Fisheries Science最新文献

The objective of this study was to examine the effectiveness of using ultrasonography for sex determination in young carp. Ultrasound images were obtained from anesthetized captive carp aged 11 to 13 months. After sacrifice, the body length and weight, gonadal sex and weight, and gonad-somatic index were measured. Well-developed testes and ovaries filled with granulated eggs were easily distinguishable on ultrasound imaging, based on their visible characteristic morphological features. In contrast, immature, small-sized testes and ovaries lacking granulated eggs were difficult to distinguish. The mean longitudinal thickness of gonads was technically the easiest to scan for measuring gonadal size, and it correlated well with gonadal weight (r = 0.91) and gonad-somatic index (r = 0.89). Based on the area under the curve of the receiver operating characteristic curve, we determined that 6.2 mm was the cutoff value for mean longitudinal gonadal thickness at which sex could be positively determined by ultrasonography, with a sensitivity of 82.6% and specificity of 100%. Ultrasonography therefore represents an effective and non-invasive diagnostic tool for determining sex and maturity in Japanese ornamental carp.

Recently, interest in fish byproduct-derived bioactive components as potential ingredients for treating and preventing osteoporosis is increasing. In this study, we investigated the antiosteoporotic effects of mackerel Scomber japonicus extracts in MC3T3-E1 preosteoblasts in vitro and ovariectomized rats in vivo. Scomber japonicus neutrase-assisted protein hydrolysate (SJNH) treatment enhanced alkaline phosphatase (ALP) activity and osteoprotegerin (OPG) level, and attenuated receptor activator of nuclear factor κB ligand (RANKL) level in MC3T3-E1 cells. In an osteoporotic animal model, ovariectomized (OVX) rats were administered SJNH (200 mg/kg/day) for 8 weeks. SJNH prevented OVX-induced bone mineral density (BMD) loss and restored bone structural compartment loss based on micro-computed tomography (CT). In addition, SJNH administration normalized bone remodeling by regulating bone regeneration and resorption-related proteins such as ALP, osteocalcin (OC), and tartrate-resistant acid phosphatase 5b (TRACP-5b) as well as calcium contents in serum. Taken together, our findings suggest that SJNH can promote antiosteoporotic effects both in vitro and in vivo. Thus, SJNH might be a potent therapeutic agent or functional food ingredient for preventing osteoporosis.

This study examined whether the potential early survival of sand lance in the Bisan Strait, central Seto Inland Sea, can be explained by variations in the growth rate and duration in the early life stages. Otolith microstructure analysis was conducted to examine the growth trajectories of specimens collected in six sampling years: 2011–2014, 2019, and 2020. There were significant differences in the growth rates of larvae and juveniles among sampling years, but such differences were likely attributable to variations in temperature in given seasons. Relative growth rates standardized by temperature were negatively correlated with the duration of the larval stage, suggesting that faster-growing individuals at given temperatures had a shorter larval stage. In each sampling year, there was a significant relationship between standardized hatch date and relative growth rate during the larval stage but not the juvenile stage. Within a given season, later-born larvae seemed to grow faster relative to the temperature experienced, and the higher percentages of the faster-growing larvae were likely associated with higher recruitment and recruitment per egg production. These findings suggest that the proportion of faster-growing sand lance larvae in a cohort at given temperatures explains the variation in potential early survival, but the higher temperatures in recent years may not necessarily contribute to improved early survival.

Whiteleg shrimp Penaeus vannamei, a highly valuable commercial species in aquaculture, is known to be susceptible to environmental stressors. In this study, we examined how dietary astaxanthin impacts the survival, behavior, and molecular responses of shrimp under acute cold stress. Shrimp were split into two groups: one fed a standard diet, the other fed an astaxanthin-enriched diet. Following feeding periods of 2 and 4 weeks, the shrimp were exposed to an acute temperature stress of 10 °C. Survival rates, behavior, and gene expression (heat shock protein [HSP]70, HSP90, hepatic lectin-like, prophenoloxidase [proPO], lysozyme, hemocyanin C chain-like, catalase [CAT], superoxide dismutase [SOD]) were studied. Astaxanthin as dietary supplement significantly improved survival under cold stress, suggesting enhanced stress tolerance. Molecular analysis showed slightly lower HSP70 and HSP90 expression in the astaxanthin group across various tissues, indicating a potential mechanism by which astaxanthin aids in stress mitigation. The astaxanthin-supplemented diet positively influenced immune and antioxidant gene expression, implying a stronger immune response and defense. These findings highlight astaxanthin’s potential to boost stress resilience and overall health in Whiteleg shrimp in aquaculture, resulting in enhanced immune responses and increased disease resistance. The results showed an effect on immunity, increasing their resistance to challenge and effectively protecting shrimp against Vibrio parahaemolyticus infection, resulting in increased resistance and high survival. Understanding these effects can contribute to better aquaculture practices, ensuring the well-being of this commercially important species in varied environmental conditions, especially in the temperate region.

This study examined the characteristics and effects of the quota transfer system implemented in the Japanese Pacific bluefin (PBF) tuna Thunnus orientalis fisheries. Social network analysis revealed that from fishing year (FY) 2018 to FY2021, the number of management units involved in quota transfer increased, the network became denser, and approximately half of the transfer pairs were maintained in the following year. The results of network structure analysis, including triad census and block modeling, showed that some management units (e.g., minister-managed purse seines, Ishikawa prefecture) play an important role in facilitating unilateral transfers and virtually mediate transfers between other units. A brief analysis using initial/final quota and catch data suggested that while the system helped with quota compliance and contributed to effective quota use, there was little evidence that quota allocation or catch was significantly concentrated after the introduction of the quota transfer system. These findings suggest that quota transfers could be further promoted by: (1) sharing up-to-date information on quota use and transfer networks; (2) providing highly accurate forecasts of sea conditions and PBF arrival; (3) semi-automating the matching and approval process; (4) encouraging multi-level quota transfers; and (5) creating more incentives for transferors.

Sakura shrimp Lucensosergia lucens are pelagic shrimp that reside in the North Pacific Ocean. In Japan, commercial fishing activities aimed at this shrimp species only occurs in Suruga Bay in Shizuoka prefecture, but there has been a dramatic decrease in the magnitude of the harvest in recent years. Because sakura shrimp reside in the deep sea, their food habits and feeding behaviors are not well understood. The objective of this study was to establish a method for efficiently raising sakura shrimp larvae to juvenile shrimp. When a newly hatched larva was cultured individually, it developed to the post-larval stage when fed a sufficient amount. However, when ten individuals were cultured together, the survival rate sharply declined after 10 days owing to the cannibalism by elaphocaris III-stage larvae. This cannibalism was not due to the shortage of food because the cannibalism rate significantly dropped when larvae density was decreased to less than 1 individual/mL. The longest lifespan of a larva was 97 days, which is the longest recorded time for a sakura shrimp larval culture. Our results suggested that sakura shrimp larvae can develop to the post-larval stage in a laboratory-scale culture if the expression of cannibalism is inhibited by decreasing the larva density.

The greater amberjack Seriola dumerili is economically important in both capture fisheries and aquaculture. It is a gonochoristic species with no noticeable sexual dimorphism, usually reaching maturity at 3–4 years. Spawning occurs in the Pacific from May to June but varies between regions. During a study on the maturity of greater amberjack, abnormal hermaphrodites (AH) with ovotestes were found. Of the 51 fish examined from June 2017 to April 2018, 2 individuals (3.9%) were classified as AH, with one each identified in February and April 2018. These AHs were larger than the gonochoristic (GC) individuals of the same age. In February, both AH and GCs had sperm-filled seminal lobules and ovaries at the primary yolk stage. By April, atresias were seen in both the AHs and GCs. While oocyte diameter increased in both AHs and GCs between February and April, the gonadosomatic index was lower in AHs. Plasma estradiol-17β and 11-ketotestosterone levels of AHs were similar to those of male GCs. These results suggest that AHs have accelerated growth with potential maturation as functional males. This is the first report on hermaphroditism in the Seriola genus.

Understanding consumer choice behavior for seafood is important for the efficient and sustainable use of marine resources and the improvement of human health. This study aims to identify the information content that effectively motivates Japanese consumers to purchase fresh fish products. Group interviews with 12 consumers were conducted in September 2021 to collect qualitative information on consumer evaluations of the presentation of package labels for freshness, taste, and serving suggestion. Subsequently, data were collected through a web-based survey, administered to 3651 consumers in the Kanto area, Japan from October to November 2021. A latent class logit model was applied to the data to estimate the influence of product attributes and personal characteristics on the choice and willingness-to-pay for each product attribute. The consumers gave the highest rating to freshness labels. The taste label was evaluated highly by consumers in one class. The group interview showed that when the serving suggestion label recommending meunière use was presented, consumers associated it with the recommendation to heat the fish because of less freshness. The results of the choice experiment also showed that the “meunière” label was evaluated negatively. The consumer segment characterized by a high income and frequent purchases of fish tended to respond to all types of labels.

Japanese flounder Paralichthys olivaceus is one of the most important coastal fish species in Japan. However, its catch in the southwestern Sea of Japan has been decreasing. Therefore, there is a need to improve the accuracy of stock assessment. Catch-at-age, which is the basis for stock assessment, is calculated based on the length–frequency distribution using age-length keys. It is recommended that this basic information is revised annually. However, the information for this species has not been updated for a relatively long period. In this study, growth curves were estimated and compared with those recorded from other areas. A multinomial logistic age-length key was generated and compared with the classical catch-at-age calculation method to examine potential errors. On the basis of the results obtained, a sex-specific von Bertalanffy growth curve was selected using the Bayesian information criterion. A model of sex and season was chosen for the multinomial logistic age-length key. The relative error was smaller and the estimated age composition was more accurate with the multinomial logistic age-length key, even when data with missing values were used. The improved accuracy of catch-at-age achieved due to the superior characteristics of the multinomial logistic age-length key is expected to be useful for the advancement of stock assessment.

We investigated the geographical distribution and feeding habits of Arabesque greenling Pleurogrammus azonus larvae along the Tatehama coast of Hokkaido Japan and its eastern waters from November to February. The goal was to gain insights into choice of spawning grounds and early life history. Yolk-sac larvae were predominantly found in the surface water layer near the Tatehama coast during late January to late February, and they were transported to the offshore regions by the Tsushima-Tsugaru Warm Current. During the early developmental stages, the yolk-sac larvae primarily fed on Oithona similis copepodites, which are larger than the copepod nauplii consumed by other marine fish species. Our observations of high feeding activity in the surface layer in offshore deep-water areas led us to hypothesize that the Tatehama coast may serve as a spawning ground for adult P. azonus due to its proximity to offshore areas, allowing larvae to quickly reach suitable feeding grounds after hatching. The larger egg diameter, longer body length, larger eyes with guanine pigmentation, coiled digestive system, and heavy body pigmentation of P. azonus suggest their ability to prey on copepodites and maintain sustained feeding intensity.