Journal of Fish Biology

Many actinopterygian fish groups, including fossil and extant polypteriforms and lepisosteiforms, fossil halecomorphs, and some basal teleosts, have stout bony scales covered by layers of ganoin-an enamel layer ornamented with minute tubercles. Ganoid scales preserve well as disarticulated remains and notably constitute most of the fossil record for polypteriform in both South America and Africa. Based on two variables (tubercle size and distance between tubercles), some authors reported that the ganoin tubercle ornamentation in these scales is constant within a species and differs between species and allows distinguishing species or at least groups of species...

The Yarlung Zangbo River is a river with abundant hydropower resources but fragile biodiversity in China. As an important benchmark for both research and ecological management, there is still a lack of knowledge about the swimming ability of fishes in the Yarlung Zangbo River. The induced flow velocity (Uind ), critical swimming speed (Ucrit ), and burst swimming speed (Uburst ) of five Schizothoracinae species were tested in this study. Relative swimming ability related to body length and body shape was calculated...

In a recent study based on the generalized mixed Yule coalescent method for delimiting species, a threshold of 2% genetic distance using cytochrome c oxidase subunit I sequences was used to delimit the species of Microglanis. That action resulted in assembling several populations of Microglanis from Atlantic coastal rivers between Rio Grande do Sul and São Paulo states as a single species, Microglanis cottoides, including Microglanis cibelae as a junior synonym. We reexamined these populations and found three species diagnosed by their morphology and that constitute separate mtDNA lineages, including a new species...

Intending to compare in vitro cell growth in different conditions, we established cell cultures using fin biopsies of two freshwater fishes, Astyanax bimaculatus and Geophagus proximus. Three different culture media (Leibovitz-L-15, Dulbecco's Modified Eagle Medium [DMEM], and 199) were employed, with or without the addition of AmnioMax, maintaining a standard temperature of 29°C. Based on the results obtained, we standardized a cell growth protocol in which medium 199 was less efficient for both species...

The current study investigated the structure and function of the olfactory system of the Lusitanian toadfish, Halobatrachus didactylus, using histology and electrophysiology (electro-olfactogram [EOG]), respectively. The olfactory system consists of a digitated anterior peduncle, of unknown function, containing the inhalant nostril. This then leads to a U-shaped olfactory chamber with the olfactory epithelium-identified by Gαolf -immunoreactivity-on the ventral surface. A large lacrimal sac is connected to this tube and is likely involved in generating water movement through the olfactory chamber (this species is largely sedentary)...

Rock hind (Epinephelus adscensionis) and spotted moray (Gymnothorax moringa) are ubiquitous mesopredators that co-occur in the nearshore waters of Ascension Island in the South Atlantic Ocean, where they have significant cultural and subsistence value, but management of their non-commercial take is limited. This isolated volcanic system is home to high biomass and low species diversity, which poses two key questions: How can two mesopredators that perform similar ecological roles coexist? And if these two species are so ecologically similar, can they be managed using the same approach? Here, we combined acoustic telemetry, stomach content analysis, and stable isotope analysis to (i) explore space use and diet choices within and between these two species and (ii) to assess appropriate species-specific management options...

The availability of resources varies across a species distributional range, and a low-productivity area can make a species more vulnerable. We investigated the invertebrate composition and prey choice of juvenile Atlantic salmon (Salmo salar L.) in low-productivity rivers in northeast Iceland, which is one of the species' most northerly distributions. By sampling benthic and drift invertebrate populations, we found that prey availability was similar within and between rivers. Gut content samples showed that the main prey choice for juvenile S...

The current epoch in fisheries science has been driven by continual advances in laboratory techniques and  increasingly sophisticated approaches to analysing datasets. We now have the scientific knowledge and tools to proactively identify obstacles to the sustainable management of marine resources. However, in addition to technological advances, there are predicted global environmental changes, each with inherent implications for fisheries. The 2023 symposium of the Fisheries Society of the British Isles called for "open and constructive knowledge exchange between scientists, stakeholders, managers and policymakers" (https://fsbi...

The blue shark is a highly migratory species with a worldwide distribution, making it susceptible to multiple fishing fleets across the globe. In southern Brazil, it is an important target, comprising up to 40% of the total biomass landed by the commercial surface longline fleet. This study aims to contribute to a better understanding of how the species uses the region and to update its life-history information available for future assessments. Over five consecutive years (2018-2022) of landings and onboard monitoring, we gathered size data and vertebral samples to describe the species size composition in the region, as well as its seasonal and interannual variability and to update estimated life-history parameters...

Many organisms rely on migrations between habitats to maximize lifetime fitness, but these migrations can be risky due to a suite of factors. In anadromous salmonids, the smolt migration from fresh water to sea is a critical life stage, during which smolts can experience high mortality from multiple sources. This study investigated the migratory behavior and survival of Atlantic salmon (Salmo salar) and anadromous brown trout (Salmo trutta) smolts during their seaward migration using acoustic telemetry between March and May 2021...

The blue shark Prionace glauca plays a critical role as a predator in marine ecosystems but is threatened by by-catch. To obtain more precise biological data, a Bayesian approach was used, and 536 vertebrae samples collected during 1 year at the landing stage called "Playita Mía" Manta, Ecuador, were analysed. The objective was to estimate the age and growth parameters of the species. The size of the specimens varied between 116 and 310 cm in total length (TL). Using a Bayesian approach based on the Markov Chain Monte Carlo (MCMC) method, growth parameters were evaluated...

Remoras are a highly specialised group of fishes known to associate with a range of marine megafauna, including elasmobranchs, cetaceans and marine reptiles. Remoras appear to benefit from these interspecific interactions through consumption of host dermal parasites or reduced cost of transport. Shark-remora associations are widely documented, yet our understanding of the costs and benefits involved in these interactions is poor. Studies frequently make claims about mutualistic, commensalistic or parasitic relationships without providing the necessary quantitative information necessary to make these claims...

Animals routinely encounter environmental (e.g., high temperatures and hypoxia) as well as physiological perturbations (e.g., exercise and digestion) that may threaten homeostasis. However, comparing the relative threat or "disruptiveness" imposed by different stressors is difficult, as stressors vary in their mechanisms, effects, and timescales. We exploited the fact that several acute stressors can induce the loss of equilibrium (LOE) in fish to (i) compare the metabolic recovery profiles of three environmentally relevant stressors and (ii) test the concept that LOE could be used as a physiological calibration for the intensity of different stressors...

Understanding recruitment, the process by which individuals are added to a population or to a fishery, is critical for understanding population dynamics and facilitating sustainable fisheries management. Important variation in recruitment dynamics is observed among populations, wherein some populations exhibit asymptotic productivity and others exhibit overcompensation (i.e., compensatory density-dependence in recruitment). Our ability to understand this interpopulation variability in recruitment patterns is limited by a poor understanding of the underlying mechanisms, such as the complex interactions between density dependence, recruitment, and environment...

The pervasive utilization of plastics and their integration into ecosystems has resulted in significant environmental issues, particularly the pollution of microplastics (MPs). In aquaculture, high-fat feed (HFD) is frequently employed to enhance the energy intake and economic fish production. This study utilized zebrafish as a model organism to investigate the impact of concurrent exposure to HFD and MPs on fish intestinal pathology damage and intestinal microbiome. The experimental design involved the division of zebrafish into two groups: one receiving a normal diet (ND) and the other receiving HFD...

Growth is one of the most direct and common ways fish respond to climate change, as fish growth is intimately linked to the temperature of the environment. Observational studies on the effect of shifts in temperature on fish growth are scarce for freshwater fish, and particularly lacking for lake populations. Here, changes in growth rate of bream (Abramis brama), perch (Perca fluviatilis), pikeperch (Sander lucioperca), and roach (Rutilus rutilus) over three decades were studied and compared with changes in temperature in the two largest lakes of western Europe: Lake IJsselmeer and Lake Markermeer in the Netherlands...

The present study delved into the world of hidden diversity by examining specimens identified as Leporinus piau from the river basins of the northern Brazilian states of Maranhão and Piauí. Using genetic analyses that combined data from three mitochondrial markers and one nuclear marker, the study identified two well-supported groups, reinforcing the findings of previous publications. The first group, found in samples from the Itapecuru, Mearim, Turiaçu, and Pericumã basins, in Maranhão, appears to represent a relatively ancient diversification and the possibility of concealed cryptic diversity...

The challenge of managing aquatic connectivity in a changing climate is exacerbated in the presence of additional anthropogenic stressors, social factors, and economic drivers. Here we discuss these issues in the context of structural and functional connectivity for aquatic biodiversity, specifically fish, in both the freshwater and marine realms. We posit that adaptive management strategies that consider shifting baselines and the socio-ecological implications of climate change will be required to achieve management objectives...

Otolith shape is often used as a tool in fish stock identification. The goal of this study was to experimentally assess the influence of changing temperature and ontogenic evolution on the shape component of the European seabass (Dicentrarchus labrax) otolith during early-life stages. A total of 1079 individuals were reared in a water temperature of 16°C up to 232 days post hatch (dph). During this experiment, several specimens were transferred into tanks with a water temperature of 21°C to obtain at the end of this study four different temperature treatments, each with varying ratios between the number of days at 16 and 21°C...

This study aimed to understand the reproductive biology and migrative behavior of the largehead hairtail Trichiurus lepturus in a tropical area, specifically off Pernambuco coast, northeastern Brazil. Commercial catches from fish corrals provided samples for analysis, including measurements, weight recording, and examination of gonads to determine its maturation stage. Reproductive analyses were performed, such as sex ratio, gonado-somatic index, and sizes at first maturity. There was a slightly higher proportion of females among the 141 largehead hairtail specimens analysed...