Molecular hydrogen (H2) has been reported to have important biological effects on bone tissue in several in vitro and in vivo models. Danio rerio (zebrafish) embryo is a good model to study osteogenesis because of its transparency, size and rapid development. In zebrafish embryo, hydrogen‐rich water (HRW) does not affect vitality or growth rate up to 15%. In addition, 7% HRW treatment enhances zebrafish

Identification of introduced species can be important to understanding ecological systems and meeting conservation and management goals, but the process can be surprisingly challenging. The Klamath smallscale sucker Catostomus rimiculus seems likely to be native to the Smith River because the drainage separates two basins believed to be within the fish's native range, the Rogue and Klamath rivers.

Haematological and serum biochemical parameters are a valuable tool in determining the wellbeing status of different fish species and response in close association to various biological and environmental factors, therefore the aim of the present study was to establish sex‐wise reference values of haemato‐biochemical parameters of S. labiatus. The haematological parameters such as haemoglobin (Hb) concentration

Anthropogenic factors that negatively impact reef fishes can include changes in life‐history patterns of fisheries‐targeted species. Understanding these impacts on growth and population age structure is essential in the management of exploited populations of fishes. This is the first study to directly compare age and growth for a major fisheries species between east and west populations of a transatlantic

A new species of Poptella is described from the Río Putumayo, Upper Río Amazon basin, Peru. The new species is distinguished from congeners by having a dense field of dark chromatophores homogeneously spread over the posterior half of the body, posterior humeral blotch extending to three to four horizontal scale rows below the lateral line, and a higher number of branched dorsal‐fin rays. The new species

In southern Brazil, we investigated shark and ray capture records in an integral protection marine protection area (MPA) that allows fishing in that area. We found 10 shark and nine ray species, of which 88.5% and 66.2%, respectively, are endangered. Female adults and neonates of both sexes are abundant in the area, with records of stranding of large specimens, postcapture abortions and ovigerous capsules

The tropical eastern Pacific (TEP) is a highly dynamic region and a model system to study how habitat discontinuities affect the distribution of shorefishes, particularly for species that display ontogenetic habitat shifts, including snappers (Lutjanidae). To evaluate the genetic structure of the Pacific red snapper (Lutjanus peru) and the yellow snapper (Lutjanus argentiventris) throughout their distribution

Sex change in teleost fishes is commonly regulated by social factors. In species that exhibit protogynous sex change, such as the orange‐spotted grouper Epinephelus coioides, when the dominant males are removed from the social group, the most dominant female initiates sex change. The aim of this study was to determine the regulatory mechanisms of socially controlled sex change in E. coioides. We investigated

Different studies suggest some social calls could be used in fish identification if their specificity is unambiguously assessed. Sounds of different populations of piranhas Serrasalmus maculatus Kner, 1858 were recorded to determine their homogeneity between rivers inside a single basin (Araguari and Grande River, upper Paraná River basin) and between separated basins (Amazon and Paraná basins). All

This study examines the impact of boldness on foraging competition of the highly invasive round goby Neogobius melanostomus Pallas 1815. Individual risk tolerance, or boldness, was measured as the time to resume movement after a simulated predation strike. Fish that resumed movement faster were categorized as “bold,” fish that took more time to resume movement were categorized as “shy” and those that

This analysis shows good intentions in the selection of valid and precise oxygen uptake (O2) measurements by retaining only slopes of declining dissolved oxygen level in a respirometer that have very high values of the coefficient of determination, r2, are not always successful at excluding nonlinear slopes. Much worse, by potentially removing linear slopes that have low r2 only because of a low signal‐to‐noise

Global warming is having a significant impact around the world, modifying environmental conditions in many areas, including in zones that have been thermally stable for thousands of years, such as Antarctica. Stenothermal sedentary intertidal fish species may suffer due to warming, notably if this causes water freshening from increased freshwater inputs. Acute decreases in salinity, from 33 down to

This study compared the repulsive effects of sound playbacks of intermittent 30, 150, 300, 600 and 900 Hz tones on two fish with different auditory capabilities: juvenile chum salmon (Oncorhynchus keta) and common carp (Cyprinus carpio). When 150 and 300 Hz tones were emitted from an underwater speaker, O. keta exhibited a moderate repulse reaction. Conversely, C. carpio exhibited a moderate repulse

Taste preferences in fishes are known mainly for carnivorous species while herbivorous consumers were rarely used in such studies. The main goal of the present study was to evaluate the taste preferences in the herbivorous African cichlid fish, Nile tilapia Oreochromis niloticus. In laboratory settings, the palatability of widely used taste substances (4 taste substances, that are considered to be

Argyrops spinifer and Rhabdosargus haffara are two sympatric seabream species making important contributions to fisheries landings in the western Arabian/Persian Gulf. We identify the strengths and weaknesses in the long‐term sustainability of A. spinifer and R. haffara stocks by integrating multiple sources of data, including fisheries catch and effort statistics, life history traits, scientific trawl

Central Mexico is characterized by a complex topography that is the result of historic and contemporary tectonic and climatic factors. These events have influenced the evolutionary history of numerous freshwater fishes in the region. Nonetheless, recent studies have shown that life‐history traits and ecological characteristics of species may influence dispersal capabilities and the degree of genetic

As we emerge from the festive season, it seems appropriate to focus the current ‘Between the Covers’ article on the paper by Alessandro Macario and colleagues (Macario et al. 2021) which focuses on inhibitory control in guppies. They describe inhibitory control as the ability to overcome prepotent responses, in other words the ability to suppress or override impulsive responses in such a way that this

When rehabilitating and reintroducing trout Salmo trutta in rivers, it is a goal that as many as possible survive, home and form self‐sustaining populations. Hatchery‐reared, anadromous Salmo trutta have significant lower ability to return to the area where they were raised if (a) transported in a closed tank to sea and released 5 km from the River Imsa, relative to those that were (b) transported

Environmental disasters affecting Brazilian rivers have been frequent recently, especially involving mining activities. Two recent dam‐rupture events suddenly released millions of cubic meters of iron tailings downstream into two major Brazilian watersheds. These events generated major losses to the environment and human life. Additionally, the biodiversity in both watershed was still incompletely

This study focused on the distribution of fish with high reproductive activity along a basin, using a 430 km stretch of the Cuiabá River in Brazil as a model. The main objective of this study was to identify those fish that migrate long distances for reproduction, among all the basin species. Thus, a set of working criteria are proposed to classify species according to their reproductive behaviour

Carotenoid pigmentation in Salvelinus alpinus has been connected to stress responsiveness in earlier studies. This has, however, only been tested with time‐consuming image analysis from photos. Here, we used quick visual categorization of carotenoid pigmentation to investigate the stress responsiveness of the extreme groups. The visually selected charr were then exposed to a net restraint stressor

This study finds significant differences in hepatic fatty acid composition between four groups of Atlantic salmon (Salmo salar) consisting of offspring from families selected for high and low capacities to express the delta 6 desaturase isomer b and fed diets with 10% or 75% fish oil. The results demonstrated that hepatic lipid metabolism was affected by experimental conditions (diet/family). The fatty

Availability of shelter is an important component of habitat selection for animals as it can influence survival (protection against harsh physical conditions and predation) and growth (energy acquisition and expenditure). Few studies address the effect of shelter on metabolic expenditures associated with non‐mechanical tasks (excluding station holding or movement). The main goal of this study was to

Red cusk‐eel (Genypterus chilensis) is a native species with potential for Chilean aquaculture diversification. However, no information exists on the effects of temperature on oxidative stress and eggs quality markers in post‐ovulatory eggs and ovary of this species. We determine that high and low temperature generate oxidative damage on post‐ovulatory eggs, with no effect on ovary. Temperature induces

A new species of the genus Cirrhimuraena (Anguilliformes: Ophichthidae), Cirrhimuraena indica sp. nov., is described based on eight specimens collected from the Paradip (Odisha) and Petuaghat harbours (West Bengal) along the Bay of Bengal. The species is distinct in having upper jaw fringed with 16–17 cirri before posterior nostril and 4–5 in between anterior and posterior nostrils on side; dorsal‐fin

Isotopic values of two Caribbean sharpnose shark Rhizoprionodon porosus litters (Poey, 1861) with two and three embryos and one litter of 11 smalltail shark Carcharhinus porosus embryos showed enriched 15N and 13C compared to their mothers. In R. porosus, embryonic isotope values were 3.06 ± 0.07‰ and 0.69 ± 0.15‰ greater than their mothers' for δ15N and δ13C, respectively, whereas in C. porosus, δ15N

Hybrid advantage, described as the superiority of hybrids in some traits over their parents and termed the “heterosis effect,” is widely documented in the case of reciprocal crosses of parental species (i.e., hybrids representing the F1 generation). In fish, high survival, fast growth and better health status have been widely documented in F1 hybrids. Nonetheless, the effects of interspecific hybridization

Chaetostoma chimu sp. nov. is described from 119 specimens collected in the Andean foothills of the Orinoco River in Colombia. The new species can be distinguished from congeners by a combination of characters, including shape of cheek odontodes, presence of a supraoccipital excrescence, sexual dimorphism characters and colour pattern. In addition, this species can be distinguished from the sympatric

Fishes show remarkably diverse aggressive behaviour. Aggression is expressed to secure resources; adjusting aggression levels according to context is key to avoid negative consequences for fitness and survival. However, despite its importance, the physiological basis of aggression in fishes is still poorly understood. Several reports suggest hormonal modulation of aggression, particularly by androgens

We report the effects of food deprivation on the early development of Pacific red snapper Lutjanus peru during the first days of development. The point of no return (PNR) was determined using the feeding incidence after a delay in first feeding. The gradual deterioration of the larvae during food deprivation was recorded using morphometric, histological, enzymatic and biochemical analysis. The time

A ventral midline surgical approach for fish celiotomy is commonly performed in veterinary clinical medicine and research, although the relevant ventral body wall anatomy of many fish species is not well documented. Histological evaluation of tissue samples from the ventral body wall of 12 fish species was performed to provide a reference for surgical approach and closure decisions. The width between

Angel sharks (Squatina spp.) are distributed in warm temperate to tropical waters around the world. Many species occur in shelf seas and exhibit seasonal inshore–offshore migrations, moving inshore to give birth. Consequently, there can be high spatial overlap of angel shark populations with fisheries and other human activities. Their dorso‐ventrally flattened body shape, large size (most species attain

Despite several studies on fish hormone therapy, finding new candidates may provide more reproductive efficiency in artificial propagation. Kisspeptins, being upstream of the hypothalamic–pituitary‐gonadal axis, appear to play a key role in the reproduction process. In the present study, the effect of different variants of kisspeptide, including goldfish (Carassius auratus) kiss1 kisspeptin (Kiss1)

Otolith morphology is a widely accepted tool for species identification in teleost fish, but whether this holds true for very small species remains to be explored. Here, the saccular otoliths of the cryptobenthic Mediterranean clingfish Gouania (Gobiesocidae) are described for the first time. The new data, although preliminary, indicate that otolith morphology and morphometry support the recognition

The Chilean jack mackerel (Trachurus murphyi) is a predominantly Southeast Pacific Ocean species. It is relatively difficult to determine its age, and multiple studies of its growth off South America have produced markedly different sets of von Bertalanffy parameters. T. murphyi was first identified from New Zealand waters in the mid‐1980s and has comprised part of the commercial landings of Trachurus

Stable‐isotope analysis (SIA) provides a valuable tool to address complex questions pertaining to elasmobranch ecology. Liver, a metabolically active, high turnover tissue (~166 days for 95% turnover), has the potential to reveal novel insights into recent feeding/movement behaviours of this diverse group. To date, limited work has used this tissue, but ecological application of SIA in liver requires

The management of bonefishes Albula spp. has been hindered by unresolved species distributions and a general lack of life‐history information. This study provides the first genetic species identifications of Albula spp. from the northern Indian Ocean. The roundjaw bonefish Albula glossodonta was documented in the Red Sea, and the smallscale bonefish A. oligolepis was identified in the Gulf of Aden

The estimation of growth rates in young herring larvae (Clupea harengus) in the field can be difficult because the primary increments in the otoliths may not be discernible or formed at a daily level. Likewise, the estimation of mortality rates of fish larvae in the field is very difficult to achieve, especially in a rigorous quantitative manner. In this study, the authors suggest the use of a stage‐based

An easy method to measure the uptake rate of the persistent dye alizarin red S (ARS) during marking of whitefish eggs was established and used to measure the ARS content in three different whitefish species during and at the end of the marking procedure. Those values show that only 6–10% of the ARS in the marking solution will be absorbed by the eggs (0.0061–0.0119 mg per egg). Additional analyses

Freshwater fish face a variety of spatiotemporal thermal challenges throughout their life. On a broad scale, temperature is an important driver of physiological, behavioural and ecological patterns, and ultimately affects populations and overall distribution. These broad patterns are partly underpinned by the small‐scale local effects of temperature on individuals within the population. Climate change

The Pehuenche spiny‐chest frog Alsodes pehuenche is an endemic species from the Andes of Argentina and Chile and is considered to be critically endangered. Its population has been declining over the past 10 years, principally as a consequence of the paving of a road that crosses the streams the frog inhabits. Until recently, exotic fish species had not been recorded in these streams. This study documents

Reef fish assemblages are exposed to a wide range of anthropogenic threats as well as chronic natural disturbances. In upwelling regions, for example, there is a seasonal influx of cool nutrient‐rich waters that may shape the structure and composition of reef fish assemblages. Given that climate change may disrupt the natural oceanographic processes by altering the frequency and strength of natural

Intraspecific variation in key traits such as tolerance of warming can have profound effects on ecological and evolutionary processes, notably responses to climate change. The empirical evidence for three primary elements of intraspecific variation in tolerance of warming in fishes is reviewed. The first is purely mechanistic that tolerance varies across life stages and as fishes become mature. The

Group swimming size influences metabolic energy consumption and swimming behaviour in fishes. Hydrodynamic flows and vortices of other fish are thought to be beneficial in terms of the energetic costs of swimming. Similarly, abiotic obstructions have been shown to have similar benefits with respect to metabolic consumption in swimming fish such as rainbow trout Oncorhynchus mykiss. The current study

The aquaculture of tilapia (Oreochromis sp.) is adversely affected by the sensitivity to cold stress. A large number of genes in tilapia were found to be regulated by cold stress, but their functions and mechanisms in cold tolerance remain largely unknown, partially due to the lack of a suitable in vitro model. An immortal neural cell line designated as tilapia brain neural (TBN) was established from

We explored patterns, rates and unexpected socio‐ecological consequences of tooth replacement in serrasalmids and characids of the Peruvian Amazon using microcomputed tomography. Of 24 specimens collected in February 2019, representing a mix of red‐bellied piranha Pygocentrus nattereri, redeye piranha Serrasalmus rhombeus, silver dollar fish Ctenobrycon hauxwellianus and mojara Astyanax abramis, six

Among highly migratory fish species, nursery areas occupied by juveniles often differ from adult habitats. To better understand the spatial dynamics of Canada's Northern cod stock, juveniles caught off the east coast of Newfoundland and Labrador were compared to adults from the same region as well as individuals from other areas in Atlantic Canada using double‐digest restriction site‐associated DNA

The Rasptail skate Rostroraja velezi is commercially exploited in artisanal elasmobranch fisheries along the west coast of Baja California Sur, Mexico, but information on its life history is limited. This study aimed to investigate the reproductive biology of R. velezi. A total of 105 specimens were caught from April 2008 to May 2012, including the largest reported specimen with 121 cm total length

The Neotropical catfish genus Kronichthys contains three species distributed along coastal rivers of southern and southeastern Brazil. Although phylogenetic hypotheses are available, the molecular and morphological diversity and species boundaries within the genus remain unexplored. In this study, the authors generated mitochondrial data for 90 specimens combined with morphometric and meristic data

The Peruvian sea represents one of the most productive ocean ecosystems and possesses one of the largest elasmobranch fisheries in the Pacific Ocean. Ecosystem‐based management of these fisheries will require information on the trophic ecology of elasmobranchs. This study aimed to understand the diet, trophic interactions and the role of nine commercial elasmobranch species in northern Peru through

Gobies are generally small fishes which play important roles in estuarine ecosystems, yet little attention has been paid to their life‐history traits in the western Pacific region. In the present study, the reproductive traits of the dwarf gobies Pandaka trimaculata and Pandaka lidwilli were explored by examining their populations in a subtropical estuary on Okinawa‐jima Island, Japan, over 15 months

Two specimens of Micromyzon akamai, an eyeless and miniaturized species previously known only from the deep channels of the eastern Amazon basin in Brazil, are reported from the Curaray River, a tributary of the Napo River in Ecuador. The new specimens are the first records of Micromyzon in the headwaters of the Amazon River and the first records of M. akamai outside Brazil. External morphological

Nitrogen stable isotopes ratios (δ15N) were determined for selected tissues (muscle, liver, blood and yolk) of pregnant females and their embryos of a placental viviparous species, the Pacific sharpnose shark (Rhizoprionodon longurio), and a yolk‐sac viviparous species, the speckled guitarfish (Pseudobatos glaucostigmus). The R. longurio embryo tissues were 15N enriched compared to the same tissues

Highly variable thermal environments, such as coral reef flats, are challenging for marine ectotherms and are thought to invoke the use of behavioural strategies to avoid extreme temperatures and seek out thermal environments close to their preferred temperatures. Common to coral reef flats, the epaulette shark (Hemiscyllium ocellatum) possesses physiological adaptations to hypoxic and hypercapnic

A 193 cm total length female bull shark Carcharhinus leucas was captured in Florida bearing intentionally attached materials which resembled a harness. Harness‐type live bait rigs are commonly used for small baitfish; some anglers use such devices with small sharks when targeting large sharks and bony fish. Biofouling on the apparatus and the extent of the injuries indicated the material had likely

Animal behaviour has been broadly studied for its social or functional aspects but less often for understanding the interactions between organisms and their ambient conditions. A pilot observational study was performed by means of underwater camera to investigate the correlation between environmental factors and the density of fish in the epipelagic habitat of a European temperate reservoir. Explored

Oxygen uptake, heart rate and contraction frequencies of slow oxidative (SO) and fast glycolytic (FG) muscle were measured simultaneously in gilthead seabream Sparus aurata submitted to stepwise increases in current speed in a swimming respirometer. Variation in oxygen uptake was closely related to variation in heart rate, over initial steps these rose in concert with an increase in contraction frequency

This study presents the diet composition of western Baltic cod Gadus morhua based on 3150 stomachs sampled year‐round between 2016 and 2017 using angling, gillnetting and bottom trawling, which enhanced the spatio‐temporal coverage of cod habitats. Cod diet composition in shallow areas (<20 m depth) was dominated by benthic invertebrate species, mainly the common shore crab Carcinus maneas. Compared

The reproductive strategy of the non‐native predator cichlid Cichla kelberi was determined to explain its success after more than 60 years of being introduced into an isolated reservoir in southeastern Brazil. This was one of the first‐known translocations of the genus Cichla out of its natural range. Macro‐ and microscopy characteristics of the gonadal development stages and the maturation phases