علوم زیستی دریا
Ali Sadough Niri; Ehsan Kamrani; Iman Sourinejad
Abstract
The present study was conducted to investigate length selectivity and determine optimal meshsize for fishery of Longtail Tuna (Thunnus tonggol) surface drift gillnets in northeast of Oman Sea and fishing grounds of Chabahar, Konarak and Ramin (Sistan and Baluchistan Province) from October 2016 to June ...
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The present study was conducted to investigate length selectivity and determine optimal meshsize for fishery of Longtail Tuna (Thunnus tonggol) surface drift gillnets in northeast of Oman Sea and fishing grounds of Chabahar, Konarak and Ramin (Sistan and Baluchistan Province) from October 2016 to June 2017. Fishing gear was included Longtail Tuna surface drift gillnets with 100, 110, 130 and 165 mm stretched mesh size. During 45 stages of navigation with fiberglass boats and wooden vessel, 477 fish specimen were caught, which recorded length frequency data, total weight, and operculum and body girth. A total of 228 samples were Dissected and their ovarian maturation stages were determined to estimate the length of sexual maturity (Lm50). The minimum, maximum and mean (± standard deviation) fork length of the samples were 32, 90 and 55.1±13.35 cm, respectively. Operculum girth-fork length and maximum girth-length relationship were obtained as: Gop = 0.5379 FL+0.4955 and Gmax = 0.5879 FL+ 0.5095, respectively. Size at first maturity (Lm50) of Longtail Tuna was obtained 53.7 cm FL. Using Sechin selectivity method, optimal catch size of 100, 110, 130 and 165 mm gillnet mesh sizes were determined as: 35, 38, 46 and 57 cm, respectively. Using selection coefficient and Lm50, standard mesh size for fishing Longtail Tuna were determined 170 mm. Due to the fact that immature fish are not caught by a 165 mm mesh, this mesh may be suitable, and this confirms the calculation of the standard mesh size of this net by the Sachin method.
علوم زیستی دریا
Mehran Parsa; Seyed Yousef Paighambari; Ehsan Kamrani; Ali Nekuru
Abstract
CPUE, CPUA and biomass of Pomadasyskaakanassessed in the waters of Bushehr province in 2011. The study area was divided into three areas (Northern, Central and Southern) and depth zones (10-20, 20-30 and 30-50 m). In this study,a stratified random sampling was used to collect data. Samples were taken ...
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CPUE, CPUA and biomass of Pomadasyskaakanassessed in the waters of Bushehr province in 2011. The study area was divided into three areas (Northern, Central and Southern) and depth zones (10-20, 20-30 and 30-50 m). In this study,a stratified random sampling was used to collect data. Samples were taken from 45 stations. Total length and mean total length were calculated 27-56 cm and 42.7±4.95 cm, respectively. Total biomass was estimated to be approximately 5943.55 tonnes. Total CPUE and total CPUA were calculated 803.25 kg/h and 9269.05 kg/nm2, respectively. The lowest mean CPUE was observed in 20-30 m depth zone with 8.82 kg/h and the highest mean CPUE was observed in 10-20 m depth zone with 21.45 kg/h. The lowest and highest mean CPUA were calculated in 20-30 m depth zone with 95.91 kg/nm2 and 10-20 m depth zone with 259.35 kg/nm2, respectively. Also, the central area of Bushehr province showed the highest CPUA with 8913.9 kg/nm2. The results of this study showed that the highest distribution and biomass of Pomadasyskaakanare concentrated in the central areas and 30-50 m depth zones.