Journal of fish biology最新文献

Mormyridae, a species-rich family endemic to Africa, remains taxonomically understudied. This has been the case for the genus Pollimyrus Taverne, 1971, which hinders further understanding of the distribution, ecology, and conservation of its species. Therefore, an in-depth morphometric comparison of all currently valid species is carried out using most of the available type specimens. Species delineations were re-evaluated, and four species new to science described: Pollimyrus ibalazambai sp. nov. (the Luki River, the Democratic Republic of the Congo), Pollimyrus krameri sp. nov. (the Lugenda River, Mozambique), Pollimyrus vanneeri sp. nov. (the Kouilou-Niari River, the Republic of the Congo), and Pollimyrus weyli sp. nov. (the Buzi River, Mozambique). In this study, Pollimyrus guttatus is confirmed to belong to Pollimyrus, whereas Pollimyrus eburneensis and Cyphomyrus plagiostoma seem more similar to species allocated to other genera. No or only little morphological differences were found between the type series of several species, which could indicate the need for synonymization of these species (Pollimyrus cuandoensis with Pollimyrus marianne and Pollimyrus nigripinnis with Pollimyrus pulverulentus). As such 20 species are currently morphologically identifiable in the genus Pollimyrus. The present study highlights the critical need for further synthetic efforts and new collecting efforts across Africa for this and other Mormyridae genera.

The presence of cryptic species can hinder effective conservation planning and implementation, as has been the case for speciose groups of freshwater fishes that are difficult to differentiate due to conserved morphologies. The West Texas shiner Notropis megalops and the Texas shiner Notropis amabilis are a cryptic pair of leuciscids (minnows) that co-occur in spring-fed tributaries of the Rio Grande in Texas and Mexico. Both N. megalops and N. amabilis are listed as Species of Greatest Conservation Need by the Texas Parks and Wildlife Department. Notropis amabilis is widespread and listed as apparently secure by Texas Parks and Wildlife Department whereas N. megalops has a very limited distribution and has not been ranked by Texas Parks and Wildlife Department because of data deficiency. Morphological differences between these species have been described; however, proper identification in situ remains problematic. Furthermore, given their range of overlap there is potential for hybridization, and limited genetic data have been collected comparing the species. Therefore, reduced representation genomic and mitochondrial sequencing data were used to reassess the distinctness of the species, screen for hybridization, and characterize their relative frequencies throughout their range of overlap. Genomic analyses recovered two distinct genetic groups corresponding to the species (F'_CT = 0.89) with no evidence of admixture or introgression. The species were found to co-occur at three sampling locations, two in the Devils River and one in the Pecos, but not in equal frequencies. Overall, these results provide data and tools for further research on N. megalops needed for accurate conservation policies and management practices.

The gut microbiota plays a crucial role in various physiological functions of the host and can be modulated by numerous factors, including feeding habit or trophic level. In this study, the impact of host feeding habits on the gut microbiota of freshwater fish was explored. Ten fish species, classified into four feeding habit categories (herbivorous, omnivorous, planktivorous, and carnivorous) were sampled from West Lake, a renowned urban scenic lake, and their gut content microbiota was analysed using 16S ribosomal RNA gene sequencing. A total of 2531 operational taxonomic units, belonging to 34 bacterial phyla, were identified, with 33.4% shared across all feeding habits. Firmicutes and Proteobacteria were the predominant phyla. However, at the family level, Peptostreptococcaceae and Clostridiaceae_1 were the most dominant. Microbiota composition diversity was highest in herbivorous fish, followed by omnivores, carnivores, and planktivores. Statistically significant differences in microbiota diversity were found between different feeding categories, except for the omnivores, which did not differ from the carnivores or planktivores. The most abundant predicted metabolic pathways across all feeding habits were similar, with amino acid metabolism, carbohydrate metabolism, metabolism of cofactors and vitamins, and metabolism of other amino acids being dominant. However, comparing the relative abundance of gene functions between different feeding habits revealed notable variations across most comparisons. Co-occurrence network analysis for each feeding habit revealed that all networks were dominated by the strong positive correlation among pairs of bacterial genera abundances, while the basic properties varied, implying differences in gut microbiota interactions based on the feeding habit. In conclusion, these results confirmed that the feeding habit could affect the structure and composition of the gut content microbiota but also changed their functions and interactions.

Although the deep oceans represent Earth's largest habitat, the challenges of studying deep-sea organisms in situ have limited our understanding of adaptation, ecology, and behaviour in these important ecosystems. One fundamental trait of fishes that remains largely unexplored in the deep ocean is swimming, a vital process for movement, migration, and dispersal in marine habitats. Deep-sea conditions such as temperature, pressure, and food availability could each impact the speed and efficiency of swimming in fishes. To investigate swimming kinematics of fishes with increasing depth, we analysed in situ video of bony fishes across a 6000-m depth gradient. We compared open-source videos of fishes from National Oceanic and Atmospheric Administration (NOAA) Ocean Exploration with tank-based recordings of shallow-water relatives from Puget Sound, Washington, USA to understand how both habitat depth and phylogeny influence swimming in fishes. We analysed kinematics in four dominant demersal fish groups, the orders Anguilliformes, Gadiformes, Ophidiiformes, and Perciformes. Deep-sea fishes swam consistently slowly. Swimming kinematics varied across temperature, oxygen, body elongation, and depth. These results suggest that swimming kinematics do not change linearly with increasing habitat depth in fishes and that the impacts of deep-sea conditions such as low temperatures, high pressures, and low nutrient availability on swimming behaviour need to be considered independently of one another. These findings provide insight into the evolution of fish form and function in the deep ocean.

Field studies of cleaning mutualisms use a variety of methods to quantify behavioral dynamics. Studies in marine systems typically utilize data recorded by human observers on scuba or snorkel or via remote underwater video. The effects of these different methods on cleaner-client behaviors have not been rigorously assessed. We quantified cleaner-client interactions at 13 bluestreak cleaner wrasse (Labroides dimidiatus) cleaning stations in Moorea, French Polynesia using hand-held and remote videos. We found that cleaning, cheating, and client posing rates, cleaning duration, and client species richness were all greater in the remote than in the hand-held videos, suggesting that human presence disrupts cleaning interactions by inducing antipredator responses among clients. Some metrics, such as the ratio of cleaner chasing to cleaning behavior and the cleaners' benthic feeding rate, were higher for the hand-held than the remote videos, possibly due to limited access of cleaners to clients in the presence of humans. Other metrics, such as cleaner and client chasing rates, the ratio of cleaning to cheating behaviors, and the duration of cleaner chases, did not differ between video types. Finally, piscivorous clients were far more abundant in the remote than the hand-held videos, suggesting that piscivores are particularly sensitive to human presence, likely because they are targeted by fishers. Overall, our study suggests that human presence can bias studies of cleaning behavior and cleaner-client interactions, and that remote cameras should be used to conduct behavioral studies. These potential biases should be considered when interpreting existing behavioral data.

Novel introductions of largemouth bass, Micropterus salmoides, often cause negative impacts on endemic populations of prey fishes and interspecific competitors. Although many studies have investigated trophic interactions between M. salmoides and smallmouth bass, Micropterus dolomieu, few have included chain pickerel, Esox niger, as a competitor despite similarities in their habitat use. We used stable isotope analysis to investigate the trophic ecology of a recently introduced population of M. salmoides in the Wolastoq|Saint John River. Specifically, we measured carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes to describe isotopic niches and infer resource use of introduced M. salmoides, M. dolomieu, E. niger, and native yellow perch, Perca flavescens, at various life stages. Our results showed that isotopic niche overlap occurred between M. salmoides and other study species, indicative of resource competition. However, resource use plasticity, as demonstrated by a wide variety of resources (marine, terrestrial, littoral, and pelagic) used by all study species, could potentially reduce interspecific competition. Our findings indicate that competition is highest between adult M. salmoides and E. niger, but the presence of a seasonal marine resource can provide important contributions to diets and potentially reduce competition. Further research should focus on monitoring of long-term trends to identify the dynamics of all study species as M. salmoides populations become further established and dispersed.

Oreichthys warjaintia, new species, is described from the Pyrngang stream (Surma-Meghna basin), Meghalaya, northeast India. It can be distinguished from all known species within the genus Oreichthys in having the following combination of characters: complete lateral line with 25-27 pored scales, 13 branched pectoral-fin rays, 5-5½ branched anal-fin rays, 14 rows of papillae on suborbital, ½3/1/2½ scale rows in transverse line on body, presence of a black blotch on caudal-fin base, and in the coloration of dorsal, caudal, and anal fins. Oreichthys warjaintia is distinct from all known Oreichthys species for which mitochondrial cox1 sequence data are available by a raw genetic distance ranging from 8.3% to 11.1%.

New approaches to abundance surveying utilizing unoccupied aerial vehicles (UAVs) are proving to be effective tools in marine and terrestrial environments. We explored UAV efficacy for surveys in the Galapagos Marine Reserve (GMR), where relative abundance patterns of juvenile sharks and subsequent classifications of putative nursery areas based on environmental drivers are lacking. The UAV method allowed greater temporal and spatial coverage. We expanded classification of shark nursery habitat through monthly drone surveys and environmental data collection at 14 sites around San Cristobal Island (GMR) from November 2018 to July 2019. In the period of surveying, 56 flights identified 453 juvenile Carcharhinus limbatus (blacktip shark). Classification of nurseries followed three criteria, necessitating higher density, short-term residency, and annual site fidelity in target locations. We developed preliminary generalized linear models to elucidate potential environmental parameters influencing the perceived abundance and habitat preference of juveniles. Four sites were identified as either potential nurseries or nursery areas for the target species based on previous excursions. An averaged model was subsequently created from the models found to best explain deviance patterns (R² = 0.10-0.44) in perceived shark abundance and habitat preference. Relative variable importance (RVI) values further clarified the parameters most associated with higher juvenile presence. This approach provides a systematic method of abundance surveying while simultaneously beginning the process of defining when and where we expect to find higher abundance through environmental modelling of most influential parameters to perceived abundance in this environment.

This paper is part of the Special Issue ‘Celebrating recent innovations in the application of stable isotopes to fish biology’ but was published in error in the normal run of the journal, the paper can be found at this link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/jfb.14939.

Urban stream syndrome is the collective term used to describe the physical and ecological degradation of streams draining urban lands that poses substantial threats to freshwater ecosystems. Among various consequences of urban expansion, microplastic pollution and shifts in predator-prey dynamics are prominent alterations to natural habitat that could impact the cognitive and behavioral responses of aquatic species. To explore how symptoms of urban stream syndrome impact the cognitive and behavioral responses of fish, we conducted two experiments using a delayed detour test to measure risk-taking and inhibitory control in Gambusia affinis. In the first experiment, we hypothesized that G. affinis exposed to different concentrations of microplastics would show altered inhibitory control and risk-taking. In the second experiment, we hypothesized that exposure to predator chemical cues during the detour task would alter inhibitory control and risk-taking in G. affinis. We did not find significant differences in inhibitory control or risk-taking in G. affinis exposed to microplastics or predator cues. We then compared the effect size and confidence intervals (CI) of these results with published results that used the same detour test to study inhibitory control and risk-taking in G. affinis in response to different environmental conditions. Our investigations revealed that the CIs of the two studies presented here were larger than the CIs in the previously published studies. We consider potential changes to the experimental design that might have affected our ability to detect differences, such as the dimensions of the testing tanks. We also suggest extending the duration of the test to allow ample time for both exiting the starting chamber and solving the detour. We also propose considering the size and age of the species under study and adjusting the dimensions used in the detour paradigm design. Although our findings are specific to G. affinis, our results underscore the importance of considering aspects of the detour test design that are ecologically relevant to the study species when analysing cognitive and behavioral responses in fish. With our discussion, we contribute to the understanding of detour test methodologies and highlight potential ecological factors that could influence cognitive and behavioral outcomes.