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The number of people with dementia is increasing annually worldwide. Alzheimer's disease (AD), which accounts for the highest percentage of dementia-causing diseases, remains difficult to cure, and prevention of its onset is important. We aimed to discover new AD-preventive ingredients and investigate the inhibitory effects of ten different species of seafood digests prepared by protease treatment on β-secretase 1 (BACE1) activity. Substantial inhibition of BACE1 activity was observed in five species of seafood, and protease-digested whitebait (WPD) showed the highest inhibitory effect among the ten marine samples. We further examined the potential of WPD as an AD preventive component using a familial AD strain (5xFAD) murine model. The intraperitoneal administration of WPD for 28 days substantially decreased the insoluble amyloid β1–42 content and the expression of glial fibrillary acidic protein, a marker of astrogliosis, in the cerebral cortex of the 5xFAD mice. These results strongly suggest that WPD is a novel functional food-derived ingredient with preventive effects against AD. [ABSTRACT FROM AUTHOR]

Īnanga (Galaxias maculatus) is a widespread freshwater fish, found around coastal New Zealand, Chatham Islands, southern Australia and southern South America, exhibiting both diadromous and land-locked life history patterns. We assessed population size structure, size at maturity, timing of reproduction, and post-reproductive survival in the Waikouaiti and Kakanui rivers, two regionally important G. maculatus populations in southern New Zealand. Size at maturity varied between rivers and sexes, with males generally maturing at smaller sizes than females. The timing of reproduction and recruitment was observed to vary across a relatively small spatial scale. Population length-frequencies indicated that both populations exhibited annual population dynamics, with most individuals spawning in their first year, then apparently dying soon afterwards (as indicated by a marked drop in post-spawning abundance). However, a few individuals with recently spent or resting gonads were present over the winter months, indicating some post-spawning survival. There was a lower frequency of exceptionally large (putatively 1+) individuals than reported for other populations around New Zealand and elsewhere, suggesting over-winter survival following spawning varies. Based on the variation in life history characters over small spatial scales, we suggest that management of regionally important G. maculatus populations should be based on catchment level information. [ABSTRACT FROM AUTHOR]

The number of people with dementia is increasing annually worldwide. Alzheimer’s disease (AD), which accounts for the highest percentage of dementia-causing diseases, remains difficult to cure, and prevention of its onset is important. We aimed to discover new AD-preventive ingredients and investigate the inhibitory effects of ten different species of seafood digests prepared by protease treatment on β-secretase 1 (BACE1) activity. Substantial inhibition of BACE1 activity was observed in five species of seafood, and protease-digested whitebait (WPD) showed the highest inhibitory effect among the ten marine samples. We further examined the potential of WPD as an AD preventive component using a familial AD strain (5xFAD) murine model. The intraperitoneal administration of WPD for 28 days substantially decreased the insoluble amyloid β1–42 content and the expression of glial fibrillary acidic protein, a marker of astrogliosis, in the cerebral cortex of the 5xFAD mice. These results strongly suggest that WPD is a novel functional food-derived ingredient with preventive effects against AD.

Abstract Using live feed in fish larviculture is more expensive and challenging than formulated feeds, incentivizing the early weaning of larvae. In New Zealand, the aquaculture of larval giant kōkopu, Galaxias argenteus, is being commercialized because of its high value and to supplement the wild fishery. As an emerging aquaculture species, inefficiencies remain in the production process, inhibiting financial viability. This study reports on the ability of these larvae to consume formulated larval diets across four ages (18, 21, 25, and 28 days after hatching, DAH) at each of the three daily feeding events (Morning, Midday, and Afternoon) during commercial production. At 18 DAH, little to no formulated feed was consumed at either of the three feeding events throughout the day. At 21 DAH, mean gut fullness increased and the number of fish with empty stomachs reduced by the end of the Morning and Afternoon feeding events. Both variables improved further for larvae at 25 and 28 DAH. Formulated feed consumption did not differ between larvae aged 25 and 28 DAH indicating that 3 days of feeding live feed could be removed from the feed regime. This change would save 13% on the cost of live feed; however, further research is required to determine the potential impacts on growth and survival.

Understanding how fecundity and egg size respond to density‐dependent and density‐independent processes is essential for fisheries assessments because it shows managers how exploited populations respond to fishery closures. Similarly, the extent to which density‐dependent and density‐independent processes influence fecundity and egg size in freshwater protected areas (FPAs) is important for determining their conservation potential and effectiveness as a fisheries enhancement strategy.The fecundity and egg size of 164 sexually mature Galaxias maculatus females collected from coastal waterways on the West Coast of New Zealand's South Island were determined from a combination of techniques. Specifically, the additive and interactive effects of density, temperature, and body size on fecundity and egg size were examined in 10 G. maculatus populations across a density gradient mediated by fishery closures and tested for an egg size/fecundity trade‐off.There was no evidence of an egg size/fecundity trade‐off, or of negative density‐dependent effects on fecundity or egg size within FPAs. Egg size, gonadosomatic index, and water temperature were correlated with latitude.Fecundity increased with body size, but egg size did not. This highlights the importance of available forage (terrestrial‐ and stream‐based prey) for G. maculatus to maintain individual growth to increase egg production and larval export derived from no‐take FPAs.For the current network of no‐take FPAs to be more effective as a management tool, efforts should focus on the remediation of in‐stream and requisite riparian spawning habitats, the degradation of which has caused population bottlenecks for this culturally and economically important amphidromous species. The major subsidy from FPAs for the G. maculatus metapopulation is sustainable egg production if migration to sea of the greatest possible number of larvae can be ensured. [ABSTRACT FROM AUTHOR]

Using live feed in fish larviculture is more expensive and challenging than formulated feeds, incentivizing the early weaning of larvae. In New Zealand, the aquaculture of larval giant kōkopu, Galaxias argenteus, is being commercialized because of its high value and to supplement the wild fishery. As an emerging aquaculture species, inefficiencies remain in the production process, inhibiting financial viability. This study reports on the ability of these larvae to consume formulated larval diets across four ages (18, 21, 25, and 28 days after hatching, DAH) at each of the three daily feeding events (Morning, Midday, and Afternoon) during commercial production. At 18 DAH, little to no formulated feed was consumed at either of the three feeding events throughout the day. At 21 DAH, mean gut fullness increased and the number of fish with empty stomachs reduced by the end of the Morning and Afternoon feeding events. Both variables improved further for larvae at 25 and 28 DAH. Formulated feed consumption did not differ between larvae aged 25 and 28 DAH indicating that 3 days of feeding live feed could be removed from the feed regime. This change would save 13% on the cost of live feed; however, further research is required to determine the potential impacts on growth and survival. [ABSTRACT FROM AUTHOR]

Optimizing the initial live feed is critical to success in fish larviculture in terms of both larval health and productivity. It is also vitally important due to the significant cost of provisioning live feeds. Glaxiids are high-value diadromous fish species found in parts of the Southern Hemisphere, which are wild-harvested and sold for human consumption in their larval form. In the emerging aquaculture of galaxiids, the live feed makes up a great proportion of the production cycle and is therefore a significant factor in achieving the economic viability of their production. In New Zealand, the endemic galaxiid species giant kōkopu (Galaxias argenteus) is considered suitable for aquaculture; however, little is known of their larval-feeding requirements. This study compares the growth performance and survival of giant kōkopu larvae over a four-week period when fed different proportions of first-molt Artemia nauplii (instar-I) and enriched, second-molt-onward Artemia (instar-II+) for different durations. The larvae in the treatment group which received the greatest proportion of Instar-I Artemia for the longest duration had the lowest mean wet weight and survival, leading to the production of the lowest total biomass of fish larvae when compared to the other feed treatments. The feed treatment that received only instar-II+ Artemia achieved an equally best total productivity. While the treatment fed a partial initial duration of mixed instar-I and instar-II+ Artemia achieved the same total productivity, the individual larvae were heavier and their body length was longer. The latter feed treatment appears to offer the best balance between the availability of feed particles in the optimum size range and a higher level of digestibility given that instar-I Artemia had higher levels of highly unsaturated fatty acids and polyunsaturated fatty acids. [ABSTRACT FROM AUTHOR]

The selection of artificial feed is critical to the success of larviculture of fin fish and requires knowledge of the varied species-specific dietary and nutritional requirements. With the emergence of commercial aquaculture of giant kōkopu, Galaxias argenteus, there is a need to understand the species-specific needs for artificial feeds in larviculture. Consequently, this study compares three commercial artificial dry feeds; Otohime, Artemac and O.range on the growth of recently weaned giant kōkopu. Larvae fed with Otohime outperformed both Artemac and O.range treatments by achieving the highest wet weight after 67 days, greater by at least 47% on average than both Artemac and O.range. These differences in larval performance are likely to be due to the higher protein:energy ratio and EPA content of Otohime. High DHA and ARA in the diets in absolute terms or in relation to EPA did not result in added benefit for growth performance. This study provides an important first step in identifying the nutritional needs of larval giant kōkopu which can assist in improving their commercial aquaculture production. [ABSTRACT FROM AUTHOR]

Galaxiid post-larvae constitute five of the six species in New Zealand's iconic whitebait fishery. Distinguishing the five species needs to occur at a younger age than is convenient for easy identification. Traditional identification uses subjective characteristics such as colouration of fresh specimens and fin position, but supervised classification methods could be more accurate and less labour-intensive. We compared the accuracy of six methods (multinomial logistic regression, linear discriminant analysis, quadratic discriminant analysis, naive Bayes, decision tree, and random forest) using total length, wet weight, body depth, and date, latitude and longitude of capture as predictive variables. Four of the galaxiid species were represented in 17,546 observations, but the other species was too rare to analyse. The best method, determined using 10-fold cross-validation classification accuracy (95.2% overall), was random forest across all species. The most difficult species to classify correctly (giant kōkopu) was the rarest species included in data with 66.1% accuracy at best. In addition to examining overall accuracy, we show how use of a cost function can improve classification performance with respect to rare species. This research could improve the efficiency of monitoring the composition of the whitebait fishery, and thus management of this occasionally overfished group of fish. [ABSTRACT FROM AUTHOR]

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]

As management tools, freshwater reserves are under‐represented in protected area networks for fisheries conservation and enhancement. This is surprising considering that freshwater ecosystems, and the biodiversity they support, are among the most threatened worldwide.We compared freshwater reserve types established to prevent overexploitation of migratory galaxiids (mostly īnanga Galaxias maculatus) from fishing and evaluated their performance as reproductive reservoirs. We studied 10 streams classified into three a priori types: (a) closed, (b) partially closed and (c) open streams.Closed streams had greater abundances, biomasses and egg production of G. maculatus despite having a greater proportion of smaller fish compared to partially closed and open streams. Community‐level analyses indicated differences in fish assemblages between closure types. Large, native, predatory fish (longfin eel Anguilla dieffenbachii, shortfin eel Anguilla australis and giant kōkopu Galaxias argenteus) were more common in closed streams.Overall, there were notable reserve effects related to closed streams. There was slight evidence that partially closed streams conferred some fisheries benefits compared to streams open to fishing. While the limited number of reserve streams warrants some caution in conclusions, partial closures may still be worthwhile as a management tool where complete closure to fishing is not feasible.Closures can be effective in increasing fish numbers, albeit at a cost of smaller sized individuals, most likely because of density‐dependent processes relating to food and habitat. Despite clear benefits in total egg production of populations in closed streams, it remains unclear how these benefits may translate across the full life history of the annual G. maculatus.Synthesis and applications. We demonstrate that freshwater reserves have many of the 'reserve effects' observed in more common marine reserves, but there are also important differences. Stream closure should be considered as one potential management tool that is unlikely to be effective unless stream habitats are returned to more pristine states. Our effort to evaluate the explicit effects of different reserve types across different spatial scales is the first we know of for migratory freshwater fishes, providing useful insights for adjusting the current reserve network and establishing new reserves. [ABSTRACT FROM AUTHOR]

Understanding of trophic structure and flow of energy within river systems is essential for informed management of these ecosystems and conservation of native fish fauna and fisheries resources. Food resources used by riverine fish depend on productivity within the main stem and adjacent floodplains, terrestrial inputs, and longitudinal and lateral hydrologic connectivity.Trophic ecology of puye (Galaxias maculatus Jenyns, 1842) in Chilean river systems remains poorly understood and studies that combine short‐term (stomach content) and long‐term (stable isotope analyses) analyses have not been performed to date. In this study, we assessed spatial variability in diet of puye based on both stomach content and analyses of stable isotopes of carbon and nitrogen in 10 river systems of southern Chile (including main stem, headwater lakes, and estuaries). Fish in the main stems of more northern rivers, with predictable flow regimes, were characterised by the most diverse diets, broad niche space, and high proportion of terrestrial prey items and zooplankton in diet. Fish collected in lakes were characterised by narrow isotopic niche space and diet dominated by zooplankton.Diet of G. maculatus in Chilean river systems is associated with characteristics of riverine habitats within each river system (lentic, lotic, and estuarine) and hydrologic connectivity among them. Indeed, connectivity with floodplain habitats and direct supply from headwater lakes appeared to be primary drivers of fish diet in systems where these are present. These supplies maintain fish populations of good condition and allow freshwater recruitment. Therefore, maintaining seasonal flow dynamics and connectivity is essential to preserve the natural function of these river systems and conserve native fish populations. [ABSTRACT FROM AUTHOR]

Partial migration, or variation in migratory propensity within populations, has been reported across a range of taxa, including fish. Otolith microchemistry has revealed a high degree of life history plasticity in many amphidromous species, with diadromous and non-diadromous recruitment occurring. We examined this plasticity and its effect on population structure, dispersal and recruitment in Galaxias brevipinnis, an amphidromous fish widespread around New Zealand. We used otolith microchemistry analyses to examine recruitment sources and fish surveys to assess abundance and size structure in two large river systems, each containing naturally formed lakes and no obvious physical barriers to migration. Otolith analyses revealed discrete recruitment sources for stream-resident populations, with marine recruitment supporting populations downstream from lakes and exclusively lake-derived recruitment for populations upstream of lakes. Although diadromous G. brevipinnis were abundant within 10 km of the sea, the abundance and relative proportion of younger fish declined as distance upstream increased, until a lake was reached, at which point abundance and the proportion of small individuals increased. The results provide a strong indication that supply is limiting recruitment for G. brevipinnis as distance from pelagic larval habitat increases, and that discrete recruitment sources and population structuring exist even within drainages. [ABSTRACT FROM AUTHOR]

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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]

Terrestrial egg development is advantageous for the amphidromous fish Galaxias maculatus because it increases access to oxygen, increases incubation temperatures, and reduces aquatic predation. The characteristics of New Zealand's riparian vegetation have changed considerably since colonial times from native vegetation to exotic grasses, with potential effects on the spawning dynamics of fish. Here, we used a series of experiments to test preferences of G. maculatus for egg laying in combinations of a native sedge and rush, and two exotic grasses. In laboratory experiments, G. maculatus spawned in all available habitats with no preference for native over exotic vegetation. Egg survival did not differ between the vegetative habitats, but in a treatment where only river stones were available, eggs were laid but they dehydrated and died. In a field experiment, there was no evidence for a preference for spawning in native vegetation, and no association between a “key” feature of vegetation—tiller density—and the number of eggs laid. The microclimate beneath dense vegetation in experimental treatments was more constant than ambient conditions with few extreme temperatures and low humidities. Given the readiness of G. maculatus to spawn in exotic vegetation, there appears to be no benefit in restoring native vegetation to enhance egg laying or survival of these taxa. [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]

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. [ABSTRACT FROM AUTHOR]

Attempts at artificial propagation and rearing of juvenile galaxiids ('whitebait') have been hindered by low fecundities and survival. To circumvent these issues, we subjected wild and captivity-acclimated giant kokopu (Galaxias argenteus), a hitherto unexplored galaxiid, to captive breeding protocols and evaluated the effects of salinity and temperature on egg fertilisation, incubation duration and hatching. Eggs sourced over several spawning seasons were subjected to different salinity (0, 9, 15, 20 and 30-35 PSU) and temperature (4, 10, 15 and 17°C) combinations. Average fertilisation rates were highest (95%) when gametes were activated in fresh water (0 PSU) and declined as salinity increased. Average hatch rates were highest (71-68%) when eggs were incubated in fresh water (0 PSU) at 10°C and decreased as salinity and temperature increased. Sequential stages of embryonic development were documented and several year classes of offspring were produced to form a captive breeding colony. We conclude that the giant kokopu has notable reproduction-related qualities that may be useful for future aquaculture exploitation of this species. [ABSTRACT FROM AUTHOR]

The upstream migrations of juvenile galaxiids, or ‘whitebait’, form the basis of an important New Zealand fishery. This study used mark and recapture experiments with juvenile galaxiids in the Mokau River to examine the effect of flow on migration and capture rates. Recapture rates of marked fish ranged between 2.7% and 26.9%, with the proportion of fish recaptured positively correlated with increasing river flow. Increasing river flow negatively affected the upstream migration rates of fish. Migration rates through the tidal zone could be rapid, with fish travelling upstream at speeds up to 1.4 km h−1within 24 h of release. However, not all marked fish exhibited rapid upstream movement. Fish captured on the second day following release had travelled at slower speeds up to 0.7 km h−1, suggesting that these fish did not initiate their migration on the tidal cycle subsequent to their liberation. A small proportion of fish were also found to travel up to 15 km downstream following release at the upper end of the tidal zone. Results indicated that some fish migrated on both diurnal and nocturnal tidal cycles. Nocturnal migrations by juvenile galaxiids could reduce capture rates and increase recruitment, especially in smaller rivers and streams where fish can pass the tidal fishing area on a single overnight tidal cycle. These results have management implications for river systems where juvenile galaxiids are exposed to multiple days fishing pressure, as reducing fishable zones could be one means of reducing pressure on unstable or declining galaxiid populations. [ABSTRACT FROM AUTHOR]

Riparian vegetation has been compromised worldwide by anthropogenic stressors, including urbanization and livestock grazing. In New Zealand, one consequence has been a reduction in the obligate riparian spawning habitat of Galaxias maculatus. This diadromous species forms the basis of an important fishery where juveniles are caught as they migrate into freshwater. Spawning success of G. maculatus is closely associated with the nature of available riparian habitat. We used a field experiment in a rural stream to test whether livestock grazing limits egg production and whether there is a lag in increased egg production after protection from grazing because of the recovery time of riparian vegetation. In a separate experiment in an urban stream we tested whether improved riparian management can increase egg production. Livestock exclusion produced an immediate and long-lasting increase in the height and density of riparian vegetation with reduced fluctuations in the ground-level physical environment, and positive changes to the density and survival of eggs. After 4 years, egg densities in exclosures were 400 times greater than in grazed controls and egg survival had doubled. Mowing riparian vegetation 2 months prior to spawning reduced egg densities by 75% and survival by 25%. Our experiments showed that altering grazing and mowing in spawning sites produced dense riparian vegetation, that this improved the microsite environment and resulted in greatly increased egg deposition and survival over several years. This clearly indicates that the single most effective step in rehabilitating G. maculatus spawning habitat is a simple reduction in grazing/mowing pressure. [ABSTRACT FROM AUTHOR]

Anthropogenic impacts from urbanization, deforestation, and agriculture have degraded the riparian margins of waterways worldwide. In New Zealand, such impacts have caused changes in native vegetation, enhanced invasion by exotic grasses, and altered river bank morphology. One consequence has been a great reduction in obligate spawning habitat of a diadromous fish, Galaxias maculatus. Juvenile G. maculatus comprise a culturally important fishery that has been considerably reduced over recent decades. Rehabilitation of riparian vegetation needed for spawning is relatively straightforward, but slow. We hypothesized that artificial spawning habitats could accelerate restoration of fish egg production by creating an environment that would support at least the same density and survival of eggs as non-impacted vegetation. We tested three artificial devices (straw bales, straw tubes, and moss tubes) in degraded and intact sites. Eggs were laid in all of these with numbers and survival usually exceeding that in riparian grasses. Where habitat was degraded, artificial spawning habitats yielded up to 10,000 eggs compared to none in nearby natural spawning habitat. The ground-level environment of artificial habitat was similar to that of intact vegetation in buffering ambient temperature and humidity fluctuations. Crucial properties of the artificial habitats were (1) shelter to provide shade and hold moisture; (2) accessibility to allow adult fish to deposit and fertilize eggs; and (3) robustness to provide reliable surfaces and protection for the eggs during their development. We show that artificial spawning habitats are a viable short-term alternative to rehabilitating spawning habitat while legacy effects abate and riparian vegetation recovers. [ABSTRACT FROM AUTHOR]

AIM: To establish a method of gonad biopsy for ovarian tissue collection in the declining giant kokopu Galaxias argenteus (Gmelin 1789) as an alternative to lethal sampling in order to understand the species' reproductive biology. METHODS: Six female giant kokopu weighing between 200 and 350 g were caught from the wild in early December of 2009 and transferred to a holding facility (Department of Zoology, University of Otago, Dunedin) where they were kept under a simulated natural photo-thermal regime for 10 months. Fish were repeatedly biopsied for ovarian tissue at near-monthly intervals (mean number of days between biopsies = 33) until ovulation. RESULTS AND CONCLUSIONS: Ovarian samples were successfully collected from giant kokopu by biopsy for use in downstream analyses. Among a total of 23 biopsy events, a single death occurred when a two-layered suturing approach was used, highlighting the value of this method for study of the reproductive biology of valuable fish. CLINICAL RELEVANCE: This biopsy method may have implications for veterinary research on fish physiology, pathology, conservation and development, when repeated tissue samples need to be collected over a prolonged period of time or for general surgical manipulations on fish when accessing the coelom. Furthermore, this approach allows the implementation of a more powerful experimental design, as repeated measures reduces the variability of estimates due to the removal of inherent stage differences among individuals. [ABSTRACT FROM AUTHOR]

Large river-floodplain systems are characterised by seasonal flow variability. High flows lead to hydrological connection between the main channel and inundated off-channel lakes, wetlands and floodplains, which provide essential habitats for riverine biota. We tested the following hypotheses: (i) that crustacean zooplankton are more abundant in connected lentic habitats such as riverine lakes and wetlands and have a different community composition compared with the main channel and (ii) that vegetation structure will moderate abundances of crustacean zooplankton in the lower reaches of the Waikato River, New Zealand., Zooplankton densities in main channel inflows and inundated floodplains showed clear seasonal changes, with cladoceran and copepod abundance peaks occurring in the majority of sites 2-3 weeks following the peak spring discharges (coinciding with the retreat of water from floodplains into the main channel)., Mean densities of zooplankton were highest in the inflows originating from riverine lakes (10-20 ind. L−1) where rotifers were dominant. We recorded significantly higher abundances of copepods in peat bog and swamp wetland inflows ( c. 5 ind. L−1) relative to the main river channel and riverine lake inflows (0.1-1 ind. L−1). Some lake inflows also had high numbers of cladocerans (5-10 ind. L−1)., Inundated floodplains displayed heterogeneity in zooplankton community composition in relation to their structural complexity. Flooded forest accommodated higher numbers of copepods ( c. 8 ind. L−1) and cladocerans ( c. 17 ind. L−1) than flooded grassland, where zooplankton assemblages resembled those in the main river channel and were characterised by dominance of rotifers and low overall zooplankton densities (1-2 ind. L−1)., Our results suggest that seasonal flow and flood pulses, which determine the degree of connectivity of the main channel with the floodplain and off-channel habitats, govern zooplankton densities and community structure in this large temperate river. Furthermore, the structural complexity of floodplain habitats may play an important role in enhancing riverine zooplankton diversity. We postulate that the post-flood peak of large-bodied cladocerans and copepods might have historically played an important role in the provision of food for juvenile fish such as migrating Galaxiidae. [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]

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]

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Applying uniform population models and management strategies to widespread species can be ineffective if populations exhibit variable life histories in response to local conditions. Galaxias maculatus, one of the world's most widely distributed fish species, occurs in a broad range of habitats and is highly adaptable, making it an ideal species for examining variation in life history traits across large geographic scales. Here, we examine the spawning biology and early life history of diadromous G. maculatus in coastal rivers in Victoria, Australia, and compare them to other populations throughout its range. We predicted that traits associated with these critical life stages, especially those that respond to environmental conditions that vary geographically, such as seasonal cues and temperature, are likely to vary across large spatial scales. We found that spawning occurs later in Victoria than in New Zealand (NZ) and South America, but migration back to rivers occurs at the same time in Victoria and NZ, but not South America. G. maculatus returning to rivers are also smaller and younger in Victoria than those in NZ. Other traits, like some attributes of spawning schools and spawning habitats, did not vary across large scales. Researchers and managers should be cautious when making broad assumptions about the biology of widely distributed species. [ABSTRACT FROM AUTHOR]

Galaxias maculatus is an osmeriform native fish 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 fisheries 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 fish culture. In order to optimize stocking densities for fish 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 and that adults tolerated dissolved oxygen levels as low as 1.3 mg L. The results showed that G. maculatus individuals with an average weight of 0.04 g consumed 0.048 mg O h, whereas individuals with an average weight of 1.4 g consumed 0.345 mg O h. Galaxias maculatus increased the OC rate by 31%, from 0.39 to 0.51 mg O h g, occurring 14 min after food intake. The carrying capacities for industrial cultures of G. maculatus, were estimated using an allometric equation (OC=0.2363 × W), a water flow rate of 1 m h and an input oxygen concentration of 10 mg L at 12 °C. The density culture of whitebait (4 g) can be allowed to reach 8-11 kg m; therefore, these stocking densities reduce the risk of hypoxia and mortality, ensuring the appropriate growth and feed conversion rates. [ABSTRACT FROM AUTHOR]

Regression models are built based on the literature and original data on the abundance, biomass, and production dynamics of zooplankton, taking into account the biology and feeding peculiarities of whitebait ( Osmerus eperlanus morpha spirinhus Pallas) and Baltic herring ( Clupea harengus membras L.) in the Curonian and Vistula lagoons. These models may be used to predict the commercial planktivorous fish yield. [ABSTRACT FROM AUTHOR]

The article discusses the utilization of mussel spat ropes for the passage of banded kokopu under laboratory trials in New Zealand. It notes the fitting of a 0.5 meter high simulated perched culvert on the two types polypropylene ropes such as the russet loop and the super xmas tree. It examines the four random replicate trials conducted to test the passage for the two rope types. Furthermore, results of the trials show a successful passage with the integration of ropes to perched culverts.

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. [ABSTRACT FROM AUTHOR]

Abstract: The experiences of nascent local institutions in regional resource management issues in New Zealand can help to inform the important analytical projects of considering the impacts of neoliberalism on environmental management as well as the meanings of governance as the new order in rural and natural resource management. This study considers how devolved governance shapes individual subject positions relative to the environment in a neoliberal context, deploying Agrawal''s optics of “environmentality” to analyze a case study of the political ecology of the whitebait fishery in Southland, New Zealand. This research demonstrates that the devolution of resource governance in New Zealand has cultivated empowered, ‘accidental environmentalists’ and related environmental subjectivities. The extent and quality of individual involvement in governance influences whitebaiters’ perceptions of environmental change and resource management priorities. At the same time, a strong ‘eco-populist’ conceptualization of resource management infuses the fishers’ environmental subjectivities and potentially constrains the depth and degree of fishers’ opposition to environmental degradation. [Copyright &y& Elsevier]

The common house mouse Mus musculus was observed feeding on the eggs of the indigenous fish, the inanga Galaxias maculatus. This mouse is an introduced species to New Zealand and could potentially be a major predator of the eggs of inanga and other galaxiids that utilise the terrestrial environment for spawning. Further investigation into mice densities and egg predation within known inanga spawning grounds is warranted to determine whether mice are indeed major predators of inanga eggs. If so, whitebait spawning ground management may need to incorporate rodent control measures. [ABSTRACT FROM AUTHOR]

A methodology has been developed and used to investigate a direct link between juvenile whitebait (Hyperlophus vittatus), the key prey species sampled from the stomachs of Little Penguins (Eudyptula minor), and the specific nursery area of that prey. A unique application of existing methodology initially involved the measurement of the stable isotopes of oxygen (δ18O:δ16O) and carbon (δ13C:δ12C) in sagittal otolith carbonate, using standard mass spectrometric techniques. The results indicated that the inshore distribution of juvenile (0+ year old) whitebait between Cockburn Sound and Koombana Bay, Western Australia consisted of a number of separate assemblages. Measured differences in stable oxygen isotope ratios were attributed to variations in freshwater input to the embayments that provided the whitebait habitats. In contrast, the measured stable carbon isotope ratios probably resulted from the different isotopic compositions of the food webs in the various habitats. Secondly, a comparison of the average value of carbon and oxygen isotope signatures of pooled otoliths from samples of whitebait from a number of different nearshore coastal sites (assemblages), with that of whitebait obtained from the stomachs of penguins at their main breeding site (Penguin Island) indicated that the values from the penguins resemble most closely those of the average otolith values obtained from whitebait from only one site (Becher Point). Assuming that the whitebait sampled were representative of the whitebait in the nearshore habitats and the diets of the penguins, then these results imply that at the time of sampling the penguins were feeding on whitebait from only one site. [Copyright &y& Elsevier]