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A total number of 100 Nemipterus japonicus was collected randomly from the Western Gulf of Suez, Red Sea, Egypt from September to April 2021. After external and internal examinations, two species of parasites were found. The first species was Mothocya melanosticta isopods (both sexes) with a prevalence of 52% and attached externally to the gills and inside the buccal cavity. The second species, Hysterothylacium aduncum nematodes that was found in three types of distributions in 53 fishes. Firstly, adults were found in the gastrointestinal (GI) tract with a high prevalence of about 58%. Secondly, larval stages were found in 52 fishes with a high prevalence of about 57%. Thirdly, adults and larvae were found mixed together in 91 fishes with a high prevalence of 91% inside the GI tract of the same host. There was mixed infestations with M. melanosticta and H. aduncum with a percentage of 51% with several observed signs on the infested fishes. To determine the correct identification of detected parasites, both species were subjected to morphological and electron microscopic examination. Based on the present findings, further studies are recommended on the host-parasites relationship.

The Beibu Gulf is the fourth largest Chinese fishing ground, with rich fishery resources and a significant role in marine fishery production. The feeding ecology of fish is important to explain the structure and function of marine ecosystems. As one of the most important fish species in the Beibu Gulf, Nemipterus japonicus plays an essential role in energy flow and other aspects of the marine ecosystem. Understanding its feeding ecology could provide a basic theoretical basis for the rational utilization and protection of this resource. A total of 248 N. japonicus specimens were collected from Beibu Gulf from January to April and August to December in 2018. The food content composition, feeding intensity, and feeding niche of N. japonicus were analyzed using stomach contents to reflect feeding habits. Combined with carbon and nitrogen stable isotopes, the food source and trophic structure characteristics were analyzed, the trophic level was determined, and the feeding ecology of N. japonicus in the Beibu Gulf was discussed. The stomach content analysis revealed that N. japonicus is a broad-feeding benthic carnivore, which feeds on a large number of species, including eight prey groups, including fish, shrimp, and crab, among which fish and shrimp are the dominant food groups, with a relative importance index of 92.92%. The proportion of food species varied with the season and growth. Fish were an important prey group across all seasons. Moreover, N. japonicus preyed on shrimp in spring, crab in summer, shrimp and polychaetes in autumn, and shrimp and sipunculoidea in winter. With an increase in body length, the feeding habits of N. japonicus gradually change from primarily feeding on shrimp and fish to mainly feeding on fish, and the body length node of feeding transition was approximately 130 mm. There were clear seasonal variations in feeding intensity, with the highest intensity in autumn, followed by that in spring and summer, and the lowest in winter. N. japonicus had a high prey diversity; the Shannon-Wiener diversity index (H') was 1.77, and the Pielou evenness index (J') was 0.64. From spring to winter, the H' and J' values tended to increase and then decrease, and the highest value occurred in autumn, which meant that the feeding niche was the highest in autumn. The number of prey species increased with individual growth, and H' and J' showed an increasing trend with body length. The group with a body length ≥ 160 mm had the largest niche width, which suggested that the food diversity increased with individual growth, and the diet changed to broad-feeding.Based on stable isotope analysis, δ13C was positively correlated with the body length of N. japonicus (P < 0.05), indicating that the trophic source changed with growth. The span of the δ13C (CR) range was 2.86%, indicating extensive basic food sources. The span of the δ15N (NR) range was 4.23%, and the trophic span was more than one trophic level, indicating considerable differences in feeding among individuals. A significant positive correlation was found between body length and δ15N (P < 0.01), which indicated that the trophic level increased with an increasing body length. The trophic level of N. japonicus ranged from 3.21 to 4.46, with an average value of 3.97, indicating that N. japonicus species were middle-high carnivorous animals, and were at a high trophic level in the fish food web of the Beibu Gulf. The trophic level obtained in this study is higher than that obtained in other studies, which may be related to the changes in the composition of the prey, N. japonicus has shifted from feeding mainly on the low trophic level (crustaceans) to the high trophic levels (fish).In terms of trophic structure, the CR value of N. japonicus in the Beibu Gulf in spring and winter was lower than that in summer and autumn, indicating that the basic food source diversity in spring and winter is lower than that in summer and autumn, however, there are fewer prey species in summer, which might be caused by the feeding preference of N. japonicus. Simultaneously, the NR values in spring and summer were greater than those in summer and autumn, indicating that the span of the main trophic sources in the feed was higher than that in summer and autumn, consistent with the seasonal variation of dominant prey. Although the standard ellipse area (SEA) overlaps to different degrees among seasons, the total niche (TA) had clear seasonal differences, signifying that there were certain similarities and specific differences in prey resource utilization, which is beneficial for alleviating the seasonal pressure on the dominant prey. Furthermore, the CR value in different body length groups of N. japonicus showed an overall upward trend with individual growth, indicating that the food source diversity increased with growth. The NR value decreased when body length was greater than 130 mm, which indicates that the average trophic level of the population was concentrated when individuals grew to a certain stage. The SEA overlap rate was higher among length groups, implying that the trophic source components were similar at different growth stages; however, TA tended to increase and then decrease with body length, which may reduce food competition within species by niche differentiation.

This study has aimed to determine the food regime of Nemipterus japonicus in Bushehr province water, between Bushehr and Nyband using the vacant stomach index (VI), food behavior index (FB) and gonado-somatic index (GSI) in 2012-2013. Two hundred sixteen filled stomach, 14 semi- filled stomach and 215 empty stomach were analyzed. Small fish and Crustaceans were constituated main and secondry foods with 51.03% and 15.66% respectively. Mollusca were random food (5.52%). VI of stomach was estimated 48.32%. This value demonstrated that this species was moderate feeder. The result of Non-Parametric Multi-Divisional Scaling, shows the stomach contents difference between length classification. Also, determined some independent population which different length group, has no overlap from feed aspect.

Background: Anisakid nematodes are common parasites of fish, mammals, fish-eating birds, and reptiles with a worldwide distribution, causing diseases in human, fish and important economic losses. Methods: A preliminary epidemiological study was carried out on Anisakid nematodes larvae in some commercially important fish species to evaluate the anisakid nematode larvae from greater lizardfish, (Saurida tumbil), Japanese thread fin bream (Nemipterus japonicus), crocodile longtom (Tylosurus crocodilus crocodiles) and longfin trevally (Carangoides armatus) from the Persian Gulf of Iran. Result: The collected larvae were identified mainly as the third larval stage (L3) of Hysterothylacium larval type A, B and C, Anisakis sp., Raphidascaris sp., Pseudoterranova sp. and Philometra sp. (Nematoda: Philometridae). The prevalence of Anisakid larvae infection of examined fishes was 97.2% in N. japonicus, 90.3% in S. tumbil, 20.5% in crocodile longtom and 5.5% in longfin trevally. Anisakis type III for the first time was different from Anisakis type I and Anisakis type II. Discussion: Zoonotic anisakids by high prevalence in edible fish could be a health hazard for people. So health practices should be considered in these areas.

Gonado-somatic index (GSI) of Nemipterus japonicus was studied during the period August 2003 – January 2004. Size wise gonadal maturation was determined quantitatively by gonodo-somatic index in both sexes. A positive relationship between GSI values and stages of development of gonad was found. High GSI values at 230-260 mm TL in males and at 210 mm, 220 mm, 230-250 mm and 270 mm TL in females indicate the cent percentage maturation.

The aim of this study was to investigate and estimate the CPUE (Catch Per Unit of Effort), CPUA (Catch Per Unit of Swept Area), biomass and length frequency of Threadfin Bream (Nemipterus japonicus) in Coastal waters of Bushehr. This study was carried out in March 2011. The study area was divided into three area (Northern, Central and Southern) and depth zones (10-20, 20-30 and 30-50 m) and stratified random sampling was used to collect data. The sampling data was collected from 41 stations. The forked length of Nemipterus japonicas was ranged from 14 to 29 cm and the average forked length was calculated 20.29±2.64. Total CPUE and biomass of Nemipterus japonicas were calculated 16259 tonnes and 1771 kg/hours, respectively. The minimum and maximum CPUE were observed in 20-30 m depth zone (169.1 kg/hours) and 30-50 depth zone (1370.8 kg/hours), respectively. Total CPUA of Nemipterus japonicus was calculated 19678.8 kg/nm2. The minimum and maximum CPUA were observed in 10-20 m depth zone with 4.1 kg/nm2 and 30-50 m depth zone with 2147.7 kg/nm2, respectively. The results showed that the most abundance of Nemipterus japonicus was in higher than 30 m depth zones in Bushehr waters.