Population dynamics and management of two cichlid species in the Shatt Al-Arab River, Iraq

Abstract

Cichlids are invasive fish to Iraqi waters and became well established and prevailing in different waters. Despite that, there is no stock assessment study conducted for these fish. So, growth, mortality, recruitment and yield-per-recruit of two cichlid’s species; Coptodon zillii and Oreochromis aureus from the Shatt Al-Arab River, Iraq were evaluated from November 2015 to October 2016 using the FiSAT software. A total of 1285 C. zillii (2.9-24.0 cm TL) and 1353 O. aureus (4.5-25.0 cm TL) were examined. Length-weight relationships were derived, indicating allometric growth for both species. The growth parameters (L?, K, Rn, to and ?) obtained for C. zillii were 25.5 cm, 0.320, 0.212, -0.793 and 2.318, respectively, while for O. aureus were 27.8, 0.490, 0.214, -0.271 and 2.578, respectively. The annual rate of total mortality (Z), fishing (F) and natural (M) for C. zillii was found to be 1.51, 0.84 and 0.68 respectively, and for O. aureus 2.49, 1.08 and 1.41, respectively. The present exploitation rates (Epresent) for C. zillii and O. aureus were computed to be 0.454 and 0.57, respectively. Lengths at first capture (LC) were 12.97 cm for C. zillii and 13.25 cm for O. aureus. The peaks of recruitment of C. zillii and O. aureus were from February to May and May to July, respectively. The Epresent for C. zillii and O. aureus were below the biological target reference points (F0.1 and Fmax), indicating that these species were not overexploited. For management purposes, more yields could be obtained by an increase in the fishing activities on cichlids.

Population Dynamics and Management of Invasive Blue Tilapia (Oreochromis aureus) in Garmat Ali River, Basrah, Iraq

“…However, some authors used scales for determining age and growth, and also reported mortality and yield-per-recruit of O. aureus such as [16] in Rosetta branch of the Nile River, Egypt and [17] in Nozha Hydrodrome, Egypt. Recently, the population dynamics and management of O. aureus in Shatt Al-Arab River, Iraq has been reported by Mohamed and Abood [18], and the present study is a continuation of investigation on this species in Iraq.…”

“…The growth parameters obtained in this study eported from different geographic locations which were obtained by applying FiSAT II software and scales analysis are presented in ∞) in this study was higher than those recorded for this species Rosetta branch, Shatt Al-Arab River, Iraq [18], whereas these were lower than those found in Aguamilpa Reservoir, Mexico Nozha Hydrodrome, Egypt [17]. The value of K was within the range observed in other populations of O. aureus, where the lowest value (0.21) was documented by Mahmoud et al [17] from the Nozha Hydrodrome, Egypt, highest one was 0.56 reported by Mehanna [13] from the El-Raiyan Lakes, Egypt.…”

“…The values of Z, M and F obtained were within the ranges of these parameters observed in other populations of the species. The present exploitation rate (E present ) was 0.43, and the lowest value of E for the species was 0.40 recorded by Mahmoud et al [17] from the Nozha [18], whereas these were lower than those Aguamilpa Reservoir, Mexico [15] and [17]. The value of K within the range observed in other , where the lowest value Mahmoud et al [17] Nozha Hydrodrome, Egypt, and the highest one was 0.56 reported by Mehanna [13] Raiyan Lakes, Egypt.…”

Growth, Mortality and Yield-per-recruit of Nile Tilapia (<em>Oreochromis niloticusM/em>) in Garmat Ali River, Iraq

“…Also, El-Kasheif et al [11] noted that the values of Epresent, E0.1 and Emax were 0.43, 0.51 and 0.64, respectively for the species in El-Bahr El-Faraouny Canal, Egypt. Mohamed and Abood [31] reported that the exploitation rates for C. zillii and O. aureus in the Shatt Al-Arab river were below the biological target reference points (F0.1 and Fmax), indicated that these species were also not overexploited.…”

“…Consequently, it became necessary to compiled information about the population status of these invaded cichlids in Iraqi waters. Recently, the population dynamics and management of two cichlid species (C. zillii and O. aureus) in Shatt Al-Arab River have been studied by Mohamed and Abood (2020) [31], and the present study is a continuation of investigation on tilapia fish in Iraq.…”