Non-commercial fish species of shrimp trawls were studied monthly from October 2005 to September 2006 in Mahshahr creeks (Darvish, Doragh, Bihad, Ghazaleh, Ghanam, Zangi and Patil). The trawl nets had a cod-end mesh size of 24mm. Total catch was 6431 individuals weighing 55.5kg, and included 14 species of non-commercial fish species belonging to 14 families. The caught shrimp species were from Penaeidae; comprising only 30% of the total catches (4506 individuals weighting 44kg).Dominant species were Lieognathus bindus (54.8%), Metapenaeus affinis (18.2%) and Parapenaeopsis stylifera (9.8%). Maximum fish abundance was observed in March 2005 (98/3%) and for shrimp in June (66.2%). Bihad creek had the maximum percentage of fish (91.8%) by-catch and shrimp (42.9%) abundance. We conclude that the by-catch percentage of non-commercial fish is higher than shrimps in the study areas. Warm months witnessed the highest abundance of shrimp while January-March was the time period when by-catch was most abundant.

The present study was conducted to investigate the species composition, length frequency composition and by-catch amount in longtail tuna pelagic gillnets in northeast of Oman Sea and fishing grounds of Chabahar, Konarak and Ramin (Sistan and Balouchestan Province). Sampling operation was carried out using the fiberglass boat and wooden vessel from October 2016 to June 2017. Fishing gear was included longtail tuna pelagic gillnets with 100 and 110 mm stretched mesh size in fishing boats and gillnets with 130 and 165 mm stretched mesh size in wooden fishing vessels. Totally, by-catch species composition were 15 species belonging to 8 family including Scombridae, Istiophoridae, Coryphaenidae, Alopiidae, Carcharhinidae, Carangidae, Sphyraenidae and Trichiuridae. The significantly variation of by-catch species composition observed in used nets by boats and wooden vessels. In the entire study period, in boats, minimum and maximum catch amount was related to Carcharhinus sorrah with 35 kg and Euthynnus affinis with 1622 kg, respectively. Maximum catch was obtained for Euthynnus affinis as 260 kg per each netting and fishing operation. Maximum mean catch (± S. E) was obtained to Euthynnus affinis as 47. 71± 9. 26 kg per each fishing operation. In wooden vessels, minimum and maximum catch amount was related to Alopias pelagicus with 93 kg and Thunnus albacares with 90013 kg, respectively. Maximum catch was observed for Thunnus albacares as 8219 kg per each netting and fishing operation. Maximum mean catch (± S. E) was related to Thunnus albacares as 1250. 18± 186. 61 kg per each fishing operation.

According to recognition and abundance of larve of commercial fish, caught during shrimp fishing season in eastern Chahbahar in the period of 7 to 27, November 1999, sampling was conducted from catch component during this time. Randome sampling was done 3 days a week for 3 weeks. Catch composition in this research divided to six groups, Osteal fish with 92.88% and Echinoidae with 0.12% has maximum and minimum frequency respectively. In catch composition 45 different marine species were identified and between commercial fish, 8 species were studied, but more study was done on Pampus argenteus, which has the most aboundance. It has the maximum frequency in length 8 and 10cm. The minimum and maximum size of this species was 3 and 19.5cm, respectively. Besides this research was determined all commercial fish catched in larvale and juvenile stage.

The aim of this study was to determine the catch composition differences (morning and evening) during the fishing season of ribbon fish (Trichiurus Lepturus Linnaeus 1785) in the winter of 2020 from the Hormozgan province. The fishing operation was carried out by a mid-water trawler for a week from 6 am. to 6 pm. The average duration of each hauling was 4 hours and the depth of hauling was recorded between 58-68 meters. The ship was equipped with a trawl net with a 41-m head rope and a 75 mm stretched mesh size in the codend. Results of 21 hauling, 23 fish species belonging to 17 families were identified. The frequency of target fish (ribbon fish) was calculated 12719 fishes, with total catch of 21423 kg and CPUE of 1020.14 kg/hauling. The total by-catch was recorded 1828.28 kg, and CPUE of 87.10 kg/hauling. There were no significant differences between total catch of target fish, total by-catch in the morning and evening time, also CPUE and CPUA of target fish(p>0.05). The highest participation rates of fishes were croakers (4.85%), wolf-herring (3.03%), king soldier bream (2.65%), four-finger threadfin (2.59%), queen fish (2.50%), barracuda (2.29%), lizardfish (2.22%), pick-conger (2.01%), king mackerel (1.93%) and trevally (1.85%) respectively.

The present study was carried out in the fishing grounds of small pelagic fish on Qeshm Island (namely Ramcha, Souza, Messen, and Salakh) from September 2022 to June 2023. Field sampling was performed by double-boat purse seiners and conducting 57 netting. The length, height, and mesh size of purse seines were 300 m, 50 m, and 10 mm (STR). Data of date, time of setting, location, and weight of target species and bycatch were recorded for each setting net. The mean CPUE (±95% CI) of small pelagic fish was overally obtained at 991.23 ± 157.14 kg per set. This was 1300 ± 364.01 for Salakh, 1246.88 ± 295 for Ramchah, 669.23 ± 214.20 for Messen, and 587.5 ± 155.71 for Souza, which there was a significant difference between Salakh and Ramcha compared to Souza and Messen (P<0.01). Also, the mean CPUE (±95% CI) of target catch for warm and temperate seasons were 1227.42 ± 224.11 and 709.62 ± 174.20 kg per setting net, which was significantly differ (P<0.01). The maximum and minimum of occurrence percentages were attributed to anchovy (with 100%) and Trichiurus lepturus (with 1.75%). The highest and lowest of mean CPUE (±95% CI) for bycatch species/groups, were related to the Trichiurus lepturus (1.75 ± 3.51) and Dasyatidae (0.07 ± 0.10) kg per setting. Given that fishing efforts have increased in recent years in the region, the estimated values of CPUE for target catch were smaller than in previous studies. Therefore, the fisheries managers must take immediate action to optimize the ongoing fishing effort.

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.

In an attempt to recognize the harmful fishing times and locations for sturgeons, we used catch statistic to evaluate by-catch of sturgeon juveniles during beach seine fishing over the years 2001-2002 in Mazandaran Province. We found that over the fishing period, 23760 hauls were conducted during which 103000 sturgeons were caught. The highest by-catch occurred in October (37% of the catch) and the lowest occurred in January (5% of the catch). The maximum sturgeon catch per haul was 14.2 in autumn decreasing through the year with 1.26 sturgeon fish caught in each haul in spring. The species composition of the by-catch sturgeon juveniles was determined to be Persian sturgeon (54%), Stellatus sturgeon (37%), Beluga (6%), Russian sturgeon (2%) and Spiny sturgeon (1%).

This paper is a comprehensive study of the shrimp trawl by-catch from Bushehr coastal waters (N. Persian Gulf). Sampling operation was carried out in two shrimp fishing seasons using the (Saber and Jahanara) commercial trawlers Generally, 87.5% of the total catch was by-catch and 12.5% was target species (shrimp). The catch composition included: 114 species from 45 teleostei families, 13 species from 7 elasmobranchs families and 13 species from 13 invertebrate families. Species composition of By-catch included: 72% teleosts, 14% elasmobranchs and 13.9% invertebrates. By-catch-to-shrimp ratio, CPUE index and catch percentage of species (based on Wt %) were computed. On average By-catch-to-shrimp ratio was estimated 7:1. It's estimated that 283.4 tonnes of By-catches are taken annually in Bushehr coastal waters by 12 steel trawlers.

Fishing vessels equipped with bottom trawls cause high amount of by-catch and discards. We investigated the catch composition and by-catch percentage in October -November 2002 during shrimp fishing season in Hormuzgan Province waters. The studied area was located in Dar-Soorkh area, east of Hormuz Island and Toola area. Sampling was done using wooden fishing dhows. During shrimp season, 36 hauls with a total catch of 6050kg were treated. The catch composed of 88 species belonging to 50 families of which 67 species were bony fish from 38 families, 9 species were cartilaginous fish from 6 families, and 3 species were mollusks from three families and also 9 species of crustacean were found belonging to 3 families. The percentages of different groups of by-catch and target catch (shrimp) were 49.4% small discards, 18.7% large discards, 4.7% commercial species and 27.2% shrimp. The ratio of total by-catch to shrimp was estimated to be about 2.7 times that of the shrimp.