Fisheries Science最新文献

Salmonid fish are known to have the potential to induce allergies. Therefore, from the perspective of food safety, it is crucial to assess the contamination of salmonid components in food. In this study, we aimed to develop a highly sensitive detection method using real-time polymerase chain reaction (PCR) for the accurate identification of minute quantities of salmonid DNA in food. To enhance detection sensitivity, three types of repetitive DNA elements with high copy numbers per genome, that is, the Hpa I element, ribosomal DNA (rDNA), and mitochondrial DNA (mtDNA), were initially selected as candidate PCR targets. The copy numbers of these elements across 11 salmonid species were quantified using real-time PCR. The salmonid-specific retrotransposon with the highest copy number, Hpa I, was chosen as the target gene for the highly sensitive salmonid detection method. By conducting real-time PCR using DNA templates from 11 salmonid species and 71 non-salmonid species, the method demonstrated exceptional specificity to salmonids. By optimizing the conditions of the real-time PCR, the detection limit of salmonid DNA reached 20 fg, and the limit remained unaffected even in the presence of mixed DNA from other species. Compared with existing detection methods for salmonid fish, our approach signifies a substantial 250-fold advancement in detection limits. Application of our method to 16 processed foods containing components of salmonid fish and 5 processed foods devoid of salmonid fish components resulted in successful determination of the presence or absence of salmonid fish in all tested food samples.

This study presents a novel method for the rapid and precise detection of mackerels belonging to the genus Scomber, which are prevalent in the Japanese market and are subject to labeling regulations owing to allergenic concerns. We developed loop-mediated isothermal amplification (LAMP) methods targeting the ribosomal DNA sequences of four Scomber species: S. japonicus, S. australasicus, S. scombrus, and S. colias. By incorporating hydroxynaphthol blue for colorimetric detection, our method enables visual inspection of results, eliminating the need for complex instruments. Optimization of LAMP conditions and verification of specificity demonstrated reliable detection of Scomber DNA with a minimum detection limit of 1–100 pg, depending on the Scomber species, and enabling efficient detection within 30–60 min using a simple incubator. No cross-amplification occurred among closely related species. Additionally, we successfully detected Scomber DNA in processed foods, demonstrating the usefulness and practicality of our LAMP methods. Despite relatively lower sensitivity compared with real-time polymerase chain reaction (PCR), our LAMP methods offer advantages in simplicity, rapidity, and ease of use, making the methods suitable for broader application beyond specialized laboratories. Thus, our LAMP methods provide a practical solution for monitoring food labeling compliance, thereby enhancing consumer confidence and regulatory efficiency.

In recent years, food technology researchers have focused on improving the functional properties of proteins; several technologies have been used for this purpose, ultrasound being one of the most promising technologies. For this reason, the effect of ultrasound (20 kHz; 20% and 40% amplitude; 30, 60, and 90 s) on emulsifying properties of proteins from giant squid (Dosidicus gigas) mantle was studied. Changes in particle size, zeta potential, rheological properties, and micrographs were obtained. Emulsion stability was monitored by determining the size of the droplets as well as changes in their viscosity over 15 days. Treatment with 40% amplitude for 90 s showed lower particle size, and they were consistent with the micrograph images. Protein solutions showed a pseudoplastic behavior, being considered as non-Newtonian fluid. After 15 days of storage, the untreated sample presented a Sauter diameter (3, 2) of 20.06 ± 0.17 µm, while samples treated with ultrasound showed values of 13.64 ± 0.15 µm. The apparent viscosity of emulsions decreased by the ultrasound effect. In this regard, the ultrasound treatment improved the physicochemical and emulsifying features of the squid proteins, showing that it can be a potential technology for industrial applications to improve the functional properties of jumbo squid proteins.

The present study evaluated the potential of a saccharide mixture (galactose, glucose, fructose, and sucrose in a 2:1:1:1 ratio) as a chemoattractant (attraction) or/and feeding stimulant (ingestion) for the purple mud crab Scylla tranquebarica. In Experiment I, the S. tranquebarica appetitive response toward the 3%, 5%, or 7% (w/v) saccharide mixture solutions was examined and evaluated by a scoring method. The 5% and 7% treatments yielded the highest mean score (2.05 out of 3.00), with 20% of the S. tranquebarica exhibiting the highest response order (probing movement) in the latter treatment. In Experiment II, the S. tranquebarica feeding response toward the pelleted feeds containing the saccharide mixture at 3%, 5%, or 7% (SAC3, SAC5, or SAC7) was examined and evaluated using a scoring method. No significant difference (P > 0.05) was found among the mean scores of SAC3, SAC5, and SAC7. However, the mean score of the SAC7 diet was significantly higher (P < 0.05) than that of the control feed (without saccharide mixture inclusion), with 25% of the S. tranquebarica ingesting the feed. These findings highlight the potency of the saccharide mixture as a feeding effector for S. tranquebarica.

It is essential to understand the spatial distribution of a target species for effective stock management, particularly in the case of less mobile rock-dwelling species such as sea urchins. However, sea urchins exhibit an aggregated distribution within fishing grounds, thereby necessitating diving surveys at multiple sites to elucidate their spatial distribution at a fine scale. In Mikuni, Sakai City, Fukui Prefecture, Japan, female divers are well-acquainted with the underwater landscape and can determine the sea urchin catch per fishing ground. They also conduct voluntary fishery management for the sea urchin. Therefore, we enlisted female divers to report the sea urchin Hemicentrotus pulcherrimus catch during the 2020–2022 period and subsequently visualized the spatial distribution of these catches and estimated initial abundance using the Leslie method according to the fishing ground. The catch per unit effort did not decrease although the cumulative catch increased in many fishing grounds. This was because divers sensibly perceived the status of sea urchin stocks at each fishing ground through the dive fishery and they voluntarily controlled their fishing efforts to prevent stock depletion. Our results highlight that the catch data are often used for stock estimation but are influenced by fishermen’s management of the fishery.

The trans-molting retentive external eye (TRAMORE) tag is inexpensive, easy to apply, and immediately detectable without specialized detection devices. Its conspicuousness ensures almost no risk of consumption by humans, and it does not affect the survival and growth of Penaeus japonicus juveniles under experimental conditions without predation risks. However, during predator escape, the TRAMORE tag may become an obstacle during submerging into sand and/or swimming. Similar to traditional marking methods such as uropod ablation for identifying released individuals, little is known about whether TRAMORE tagging increases predation risk. If it does, the effectiveness of stock enhancement programs might be underestimated. This study aimed to determine whether TRAMORE tagging and uropod ablation marking influence the predator avoidance of P. japonicus juveniles through laboratory experiments. The time required to submerge into sand was not significantly affected by TRAMORE tagging nor uropod ablation marking. Neither TRAMORE tagging nor uropod ablation marking significantly affected the angle and distance of escape jumps. However, uropod ablation marking significantly slowed escape speed. These results indicate that the newly developed TRAMORE tag is more suitable for identifying released P. japonicus juveniles than the traditional uropod ablation marking method.

False killer whales, striped dolphins, and Pacific white-sided dolphins have been targeted by dolphin fisheries in the coastal waters off Japan. Annual catch quotas are allocated on the basis of past abundance estimates, but those estimates were unpublished or more than 30 years old. Here, we reanalyzed the line-transect data collected from the sighting survey on the Pacific coast of Japan from 1985 to 2021 and estimated the past and latest abundances of those three species using a standard distance sampling approach. The surveys were conducted as part of the JAFRACSS-SC (Japan Fisheries and Education Agency Cetacean Sighting Survey-Small Cetacean Survey Program). This program mainly targets other fishery-targeted cetacean species and, thus, covers only a part of the above three species’ distribution ranges. As a result, we obtained the latest abundance estimates of 4105 false killer whales, 84,657 striped dolphins, and 28,052 white-sided dolphins. Considering the current estimates represent only a part of the entire population size and that annual catch records did not largely exceed potential biological removals calculated based on these abundances, the current harvest level will not lead to a severe depletion or extinction for these three species.

The physiological impacts of polysaccharides and lipids in seaweed on human health are becoming clearer, but the behavior of the protein components, especially lectins, after ingestion remains poorly understood. In this study, we examined the resistance of edible red algae-derived lectins to digestive enzymes. We found that a lectin extracted from Meristotheca papulosa (MPL-1), belonging to the Jacalin-related lectin family, was relatively stable when subjected to both peptic and tryptic digestion and retained its hemagglutination activity after 24 h of digestion. The activity of MPL-1 was also maintained without a large change for 24 h following exposure to enzymes such as papain, Actinase E, and proteinase K, suggesting that MPL-1 possesses a strong resistant property against proteolytic digestion. We examined the anti-proliferation activity of the MPL fraction from the algal body against HT-29, a human colon cancer-derived cell line, and found that it showed a strong inhibitory activity with a half-maximal inhibitory concentration of 4.5 μg/mL. This activity was nullified in the presence of yeast mannan, an inhibitory sugar compound of lectin, demonstrating that MPL expressed its activity through binding to the glycan moieties on HT-29. This study indicates that this proteinase-resistant lectin could play a vital role after ingestion and is expected to have an inhibitory effect against colorectal cancer.

Japanese common squid Todarodes pacificus was exposed to the red tide-causing dinoflagellate Karenia mikimotoi, collected from a red tide event in Hakodate Port, in seawater at four densities (0, 90, 320, and 1900 K. mikimotoicells mL⁻¹) for 24 h. The number of squids that sunk to the bottom every hour and the survival of squids were recorded every 3 h. Squids in the group exposed to the highest cell density of K. mikimotoi began to sink to the bottom within 1 h of the start of the exposure test, and the frequency of anomalies (sinking or death) was significantly higher in this group than in the other groups (Wilcoxon signed-rank test with Bonferroni correction, P-values < 0.001). Hazard ratios for squid mortality were affected by K. mikimotoi cell density (Cox proportional hazards model; P-values < 0.01). These results suggest that K. mikimotoi is harmful to the Japanese common squid and that even short-term exposure to high densities of this alga causes debilitation and loss of swimming ability, leading to death. The debilitation and death of the Japanese common squid by K. mikimotoi has the potential to cause a loss of freshness and a decline in their commercial value, as has been observed during red tide events.