Journal of Applied Ichthyology最新文献

Four loaches, namely, Lepidocephalichthys guntea (Hamilton, 1822), Lepidocephalichthys annandalei (Chaudhuri, 1912), Lepidocephalichthys thermalis (Valenciennes, 1846), and Lepidocephalichthys berdmorei (Blyth, 1860) from the Cobitidae family, were collected from the Surma River, Bangladesh. Of the total 376 speciminia, 193 males (51.32%) and 183 females (48.67%) in number; were collected with the support of local fishermen using a variety of nets at 15-day intervals from November 2022 to April 2023. The length-weight relationship (LWR) parameters were analyzed using the equation W = aL^b. L. annandalei displayed a notable isometric growth pattern, with a condition factor (K) ranging from 0.725 to 0.734. In addition, L. thermalis exhibited isometric growth among males, while females showcased positive allometric growth with a condition factor (K) varying between 0.697 and 0.714. L. guntea exhibited a consistent positive allometric growth pattern across all aspects, with a condition factor (K) ranging from 0.729 to 0.738. In contrast, L. berdmorei demonstrated positive allometric growth, but males and females both exhibited a negative allometric growth pattern. The condition factor (K) for L. berdmorei ranged from 0.699 to 0.702. This suggests a complex growth pattern influenced by both length and weight in every experimental loach. The research underscores the importance of recognizing gender-specific variations in growth patterns within species.

In this study, a significant difference was demonstrated between the otolith increments of wild and reared Hedinichthys yarkandensis (day, 1877) (P < 0.05). By comparing the width of the first 40 daily increments of otoliths, it was found that the otolith width of the wild H. yarkandensis was significantly wider than that of the reared H. yarkandensis. The otolith daily increment width of wild H. yarkandensis tends to increase significantly with age and then decreases slowly, while the otolith daily increment width of reared H. yarkandensis grows more steadily. This may be related to the different growing conditions of the two groups. This study investigates the relationship between the early life history of H. yarkandensis and the daily otolith increment and provides a basis for identifying fish groups and fish life histories through differences in otolith microstructure.

Length-weight relationships (LWRs) were reported for ten fish species (Abbottina rivularis, Hemibarbus labeo, Hemibarbus maculatus, Onychostoma macrolepis, Opsariichthys bidens, Rhynchocypris lagowskii, Schizothorax prenanti, Sinibrama macrops, Zacco platypus, and Siniperca scherzeri). Fishes were collected from 62 sampling stations covering an area of ∼7000 km² in the Qinling Mountains, characterized by unique fauna and distribution pattern, using gillnets and ground cages during June to December 2022. The intercept a ranged from 0.013 for S. prenanti to 0.060 for H. labeo, and the slope b ranged from 2.537 for H. labeo to 3.079 for Z. platypus.

Aquaculture is one of the fastest growing sectors worldwide. Currently, 50% of global fish consumption is provided by aquaculture. In India, the major cultivated fishes are Labeo catla, Labeo rohita, Cirrhinus mrigala, Hypophthalmichthys molitrix, Ctenopharyngodon idella, and Cyprinus carpio. Among these, L. rohita is a widely consumed fish. We aimed to study the effect of one of the most widely used herbicides, glyphosate, on the embryonic development of L. rohita. The 96 h LC₅₀ of glyphosate for L. rohita embryos was found to be 20.89 mgL⁻¹. The embryos were exposed to 1/10^th, 1/5^th,^, and 1/3^rd concentrations of LC₅₀ for 96 h. The observed deformities included abdominal curvature, kink formation in the tail, yolk sac edema, pericardial edema, and improperly flattened swim bladder. Besides, we could observe a reduction in pigmentation at 96 h and a decrease in heart rate at 24, 48, 72, and 96 h. All these deformities led to the mortality of embryos. This study indicated that the herbicide (glyphosate) can adversely affect the natural population of the Indian major carp, L. rohita.

The river shad, hilsa (Tenualosa ilisha), is an anadromous fish that migrates from marine to freshwater for spawning. This transition/migration poses severe osmotic stress that hilsa needs to successfully minimize. The present study was conducted to evaluate the cellular (ultrastructure of gill and kidney), physiological (hemocyte counts, blood, and water osmolality), and biochemical (free amino acids, free fatty acids, blood glucose, and cortisol levels) parameters of hilsa collected from four different environmental salinity levels (0‰, 10‰, 20‰, and 30‰ salinity levels; using 10 fish samples from each salinity). Results indicate that increased amount of fatty/mucus cells in the gill and lower number of glomerular capsules in kidney were observed at low (0‰ and 10‰) salinities compared to high (20‰ and 30‰) salinities. Water and blood osmolality (total ionic content) showed declining trends with lowering salinities. Total number of blood cells was also found to vary significantly (P  <  0.05) among salinities. Salinity-specific blood cortisol and glucose levels of hilsa were observed as 0‰ > 10‰ > 30‰ > 20‰. Total essential and free amino acids of hilsa blood showed significantly declining trends (P  <  0.05) with salinity reductions. No significant differences were observed between 10‰, 20‰, and 30‰ salinities for different types of fatty acids, while hilsa collected from 0‰ showed significantly higher (P  <  0.05) levels of fatty acids compared to the remaining three salinities. Findings indicate that hilsa rapidly alters cellular, physiological, and biochemical traits for successful transition between different salinity habitats.

Length-weight relationships (LWRs) were described for four fish species inhabiting the tributaries of the Dongting Lake, China. Fish were sampled using stationary gillnets (50 m long × 2.0 m high and mesh size: 2, 6, 10, and 14 cm) and lobster pots (18 m long × 0.33 m high × 0.45 m width and mesh size: 1 cm) twice a year from May 2021 to July 2023. All fishes were measured in the field immediately after collection for total length (L) to the nearest 0.1 cm and body weight (W) to the nearest 0.1 g. There was a strong correlation between total length and weight in all four species (r² > 0.98). The values of parameter b in LWR ranged from 2.9709 to 3.4373. The LWR of Sinilabeo tungting, Acrossocheilus jishouensis, Onychostoma rara, and Onychostoma barbata provide new data for https://Fishbase.org and can be useful for establishing conservation measures of fish resources after fishing closure in the Dongting Lake basin, China.

The jellyfish Nemopilema nomurai occupies an important position in the Northwest Pacific ecosystem, and monitoring its biomass is necessary to ensure the protection of fishery resources and the safety of offshore industrial production. The acoustic method has been proposed for jellyfish flux estimation and bloom warning, in which the target strength (TS) of the jellyfish is a crucial parameter. However, varied swimming orientations of jellyfish aggregation result in different backscatter strengths. The acoustic echo characteristics in horizontal swimming orientations and multi-frequency broadband signals are yet to be revealed. This study aims to obtain the TS of jellyfish in various orientations and to comprehensively investigate the jellyfish acoustic echo features at various frequency broadband sounds. In an anechoic tank, we used wide-band echosounder and 70 kHz, 120 kHz, and 200 kHz split-beam transducers to measure the TS of jellyfish swimming omnidirectionally. The results show a difference of approximately 4 dB in the jellyfish’s normalized TS at 70 kHz (frequency range: 45 kHz to 95 kHz) and 200 kHz (frequency range: 160 kHz to 260 kHz) center frequency. The normalized TS of jellyfish varies by around 8 dB between horizontal and vertical swimming orientations. For jellyfish swimming horizontally, the TS and bell diameter have the following least squares fits: TS_D70kHz = 20 log D − 89.36(r² = 0.83); TS_D200kHz = 20 log D − 93.85(r² = 0.83). The swimming orientation has significant effects on TS estimation and model construction.

Fish larvae in riverine environments often disperse (e.g., drift) from areas of egg deposition at the time of hatch. Several components of drift can be important in terms of survival including timing, distribution in the water column, and body size. The longitudinal and cross-sectional aspects of larval lake sturgeon (Acipenser fulvescens) drift from upstream spawning sites have received considerable study. However, the vertical distribution of larval lake sturgeon in the water column has not been comprehensively evaluated with respect to river size, water depth, the size of larvae in drift over the entire drift period, and the effectiveness of traditional sampling gear (D-frame nets) designed to collect larvae along the river bottom. In 2013, we sampled larval lake sturgeon drifting from upstream spawning sites in the Menominee and Oconto Rivers (Wisconsin, USA) using traditional D-frame nets and custom fabricated sampling nets that vertically partitioned the water column. Drifting larval lake sturgeon were observed from the river bottom to the top of the water column in both systems. Vertical net section was a significant predictor of total larval catch with the highest catch occurring in nets towards the center of the water column but was dependent on net location within the rivers’ cross section and downstream distance from spawning locations. 42% of larvae captured across both rivers were outside of the sampling capability of the traditional D-frame nets (i.e., fish would have drifted over the top). Studies seeking to describe larval production for lake sturgeon, as well as other fish species that exhibit drift in larval dispersal, need to consider a balance between net design and sampling the vertical/cross sectional profiles of rivers. Size-based vertical drift may also have consequences for studies seeking to estimate genetic parameters (e.g., diversity and parentage).

Streptococcus agalactiae has a serious negative impact on tilapia aquaculture, and rapid detection of trace S. agalactiae in aquaculture waters and timely and effective sterilization measures could significantly reduce the probability of its outbreak in tilapia farming. Here, we established a fluorescence quantitative detection method of S. agalactiae in tilapia aquaculture waters based on the Streptococcus agalactiae CAMP factor (cfb) (GU217532.1) sequence of its CAMP factor. The results showed that the Ct value and logarithm of plasmid copy number presented a good linear relationship (y = −3.49x + 38.78; R² = 0.997) in the plasmid concentration range of 1.57 × 10²−1.57 × 10⁹ copies/μL, and the lowest concentration for sensitive detection of the established method was 1.57 × 10² copies/μL. The method exhibited high specificity for the detection of S. agalactiae and generated negative results when using the DNA of Aeromonas veronii, Staphylococcus epidermidis, Aeromonas hydrophila, and Edwardsiella tarda as templates for qPCR. Intra- and inter-group repeated experiments produced variation coefficients lower than 2%, indicating high stability and specificity of the method. The method was then used to detect S. agalactiae in two tilapia aquaculture waters. The results showed that the concentration of S. agalactiae was 12 copies/mL and 2 copies/mL in the two water samples, respectively. The method can directly detect trace S. agalactiae in the aquaculture water and facilitate the diagnosis, prevention, and control of S. agalactiae in tilapia aquaculture, which will greatly reduce the probability of large-scale outbreak of S. agalactiae and economic loss.

The current study examined the length-weight relationships (LWRs), length-length relationships (LLRs), and condition factor (K) of four threatened riverine catfish species (Pangasius pangasius, Rita rita, Sperata aor, and Bagarius bagarius) sampled from the Meghna River Estuary (MRE), Bangladesh. A total of 578 individuals were collected from contracted fishermen between January and October 2022. The length and weight of each species exhibited a highly positive correlation. The regression coefficient was 2.24 for P. pangasius, 2.90 for R. rita, 2.91 for S. aor, and 3.25 for B. bagarius. Furthermore, all species demonstrated a highly positive correlation between total length and standard length (r > 0.90). The calculated condition factor (K) values were 0.87 for P. pangasius, 1.18 for R. rita, 0.66 for S. aor, and 0.99 for B. bagarius indicating variations among the species. This study provides the first comprehensive documentation of all four major catfish species found in the MRE.