Fisheries Science最新文献

The present study assessed the growth and fish performance of juvenile red sea bream fed four isonitrogenous (46–48%) and isolipidic (15%) diets containing 45% fishmeal (control) and 15%, 30%, and 45% defatted black soldier fly (BSF) Hermetia illucens meal for 67 days. Subsequent analyses showed that there were no significant differences in the growth parameters, nutrient digestibility, and body composition of fish among all treatments. Although no significant difference was observed in fish growth, low growth was observed when the fish meal was totally replaced with the BSF meal. Higher alpha diversity of intestinal microbiota was observed in fish fed the BSF meal-based diet compared to that of the control. In the treatment groups fed the BSF meal, elevations in the presence of microbial genera that produce digestive enzymes, such as chitinase (Nocardia, Vibrio, Paenibacillus, Photobacterium), lipase (Paenibacillus, Photobacterium), and trypsin-like serine protease (Bacillus, Paenibacillus) and vitamin B group [biotin (Vibrio, Paenibacillus, Bacillus), cobalamin (Pseudomonas, Bacillus, Propionibacterium), and pyridoxin (Photobacterium)], were observed. We also found an increasing trend of bacteria producing antioxidative enzymes, such as superoxide dismutase and catalase (Nocardia, Pseudomonas, Photobacterium) in the BSF groups. These results suggested that the BSF meal could replace 67% of fishmeal without causing a negative impact on growth and lead to beneficial effects on the intestinal microbiota of the red sea bream.

Euryhaline fishes acclimate to various osmotic environments by changing the direction of water and ion transport between body fluids and environmental waters. Ionocytes in the gills are one of the most important cells for the active ion transport. This study aimed to identify the molecules responsible for apical Cl⁻ transport in rainbow trout ionocytes. Tissue distribution and time-course changes after seawater transfer were analyzed for mRNA expression of slc26a6, cftr1, and cftr2. slc26a6 was specifically expressed in the freshwater gills and decreased after seawater transfer. Both cftr genes were expressed in the gills and higher in seawater; however, the magnitude of expression increase after seawater transfer was greater in cftr1 than in cftr2. These results suggest that Cftr1 is mainly functioned in hypo-osmoregulation and that Cftr2 may also be involved in ion transport under freshwater conditions, such as acid–base regulation. Slc26a6 was localized at the apical membrane of Nkcc1-negative ionocytes only in freshwater-acclimated trout. Apical Cftr1 localization was also identified in most of ionocytes in seawater-acclimated fish. These results indicate that Slc26a6 in freshwater and Cftr1 in seawater contribute to osmoregulatory Cl⁻ transport across the apical membrane of ionocytes in rainbow trout.

The knowledge regarding the feeding ecology of the greater amberjack remains limited despite its ecological and economic importance. Therefore, this study investigated the feeding dynamics of the greater amberjack and its key prey species in Taiwanese waters. Samples were collected from the Taiwan Bank (22.5° N–24.5° N, 118.5° E–121.5° E) and Northern Taiwan waters (25° N–26° N, 121° E–123.5° E). Analysis of samples obtained between June 2020 and June 2022 indicates that environmental factors influenced the availability of prey species, thereby affecting dietary preferences. The prey-specific index of relative importance indicated that the predominant prey species were pelagic species (52.81%), followed by demersal species and unidentified teleosts (18.74% and 16.58%, respectively); squid and crustaceans were the least frequently consumed prey species (6.11% and 5.76%, respectively). Although no difference was discovered between males and females in terms of diet, seasonal and size-related variations were noted in the feeding patterns, as evident from the substantial ontogenetic shift observed in the dietary composition of the samples during the study period. The findings of this study improve the understanding of the feeding dynamics of the greater amberjack and the association between oceanographic factors, such as sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), mixed-layer depth (MLD), and eddy kinetic energy (EKE), and prey availability in the coastal waters of Taiwan.

Marine sponges harbor diverse secondary metabolites with a variety of biological activity, many of which are considered as chemical defense substances for the sponges themselves. Recently, we observed that Thromidia catalai, one of the largest species of starfish, feeds on the sponge Theonella swinhoei (chemotype Y), known to contain diverse biologically active metabolites. Here we report the isolation of three novel brominated indole alkaloids, catalindoles A–C, from the arms of T. catalai as well as the elucidation of their structures. Their structures were determined by a combination of spectroscopic data analyses and chemical methods, and they were further confirmed by chemical syntheses of the molecules. Moreover, we revealed the predator–prey relationship between T. catalai and Theonella sponges in terms of chemical components, noting that T. catalai feeds not only on T. swinhoei (chemotype Y) but also on T. swinhoei (chemotype W).

The catch of butterfly kingfish Gasterochisma melampus, a large pelagic species in southern temperate waters, is strongly biased (73%) towards females. Whether this is caused by differences in sex-specific spatiotemporal distributions or mortality of sexes is investigated herein. Analysis of sex ratios using a generalized additive model (GAM) for year, month, latitude, longitude, sea surface temperature, and fork length from Japanese longline catch data for areas where immature and adult fish occur revealed the influence of space and time on sex ratios to be small, and that of fork length to be large. Based on observation of the increments in vertebrae of immature fish (N = 179), the fork length at the time of increment formation was back-calculated from distances between increments on the anterior and posterior cones, generating 2–8 measurements per vertebra and 865 data points in total. Growth equations were calculated for each sex, with females growing faster. The age composition of males and females in the catch was similar, meaning that the mortality rate in males is unlikely to be higher than that of females. The data suggest that biased sex ratios in catches are representative of the natural sex ratio in a population for fish more than 60 cm in fork length.

Japanese anchovy Engraulis japonicus is a small-sized fish, and it is difficult to obtain its flesh by hand. To enhance the utilization of this fish, this study aims to determine the effect of extraction methods on the amino acid, mineral, and fatty acid profile of recovered protein (RP) from Japanese anchovy, as well as the functional properties of RP. The protein was extracted from minced fish by three methods, including salt water treatment (RP-S) and pH-shifted processes at both acidic (RP-A) and basic (RP-B) solubilization. All RPs had more total essential amino acids than minced fish. Among RP, the highest Na and Fe content was found in RP-S, whereas RP-A showed the highest calcium content. RP-S possessed a lower amount of total polyunsaturated fatty acids than that of RP-A and RP-B. Water- and oil-absorption capacity and foam stability of RP-S and RP-B were on the same level and higher than those of RP-A. The highest emulsion activity index and emulsion stability index was found in RP-B. However, no difference was found in emulsion stability index between RP-S and RP-A. Overall, salt water treatment indicated that this method can be used as an alternative method to recover protein from Japanese anchovy.

The operating efficiency of fishermen’s associations is significant for developing the fishery industry and fishing villages. Since fishermen’s associations have economic, financial, and service sectors, this study evaluates their efficiency through multiactivity data envelopment analysis. In addition to exploring the overall efficiency of each fishermen association, this study further investigates the differences in the operating efficiency of each of the economic, financial, and service sectors. Fishermen’s associations were divided according to their sizes and geographic areas for analyses and comparisons by considering the differences in their organizational scales and fishing activities. In the empirical study, 24 fishermen associations in Taiwan were selected as the research subjects, and the shared inputs of economic, financial, and service sectors were taken to conform to their practical operation. The overall efficiency of fishermen’s associations was affected by their size and mainly varied by economic sector. The research results indicate room for improvement in the overall efficiency of fishermen’s associations, but improving the efficiency of different fishermen’s associations should occur in various sectors.

The hypervariable region (HVR) in the control region of the mitochondrial DNA has frequently been used for population genetics and phylogeographic studies because of its highly variable nature. Although the HVR is beneficial for evaluating recent evolutionary history, including population demography, recent studies have implied the incidence of homoplasy in this region. To assess the accuracy of relying solely on the HVR for population genetics studies, molecular evolutionary analysis of the HVR, NADH-dehydrogenase subunit 2 (ND2), and cytochrome b genes were performed using 120 individuals of marbled flounder Pseudopleuronectes yokohamae. The HVR exhibited the highest genetic variability among the three regions, with sites showing high site-specific substitution rates. Considering the reticulate haplotype network structure and evolutionary linkages between regions, homoplastic mutations were indicated in the HVR in addition to ND2, underestimating genetic diversity. We found that homoplasy was less likely to affect coalescent-based demographic inferences in the population; however, there is still a potential risk of misinterpretation of population demography when solely using the HVR owing to its hypervariable nature. Collectively, we suggest analyzing other regions in addition to the HVR in fish population genetic research to improve accuracy and eliminate biases caused by homoplasy.

Organic selenium is a major antioxidant that can protect against oxidative stresses by stimulating the antioxidant cascades. We have evaluated the capacity of dietary selenium-enriched yeast (Se-Y) to alleviate thermal stress in juvenile Penaeus vannamei shrimp. The Se-Y level in the control group (Cont) was 0 mg Se kg⁻¹ ration and 0.4 mg Se kg⁻¹ in the AlkoSel and SelPlex groups (commercial Se-Y products). The shrimp were initially provided the three experimental diets while being maintained in their thermal comfort zone (28 °C) for 30 days, following which time the temperature was increased up to 33 °C for 1 and 6 h of induced heat stress challenge (IHSC). Variations in the levels of malondialdehyde (MDA), glutathione, and several transcriptional factors encoding antioxidant variables and stress-responsive proteins were analyzed in the gill, muscle, and hepatopancreas. The results revealed that the MDA and glutathione content of the shrimp were significantly impacted by Se-Y supplementation both before and after the IHSC. Prior to the IHSC, in all evaluated tissues, Se-Y supplementation enhanced the antioxidant variables (glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase) and heat shock protein (HSP) biosensors HSP70 and HSP90 while depressing the immune stress-related indices (gamma-interferon inducible lysosomal thiol reductase-like and aspartate aminotransferase cytoplasmic-like (AST). After IHSC, in all evaluated tissues, the AST gene was significantly downregulated in all Se-Y-fed groups while the other genes were upregulated. These results imply an important role of organic selenium in preventing organ dysfunctions after exposure to IHSC. Taken together, these findings on gene regulation after Se-Y pretreatment will be useful for monitoring organ dysfunction and preparing therapeutic agents for thermal endurance in P. vannamei.