Journal of fish biology最新文献

Active (i.e., intentional) fish sound production provides informative cues for numerous ecological functions, including larval recruitment or reproduction, and can facilitate monitoring and restoration. It is therefore important to have a holistic picture of actively soniferous tropical reef fish diversity, particularly in the face of growing threats such as noise pollution and habitat degradation. This study integrates fish biodiversity and sonifery datasets to assess the prevalence and ecological characteristics of actively soniferous tropical reef fishes. There are 258 known sound-producing species, which span 46 families, encompass a variety of life-history (e.g., lifespan) and distribution (e.g., depth) attributes, and include many vulnerable and commercially valuable species. Furthermore, up to 75% of tropical reef fish species are considered likely to produce active sounds. This synthesis should encourage a greater appreciation for active fish sound production in tropical reef environments and advance efforts to incorporate soundscape ecology into management and restoration strategies.

Ideally, protection of a threatened fish will lead to their recovery in abundance, distribution, and size structure within the population, to a point where they are no longer considered threatened. Monitoring abundance and size is crucial to evaluate this, although low numbers associated with being threatened can strongly constrain the methods used. To assess if population recovery is occurring for the black rockcod Epinephelus daemelii, a large subtropical grouper endemic to shallow reefs in the southwest Pacific, surveys were undertaken across northern New South Wales and Lord Howe Island using roving diver timed counts and diver stereo-video measurements to assess relative abundance and length. Surveys in 2023 were compared with initial baseline data captured in 2009-2011 using the same methods. Relative abundance of E. daemelii at long-term monitoring sites has remained relatively constant or declined since 2010 rather than increasing. Comparisons between 84 broadscale sites in 2009-2011 versus 2023 (117 vs. 69 observed E. daemelii) indicate a recent decline in abundance. Although protected from fishing and spearfishing for over 40 years, the relative abundance of E. daemelii does not appear to be increasing over the past 15 years since monitoring commenced. This is a concerning trend that does not indicate recovery, although an increase in the proportion of mature females in the population from 2010 to 2023 is positive. As E. daemelii is slow growing, long lived, late to mature and still susceptible to incidental capture mortality, more active management may be needed to help assist with the slow recovery of this threatened species.

Here, we provide the first in situ observations of foraging habitats of Chaetodon daedalma, which is endemic to the subtropical north-west Pacific. Overall, 62.4% of bites were from the substratum, 30.7% from scleractinian corals, 3.3% from crustose coralline algae, 2.1% from macroalgae, and 1.2% from hydroids. The range in the percentage of bites taken from scleractinian corals among individuals was 0%-76%, and no fish fed exclusively on coral. Our in situ feeding observations confirm that the species is a facultative corallivore.

Wild Atlantic salmon migrate to sea following completion of a developmental process known as parr-smolt transformation (PST), which establishes a seawater (SW) tolerant phenotype. Effective imitation of this aspect of anadromous life history is a crucial aspect of commercial salmon production, with current industry practice being marred by significant losses during transition from the freshwater (FW) to SW phase of production. The natural photoperiodic control of PST can be mimicked by exposing farmed juvenile fish to a reduced duration photoperiod for at least 6 weeks before increasing the photoperiod in the last 1-2 months before SW transfer. While it is known that variations in this general protocol affect subsequent SW performance, there is no uniformly accepted industry standard; moreover, reliable prediction of SW performance from fish attributes in the FW phase remains a major challenge. Here we describe an experiment in which we took gill biopsies 1 week prior to SW transfer from 3000 individually tagged fish raised on three different photoperiod regimes during the FW phase. Biopsies were subjected to RNA profiling by Illumina sequencing, while individual fish growth and survival was monitored over 300 days in a SW cage environment, run as a common garden experiment. Using a random forest machine learning algorithm, we developed gene expression-based predictive models for initial survival and stunted growth in SW. Stunted growth phenotypes could not be predicted based on gill transcriptomes, but survival the first 40 days in SW could be predicted with moderate accuracy. While several previously identified marker genes contribute to this model, a surprisingly low weighting is ascribed to sodium potassium ATPase subunit genes, contradicting advocacy for their use as SW readiness markers. However, genes with photoperiod-history sensitive regulation were highly enriched among the genes with highest importance in the prediction model. This work opens new avenues for understanding and exploiting developmental changes in gill physiology during smolt development.

Age and growth patterns of fish provide important information about the effects of environmental disturbances, which can be used as comparative tools in subsequent studies that attempt to assess freshwater quality. The main goal of our study was to provide information on relevant biological aspects of a native fish species used as a bioindicator in an extensive area of South America. In particular, we evaluated the age and growth patterns of Cnesterodon decemmaculatus (Poeciliidae) to establish reference species values and to compare them in different sites along an environmental quality gradient in a South American freshwater system. Water quality assessments indicated increasing environmental degradation downstream, reflecting anthropogenic impacts. The estimated ages of C. decemmaculatus along this quality gradient varied across sampling sites. The longest-lived individuals were those from the reference site, also presenting the highest average age value (almost 2 years). The best model to describe the growth in length of the individuals was the Logistic model. According to the parameters estimated from the growth curves, individuals from the most disturbed site showed slower growth although they reached greater maximum lengths than fish from the other sites. These results suggest that fish would tolerate the adverse conditions of the most altered sites, allocating their energy differentially. Our study provides valuable information on the age and growth patterns of C. decemmaculatus, a species endemic to the Neotropical region and a useful bioindicator in ecotoxicological studies.

Takifugu obscurus (pufferfish) is an important species in aquaculture and has become widely popular in China and Japan. However, the development of the pufferfish aquaculture industry has been significantly impacted by severe diseases. Fish cell lines, as a model for in vitro studies, have the advantages of low cost, easy culture, and low genetic variation rate. A novel cell line from the fin of T. obscurus was established in this study and named TOF. TOF grew optimally with L-15 medium at 28°C and showed a multipolar fibroblast-like morphology. Mitochondrial cytochrome oxidase subunit 1 (COI) gene identification and karyotype detection confirmed that TOF cells originated from T. obscurus and the chromosome number was 44 (2n = 44). Transfection experiments showed that TOF cells were able to transfect and express exogenous genes by lipofection and electroporation. The studies of salinity (NaCl) and alkalinity (NaHCO₃) on TOF proliferation showed that the highest multiplication rate of TOF was obtained at 6‰ NaCl mass and 4 g/L alkalinity, respectively. Furthermore, the expressions of several genes associated with the immune response were significantly upregulated after stimulating TOF cells with lipopolysaccharide (LPS) and poly (I:C), including irf7, il10, myd88, and nod1. Additionally, the Aeromonas hydrophila infection assay with TOF cells showed that TOF cells were sensitive to bacteria, and pufferfish could promote antimicrobial activity through NLR/NF-κB pathway to regulate the production of cytokines. This study suggested that TOF cell line could be an advantageous in vitro model for the investigation of fish immunology and virology, and could assist us to better comprehend the T. obscurus immune response to bacterial invasion.

Two new species of Mylochromis Regan 1920 are described from specimens collected on shallow rocky habitats on the northwestern coast of Lake Malawi. The generic designation is based on their prominent oblique-striped pattern and lack of any of the unique features of other Malawi cichlid genera with this pattern. Mylochromis rotundus sp. nov. is distinguished from most congeneric species by its relatively deep, rounded body and lack of enlarged pharyngeal teeth. It is further distinguished from Mylochromis semipalatus and Mylochromis melanonotus (if they are different species) by its relatively shorter snout. Mylochromis durophagus sp. nov. is distinguished from most congeneric species by its strongly molarized pharyngeal dentition. It differs from Mylochromis mola by having a shorter snout, a less acutely pointed head profile, a deeper body, and a more continuous oblique stripe. M. durophagus has a much less steep head profile than Mylochromis anaphyrmus or Mylochromis sphaerodon. It is suggested that M. rotundus was previously identified informally as Mylochromis sp. "mollis north," and M. durophagus as Mylochromis sp. "mollis chitande." Lectotypes are designated for comparator species M. sphaerodon and Mylochromis subocularis.

Bony fishes play a pivotal role in Ecuador's social, economic, and ecological aspects. However, the current state of scientific knowledge on this group remains poorly understood. This study aims to assess the scientific output related to Ecuadorian bony fishes, identifying both well-researched and understudied areas. A scientometric analysis was conducted using the Scopus database, evaluating 265 peer-reviewed publications on marine and freshwater bony fishes. The results revealed that 55.5% of studies focused on marine environments, 41.9% on freshwater ecosystems, and 2.6% on mixed environments. The earliest study was published more than 130 years ago, with a marked increase in research output since 2018. Geographic and regional disparities in research efforts were evident, with the Galapagos Islands hosting the highest number of studies at the provincial level and the coastal region leading in regional publications. Additionally, there has been a notable increase in the participation of women in research over time; however, it remains significantly below parity. English was the dominant language in these publications. On average, the delay between data collection and publication was 8.43 years, which may lead to outdated or ineffective management decisions. This underscores the importance of continually updating data to ensure the accuracy of conservation status assessments. Both marine and freshwater species that were endemic have been less studied compared to non-endemic species. Most of the studied species were categorized as "least concern," although a significant proportion of species classified as "data deficient" have started to be investigated by Ecuadorian researchers. The categories "endangered" and "near threatened" were the least studied, highlighting the urgent need for conservation initiatives targeting these vulnerable taxa. Biases in the number of studies among families, species, and geographic distribution indicate the need to expand research efforts to underrepresented taxa and regions. This analysis underscores the necessity of diversifying methodologies and broadening the research focus to more comprehensively address the challenges associated with the conservation and management of bony fishes in Ecuador.

In areas with high densities of salmon farming, spillover of the ectoparasitic salmon louse Lepeophtheirus salmonis poses a major threat to wild anadromous salmonids. By combining experimentally salmon louse infestation (mean ± standard deviation = 0.25 ± 0.25 lice g^-1 fish) with acoustic telemetry, we studied the behavior of wild first-time migrating sea trout Salmo trutta (n = 58, fork length = 138-204 mm) from late June to September in a marine area with naturally low infestation pressure. We observed that a similar proportion of sea trout from the control and exposed groups returned to fresh water both temporarily and permanently. However, sea trout from the control group spent nearly twice the amount of time in the fjord before first freshwater detection compared to exposed individuals (32 vs. 17 days), and statistical models indicated a dose-response of louse burden on the timing of freshwater return. This effect was combined with evidence of negative impacts of salmon louse burden on overall marine residency. Sea trout predominantly utilized waters within their natal fjord during the marine migration, with exposed fish spending significantly more time close to their home river than sea trout from the control group. In summary, the behavioral modifications caused by salmon lice could reduce individual marine growth, increase long-term mortality, and ultimately harm recruitment at the population level.