Biological investigation of tiger-toothed croaker, Otolithes rubber, in Oman Sea along Sistan and Baluchistan Province

During the years 2003-2004, biological aspects of Tiger-toothed Croaker, Otolithes rubber, was investigated in Oman Sea along Sistan and Baluchistan Province. Based on the frequency of developed maturity stages (IV, V), a prolonged spawning activity extending from August to March was determined for O. rubber. The gonadosomatic Index (GSI) suggests two peaks which a minor one in October and a major one in March-April. Comparison of hepatosomatic Index (HI) and Condition Factor with the spawning peak indicated a reverse relationship. According to length at first maturity (Lm50%= 40cm) data and exploitation of fish at lengths more than 40cm, the stretched optimum mesh size of nets was calculated at 100mm. Analysis of stomach food items, showed that fish group dominated the diet (80%), of which Anchovy accounted for 40% of the total frequency. We estimated the exploitation rate of the fish at E= 0.6. The length infinity (L∞), natural mortality (M), fishing mortality (F), total mortality (Z) and Growth Coefficient per year (K) were calculated at 68.6, 0.69, 1.05, 1.74 and 0.35 respectively. The relationship between length and weight of the fish in the province was also determined. The parameters a, b and r (correlation coefficient) of the relationship were 0.0085, 3.0435 and 0.98 respectively

Catch per unit area of batoid fishes in the northern Oman Sea

We report on results of a trawl survey to assess the abundance of Batoid fish resources in the Oman Sea. The catch per unit area CPUA as the main index was estimated. The objectives of this study were to determine the catch composition and distribution pattern of Batoid fishes in the study area and in different depth strata of the Oman Sea. A total of 82 stations were randomly selected 2012. The comparison between 5 strata indicated that, the highest CPUA was found for strata E, Beris to Gowatr (2712.56 kg / nm^2) and C, Gordim to Konarak (2079.17 kg / nm^2) and the lowest one was found in stratum B, Darak to Tang (27.11 kg / nm^2). Also the comparison of mean CPUA in different depth-layers revealed that the mean CPUA has a descending trend with increasing of depth, in which the CPUA values in depth layer 10-20 m were 101.38 times more than depth layer 50-100m

The study of fluctuation of large pelagic stock (yellowfin tuna, skipjack tuna, longtail tuna, Narrow-barred Spanish mackerel) in order to optimum exploitation in the Persian Gulf & Oman sea

The study of fluctuation of large pelagic stock (yellowfin tuna, skipjack tuna, longtail tuna, Narrow-barred Spanish mackerel ) in order to optimum exploitation in the Persian Gulf & Oman sea This study was carried out from 2005-07 in order to acquire some biological characteristics and population dynamic parameters for stock management and responsible fisheries. Thunnus albacares (yellowfin tuna), katsuwonus pelamis (skipjack tuna), Thunnus tonggol (longtail tuna) and scomberomorus commerson (Narrow- barred Spanish mackerel) were sampled. In total, length frequency of 9345 specimens of yellowfin tuna were analyzed. Size range was 37-172 cm. Teleost fishes were the most dominant prey species observed in this study (42%), Occurrence of Potunus Pelagicus was found to be the second (28%).Sthenoteuthis oualaniensis (22%), Natosquilla (5%) and octopus (3%) also were identified in the gut content of the yellowfin tuna. Length of maturity (50%) of yellow fin tuna was estimated 77.2 cm and spawning season was started from May. 8443 specimens of skipjack with size range of 32-90 cm were sampled. 48% of food items were teleost fishes. Squid and shrimp were also identified. Spawning season was begun from June. Growth parameters & fishing mortalities of yellow fin tuna and skipjack tuna were also estimated. Size range if longtail tuna was from 26-125cm Length infinity was estimated 132.3 cm with growth parameter of 0.35 per year. In total 10451 specimens of narrow- barred Spanish mackerel were sampled. Size range was from 20-164 cm. Teleost fishes were the most dominant prey species observed in the study (91.3%). Crustaceans (0.6%) and Indian squid (0.2%) also were identified in the specimens. Length maturity (50%) was estimated 83.6cm

Growth performance and age composition of Salmo trutta caspius in Iranian part of Caspian Sea

The aim of this project is to study the growth and age structure in the Caspian trout, comparison with other coldwater species and check the trend of these parameters in recent years. This study was conducted during 2013 till 2015. Totally, 43 specimens for back calculation and 101 specimens for biometrical study of the Caspian trout have been caught in two month period. Biometric parameters such as length, weight and age of the fish were recorded. Base on Back calculation method in 1393, the average length of fish at ages 1, 2 and 3 years old were 18.98 ± 3.5, 30.5 ± 7.24 and 41.7 ± 9.1 cm. So these age groups are under the adult age and don’t approaching to near the beach and rivers for spawning behavior. Therefore, these length groups cannot be observed in catch composition. The result showed, the mean of gonad weight in this fish was about 11 percent of total weight and number of eggs per gram of gonad calculated about 10.8 numbers. Minimum age and maximum age of this species determined 4 years and 7 years (mean = 5.6) and the most frequency allocated to 5 age group and the frequency of 6 and 7 years has been remarkable. The average length of salmon was 69.2 ± 6.2 cm (minimum 57 and maximum 81 cm) and the average weight was measured 3323 ± 677 g (2400 to 5600 g) in the catch composition. Growth parameters such as k, L_∞ and ø’ was measured 0.18, 104 cm and 3.289 respectively. The amount of b for relation length and weight was 2.9 which imply negative allometry. L_∞ and growth coefficient (K) on the Caspian trout were acceptable range, that it shows good growth the fish in the sea water. Most of the fishes were catched from Cheshmehkileh River. As at present Shilat uses just the broods of the Tonekaboon region for restocking of this species, we recommend using the broods of the western region separately for rehabilitation of the stocks of this region