Showing 3 results for Population Dynamic
Ebrahim Minabi , Gholamhosein Mohamadi , Gholamreza Eskandari , Mehran Javaheri , Reza Hakimi , Khalil Minabi,
Volume 1, Issue 2 (9-2009)
Abstract
This experiment was conducted in earthen ponds of the Azadegan fish culture site, Ahvaz, Iran. In this method (two - crop at year) in first stage pond were stocked at rate of 1000 silver carp fingerlings (92. 30±2.77 g), 1000 common carp (10.47±2.64g), 200 grass carp (101.43±14.92g), 200 bighead carp (107.17±14.26g) per hec. in second stage, pond were stocked at rate of 1000 silver carp fingerlings (130.80±5.77 g), 1200 common carp (9.57±2.45g), 200 grass carp (118.92±12.95g), 200 bighead carp (161.13±9.43g) per hec. In common method (one crop at year) pond were stocked at rate of 1200 silver carp fingerlings (71.23±2.62g), 1200 common carp (2±0.5g), 200 grass carp (75.07±4.42g), 200 bighead carp (79.70±3.21g) per hec. After culturing period in both systems (130, 215, 332 days) crop were harvested. The results showed that production of two-crop method was 7151 Kg/ha and in the other method was 6516 Kg/ha. The profits of two-crop system was 77196000 rials(≈8345 US$) while in the other method (one crop in year) was 37008000 rials(≈4000 US$).
Seyed Ahmad Reza Hashemi , Gholamreza Mohammadi , Gholamhossen Eskandary,
Volume 1, Issue 3 (6-2009)
Abstract
The present study was carried out growth and mortality Parameters of Hilsa shad in the coasts of Khuzestan province (including Abadan and Hendejan ) using the commercial catch data. Totally more than 13000 specimens of Hilsa shad have been measured during 2007-2008. Population parameters were estimated using FiSAT software program. The growth parameters of von Bertalanffy equation were estimated as, L∞: 54.60 and K: 0.96 and t0: -0.14. Mortality coefficients such as total mortality, Z: 4.20and natural mortality, M: 1.34 and fishing mortality, F: 2.8 were estimated. Exploitation ratio, E was estimated to be 0.68 and these high values of E showed that the Hilsa shad stock in the region was overexploited. Results showed that exploitation ratio of the hilsa shad stock was over fishing and decreases exploitation ratio proposed. According to biological characteristics and with compare to American Fisheries Society (AFS) indices, Hilsa shad is classified as low vulnerable group fishes.
Mohammad Taghi Azhir , Touraj Valinasab , Hamiedreza Jamalzadeh,
Volume 4, Issue 2 (9-2012)
Abstract
During the years 2003-2004, some biological aspects of black pomfret, Parastromateusniger, have been investigated in the Oman Sea along Sistan-Baluchistan Province. Based on the frequency of developed maturity stages (stages IV, V), a prolonged spawning activity with two peaks was designed from March to December a major one in August and a minor one in March was considered. According to Lm50percentage (39cm) and catching fish with 39cm and above, the stretched optimum mesh size of nets was calculated as 167.7mm. Based on stomach contents, annelids and shrimp larval showed the highest contribution (29% of the total frequency). Population dynamics parameters were determined through length based modals and the exploitation rate was estimated E = 0.54, suggesting a high-level exploitation. The length infinity (L∞), natural mortality (M), fishing mortality (F), total mortality (Z) and growth coefficient per year (K) were 69.1, 0.57, 0.93, 1.5 and 0.26 respectively. also the fish length-weight relationship was determined and parameters a, b and r (correlation coefficient) were obtained as 0.048, 2.8121 and 0.98 respectively.
