The main goal of this study was estimating discards of trawl nets in north western part of the Persian Gulf. Data were collected from fishing boats in fishing areas of Khuzestan from October 2011 to September 2012 with collaboration of fishery office. Discard samples include 101 species from 61 families which are 39.5% of commercial catch and 60.4% of non-commercial catches. Rayfish and catfish have been observed in most fishing nets. The average size of bony fishes in discard samples was lower than 15 cm. Total weights of discards was estimated about 1109 tons per year. Total weight of commercial fishes with small size in discards was estimated 2736 tones. The rate and proportion of discards in total catch of trawl was estimated 0.5 and 1.03 respectively. Osteichthyes with 70 species and 50.7% of trawl catch has the highest percentage of discards in trawl nets. High rate of small fishes in commercially important species of discards is probably due to nursery role of Khuzestan coastal waters.

In order to estimate the by-catch of demersal in a part of Khuzestan coastal waters (North West Persian Gulf), a sea Survey was carried out by using research ship. Study area was divided to three strata (khore Musa, Baherkan and Life-boseif) and 164 stations were selected randomly and were ampled by swept area method.25, 29 and 28 species were identified in these substrata respectively. Mean catch per unit area and bycatch in Musa khore, Baherkan and Life-bosif were 3343 (kg/nm), 4928 (kg/nm), 5467 (kg/nm) and 2885 (kg/nm), 4029 (kg/nm), 4860 (kg/nm) respectively. Cynogloss arel (14.74%) and Scomberoides commersonnianus (0.3%) were maximum and minimum biomass species respectively. Mean bycatch value and ratio between bycatch to total catch in these areas were estimated 3924.73 (kg/nm) and 0.44 respectively.

The Polynemidaes is one of the great importance demersal fishes in the Oman Sea that research about them seems to be necessary. This research was down with the research trawler (Ferdos 1). The area was researched is from field (58 o55') to the Goiter Gulf (61 ْ 25') and depth of 10 to 100 meters that all of them are 1164 square mile of the sea. This area divided from west until east to the 5 regions (A, B, C, D, E) with 30 minutes of longitude and every area with deep layer of 10-20 meters, 20-30 meters, 30-50 meters and 50-100 meters were determined. In all of research, the number of station determined and the catch sampling with the trawl in one hours was down then the statue of the spices per unit area (CPUA) and the biomass of Polynemidaes separately in ever deep layer was estimated that the maximum average in per unit for one spices in one layer corresponding to the Polynemidae five filament in layer B with 8387.25 Kg and the least (minimum) average related to Polynemidae six filament in layer D with 1.02 Kg in square mile. The six filament spices in layers E and C not exist and the spices (Eleutheronema tetradaytylum) its maximum value in layer E with 571.78 kg in square mile. Although the average index in per unit based on deep layer indicated that Polynemidae six filaments (Polydactylus sextarius) with 1 kg at the depth of 20-30 meter have minimum and with the 5358 kg at the depth of 30-50 meter have maximum value catch. The value of the critical p for comparison of the catch spices in per unit (CPUA) indicates that Polynemidae with filament (P. plebeius) in the layer and the normal (general) Polynemidae in the depth layer have significant different but this significant various not exist in layer but in depth have significant different for polynemidae six filament. According to the calculated CPUA, the result showed that there is a schooling stock of Polynemidae in deep area of 30 to 100m (Biyahi to the head of Meydani) in the region.

Length-weight relationship, length abundance, maturity percentage and growth parameters of green tiger prawn caught using trawl nets in Mond and Dayyer-Nakhilo areas located in Bushehr province during the years 2020 (13 August to 15 February) and 2021 (11 April to 9 September). A total of 658 tiger shrimps, including 420 female shrimp and 238 male shrimp were bioassayed. Based on the carapace length of 43.43 mm in the first sexual maturity of the females, 50.71% (213 specimens) were mature and 49.29% (217 specimens) were immature. Also, the relationship between the total length and carapace length of female shrimps was y=0.3679 x - 2.1648 based on linear regression. The relationship between the length and weight of 420 female shrimps and 238 male shrimps caught showed that parameters a, b, and r2 were 0.0099, 3.057, and 0.92 for females and 0.0115, 2.9962, and 0.912 for males, respectively. Based on the Sturges formula, 10 length classes were observed for male and female shrimps caught. The length class of 108-12.3 cm for both males and females had the highest frequency with 110 specimens (46.22%) and 141 specimens (33.57%), respectively. The results of this study showed that the maximum length of male (16 cm) and female (20.5 cm) caught shrimps was less than the infinite length and more than the optimal length. Growth parameters (Clinf, K, t0) for females were -0.057, 2.1 and 72 (mm) and for males -0.075, 1.7 and 62 (mm), respectively. The values of Z, F and M parameters for females were 9.2, 7.4 and 2.16 and for males 7.58, 5.62 and 1.96. The exploitation rate (E) was 0.77 for females and 0.74 for males. These values indicate overexploitation and fishing pressure in the area. Therefore, it is necessary to implement fishing management approaches in these habitats.

This study was conducted to estimating the amount of non-standard sizes (with lengths less than LM50) fishes of shrimp trawls in the Hormozgan Province coastal water during shrimp fishing season Sampling was carried out using the Tabas otriger commercial trawler during 55 hauls. Eight commercially valuable species including Pampus argenteus, Parastromateus niger, Plicofollis dussumieri, Saurida tumbil, Nemipterus japonicus, Scomberomorus guttatus, Platycephus indicus and Otolithes ruberwere were investigated in this study. S. guttatus (94.33%), P. argenteus (93.19%), O. ruber (91.57%), P. niger (89.86%), P. indicus (66.66%), S. tumbil (60.4%), N. japonicas (35.38%) and P. dussumieri (4.42%) had most high non-standard length in catch, respectively. LOPT were calculating for P. dussumieri. The results showed a high pressure on the species of the shrimp trawl that can be the reason of species composition change in the Persian Gulf fisheries.

The Persian Gulf waters, like other tropical regions, are rich in aquatic animal fauna and demersal trawling is one of the most common and practical methods to exploit aquatic resources. In the meantime, fishing vessels equipped with trawl nets can generate large amounts of bycatch and subsequent discards. This study aimed to identify fish species and estimate catch per unit area (CPUA) in the shrimp trawl bycatch off northwestern coasts of the Persian Gulf. The data were collected during trawl hauls for one year (September 2021– September 2022) between Delwar and Helle fishing grounds at three depth layers. The bycatch samples included 75 fish species with a total CPUA of 2392. 4 kg/nm2. The largest amount of the discarded bycatch (77. 8%) belongs to teleost and cartilaginous fishes, of which gilded goatfish and Japanese threadfin bream accounted for the first and second places with a total CPUA of 433. 9 kg/nm2 and 202. 8 kg/nm2, respectively. The abundance of the identified bycatch varied at different water layers, and the highest bycatch rate was obtained in the depth water (21-30 m,44. 1%) and the lowest value was recorded in the shallow water (up to 10 m,21. 7%). Fifteen fish species had percentage of occurrence (100%) at all studied depths. According to the distribution map provided by ArcGIS software, the density of discards was increased by moving toward the western part of the Persian Gulf. The assessment of the bycatch composition of traditional shrimp trawler fisheries is not only practical to take preventive actions regarding the marine ecosystem balance but also the results can be used as an ecological model to evaluate the risk of the trawlers in the study area.

This study was conducted for estimation of bycatch shrimp trawl from fishing grounds of Hormozgan province.Sampling operation was carried by commercial trawler around Hormoz and Qeshm Island during fishing season in October and November 2012. Towing duration was between 1 to 3.5h (2±0.08h). Contribution of bycatch and target species was 86.26% (18918.80 kg) and 13.74% (3014.22kg) respectively. By-catch-to-shrimp ratio was estimated 6.27. Small discard species, large discard species, commercial species and target species were constituted 68.02%, 3.35%, 14.7%, 13.74% of total catch respectively. In this study, species composition included 103 species belonging to 64 families that include 77 teleost species from 47 families, 13species elasmobranchia from 9 families, 3species invertebrate from 3 families, 4 species Penaeid shrimps and sea turtle, sea snake and sea stare. The results of this research indicate fishing pressure on commercial and non commercial species in this region. The little long term information exists for Bycach species shrimp trawl that used for conventional population models. The results of this study can be used for assessment damages shrimp trawl fisheries on the resources of the Persian Gulf and the ecological risk assessment models.

Fixed gill net has been used for Teleostei fishery by the fishermen in Anzali Wetland. The aim of this study was to compare the CPUE, species composition, length frequency and the vulnerability of Teleostei between fixed gill net and fyke net from 1st November 2010 to 30st March 2011 in Anzali Wetland. Ten fixed gill nets and ten fyke nets were set. Mean CPUE (±SE) was estimated 0.17±0.03 and 0.26±0.07Kg/24h for fixed gill net and fyke net, respectively. Mean CPUE differed significantly between two gears. Also mean CPUE (±SE) differed significantly between fixed gill net and fyke net for 100m2 with higher CPUE (2.14±0.54Kg/24h) in fyke net. The relative frequency of caught species in fixed gill net and fyke net were dominated by Carassius auratus (38%) followed by Esox lucius (65%), respectively. Length-frequency distributions of the species had greater range of length and weight in fyke net in relative to fixed gill net. The amount of damage differed significantly between fixed gill net and fyke net with less damage and with higher survival in fyke net. The results of this study showed that fyke net has valuable and marketability catch in relative to gill net that resulted to higher income for fishermen. Also these results demonstrated that fyke net had less pressure on environment of Anzali Wetland.