Summary
The length–weight relationships (LWR) for three fish species collected in Sirwan River, located in Kurdistan and Kermanshah provinces, western Iran, were estimated. The values of the slope parameter (b) in the length–weight relationship equations were determined as 3.086 for Alburnus mossulensis, 3.382 for Alburnus filippii and 3.425 for Capoeta damascina, all significantly different from the expected b = 3 value, indicating a positive allometric growth pattern for all the three species.
The aim of this study was to record the length-weight relationship parameters and condition factors for some commercially important fish of Bushehr coastal waters of Persian Gulf. The length-weight relationships were calculated for five species caught during fishing surveys using different types of fishing gears (trawls, pots and gill net with different mesh size) during April 2008 to December 2010. The b value ranged between 2.733 for Argyrops spinifer and 3.03 for Epinephelus coioides. The coefficient of determination (r 2 ) was very significant for all the species. Relative weight had significant differences (Kruskal-Wallis test, P<0.001) with best performance by E. coioides. This results show that this range size of specimens in these populations apparently do not reach and surpass 100% of mean weight. In this study, length-weight relationships and condition factors are reported for the first time for A. spinifer, Pomadasys kaakan and Lutjanus malabaricus from the Persian Gulf and for Lethrinus nebulosus and Lutjanus malabaricus ruber which has not been previously recorded in the Iranian waters.
Cutlassfish trawl fisheries have been used in the Persian Gulf, but very little information about species composition of the large rates of bycatch caught in this region is available. The data on total species composition of 40 hauls from vessels operating off the fishing grounds of Persian Gulf was collected from May 1 st 2009 to 10 th August 2010. From the estimated 952.3 tonnes of bycatch taken annually in the fishing grounds of cutlassfish, 39 species from 32 families were obtained which include: 30 teleost species with 88.3% of the total biomass (841.4 t) from the main composition of the catches and followed by 7 elasmobranchs with 8.3% (79.7 t) and 2 invertebrate with 3.3% (31.2 t) of the biomass. With 554.3 tonnes (58.2% of the total biomass), the major species in trawl bycatches were Nemipterus japonicas (234.1 t), Saurida tumbil (229.5) and Ilisha melastoma (90.5%). There was a significant difference in the total bycatch taken (biomass and number) from different depths. Some mean catch rates of the abundant species differed significantly between seasons which displayed dial differences in their catch values. This study provided the first comprehensive study of the species composition of cutlassfish trawl in fishing grounds of Bushehr waters in the Persian Gulf. The examination of the bycatch indicates the large impact on stocking density of commercial and non-commercial species in this region; which with respect to decline in stocking density of demersal fishes of Persian Gulf in recent years, has caused increasing concerns. The data collected in this study can be used in the quantitative assessments of fisheries pressure on bycatch stocks in the Persian Gulf.
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