جستجوی مقالات مرتبط با کلیدواژه « feeding habits » در نشریات گروه « شیلات »

This study analyzed the stomach contents of Chub mackerel, Scomber japonicus, collected from purse seine and set net fisheries samples in the South Sea of Korea in March 2020 to February 2022 for juvenile, mature, and older fish, which are useful to identify ecosystem functions and study food competition, interspecific feeding relationships, and the food web. The size of S. japonicus samples ranged from 5.5 to 46.6 cm in fork length. S. japonicus were a carnivore that feed mainly on euphausiids and pisces. The estimated average trophic level of S. japonicus ranged from 3.65±0.64 to 4.00±0.78. Examination of the feeding habits according to ontogenic feeding patterns of S. japonicus revealed that the mean weight of prey (mW/ST) continuously increased. There were differences in the composition of the stomach contents of S. japonicus by the sampling period and size class, and also the interaction between them. S. japonicus were specialized feeders with pisces and euphausiids as their dominant prey.

The juvenile Oplegnathus fasciatus were collected off the Gijang, Korea coast. A total of 203 juvenile O. fasciatus were examined, and the range of total length (TL) was 7.9-31.0 mm. The most important prey component of O. fasciatus was Copepods, with 75.0% in IRI (index of relative importance) index. Among Copepods, Paracalanus parvus s.l. in the Calanoida was the most significant dietary component. Cladocera was the second important prey component. Pisces, Amphipoda, Decapoda, and the other preys accounted for less than 1.8% of the diet by IRI index. The feeding strategy showed that O. fasciatus held a specialist niche with a considerable individual specialization. The result of analysis in ontogenetic changes was significantly exhibited among size classes. The proportion of Copepods decreased as increasing in body size, whereas the consumption of Cladocera, Pisces, Amphipoda, and Decapoda increased gradually. As body size increased, both the mean numbers of prey per gut (mN/Gut) and the mean volume of prey per gut (mV/Gut) constantly increased.

This study was conducted to determine the feeding and reproductive biology of Saurida tumbil and Rastrelliger kanagurta in the northern Oman Sea in 2020 -21. A total of 134 and 157 specimens of S. tumbil and R. kanagurta were collected from landing sites of Sistan and Baluchistan waters, respectively. The results of S. tumbil feeding analysis showed that the main diets of this species are fishes, mollusks and shrimps. Gastric emptying index (CV) indicated that this species was highly fed in winter and was identified as a gluttonous species. The results show the lowest value of Gonado-Somatic Index (GSI) in spring and the highest in summer. The reproduction of S. tumbil occurred after summer. Length (TL) at first maturity (LM50) for this species was estimated to be about 37.9 cm. The Food Preference (Fp) index showed that the main diets of R. kanagurta are phytoplankton and algae and CV reaches its maximum value in autumn. GSI of this species also shows the lowest level in spring and the highest in summer, which indicates that the peak of reproduction of R. kanagurta occurred after summer. Length (TL) at first maturity (LM50) for this species estimated to be about 25.2 cm.

Reproduction biology and feeding habits of black mouth croaker, Atrobucca nibe, was investigated monthly from September 2013 to August 2014 in the Oman Sea. The specimens were collected by bottom trawl in the Northwest of Oman Sea. A total of 637 fish specimens examined, 284 males and 353 females were sexed. The average sex ratio was F: M= 1.24:1, showing dominance of females over the males. Spawning season of A. nibe was mostly observed in June and October but spawning might be occurred in all year long . The mean absolute fecundity was calculated 97008±55553 eggs, with a moderate linear relationship between absolute fecundity and total length (Fecundity= 10802TL-280712, R2=0.7624). The mean length at first sexual maturity (Lm50 %) was 35 cm for females. A. nibe is an abstemious feeder according to the high vacuity index (VI=86.5±16.8 %). Skinny cheek lanternfish (65%), Japanese threadfin bream (13%) and deep-sea shrimps (11%) were the frequent food items of this species. Results showed that  bony fishes were consumed by all size-classes, skinny cheek lanternfish (42.1%) and Japanese threadfin bream (79.4%) were more pronounced in size-class of 34-38 cm, and also  crustacean were more frequent (29%) in 22-26 cm size classes.

Bioaccumulation and distribution of heavy metal (Se, As and Pb) in muscle, gill and hepatopancreas of blue crab Portunus pelagicus from Bushehr coast, north part of the Persian Gulf, were investigated. Analyses of samples were by a GBC-932 AA Atomic Absorption Spectrophotometer. The average concentrations of Se, Pb and As in all tissues of crab were 0.485, 1.89 and 0.615 µg g-1 respectively. The linear regression analysis showed there were a positive correlation between heavy metal levels and crab size. Also, there was a direct relationship between heavy metals levels in tissues crabs with feeding habitat. Comparison between male and female indicated that the average of heavy metal concentrations in female crabs were higher than those in the male crab, because female crabs feed on benthic animal that are close to bottom sediment and receives more sediment associated metals.

In this study, the feeding habits of blue swimming crab (Portunus segnis) in the Northeast Persian Gulf were investigated. A total of 722 specimens were collected using bottom trawl. The samples were transferred to the laboratory in order to further analysis after freezing. All individuals were dissected and their stomach was removed. The results showed the vacancy index of stomach (CV) was 34.5. This finding indicated that this species is a gluttonous crab. Also the analysis of their feeding habits showed that this species is carnivorous. The main items included crustaceans, fishes and mollusks. Their diet varied seasonally. Crustaceans were more important in summer whereas fishes and mollusks were more important during autumn and winter, respectively. The crustaceans included shrimps and other crabs. The dominant mollusks were the bivalves such as common name Marcina hiantina, Circentia callipyga, Tellina sp., Cardita bicolor and gastropods Cerithium erythraeonese, Atys sp. There were significant differences in feed items occurrence frequency between sexes.