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.

This study aimed to design a bycatch reduction device (BRD) for shrimp beam trawl, which is manufactured by flexible materials to reduce bycatch for the gear in the South Sea of Korea. The model test was carried out to understand the shape of the gear in the water and to measure the variation of flow speed due to the BRD in a circulating water channel. Catches were compared between a shrimp beam trawl without BRD (control gear) and others with BRD (treatment gears) in the field. BRDs were two different types in this study. In the case of BRD (a), a square-shaped grid net and a funnel-shaped net were installed in the front part of the cod end to help fish sorting and expelling through the outlet at the bottom. BRD (b) has one more outlet which is added at the upper part of the BRD (a). On the model test, water speed was reduced a little in the gear by installing the BRD. At the results of comparing with a control gear, the bycatch (%) of fish excluding shrimp was reduced between 17 and 68% using BRD (a) and 5 and 66% for BRD (b) respectively. By the signed test of significant level 0.05, the quantity of shrimp catches for BRD (a) was not different in comparison to the control gear but it decreased for the gear installing BRD (b).

The effect of different bycatch reduction devices in decreasing bycatch of commercial fish species with the length of less than LM50 (the length from which, 50% of them are matured) in shrimp trawlers were examined. The experiments were conducted in Persian Gulf (Bushehr and Hormuzgan provinces) during the shrimp season, years 2000-2001.In this study four types of bycatch reduction devices (Grid, Nafted, Fish eye and Square mesh window) were used. Double rig trawl was used, one of them as an experimental trawl and the other as the control.Different treatments like one device or two devices were installed on experimental shrimp net. After hauling the trawl, frquency of different commercial species with length less than LM50 was determined in both nets, and the results were tested with Paired Willcoxon test. The results have shown that although all the devices have a reductional effect on bycatch of the young and juveniles of commercial species, but the amount of reduction with setting Nafted and Grid, either single or combined with another BRD was significantly higher than the control one (P ≤ 0/05). The amount of by catch reduction devices with different treatment (different devices either single or paired) according to the season of the experiment were also tested with Kruskal- Wallis test, which shows significant differences (P≤0.05) between the frquency of young and juvenile individuals of some species during different experimental seasons.According to this study, by using Nafted and Grid devices in the trawl nets of all shrimp vessels during its season, about 400 to 500 thousand of juveniles and young individuals can escape from the nets.

This study aimed to investigate the catch per unit effort of target and non-target species and to determine the bycatch composition in boat trawlers used in Mond and Dayyer-Nakhiloo coastal waters in Bushehr province. Field operations were carried out during the years 2020 (13 August to 15 February) and 2021 (11 April to 9 September). During the research, a 27-foot fishing boat with a 200 hp engine was used. The trawl net used was made of polyamide (PA). The sampling operation was performed in 32 steps. During this study, the amount of catch per unit effort, the ratio of by-catch to the target species, and the amount of by-catch were calculated. The highest frequency of Penaeus semisulcatus in July 2021 (96.67%), the highest frequency of Metapenaeus affinis in August 2021 (21.74%), and the highest frequency of Parapenaeopsis stylifera in July 2021 (63.75%) were recorded in Mond. 37 aquatic species were observed as a bycatch composition during fishing operations. Species including Saurida tumbil, Cynoglossus arel, Portunus segnis, Gerres filamentosus, Drepane punctata, Solea elongata, and Epinephelus coioides were permanently present in the catch composition. The highest rate of shrimp fishing effort was observed in the Mond region (58 kg/h) and the lowest rate was observed in the Dayyer-Nakhiloo (1 kg/h). Also, the ratio of by-catch to target (r) was 2.32 and the weight of by-catch during the fishing season was 1478.96 kg. The results indicate high fishing pressure on commercial and non-commercial species in this area and can be used to assess the damage caused by shrimp trawl nets on fish stocks in ecological risk assessment models. In addition, the findings showed that the deletion of some species can make the food chain longer due to their role in the food chain and reduce the resistance of the ecosystem food web, and ecological and habitat efficiency.

The spatial and temporal variations of finfish bycatch assemblage cutlassfish trawl were compared in two fishing areas (Hormozgan and Bushehr). Data were collected on board of commercial vessels in the fishing grounds of Trichiurus lepturus in Bushehr and Hormozgan marine waters between early May 2010 to late November, 2010. There was a significant difference in the bycatch assemblages between Bushehr and Hormozgan fishing grounds. SIMPER showed that six species contributed as much as 65% of the biomass of the bycatch assemblages between two fishing areas as follows: Nemipterus japonicus (30.5%), Ilisha melastoma (12.5%), Saurida tumbil (8.5%), Argyrops spinifer (6%), Dasyatis bennetti (4.5%) and Arius thalassinus(4%). Differences appeared for the temporal structures of bycatch assemblage in fishing grounds of Bushehr. SIMPER also showed eight species contributed to as much as 69.3% of the dissimilarity of the biomass of the bycatch assemblages between fishing seasons. These species wereS. tumbil (17.3%), I. melastoma(16.3%), N. japonicus (13.3%), Carangoides malabaricus (17.2%), Rachycentron canadun (6.3%), Upeneus sundaicus (3.5%) D. bennetti (3.5%) and Epinephelus coioides (3.2%).

The aim of this study was to investigate catch composition and catch per unit effort of invertebrates in shrimp trawl in different areas and depths. This research was carried out in Hormozgan coastal waters (Bandar Abbas and Hormuz Island) at depths of less than 10 meters, 10-20 meters and over 20 meters in shrimp fishing season in 2015. 40 hauls that duration of each one was approximately 2 to 2. 5 hours with a total catch of 7623 kg were done. The catch composition included 1068 kg of commercial shrimp and 6555 kg of by-catch that included invertebrates and fish which were 2386. 8 and 4168. 2 kg, respectively. The results showed that the catch composition consisted of 14% shrimp (1068 kg), 31% by-catch invertebrates (6555 kg) and 55% by-catch fish (4168. 2 kg). There were significant differences among the CPUE in the different areas and depths as well as the interaction of area and depth on CPUE of the total catch, target species (Shrimp), Oratosquilla oratoria, Portunus pelagicus, Crustacea (Small crab), Sepia pharaonis, Anthozoa, Demospongiae, Rhizostomatidae (Jelly fish), Asteroidea and Octopoda (P<0. 01). The highest percentage of catch occurrence belonged to Oratosquilla oratoria, Rhizostomatidae and Sepia pharaonis and the Demospongiae was at the least.

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.

This study aimed to investigate the lenght frequency and species composition of fish caught in conical lift-net in May 2018 in two fishing ports of Babolsar and Amirabad by four fishing vessels during 33 torrents at a depth of 50-40 m. After identification, the total length and weight of the specimens were measured. Of the 27967 fish samples examined, the highest relative abundance belonged to Clupeonella caspia (98. 98%) and the lowest one Gasterosteus aculeatu (0. 032%). Number of fish caught in the Babolsar and Amirabad ports were 27610 and 357, respectively. Out of 193 fishes, the highest and lowest percentage of relative frequency fish species were for Alosa caspia (37. 8%) for G. aculeatu (4. 7%). The relative abundance of other species in the ports of Babolsar and Amirabad are Syngnathus caspius was 38. 8 and 28%, G. aculeatu 50 and 0%, Mulets 11. 11 and 18. 2%, A. caspia 0 and 41. 7%, Rutilus kutum 0% and 12%, respectively. The results show that the maximum and minimum frequencies in Babolsar port was 99. 86% for Clupeonella caspia and 0. 03% for C. engrauliformis and in Amirabad were 65. 38% and 6. 04%, respectively, for C. caspia and C. grimmi. Among the Kilka fish caught in the two zones, the abundance of C. caspia and C. engrauliformis were highly dependent on the fishing region (P<0. 01). The results show that maximum lenght abundance of conical lift net in Babolsar and Amirabad fishing ports are 11. 5-12. 5 cm.

In this study, sampling of commercial vessels of Afsoon 1 was carried out in July 2020, at a distance of more than 10 miles in longitude24 50 to 24 60 and latitude 61 03 to 61 05. At the time of the study, trawl fishing was done 13 times at different times, 8 times during the day and 5 times at night. The total catch during the study period was 12306 kg and 8720 kg were caught during the day (about 71%) and 3586 kg at night (about 29%). The average catch per fishing effort (catch per hour) of the target species was 201 kg (67%) during the day and 63 kg (33%) at night, and the average catch per fishing effort (catch per hour) discard species were 71 kg (28%) during the day and 100 kg (59%) at night (P <0.05). The mean catch per fishing effort (catch per hour) of bycatch fishing species at 18 kg during the day and 9 kg at night were not significantly different from each other (P> 0.05). The Trichiurus lepturus species (64%) had the highest catch of target species, Epinephelus coioides species (53%) had the highest catch of bycatch fishing species and Ray fish (88%) had the highest catch of discard species. The Siganidae and Megalaspis cordyla species, appear to be active during the day and pipe fish, Anguiliformes and Belonidae species of night active.