Fisheries Science最新文献

Bombay duck Harpodon nehereus has undergone a dramatic shift from a by-catch fish species to the dominant species in the southeast coast of China. This shift has led to economic growth in the fishery and has had a significant impact on community structure, biodiversity, and resource competition in the ecosystem. Strong hypoxia tolerance may be one of the contributing factors for its population growth. This study compared the transcriptional regulation and alternative splicing in H. nehereus from the normoxic and hypoxic zone near the Yangtze Estuary. Compared with normoxia, the number of alternative splicing events increased in the gill and heart but decreased in the muscle after hypoxia, among which exon skipping was the most prevalent type in different tissues. Enrichment analysis showed that differentially expressed genes and genes with differentially alternative exons were mainly enriched in transmembrane transport and glycerophospholipid metabolic process in gill, cell cycle, and FoxO signaling pathway in heart, as well as cell cycle and reduced metabolic rate in muscle. Key candidate genes may be associated with gill remodeling, elevated heart rate, and muscle angiogenesis function. This study provides valuable genetic clues for evaluating molecular regulation strategies related to hypoxia tolerance in marine fishes.

The only diet that has been capable of rearing eel larvae to the glass eel stage in captivity is the shark egg (SE)-based diet (SE). This study investigated the potential of alternative dietary components, namely hen egg yolk (HEY), milk proteins, and fish protein hydrolysate (FPH), on the growth and survival of eel larvae. In the first experiment, a diet containing HEY and skimmed milk powder (HS) was compared to SE. There were no significant differences in growth and survival rate between the two diets except in the early part of the experiment period. In the second experiment, HS was modified by the addition of FPH and casein (FC), and larval performance was evaluated for three dietary regimens (SE, HS, and FC). The performance of larvae fed HS and FC was found to be comparable or superior to those fed SE. It was observed that larvae fed the alternative diets to SE were able to progress to glass eels. However, more skeletal abnormalities were observed in HS in experiment 1. The results of this study indicate that a combination of HEY and milk proteins is suitable as a larval eel diet, and that it has the potential to replace SE.

Knowledge of fish movement ecology contributes to the improvement of fishery resource management actions. We investigated the horizontal movement of the black sea bream Acanthopagrus schlegelii around the natural coast of Nishinoumishima Island in Hiroshima Bay, using active acoustic tracking. Six adult fish equipped with depth transmitters were tracked for a total of 54 days in the bay. Five tagged fish were fully tracked for 9–10 consecutive days after release. Tagged fish were found in the intertidal zone and adjacent subtidal zones, which were shallower than 12 m, and within 170 m off the coastline. The mean daily movement distance and 95% kernel utilized density of tagged fish were 191 ± 272 m and 60,207 ± 99,437 m², respectively. The swimming depth of the tagged fish was 1–4 m above the seafloor. We opine that the littoral area (< 12 m in depth), which includes the intertidal zone and adjacent subtidal zone, is an important habitat for black sea bream.

We evaluated the potential of the euryhaline copepod Pseudodiaptomus inopinus as a prey to enhance the feeding activity of red sea bream Pagrus major larvae. Pseudodiaptomus inopinus was used to evaluate free amino acid composition and dietary effects on the rearing performance of fish larvae, in comparison to rotifers (control prey). Among free amino acids, alanine, arginine, and glycine were markedly higher in P. inopinus than in rotifers. Larvae were reared for 20 days post-hatching under three feeding treatments: rotifers (control), rotifers supplemented with copepods, and copepods only. Larvae fed copepods alone had a higher growth rate than those in the other treatments. However, the survival rates of these larvae were lower than those under control or copepod supplementation. While equivalent stocking densities of rotifers were employed in the rearing water for both larvae, whether supplemented with copepods or not, the supplemented treatment yielded diminished larval survival and failed to enhance growth rates. According to gut content analysis, larvae receiving supplemented treatment preferentially fed on copepods, and the number of ingested rotifers was reduced. As a result, total ingested mass was lower in the supplemented larvae. This study suggests that copepods containing free amino acid species negatively affect prey acceptance of fish larvae.

Tetrodotoxin (TTX), one of the most potent naturally occurring neurotoxins, has been detected in both marine and terrestrial organisms. The marine polyclad flatworm Planocera multitentaculata is known to contain high levels of TTX throughout its life cycle, including in the egg and larval stages. We recently reported that P. multitentaculata from the coastal area of Hayama, Kanagawa, Japan, possesses TTX analogs including 5,6,11-trideoxyTTX, monodeoxyTTXs, dideoxyTTXs, and 11-norTTX-6(S)-ol. It is not known whether all P. multitentaculata occurring in the Japanese archipelago possess major TTX analogs, or whether regional variations in TTX profile exist. In this study, we used high-resolution liquid chromatography–mass spectrometry to investigate the content profile of TTX and its analogs in P. multitentaculata collected from several regions of the Japanese coast. We detected TTX and its major analogs 5,6,11-trideoxyTTX, dideoxyTTXs, monodeoxyTTXs, and 11-norTTX-6(S)-ol in all specimens regardless of the sampling site. In addition, their relative proportions showed a similar pattern. These results suggest that the flatworm may have mechanisms involved in maintaining the proportions of TTX and its analogs in the body. How the toxic flatworms acquire the highly concentrated toxins and maintain the proportions of TTXs is therefore of great interest and further investigation.

The Caspian white fish or Caspian kutum Rutilus kutum is only found on the Iranian coastline of the Caspian Sea. This study investigated the extraction process of soluble/insoluble elastin from skin/swim bladder of Rutilus kutum on the basis of organic acid hydrolysis and hot alkali methods. Fourier-transform infrared (FTIR) spectroscopy analysis exhibited typical peaks at low frequency for amide I centered at ∼ 1633 cm⁻¹ and amide II at ∼ 1538 cm⁻¹. The comparative spectra indicated similar α-helix and β-sheet content of soluble/insoluble elastin in skin and swim bladder. The high content of amide I/II and increased polarity of soluble elastin can improve their reactivity in food matrices/textures or biopolymer design, whereas insoluble elastin powder, containing less amide I/II content and weaker dipoles, may be an alternative source for cell culture and tissue engineering. The purity of the soluble elastin from skin/swim bladder was confirmed through SDS-polyacrylamide gel electrophoresis (SDS-PAGE) analysis with an apparent molecular weight of 40 kDa, and hydrolyzed insoluble elastin generated an individual protein band at the same molecular mass containing some diffused ground proteins in the 35–45 kDa range and no contamination with collagen. Scanning electron microscopy (SEM) images of elastin presented fibrillar bundles with different diameters and peripheral beta sheets, with such constructions being appropriate features for the design of diverse biomimetic scaffolds.

Abstract

To assess fishery resources, it is necessary to easily obtain information on catch per unit effort, which is a resource indicator. In this study, two algorithms were developed for predicting the fishing effort (number of fishing operations, daily operating distance, and daily operating time) of a small-scale trawl fishery. These algorithms predict fishing efforts after preprocessing (including deleting outliers from the raw data), followed by classification of the operating conditions and threshold processing based on the operation period. One algorithm uses a machine-learning model for the classification process, and the other uses thresholding. The mean prediction error of the machine-learning algorithm on three datasets ranged from 1% to 11%, 2% to 8%, and 1% to 5% in terms of the number of operations, operating time, and operating distance, whereas that of the thresholding algorithm ranged from 3% to 52%, 2% to 5%, and 2% to 7%, respectively. A sensitivity analysis of the amount of training data indicated that prediction was possible using 5 days of training data. The developed algorithms are potentially useful for fish stock assessment.

The Atlantic Ocean’s little tunny is a priority for research by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Limited studies exist on Northeast Atlantic Ocean stock dynamics, and conventional catch and abundance assessments are lacking. This study assesses the impacts of tuna purse seiner fish aggregating device (FAD) and free-swimming school (FSC) fishing and proposes models for assessment using ICCAT data aggregated into different time blocks. Applying JABBA (Just Another Bayesian Biomass Assessment) and CMSY++, model diagnostics indicate that the 2011–2021 time series arrangement offers more reliable stock status estimates. Both models show overfished status (biomass/biomass max sustainable yield [B/B_MSY] < 0.5) from overfishing (fishing mortality/fishing mortality max sustainable yield [F/F_MSY] > 1.5) by the FAD and FSC techniques. FAD catches have leveled with the stock's average surplus production (ASP), while FSC catches are closer to ASP. JABBA projections suggest B_MSY for the stock in 2023–2024, with FSC and FAD catch limits of 3000–4000 tonnes. By implication, the stock may collapse from tuna purse seiner's FAD and FSC fishing unless catch limits are implemented. JABBA is most effective for little tunny with shorter catch and catch per unit effort (CPUE) data, while CMSY++ indicates overfished stock status with and without abundance indices. Both applied models are suitable for little tunny stock status prediction, but considering the abundance indices used in this study, management advice should be applied cautiously.

The life cycle of the moon jellyfish Aurelia coerulea consists of sessile polyp and free-swimming jellyfish stages. Strobilation is a polyp-to-jellyfish transition comprising sequential segment formation (segmentation), subsequent morphogenesis into ephyrae (young jellyfish), and detachment of the ephyrae. Cell proliferation is involved in metamorphosis in various animals. In the present study, we examined the relationship between cell proliferation and strobilation in A. coerulea. To visualize cell proliferation at various stages of strobilation, 5-bromo-2′-deoxyuridine labeling experiments were conducted, in which cell proliferation was distributed in the segments and prospective regions of the next segment during segmentation. Cell proliferation in segments continues during ephyra morphogenesis. Hydroxyurea, a cell-cycle inhibitor, was administered to investigate cell proliferation in animals at different stages of strobilation. In this study, hydroxyurea interrupted the initiation of strobilation, segmentation, and ephyra morphogenesis, but not ephyra detachment. This suggests that cell proliferation plays a crucial role in generating a new segment and constructing the ephyra body.

To determine the optimal method for monitoring the size distribution of cultivated yellowtail growth, we employed three different approaches: capture measurement, manual measurement using stereo cameras, and automatic measurement through stereo camera-based image recognition technology. Conventional capture measurements showed inadequate prediction interval owing to limited sample size, preventing accurate assessment of growth. Both manual and automatic camera measurements successfully conformed to a growth model exhibiting periodicity. The expected values derived from each model closely matched with the mean of landings conducted at the end of the study. However, the 95% prediction interval for manual measurement with cameras was comparable to that for the landing measurement, whereas the prediction interval for the automatic measurement with cameras was overestimated. Additionally, the growth rate of farmed yellowtail demonstrated seasonal fluctuations. Notably, the mean obtained from a single automatic measurement with cameras, prior to landing, significantly deviated from the overall mean of all measurements. This suggests a potential risk associated with relying on accidental outliers in a single measurement. Therefore, it is crucial to employ a growth model unaffected by outliers in continuous measurements to ensure reliable predictions.