The digestive system of Lepidorhombus whiffiagonis was studied using histological and histochemical techniques. The wall of oesophagus and stomach fundus consisted of four histological layers: mucosa, submucosa, muscularis and the outer layer. Mucosa, the innermost layer, usually consisted of three different layers, including epithelium, lamina propria and lamina muscularis mucosae. Submucosa of connective tissue with blood vessels and nerve fibres underlined the mucosa and usually protrudes into the mucosal folds except in the gallbladder where it is completely absent. The muscular layer of the digestive system consisted of smooth muscles arranged in longitudinal, circular or oblique layers. Striated fibres were found in the oesophageal wall. The outermost layer comes as tunica adventitia in upper parts and tunica serosa in lower parts of the digestive system. Hepatocytes were surrounded by a mass of fat-storing cells. Serous acini of pancreas were scattered down the length of the stomach. Alcian blue/PAS technique revealed that alkaline and neutral mucopolysaccharides were present in oesophagus while acidic mucopolysaccharides was found in the stomach and intestines.

Comparative studies of axial musculature in Phoxinus phoxinus and three species of the genus Rhynchocypris were conducted to analyze locomotor abilities and biotopic preferences of widespread Asian minnows. The ratio between the areas occupied by the red and white muscles, as well as the fiber diameter, was measured on histological sections. Significant between-species differences were found in the size of the both type of fibers. Mean diameter of white fibers varied from 50.7 to 69.3μm, the extreme values (min-max) of this parameter were found in typical lotic species, R. lagowskii and P. phoxinus, respectively. Mean diameter of red fibers varied from 26.4 to 33.5μm, and also does not have a clear link to the type of habitat. On the contrary, the distribution of different types of fibres was in good agreement with the data on preferred biotopes of studied species, divided into two groups. Mean proportion of red fibres in caudal peduncle in lotic P. phoxinus and R. lagowskii (9.1- 10.2%) was more than twice as high as that in lentic R. percnurus and R. czekanowskii (3.8- 4.3%). The low proportion of red muscles in R. percnurus and R. czekanowskii, in addition to poor mobility, may also indicate adaptation to wintering under hypoxic conditions. In general, the ratio of red to white muscles provides additional information for predicting the distribution of minnows in freshwaters.

The age and growth of areolate grouper, Epinephelus areolatus and six-bar grouper, E. sexfasciatus in the Terengganu waters, Malaysia, were estimated by analysis of sectioned sagittal otoliths. A total of 795 grouper samples were collected monthly for 12 months from February 2014 to January 2015 in two main fishing landing ports of the Terengganu. The recorded results showed that the ages ranged were from 1–9 and 2–9 years, for E. areolatus and E. sexfasciatus, respectively, for. The length-at-age data fitted to the von Bertalanffy growth model revealed that the growth function was TLt = 86.66 [1-e -0.06(t+2.32)] for E. areolatus and TLt = 33.86 [1-e -0.44(t+0.35)] for E. sexfasciatus. The high proportion of immature fish in the catch and the lack of adults near maximum size indicate that the population of E. areolatus in particular is in danger of being overfished and management measures should be urgently implemented to reduce the catch of immature fish and to preserve an adequate breeding stock of larger adults of these and other groupers of commercial importance.

 Population parameters of the Nile tilapia, Oreochromis niloticus were studied based on 1500 specimens (8-31cm TL) collected monthly from the Lake Manzala for one year. Age was determined based on scales’ readings and found to be five years. The lengthweight relationship can be expressed as W=0.0143*L3.08. The von Bertalanffy growth equations were Lt=34.51 [1-e -0.38(t+ 0.39)] for growth in length and Wt=776.12 (1-e -0.38(t+0.39)] 3.08 for growth in weight. The estimated total, natural and fishing mortality rates were 2.02, 0.82 and 1.20 y-1 , respectively. The exploitation rate (E) was 0.59 and size at first capture (Lc) was estimated as 14.4cm TL. The relative yield per recruit reached maximum at an exploitation rate (Emax) of 0.6. Oreochromis niloticus stock may be unsustainable due to intensive fishing pressure to meet demand of growing populations, unless proper action is taken to manage the stocks.

Indian halibut, Psettodes erumei is the single member of family Psettodidae recorded in the southern waters of Iran (north of the Persian Gulf and Oman Sea). In the present study, the feeding habit of this species was investigated. The specimens were collected monthly from October 2016 to November 2017 by shrimp trawl from three sampling sites along the northern parts of the Persian Gulf and Oman Sea (Hormozgan Province, Iran). For the diet analysis, the stomach contents of 433 individuals were analyzed. Of these, 277 were empty (VI=63.97%) which varied significantly throughout the study period. Feeding intensity of both sexes was high before the gonadal maturation peak; during the period when a maximum percentage of fully mature individuals were present, the feeding intensity was found to be low. The overall diet showed that Indian halibut is mainly a piscivorous carnivore and Teleostei were the most frequent and important food group in the diet (%F=48.08, %IRI=98.44). Crustacean and Cephalopods constituted a small portion of the diet (%F=5.77 and 1.92, respectively) and were of minor importance (%IRI=1.33 and 0.23, respectively). Diet composition showed no significant variation in relation to season, fish size and sex and only some significant differences were observed in their frequency and numerical percentage. The trophic level for this species was calculated 4.4. The present study provides partial information on feeding habits of Indian halibut, of prime importance for the fisheries management and also helps to understand the trophic role of fish in relation to other species in the ecosystem.

The Hormuz River System (HRS) is located in the southern coastal plain of the Zagros Mountains. Two main river drainages i.e., Mehran and Kol are known from this region, which are directly discharged to the Persian Gulf. The HRS has surprising diversity for tooth-carp fishes (family Aphaniidae). The present study aims to accentuate this notable diversity and discuss the possible cause of diversification of the tooth-carps in the HRS. To date, 15 Aphaniid species have been discovered from the Iranian drainage basins. Among them, 10 species belong to the genus Aphanius, four species belong to the genus Aphaniops, and a single species belonging to the genus Paraphanius. The HRS by having four species (22% of the Iranian tooth-carps) demonstrated the highest diversity among the other Iranian basins. Of these, one belongs to the genus Aphanius (A. darabensis) and three species belong to the genus Aphaniops (A. furcatus, A. ginaonis, and A. hormuzensis). By considering the degree of endemicity of the tooth-carps fauna relative to the territorial boundaries of drainages, the HRS has the highest endemicity, in which 31% of the Iranian endemic toothcarp species present only in the HRS. The last connection of the Makran Basin with the HRS dates back to the late Pliocene and lower Pleistocene about 1.8 million years ago. Also, the other vicariance-based events like those events related to the last glacial maximum (21000- 18000 BP), population migration during the Early Holocene sea-level rise, and the Holocene to present-day have promoted the intra- and interspecific differentiation of tooth-carps in the HRS. Also, the geological situation of the HRS provided various extreme environmental conditions, which caused a particular increase in the diversification of the tooth-carp species.

The present study reports the first record of two marine fish species namely the black-stripe sweeper Pempheris schwenkii Bleeker, 1855 and the black-edge sweeper Pempheris mangula Cuvier, 1829, of the family Pempheridae from Gopalpur-on Sea, Odisha coast, India. Although, we find a number of fish samples of both the species, still there is no evidence that both the species have established a breeding population in marine waters of Gopalpur coast. Therefore, at present both the species must be regarded as casual rather than native species.