Large sharks generally occupy the highest trophic levels and are important links in the structuring of trophic networks. However, the decline of these predators has been observed worldwide, with population reduction rates reaching over 90% for some species. Through these declines, it is believed that the effect of the loss of predators could result in the disturbances in ecosystems. Based on this,

Cleaning symbiosis is one of the most iconic relationships between fishes. The cleaner picks parasites and diseased tissue from the body of so-called clients. Both parties benefit from this association: the cleaner obtains food and the client has unwanted organisms and material removed. Knowledge about cleaning interactions derives mostly from tropical and temperate reefs, although this relationship

Hatcheries and breeding programs use wild-caught fish reared on artificial diets. Understanding how fish adjust to a new feeding environment in this context might contribute to improving survival and growth outcomes under artificial conditions. In this study, we examined the growth and survival of wild white-spotted charr (Salvelinus leucomaenis pluvius) on a diet of commercial pellets in an artificial

Determining how growth rates and body size vary spatially and among reef fish species is important to understanding functional traits and demographic trade-offs. Variability in reef fish growth trajectories may be influenced by intrinsic (e.g., biological, phylogenetic) and extrinsic factors (e.g., environmental), as well as their interaction via ecological processes. To assess interspecific variation

Coral reef fishes perform a range of vital ecosystem functions, and can serve as indicators of ecological stress and resilience. However, many species are not observed when using Underwater Visual Census (UVC) during biomonitoring, and therefore overall biodiversity is often underestimated. Environmental DNA (eDNA) is proposed as an advanced and non-invasive next-generation biomonitoring method for

Hatchery-raised, age-0 Florida bass Micropterus floridanus are commonly used for fish enhancement efforts to support popular recreational fisheries and are ecologically important as both a food source and consumer. Despite their importance and frequent use of submerged aquatic vegetation (SAV) habitats, critical information is lacking on the specific characteristics of SAV that influence habitat occupancy

Otolith microstructural features and morphological development of larval and juvenile fish are important for studying the early life history of fish. In this study, the analysis of otolith features was performed on Squalidus argentatus laboratory-reared larvae and juveniles (0 to 40 days post-hatching or dph) collected as eggs in the Laibin section of the Pearl River (South China) from April to August

Batoid fishes are among the most endangered marine vertebrates, yet conservation efforts have been confounded by incomplete taxonomy. Evidence suggest that the critically endangered ‘common skate’ actually represents two species: the flapper skate (Dipturus intermedius) and the blue skate (Dipturus batis). However, knowledge of the geographic range of these two nominal species is limited. Here, DNA

Outmigrating, juvenile Chinook salmon Oncorhynchus tshawytscha, with access to floodplains (e.g., Yolo Bypass California, USA), grow faster than those restricted to the main channel of the Sacramento River. How these young salmon might use rooted, vegetative structure (e.g., to decrease energy expenditures) while holding positions in flowing water on floodplains and flooded riparian zones is unknown

Many juvenile fishes have specific habitat requirements, and while some habitats may be more important than others for growth and survival, habitat-specific growth and survival information is missing for the sensitive juvenile life stage of many species. Given the potential impact of habitat productivity on growth and the importance of growth to survival, we evaluated the influence of specific estuarine

Age and growth of European eel (Anguilla anguilla) from a coastal lagoon in southwestern Europe were investigated using a sample of 871 eels. Fish were caught with fyke nets in two fishing seasons, 2011/12 and 2015/16. Age was determined by reading sagittal otoliths and age estimates were validated through semi-direct methods. The yellow and silver eels ranged in length from 174 to 904 mm corresponding

Habitat selection in drift feeding fishes, the majority of stream fishes in North America, is strongly affected by velocity, as well as other environmental and intrinsic characteristics of an individual drift feeder (e.g., size and dominance status). Our study subject, the Brook Charr (Salvelinus fontinalis Mitchill), is a widely distributed and economically important salmonid fish which exists in

This contribution applies the “mean temperature of the catch” (MTC) concept of Cheung et al. (Nature 497:365–368, 2013) to fish catch data for Lake Peipsi, Estonia/Russia, covering the years 1931 to 2019. The preferred temperature of each of the ten target fish species was obtained from the literature, and combined with the species-specific catch data to obtain MTC values for each year. The analysis

The sharp-nosed sand goby Favonigobius gymnauchen is one of the most dominant fish species around tidal flats and sandy beaches in Japan and plays an important role in the food web. To clarify the habitat utilization and secondary production of F. gymnauchen in these waters, we investigated the density, size compositions, feeding, and prey availability in sandy beaches, a muddy sand estuary, and a

Shifts in temperature as a result of climate change play an important role in the long-term dynamics of resource use and resulting species interactions. Functional responses can give ecologically relevant insights of context-specific density-dependent resource use with low intensity animal use. This is especially useful when working with vulnerable species. The Rondegat River in South Africa’s Cape

Here, I report an unexpected interaction between the introduced fish species, Poecilia (Mollienesia) latipinna and humans in Lake Vouliagmeni, Greece. In this lake, I observed the normally skittish P. latipinna approach and graze on the exposed skin of bathing humans, presumably removing dead skin cells in what amounts to an exfoliating process. The natural occurrence of this phenomenon in Lake Vouliagmeni

The tripletail Lobotes surinamensis inhabits tropical and subtropical oceans, including the South Atlantic, where information about its reproductive biology is scarce. We combined physiological and morphological tools to study the reproductive cycle of L. surinamensis in the western South Atlantic. Adult females and males were sampled in Paraty Bay (Rio de Janeiro, southeastern Brazil) for 2 years

We studied predatory fish species in relation to the biodiversity of fish assemblages and environmental variables at 511 sites in small and mid-sized rivers at the eastern edge of the European continent. The studied region has a high geographical and environmental heterogeneity. The impact of environmental factors on species occurrence was analyzed with generalized linear models. The main influential

Lake trout stocks in the Great Lakes basin show variability in the relationship between a thiamine-dependent early mortality syndrome (EMS) and egg thiamine (B1) concentration but the reasons are unclear. EMS has been linked to a diet of alewives and their high thiaminase activity. We examined the relationship among four alewife-dependent B1-deficient lake trout stocks, and determined B1 utilization

In fishes, differences in early rearing environment can have a significant impact on phenotypic development. In the present study, we examined the effect of differences in egg incubation (adhered to substrate or non-adhered and tumbled) and water temperature during early rearing on the development of escape response and volitional swimming performance in lake sturgeon, Acipenser fulvescens, throughout

Cortisol is recognized as a physiological indicator of stress in fish. However, this hormone is typically measured in plasma samples. In this study, cortisol content was evaluated for the first time in the scales of tropical tuna. The sample included 20 skipjack tuna (Katsuwonus pelamis) and 25 yellowfin tuna (Thunnus albacares) collected in the Atlantic (the Gulf of Guinea off the Ivory Coast) and

In recent decades, the Eurasian beaver (Castor fiber) has once again become the keystone species in small river ecosystems in Russia. In many places, beaver activity has resulted in a significant change in lotic habitats, affecting the diversity, density, and biomass of aquatic organisms, including fish. While many studies have considered the ecosystem impacts of beavers, relatively few have focused

Lake Tana is one of East Africa’s largest freshwater bodies, yet many of its fishes are migratory and utilize in-flowing tributaries as critical spawning habitat. However, factors such as expanding water resources developments and sand mining along these rivers and streams may disrupt this ecosystem function. We monitored juvenile and adult fish abundance and water quality across five lake tributaries

A free-swimming thornback ray Raja clavata specimen demonstrating significant morphological abnormality is reported, captured by beam trawl in the Irish Sea off north Wales, UK. The anterior sections of both pectoral fins were separated from the head section for a length of approximately 140 mm extending from the rostrum tip to a point posterior of the spiracles, along with abnormal morphology of the

A Correction to this paper has been published: https://doi.org/10.1007/s10641-021-01108-5

The racer goby (Babka gymnotrachelus), a Ponto-Caspian gobiid, has successfully established in several European rivers since the 1990s, and its range is expanding; however, information on its biology in invaded environments is still limited. Understanding the population dynamics and feeding ecology of this species may assist in predicting its potential impact on native ecosystems. The seasonal abundance

Growth in fishes is usually modelled by a function encapsulating a common growth mechanism across ages. However, several theoretical works suggest growth may comprise two distinct mechanistic phases arising from changes in reproductive investment, diet, or habitat. These models are termed two-state or biphasic, where acceleration in growth typically changes around some transition age. Such biphasic

Male guppies display an outstanding diversity of color patterns which is formed as a result of a complex interplay between sexual selection, predation, and other environmental factors. The heterogeneity of the environment affects the variability of ornamental traits in male guppies through genotype–environment interaction. Thyroid hormones (THs) are important regulators of the ontogeny of fish and

Impacts of dreissenid mussels (Dreissena spp.) on Great Lakes ecosystems are well documented, and a better understanding of mechanisms that cause variation in dreissenid abundance is needed. An outstanding question is how much dreissenid biomass is consumed by fish predation. A significant difficulty for investigating dreissenid consumption by fish is that dreissenids in stomachs are often a mix of

Mobile consumers often match their movements to short-term resource pulses. In the Arctic, seasonal ice breakup facilitates an ephemeral productivity pulse exploited by marine consumers. The migration of anadromous Arctic char (Salvelinus alpinus) to marine waters occurs around the beginning of ice breakup, but the precise timing of movement is equivocal and current evidence is conflicting. To investigate

Ariopsis felis (Hardhead Catfish) is an abundant yet understudied estuarine fish species in the US Atlantic and Gulf of Mexico. Very little is known about the species’ trophic role and place in coastal food webs. This study was designed to provide baseline information on A. felis stable isotope values and to examine for any ontogenetic changes. n = 126 A. felis were sampled in the summer of 2018 in

Princess parrotfish Scarus taeniopterus is one of the top three parrotfish species landed in the Caribbean, and the top Scarus species targeted in commercial fishing efforts; however, a paucity of information exists concerning basic life history information for Caribbean parrotfish species. Prior to this work, no comprehensive life history information existed in the literature for princess parrotfish

Morphometric and meristic data were used in this study to establish morphological variations within the largest genetically consistent groups of five wild populations of tilapia from Kyushu and Okinawa ecological regions of Japan. The genetic analysis based on mitochondrial DNA relatedness was used to determine the data range used for the morphological analyses. During the morphological analyses, the

A Correction to this paper has been published: https://doi.org/10.1007/s10641-021-01096-6

The seasonal occurrence and temporal sexual segregation of great white sharks Carcharodon carcharias have been widely documented in various temperate and sub-tropical waters across the globe. Yet, there is limited understanding of the relationship between the life stages and habitat use of C. carcharias, particularly in the Southern Cape. In this study, we investigated the population dynamics of C

This study outfitted wild-caught white seabass (Atractoscion nobilis) with electronic data storage tags (DSTs) to evaluate subsequent movements of adult fish captured along Baja California, Mexico (BC). Cefas G5 DSTs were surgically implanted into 89 wild-caught white seabass ranging in size from 66 to 152 cm TL between La Salina (32.11°N/116.90°W) and San Quintin (30.25°N/115.83°W), BC. Twenty-four

We combined a high-resolution acoustic telemetry array with presence/absence receivers to conduct a preliminary study of the seasonal movements, activity patterns, and habitat associations of the newly described Deacon Rockfish (Sebastes diaconus). Eleven mature female Deacon Rockfish were tagged and monitored during an 11-month period, at a nearshore rocky reef off Seal Rock, Oregon, USA, an area

Species conservation requires a clear understanding of habitat availability and subsequent use of those habitats. In cases where species declines have occurred and gone undetected by conservation managers, habitat alteration, fragmentation, and loss are often the largest contributors. River fragmentation often results in altered flow regimes, subsequently impacting the availability of riverine habitats

Striped Bass naturally inhabit a wide range of temperatures, yet little is known about the processes that control their acute and chronic temperature limits. The objective of this study was to determine the effect of temperature acclimation on acute thermal maxima and physiology of juvenile Striped Bass. Juvenile fish were acclimated to 15, 25 or 30 °C for 4 weeks, then split into two sampling groups:

Giant sea bass (Stereolepis gigas, Polyprionidae) are the largest reef-associated teleost in the northeastern Pacific, considered an important predator in Macrocystis kelp forest and rocky reef ecosystems. Because of the predictability of annual aggregations, giant sea bass (GSB) were fished throughout the twentieth century until they were nearly extirpated from southern California and Baja California

Sockeye salmon that spawn downstream of rearing lakes are an important example of the challenges faced by organisms with complex life histories requiring connectivity in aquatic habitat complexes. Specifically, newly emerged juvenile sockeye salmon must migrate upstream, against the flow of water, if they are to reach lake rearing habitat. Here, we examine the spatial and temporal dynamics of the water

The Potamotrygon from the Potamotrygonidae family is a freshwater stingray that is native to and distributed throughout South American watersheds. The degradation suffered by the environment in recent years, particularly in aquatic habitats, directly affects native fish species. Due to anthropic actions, some species of the genus Potamotrygon are threatened with extinction, encouraging a study on captive

Nurse sharks (Ginglymostoma cirratum, Ginglymostomatidae) are one of the most exhibited shark species in aquariums worldwide. However, in these locations, their reproductive success rate is frequently low. Considering that there is probably an olfactory mediation for nurse shark reproduction, and that environmental enrichment has a potentially positive effect on reproduction of captive animals, the

Much has been written about the abundance of fishes in estuaries, and particularly the value of the littoral zone and associated macrophyte habitats as fish nursery areas. What has not been researched or discussed in the same amount of detail is that estuaries are demanding physico-chemical environments for fishes, yet each year millions of 0 + juveniles are recruited into these supposedly stressful

Our study sought to analyze patterns and overlap in prey items consumed by elasmobranch species in southern Brazil through a complex network analysis. We hypothesized that species with the same habitat use would show greater trophic niche overlap and lower diet specialization than species with different habitat use. We conducted a literature survey of the species recorded in southern Brazil and analyzed

Eel movement patterns have been frequently studied to learn about their movements within the fresh- and brackish waters of the same river before their spawning migrations. Although otolith microchemistry analyses estimated that the eels used fresh-, brackish, and marine water habitats, inter-river movements of Japanese eels via the sea have not been observed. In previous studies silver eels appear

Many fish spawn in aggregations, but little is understood about the dynamics governing the success of spawning interactions. Here, we evaluate the influence that location of lek-like mating territories has on spawning interactions of Gomphosus varius. We used direct observations of spawning and egg predation events as well as local population counts to compare the rates of spawning, spawning interruptions

Many tropical fisheries are data-poor and lack population demographic information needed for effective management and conservation. In this study we used mark-recapture of bonefish, Albula vulpes, an important species in catch-and-release recreational fisheries, to estimate capture probabilities. Moreover, for the first time we generated key demographic parameters including apparent survival, new entries

Population declines and demographic changes of Chinook salmon (Oncorhynchus tshawytscha), have been documented throughout this species’ range, though information on natural and anthropogenic mechanisms related to these changes are not fully understood. To provide insights into marine behaviors and survival of Chinook salmon, 40 pop-up satellite archival tags (PSATs), that collected environmental data

The potential use of Sr/Ca and Ba/Ca ratios in fish otolith, as a complement to 87Sr/86Sr to study movements of Prochilodus lineatus, was evaluated in the La Plata Basin (South America). Water ratios were obtained from samples collected during the high and low water seasons at 42 sites across the La Plata Basin. Elemental and isotopic ratios in water were measured by MC-ICP-MS, ICP-MS and ion chromatography

Topmouth culter (Culter alburnus) is an economically important fish species distributed in rivers, lakes and reservoirs throughout China. This study focused on the genetic diversity and genetic germplasm resources of C. alburnus populations. We developed a set of 14 polymorphic multi-nucleotide repeat microsatellites using specific locus amplification fragment sequencing (SLAF-seq). Based on microsatellites

While it is common knowledge that Red Drum (Sciaenops ocellatus) inhabit oligohaline waters (salinity <5), lifetime reconstructions of salinity histories have been lacking, and this study provides unique insight into interannual and ontogenetic patterns of oligohaline occupancy by this economically valuable sportfish. Growth consequences of oligohaline exposure and the relationship of oligohaline residency

We evaluated how genotype (stock source, parental line, chromosomal sex) and temperature interact to influence gonad development and phenotypic sex of Oncorhynchus mykiss. Embryos were generated from single pair matings of natural-origin and first-generation hatchery-origin O. mykiss held at ambient or elevated (5 °C above ambient) water temperature. Exposure to elevated temperature lasted from fertilization

Decreasing river flows and increasing water temperatures during the summer have been associated with holding behavior by pre-spawning Pacific lamprey Entosphenus tridentatus in the mainstem Willamette River (Oregon, USA). However, it is unclear if microhabitat use (≤ 2 m) by these lamprey is associated with particular habitat structure(s) or thermal refuge. We implanted radio tags into lamprey (n = 425)

We compared body morphology of two freshwater sculpin taxa that inhabit distinct environmental conditions in the Chesapeake Bay watershed of eastern North America: Potomac sculpin (C. girardi, Robins; PS) and checkered sculpin (C. sp. cf. girardi; CS). Both taxa are endemic to the study area, but PS are more broadly distributed than CS which are limited to karst groundwater-dominated streams in the

Shorthead sculpin (Cottus confusus Bailey and Bond, 1963) in Birch Creek, Idaho, were infected with the trematode Euryhelmis cotti (Simon, 1972). Our objective was to determine if intensity of infection had an influence on growth, reproduction, and mortality of shorthead sculpin at two sites in Birch Creek. Prevalence of trematode infection was 100 % at the upstream site compared to 32 % prevalence

Environmental conditions influence ecological processes that shape stream community diversity and abundance. Deforestation has the potential to limit available particulate organic matter and raise stream temperatures. The degree to which tropical stream communities are impacted by these changes is likely to differ between systems, but empirical data from tropical regions are lacking. This lack of baseline

Millerichthys robustus is the only annual killifish distributed in America with phenotypic color variations, not yet described. Accordingly, we first describe the color pattern in both sexes to define its phenotypical variations. We then analyze the frequency of these phenotypes on a geographical scale, in four localities that represent opposite points of Millerichthys’s distribution in the Mexican

Invasions of non-native fishes are recognized as a serious threat to freshwater biodiversity across the globe. Being the China’s second-largest river, the Yellow River has experienced severe invasion pressure of non-native fishes during recent decades. However, much less is known about species composition and distribution of non-native fishes in this river basin. Here, we investigated and summarized

Many river systems have been artificially modified for various reasons worldwide. Although simplified riverbeds due to artificial modifications often alter the species compositions and interactions, methods for mitigating habitat degradation in such rivers are underdeveloped. In this study, we evaluated the effects of tree branches on the survival of juvenile masu salmon Oncorhynchus masou under predation