, adjacent to the urban area in southern South America (Chile). Samples were analyzed using a flame atomic absorption spectrophotometer. In water samples, metals except Zn were mostly below the detection limits and all metals were below the maximum levels established by local guidelines in this estuary. In whole fish samples, concentrations of Cu, Zn, Pb, Mn, and Cd were significantly higher in puyes than in silversides. Additionally, Zn, Pb, and Mn were correlated to body length and weight in puyes, whereas Cd was correlated to body length in silversides. The mean concentration of heavy metals in silverside and puyes were higher than those reported in the literature. In silversides, all heavy metal levels were below the limits permitted by current legislation (FAO), whereas in puyes Pb and Cd levels were above the recommended maximum level established by international guidelines, therefore putting the human population at risk.

Galaxias maculatus (puyen chico) es una especie de pez presa que tiene un rol importante en las redes tróficas de los lagos de la Patagonia. Estudios previos, a escala local, muestran que la riqueza y la composición de las comunidades componentes de parásitos metazoos de G. maculatus en un grupo de pequeños lagos someros en los alrededores del lago Nahuel Huapi, están afectadas por la composición del ensamble de peces nativos en cada lago. Los objetivos del presente estudio fueron: a) caracterizar la comunidad de helmintos de G. maculatus incluyendo datos de 28 lagos andinos de las provincias de Río Negro y Neuquén, y b) identificar los factores bióticos y abióticos de estos lagos que afectan la presencia y la prevalencia de las diferentes especies de helmintos que parasitan a este pez presa abundante y ampliamente distribuido en la Patagonia. El análisis indica que las comunidades de helmintos de las diferentes poblaciones de G. maculatus varían de acuerdo a la vertiente, al área lacustre, a la altitud y al ensamble de peces del lago.

Se evaluó e l efecto de la salinidad en la supervivencia embrionaria, período embrionario y período de eclosión de puye, Galaxias maculatus. Se utilizaron ocho tratamientos, con salinidades de 0, 4, 8, 12, 16 y 20 obteniéndose 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 causó 100% de mortalidad. A diferencia del estado juvenil y adulto, el embrión 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 días 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 embrión post-eclosión. Los períodos embrionarios promedios (50%) más breves fueron a bajas salinidades 0, 4, 8, 12 con 28,7; 28,0; 29,7 y 29,7 días y los más extensos en los tratamientos con salinidades de 16 y 20, con 34,0 y 34,3 días, sin diferencias significativas entre ellos. Los períodos de eclosión 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 días respectivamente, sin diferencias significativas entre ellos.

Galaxias maculatus is a diadromous riparian-spawning fish that supports an important fishery. Eggs develop terrestrially as with several other teleost fishes. Spawning habitat occurs in specific locations near rivermouths and its protection is a conservation priority. However, quantifying the areas involved is hampered by high egg mortality rates on degraded waterway margins. We hypothesised that temporary artificial habitat would detect spawning in these situations producing a useful indicator for riparian management. We installed arrays of straw bales as artificial habitat in two independent experiments over consecutive years and assessed their impact using pairwise Before-After-Control-Impact (BACI) experimental designs. We tested degraded gaps within the distribution of known spawning sites and also areas further upstream and downstream. Nine spawning occurrences were recorded on artificial habitats in 2015, 22 in 2016, and two on paired controls. Both experiments produced a significant effect for artificial habitats deployed in degraded gaps within the known spawning site distribution (p = 0.0001) providing evidence that these locations should be regarded as actual or potential spawning sites. In 2016 the technique also produced a significant effect downstream of known sites in one of the study catchments (p = 0.0375). We believe the use of artificial habitats as a detection tool could be useful in a variety of management contexts. These include identifying areas for protection, as confirmation of site suitability prior to making restoration investments, and in investigations to support the migration of habitats to new locations under climate change, since these may currently be degraded. [ABSTRACT FROM AUTHOR]

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 conservation objectives. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 (96 h) exposures were therefore performed to determine sublethal responses of inanga to waterborne cadmium at a regulatory trigger value (nominally 0.2 μg L −1 ; measured 1 μg L −1 ), an environmental level (measured at 2.5 μg L −1 ), and an effect level (measured at 10 μg L −1 ). Whole body (tissue remaining following excision of kidney and liver) cadmium burden remained constant up until an exposure concentration of 10 μg L −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 10 μg L −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. [ABSTRACT FROM AUTHOR]

Body mass and temperature are primary determinants of metabolic rate in ectothermic animals. Oxygen consumption of post-larvalGalaxias maculatuswas 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 (Rin g O2g−1d−1) declined as a power function of body mass and increased exponentially with temperature and was expressed as:R = 0.0007 *W−0.31*e0.13 * 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 ofG. maculatusis 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. [ABSTRACT FROM AUTHOR]

Se evaluó el efecto de seis temperaturas constantes en la sobrevivencia embrionaria, periodo embrionario y periodo de eclosión de Galaxias maculatus de 7 a 22°C, en condiciones de laboratorio. Los resultados de la sobrevivencia embrionaria fueron: 90,6 ± 2,0; 88,7 ± 8,6; 87,7 ± 0,7; 89,7 ± 4,2; 70,0 ± 5,6 y 49,5 ± 7,4% a temperaturas de 7, 10, 13, 16, 19 y 22°C. Exceptuando la temperatura de 22°C, no hay diferencias significativas entre ellas (P > 0,05). Estos resultados caracterizan al embrión como euritérmico independientemente de ser una especie de aguas subantárticas. En relación al periodo embrionario (tH50%), los resultados fueron de 40,8 ± 0,6; 27,0 ± 0,0; 17,3 ± 0,6; 16,3 ± 0,6 y 13,3 ± 0,6 días a temperaturas de 7, 10, 13, 16 y 19°C respectivamente, con diferencias significativas entre ellas (P < 0,05), y en el caso del periodo de eclosión (tH50%), fue de 8,3 ± 0,6; 6,3 ± 1,5; 5,0 ± 0,0; 6,3 ± 0,6; 5,0 ± 1,0 y 4,3 ± 0,6 días a temperaturas de 7, 10, 13, 16, 19 y 22°C respectivamente, con diferencias significativas entre ellas (P < 0,05). Los resultados sugieren que el rango de temperaturas entre 10 y 16°C es óptimo para la incubación de ovas de G. maculatus, ya que se obtienen combinadamente altos porcentajes de sobrevivencia embrionaria >87,7%, periodos embrionarios

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 Galaxias 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 18:3 ω-3. Larvae reared at salinities of 15 g L-1 require low levels of ω-3 PUFA for optimal survival, especially 18:3 ω-3. Eicosapentaenoic acid and docosahexaenoic acid content in the whole body of larvae was also affected by water salinity.

Galaxias maculatus (Jenyns, 1842) es un pez gourmet de importancia comercial cuyas pesquerías están sobre-explotadas, siendo esencial el estudio de su biología para desarrollar su tecnología de cultivo (galaxicultura), que se encuentra en etapa piloto. Los objetivos de éste trabajo son: 1) entregar una síntesis de la información de la literatura sobre la biología de la especie, y 2) identificar la carencia de conocimiento científico y puntos críticos para el desarrollo de su tecnología de cultivo comercial. G. maculatus es un pequeño pez carnívoro, con poblaciones eurihalinas diferenciadas en diadrómicas y dulceacuícolas. Las poblaciones diadrómicas desovan en los estuarios y la larva migra al mar, retornando a la edad de seis meses para metamorfosearse en adulto. Son escasos los estudios de su sistemática, poblaciones y estado larvario en aguas chilenas, pero los correspondientes a alimentación, reproducción y enfermedades son más numerosos. Las hembras de un año desovan, aproximadamente, 1.200 huevos adhesivos pero un número importante muere después del primer desove (40%). La especie tiene un crecimiento rápido (1,1% dia-1) y alto metabolismo, con un promedio de vida de dos años. Se puede cultivar en cautividad, desovar, incubar sus huevos y obtener larvas; los adultos comen starter pelletizado de salmón y crecen en estanques. El protozoo ciliado Ichtyophthirius multifilis (ich) produce altas mortalidades, en ejemplares en cautiverio, que pueden ser controladas con baños de sal. Los problemas de investigación a resolver para una futura piscicultura comercial son: identificar y seleccionar las poblaciones adecuadas para cultivo, aumentar el número de huevos desovados por hembra, desarrollar alimentos para larvas y reproductores, y controlar las enfermedades ectoparasitarias. El punto crítico es la masificación de la producción mediante el mejoramiento de las técnicas de reproducción y larvicultura.

The nuclear DNA content (2C value) was determined in the commercial fish Galaxias maculatus (Galaxiidae) was determined by microdensitometry of erythrocyte nuclei after Feulgen staining; rainbow trout erythrocytes with a known 2C value were used as a standard. The 2C value of G. maculatus was 2.21 ± 0.12 pg and its C value was equivalent to 1.105 pg (1,082.9 Mbp). This C value is within the range recorded for other osmeriform species (0.62-3.2 pg). The average sperm head diameter of G. maculatus is lower than the average sperm head diameter of rainbow trout (used as a standard), which coincides with the differences observed in the nuclear DNA content of both species. This information increases the genome data available for G. maculatus and might be useful in future programs dealing with its genetic manipulation.El contenido de ADN nuclear (valor 2C) fue determinado en el pez comercial Galaxias maculatus (Galaxiidae) usando microdensitometría de núcleos de eritrocitos sometidos a tinción de Feulgen, utilizando como estándar eritrocitos de trucha arco iris con un valor 2C conocido. El valor 2C de G. maculatus fue 2,21 ± 0,12 pg y su valor C es equivalente a 1,105 pg (1.082,9 pMb). Este valor C está dentro del rango registrado para otras especies de osmeriformes (0,62-3,2 pg). El diámetro promedio de la cabeza del espermatozoide de G. maculatus es menor al promedio descrito para la trucha arco iris utilizado como estándar, lo que coincide con las diferencias observadas en el contenido de ADN nuclear entre ambas especies. Estos datos contribuyen a ampliar los antecedentes genómicos disponibles para G. maculatus y podrían ser útiles en futuros programas tendientes a su manipulación genética.

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. [ABSTRACT FROM AUTHOR]

Background: Marine species have colonized extreme environments during evolution such as freshwater habitats. The amphidromous teleost fish, Galaxias maculatus is found mainly migrating between estuaries and rivers, but some landlocked populations have been described in lakes formed during the last deglaciation process in the Andes. In the present study we use mtDNA sequences to reconstruct the historical scenario of colonization of such a lake and evaluated the osmoregulatory shift associated to changes in habitat and life cycle between amphidromous and landlocked populations. Results: Standard diversity indices including the average number of nucleotide differences (Π) and the haplotype diversity index (H) indicated that both populations were, as expected, genetically distinctive, being the landlocked population less diverse than the diadromous one. Similarly, pairwise GST and NST comparison detected statistically significant differences between both populations, while genealogy of haplotypes evidenced a recent founder effect from the diadromous stock, followed by an expansion process in the lake. To test for physiological differences, individuals of both populations were challenged with a range of salinities from 0 to 30 ppt for 8 days following a period of progressive acclimation. The results showed that the landlocked population had a surprisingly wider tolerance to salinity, as landlocked fish survival was 100% from 0 to 20 ppt, whereas diadromous fish survival was 100% only from 10 to 15 ppt. The activity of ATPase enzymes, including Na+/K+-ATPase (NKA), and H+-ATPase (HA) was measured in gills and intestine. Activity differences were detected between the populations at the lowest salinities, including differences in ATPases other than NKA and HA. Population differences in mortality are not reflected in enzyme activity differences, suggesting divergence in other processes. Conclusions: These results clearly demonstrate the striking adaptive changes of G. maculatus osmoregulatory system, especially at hyposmotic environments, associated to a drastic shift in habitat and life cycle at a scale of a few thousand years. [ABSTRACT FROM AUTHOR]

The euryhaline galaxiid fish, inanga ( Galaxias maculatus ) is widely spread throughout the Southern hemisphere occupying near-coastal streams that may be elevated in trace elements such as copper (Cu). Despite this, nothing is known regarding their sensitivity to Cu contamination. The mechanisms of Cu toxicity in inanga, and the ameliorating role of salinity, were investigated by acclimating fish to freshwater (FW), 50% seawater (SW), or 100% SW and exposing them to a graded series of Cu concentrations (0–200 μg L −1 ) for 48 h. Mortality, whole body Cu accumulation, measures of ionoregulatory disturbance (whole body ions, sodium (Na) influx, sodium/potassium ATPase activity) and ammonia excretion were monitored. Toxicity of Cu was greatest in FW, with mortality likely resulting from impaired Na influx. In both FW and 100% SW, ammonia excretion was significantly elevated, an effect opposite to that observed in previous studies, suggesting fundamental differences in the effect of Cu in this species relative to other studied fish. Salinity was protective against Cu toxicity, and physiology seemed to play a more important role than water chemistry in this protection. Inanga are sensitive to waterborne Cu through a conserved impairment of Na ion homeostasis, but some effects of Cu exposure in this species are distinct. Based on effect concentrations, current regulatory tools and limits are likely protective of this species in New Zealand waters. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses articles in the issue on topics including the fish fauna of the two European rivers, species in South America's wetlands to different climatic scenarios, and use of marine resources by riverine populations of Galaxias maculatus in Chile.

Fish passage research is important to mitigate the adverse effects of fragmented river habitats caused by waterway structures. The scale at which this research is undertaken varies from small-scale laboratory prototype studies to in-situ observations at various fish passage structures and bottlenecks. Using DeepLabCut, we introduce and evaluate a machine learning based workflow to track small-bodied fish in order to facilitate improved fish passage management. We specifically studied the behaviour and kinematics of Galaxias maculatus , a widespread diadromous Southern Hemisphere fish species. Upstream fish passage was studied in the presence of three different patches of spoiler baffles at an average water velocity of 0.4 m/s. In semi-supervised mode, the fish locations were extracted, and fish behaviour, such as swimming pathways and resting locations, was analysed based on extracted positions and recorded kinematic parameters. Individual fish behaviour and kinematic parameters were then used to assess the suitability of the three different spoiler baffle designs for enhancing fish passage. Using this technique, we were able to demonstrate where different spoiler baffle configurations resulted in significant differences in fish passage success and behaviour. For example, medium-spaced smaller baffles provided more accessible and uniform resting locations, which were required for efficient upstream passage. Results are discussed in relation to fish passage management at small instream structures. • A novel small-bodied fish tracking machine learning-based workflow is presented. • Different spoiler baffle arrangements are evaluated for fish passage suitability. • Swimming kinematics and behavioural information of Galaxias maculatus are studied. • Smaller baffles with medium spatial density provide more efficient upstream passage. • Small-scale laboratory tests are shown to assist fish passage design and management. [ABSTRACT FROM AUTHOR]

Galaxias maculatus (small puyen) is a prey fish which plays a main role in lake food webs of Patagonia. Previous studies, at local scale, have shown that the richness and composition of parasitic metazoan component communities associated to G. maculatus in a group of small shallow lakes in the surroundings of the Nahuel Huapi Lake, are affected by the composition of the native fish assemblage in each lake. The aims of this work were: a) to characterize the helminth community of G. maculatus at regional scale, including data of 28 Andean lakes of the Neuquén and Río Negro Provinces, and b) to identify biotic and abiotic factors of these lakes influencing the occurrence and prevalence of the different helminth species parasitizing this highly abundant and widely distributed prey fish in Patagonia. The analysis indicates that the parasite community of different populations of G. maculatus varies according to the basin, lake area, altitude and the fish assemblage of the lake. [ABSTRACT FROM AUTHOR]

Galaxias maculatus (Pisces: Galaxiidae) commonly known as "puye" has a disjunct distribution along the Southern Hemisphere including landlocked and migratory populations at latitudes over 30°S in South America, Australia, Tasmania, and New Zealand. Chilean artisanal fishery of G. maculatus has become less important as a resource due to multiple factors including overexploitation, pollution, introduction of predators, and competitors. At the same time, the current conservation status of the species in Chile is still uncertain. Here, we used mtDNA control region sequences (925 bp) to investigate main patterns of genetic diversity and structure in populations from 2 biogeographic areas along the Chilean coast. Extremely high levels of genetic diversity characterize the species, suggesting a low amount of influence of the last glacial cycle over its demography compared with other studies in freshwater and marine South American fishes. However, we recognized contrasting genetic patterns between the Intermediate Area (between 30°S and 42°S) and the Magellanic Province (between 42°S and 56°S). On the one hand, over a narrow geographical range (<200 km) each Intermediate Area estuarine population constitutes a different genetic unit. On the other hand, the Magellanic populations of the species exhibited low levels of differentiation in an area extending for more than 500 km. Such differences may be a consequence of different coastal configurations, oceanographic regimes, and Quaternary glacial histories. Finally, our results support the existence of different stock units for G. maculatus and this information should be integrated in future management strategies and aquaculture programs for this species. [ABSTRACT FROM AUTHOR]

Major geologic and climatic changes during the Quaternary exerted a major role in shaping past and contemporary distribution of genetic diversity and structure of aquatic organisms in southern South America. In fact, the northern glacial limit along the Pacific coast, an area of major environmental changes in terms of topography, currents, and water salinity, represents a major biogeographic transition for marine and freshwater species. We used mitochondrial DNA sequences (D-loop) to investigate the consequences of Quaternary glacial cycles over the pattern of genetic diversity and structure of G. maculatus (Pisces: Galaxiidae) along two biogeographical provinces in the Chilean coast. Extreme levels of genetic diversity and strong phylogeographic structure characterize the species suggesting a low amount of influence of the last glacial cycle over its demography. However, we recognized contrasting patterns of genetic diversity and structure between main biogeographical areas here analyzed. Along the Intermediate Area (38°–41° S) each estuarine population constitutes a different unit. In contrast, Magellanic populations (43°–53° S) exhibited low levels of genetic differentiation. Contrasting patterns of genetic diversity and structure recorded in the species between the analyzed biogeographic areas are consistent with the marked differences in abiotic factors (i.e., different coastal configurations, Quaternary glacial histories, and oceanographic regimes) and to inherent characteristics of the species (i.e., salt-tolerance, physiology, and reproductive behavior). [ABSTRACT FROM AUTHOR]

The occurrence of Tylodelphys barilochensis, Acanthostomoides apophalliformis, Contracaecum sp. and Camallanus corderoi infecting Galaxias maculatus ("puyenes") was quantified for the first time in Lake Nahuel Huapi, southern Argentina. T. barilochensis was recorded in this lake for the first time. The role of G. maculatus population in transmission of parasites to the salmonids is more important for Contracaecum sp. (prevalence 14-34%) and A. apophalliformis (prevalence 30-54%) than for C. corderoi (prevalence 6-8%). The absence of Diphyllobothrium spp. in samples shows that the G. maculatus population does not play any role in the life cycles of these important zoonotic parasites. The sex of the host had no effect on T. barilochensis abundance. Statistical differences in T. barilochensis abundance between "puyenes" of the same size class between sampling stations and positive correlation between prevalence of infected snails and T. barilochensis abundance in fish suggest that different stocks have been sampled. Factors influencing T. barilochensis abundance are discussed.

The present study was conducted to determine if parasite induced mortality existed in a "puyen" population in Moreno Lake, southern Argentina. Data on both parasite abundance and degree of aggregation of parasite frequency distribution showed the absence of fish mortality induced by A. apophalliformis.Acanthostomoides apophalliformis (Trematoda: Cryptogonimidae) não causa mortalidade detectável no peixe Galaxias maculatus (Teleostomi: Galaxiidae) de Argentina do Sul. O "puyen", Galaxias maculatus, é um peixe nativo pequeno que habita a América do Sul e a Oceania. Acanthostomoides apophalliformis é um trematódeo digenético que parasita, freqüentemente, os "puyenes". O estudo atual foi conduzido para determinar se existe mortalidade induzida por parasito no população do "puyen" no lago Moreno, no sul de Argentina. Os dados de abundância do parasito e no grau de aggregação da distribuição de freqüência do parasito, sugerem a ausência de mortalidade induzida por A. apophalliformis em "puyenes".

Highlights: [•] We use fish development, morphology, behaviour and otoliths to assess metal toxicity. [•] Fish embryos exposed to metal mixtures had lower survival and delayed development. [•] This resulted in poorer quality larvae that exhibited weaker phototactic behaviour. [•] Differences in metal exposure levels were permanently recorded in embryonic otoliths. [•] Otoliths could be a useful tool for linking past exposure to poor quality phenotypes. [Copyright &y& Elsevier]

We evaluated the effect of six constant temperatures on embryonic survival, embryonic period and hatching period of Galaxias maculatus from 7 to 22°C under laboratory conditions. The results of embryo survival were: 90.6 ± 2.0, 88.7 ± 8.6, 87.7 ± 0.7, 89.7 ± 4.2, 70.0 ± 5.6 and 49.5 ± 7.4% at temperatures of 7, 10, 13, 16, 19 and 22ºC. Except for the temperature of 22°C, there were no significant differences between them (P < 0.05). These results characterize the embryo as eurythermic regardless of being a subantarctic waters species. Regarding the embryonic period (th50%), the results were 40.8 ± 0.6, 27.0 ± 0.0, 17.3 ± 0.6, 16.3 ± 0.6 and 13.3 ± 0.6 days at temperatures of 7, 10, 13, 16 and 19°C respectively, with significant differences between them (P < 0.05) and in the case of the hatching period (th50%), was 8.3 ± 0.6, 6.3 ± 1.5, 5.0 ± 0.0 and 6.3 ± 0.6, 5.0 ± 1.0 and 4.3 ± 0.6 days at temperatures of 7, 10, 13, 16, 19 and 22ºC respectively with significant differences between them (P < 0.05). These results suggest that the range of temperatures between 10 and 16°C is optimal for the incubation of G. maculatus eggs, since in that range high embryonic survival (>87.7%) combined with embryonic periods of less than 27 days and hatching periods less than 6.3 days were obtained. These results will optimize embryo survival and eventually rearing of the species for commercial purposes or restocking. [ABSTRACT FROM AUTHOR]

The relationship between metabolic rate and body size in animals is unlikely to be a constant but is instead shaped by a variety of intrinsic (i.e., physiological) and extrinsic (i.e., environmental) factors. This study examined the effect of environmental oxygen tension on oxygen consumption as a function of body mass in the galaxiid fish, inanga (Galaxias maculatus). As an oxyconformer, this fish lacks overt intrinsic regulation of oxygen consumption, eliminating this as a factor affecting the scaling relationship at different oxygen tensions. The relationship between oxygen consumption rate and body size was best described by a power function, with an exponent of 0.82, higher than the theoretical values of 0.66 or 0.75. The value of this exponent was significantly altered by environmental Po2, first increasing as Po2 decreased and then declining at the lowest Po2 tested. These data suggest that the scaling exponent is species specific and regulated by extrinsic factors. Furthermore, the external Po2 at which fish lost equilibrium was related to fish size, an effect explained by the scaling of anaerobic capacity with fish mass. Therefore, although bigger fish were forced to depress aerobic metabolism more rapidly than small fish when exposed to progressive hypoxia, they were better able to enact anaerobic metabolism, potentially extending their survival in hypoxia. [ABSTRACT FROM AUTHOR]

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 Galaxias 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 18:3 ω-3. Larvae reared at salinities of 15 g L-1 require low levels of ω-3 PUFA for optimal survival, especially 18:3 ω-3. Eicosapentaenoic acid and docosahexaenoic acid content in the whole body of larvae was also affected by water salinity. [ABSTRACT FROM AUTHOR]

Galaxias maculatus (Jenyns, 1842), is a gourmet fish of great commercial importance with overexploited fisheries. So, studies of its biology are essential in order to develop a technology for its cultivation (galaxiculture), which is at a pilot stage. The goals of this work are: 1) to provide a synthesis of the literature information on the biology of the species, and 2) to identify the lack of scientific knowledge and critical points for the development of a technology for mass commercial culture. G. maculatus is a small carnivorous fish with euryhaline populations differentiated between diadromic and freshwater. Diadromic populations spawn in the estuaries, and then the larvae migrates to the sea, returning aged 6 months and metamorphosing into adults. Studies of their systematic, populations and larvae stage in Chilean waters are scarce, but studies on feeding, reproduction and diseases are more numerous. One year old females lay about 1,200 adhesive eggs and an important number of them die after the first spawning (40%). G. maculatus has rapid growth (1.1% day-1) and a high metabolism, with an average life of 2 years. They can be cultivated in captivity, spawn and incubate their eggs to obtain larvae; adults eat salmon starter pellets and grow in tanks. The ciliate protozoa Ichtyophthirius multifilis (ich) produces high mortality in larvae and adults in confinement; mortality can be controlled with salt bath. The problems to be solved by research for future commercial fish farming are: recognising and selecting suitable populations for cultivation; increasing the number of eggs spawned by females; develop suitable diets for larvae and broodstock; and controlling ectoparasitic diseases. The critical point is achieving mass production by improving the techniques of reproduction and larviculture. [ABSTRACT FROM AUTHOR]

Abstract: In this study we explore the use of fish otoliths (‘earbones’) as a tool for detecting exposure to heavy metals in sediments. Because otoliths are metabolically inert and incorporate chemical impurities during growth, they can potentially provide a more permanent record of pollutant exposure history in aquatic environments than soft tissues. To validate this technique we cultured embryos of a native Australian fish, the common Galaxias (Galaxias maculatus), in the laboratory on sediments spiked with copper in a concentration gradient. Our aims were to test whether exposure to copper contaminated sediments is recorded in the otoliths of embryos and determine over what range in concentrations we can detect differences in exposure. We found elevated copper levels in otoliths of embryos exposed to high copper concentrations in sediments, suggesting that otoliths can be used as a tool to track a history of exposure to elevated copper levels in the environment. [Copyright &y& Elsevier]

Este estudo foi conduzido para analisar ao nível histopatológico, lesões produzidas por Acanthostomoides apophalliformis no peixe nativo Galaxias maculatus, e relacioná-las com os resultados do mortalidade induzida por parasitas na população dessa espécie, no lago Moreno, Parque Nacional Nahuel Huapi, Argentina. A ausência de inflamação na maioria das lesões, o fígado sem alterações em uma distância curta do foco das lesões e a aparência viável dos parasitas, sugerem uma boa relação parasita-hospedeiro. Esta hipótese é reforçada pelos dados que mostram a ausência de mortalidade induzida por A. apophalliformis na população dos peixes.

Abstract: Upstream migration of fish through circular culverts is often prevented by velocities in the barrel being higher than that of the natural channel. In this investigation a computational fluid dynamic (CFD) model has been used to test the effects of various spoiler baffle geometries in culverts of varying size to reduce water velocity and increase water depth and thus increase the upstream passage of small fish species. Results indicated that standard baffles designed for specific fish species or groups could be successfully retrofitted to culverts of varying dimensions. Subsequent field tests have confirmed the effectiveness of the design. [Copyright &y& Elsevier]

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 <60 mm) swimming ability of a weakly swimming fish species, īnanga (Galaxias maculatus), up an artificial ramp to evaluate the effects of fish size, ramp slope (5°, 15°, 25°), water velocity and the potential need for resting opportunities (pools) for a successful ascent. Water velocity significantly increased and fish passage success significantly decreased with ramp angle, with only one fish passing the 25° ramp. On average, fish had to be 10 mm larger to ascend a 15° ramp angle than at 5°. Pools did not enhance passage success in this study. To facilitate fish passage at barriers for weakly swimming fish species like juvenile īnanga, ramps should provide a rough surface substrate and have an optimal angle of 5° for a 3-m ramp. [ABSTRACT FROM AUTHOR]