The study described some biological characteristics of four commercially important fish species in Iraqi marine waters including Planiliza klunzengeri, P. subviridis, Acanthopagrus arabicus and Otolithes ruber from February 2020 to January 2021. The length and weight of individual fish caught were measured. The length-weight relationships were W= 0.027L2.715 for P. klunzengeri, W= 0.034L2.670 for P. subviridis, W= 0.030L2.867 for A. arabicus and W= 0.023L2.755 for O. ruber, and all species indicated negative allometric growth. The lower values of the relative condition factor (Kn) were found at the mid-lengths of P. klunzingeri and P. subviridis, and the large individuals for A. arabicus and O. ruber. Scales were used for age determination and measurements, and the back-calculated lengths-at-ages were calculated using the body proportional formula. Asymptotic total lengths (L∞) estimated were 29.6, 32.8, 44.9 and 70.6 cm for P. klunzengeri, P. subviridis, A. arabicus and O. ruber, respectively. These results could assist in fisheries management for the sustainable exploitation of these commercially important species in Iraqi marine waters.
The present study consists of the growth, mortality, relative yield recruit and virtual population analysis of tigertooth croaker, Otolithes ruber from Iraqi marine waters, northwest Arabian Gulf between February 2020 and January 2021. Analysis of population dynamics employed methods fitted in FiSAT II software using pooled length-frequencies. A total of 3835 individuals of O. ruber ranged from 17.0 to 60.0 cm have been collected. The exponent (b) of the length-weight relationship was found to be 2.755. The von Bertalanffy growth parameters (L∞ and K) were estimated as 68.5 cm and 0.36, respectively, while the growth performance index (Ø') was 3.228. The total mortality (Z) was calculated as 1.10, while the natural and fishing mortality rates were 0.69 and 0.41, respectively, and the current exploitation rate (Ecurrent) was 0.38. Fish were recruited to the fishery at a mean size of L50= 20.55 cm. The recruitment pattern of O. ruber was continuous throughout the year with two major peaks. The analysis of yield-per-recruit (Y/R’) indicates that the current exploitation rate was below the biological target reference points (E0.1 = 0.40 and Emax= 0.53), refer to the stock of O. ruber is underexploited. The 27 cm length group was more vulnerable to fishing and more harvested according to virtual population analysis. sLength at first capture was higher than the length at first maturity of the species in the region. For management purposes, more yields could be obtained by increasing the mesh sizes of the nets employed in the fishing of the species.
In this study, the population dynamics of the Arabian yellow fin sea bream, Acanthopagrus arabicus in the Iraqi marine waters, Arabian Gulf were assessed, to contributing towards the development of management plans for its sustainable exploitation. A. arabicus is one of the species caught in large quantities as commercial by artisanal fishers. Fish samples were collected by the Shaheen steel-hulled dhow and from the artisanal fishermen from February 2020 to January 2021. The length-weight relationship was described as W = 0.030L 2.867 , indicating a negative allometric growth pattern. Of 3484 individuals ranging in total length from 13.0 to 41.0 cm were used to evaluate the growth and mortality parameters. The asymptotic length (L∞), growth rate (K) and growth performance index (Ø') were 44.6 cm, 0.34 and 2.830, respectively. The total mortality (Z) was calculated as 1.17, while the natural and fishing mortality rates were 0.75 and 0.42, respectively, and the current exploitation rate (Epresent) was 0.36. Length at first capture (L50) was 21.9 cm. The recruitment pattern occurs throughout the year, with two recruitment peaks. The yield per recruit analysis indicates that the current exploitation rate was below the economic yield target and the maximum sustainable yield, indicating that this stock underexploited. Virtual population analysis results showed that the mid-lengths (16-22 cm) experienced the highest fishing mortality. So, for management purposes, more yields could be obtained by increasing the fishing activities on this species for a substantial harvest.
The stock assessment of Klunzinger's mullet, Planiliza klunzengeri was conducted, to estimate its some aspects viz. growth, mortality, recruitment, yield-per-recruit and virtual population analysis in Iraqi marine waters, northwest Arabian Gulf, Iraq, from February 2020 and January 2021. The population parameters were analyzed by the FiSAT software using monthly length-frequency data collected by the Shaheen dhow and from the artisanal fishermen at the fish landing site in Al-Fao city to derive information required for their management. A total of 3319 individuals of P. klunzingeri ranged from 11.0 to 27.0 cm have been collected. Length-weight relationship was calculated as W= 0.026L2.716. The asymptotic length (L∞), growth rate (K) and the growth performance index (Ø') were 29.8 cm, 0.34 and 2.48, respectively. The rates of annual instantaneous of total mortality (Z), fishing mortality (F), natural mortality (M) and present exploitation (Epresent) were 1.19, 0.84, 0.36 and 0.30, respectively. The recruitment pattern of P. klunzingeri was continuous throughout the year, with one peak during May. The results of virtual population analysis revealed that the majority of P. klunzingeri were harvested between 14 cm and 19 cm. The length at first capture (L50) in the current study was higher than the length at first maturity (Lm) of the species in the region. The Epresent was below the biological target reference points (E0.1= 0.770 and Emax= 0.903), referred to the stock of P. klunzingeri is underexploited. Therefore, the harvest level should increase to its maximum sustainable yield level by increasing fishing effort level with monitoring surveys and evaluate the risk associated with fishing effort increases as fishing precautionary approaches.
The growth, mortality and stock parameters of greenback mullet, Planiliza subviridis from Iraqi marine waters, northwest Arabian Gulf was assessed using FiSAT II software for length-frequency data collected from February 2020 to January 2021. P. subviridis is one of the species caught in large quantities as commercial by artisanal fishers. Fish samples were collected by the Shaheen steel-hulled dhow and from the artisanal fishermen. The total length and body weight relationship of fish was estimated as W= 0.034L2.670, indicating negative allometric growth. Of 3350 specimens, growth and mortality parameters were evaluated. The asymptotic length (L∞), growth rate (K) and growth performance index (Ø') were 33.8 cm, 0.30 and 2.535, respectively. The total mortality rate (Z), natural mortality rate (M), and fishing mortality rate (F) were 1.11, 0.74 and 0.38, respectively. The present exploitation rate (Epresent) of P. subviridis computed as 0.34. Length at first capture (L50) was 17.47 cm. Recruitment of P. subviridis was observed throughout the year, with a peak during July. The yield per recruit analysis indicates that the current exploitation rate was below the biological target reference points (E0.1 and Emax), which refers to the stock of P. subviridis is underexploited. Virtual population analysis results showed that mid-lengths (16-22 cm) experienced the highest fishing mortality. The length at first capture (L50) was higher than the length at first maturity (Lm) of the species. So, for management purposes, more yields could be obtained by increasing the fishing activities on this species for a substantial harvest.
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