Astock Assessment and Management of Hilsa Shad (Tenualosa ilisha) in Iraqi Marine Waters, Northwest Arabian Gulf - PDF

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World Journal of Fish and Marine Sciences 6 (2): , 2014 ISSN IDOSI Publications, 2014 DOI: /idosi.wjfms Astock Assessment and Management of Hilsa Shad (Tenualosa
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World Journal of Fish and Marine Sciences 6 (2): , 2014 ISSN IDOSI Publications, 2014 DOI: /idosi.wjfms Astock Assessment and Management of Hilsa Shad (Tenualosa ilisha) in Iraqi Marine Waters, Northwest Arabian Gulf 1 2 Abdul-Razak M. Mohamed and Audai M.H. Qasim 1 Department of Fisheries and Marine Resources, College of Agriculture, Basrah University, Iraq 2 Department of Aquaculture and Marine Fisheries, Marine Science Centre, Basrah University, Iraq Abstract: The stock assessment and management of Hilsa shad (Sbour), Tenualosa ilisha in Iraqi marine waters, northwest Arabian Gulf were assessed using FiSAT II software from November 2012 to October Fish total lengths ranged from 12.2 to 48.0 cm and the lengths of 26 to 44cm dominated the population comprising 93% of the total catch. Length-weight relationship was obtained as W= L. The asymptotic growth (L ) was cm, growth rate (K) was The annual instantaneous rate of total mortality (Z) was 1.66 and the natural mortality (M) was Fishing mortality was 1.11 and the exploitation rate was A bimodal recruitment pattern of unequal strength was observed. The maximum yield per recruitment could achieved at E max= 0.72 and L c= 27.8 cm. Result showed that T. ilisha is over exploited and some management policy should be taken to the stock in the areas of migration reproductive and nursery in inlands waters. Key words: Population Dynamic Hilsa Shad Mortality Fishery Management Iraq INTRODUCTION have been recorded in declining T. ilisha fisheries and other species like Zobaidy (Pampus argenteus) in the The Hilsa shad, Tenualosa ilisha, belongs to the waters of Kuwait and Iran which shares in the stocks and family Clupeidae, locally known as sbour in Iraq and fisheries with Iraq [4-6]. other Arabian Gulf countries. Its geographical Several studies have been done on the stock distribution extends from Shatt Al-Arab River, along assessment of T. ilisha at different water bodies, the coasts of Iran, Pakistan, India, Bangladesh and especially in the Indian subcontinent by Rahaman et al. Burma to South Vietnam [1]. The species is largely [7], Nurul Amin et al. [8-10], Halder and Nurul Amin [11], anadromous in nature, migrating up rivers during the Ahmed et al. [12], Rahman and Cowx [13], Milton [14], breeding season and after spawning return to the original Dutta et al. [15] and Panhwar and Liu [16], in Kuwait by habitat where they remain until the next breeding season Al-Baz and Grove [17] and in Iran by Hashemi et al. [18] [2]. and Roomian and Jamili [19]. Little work has been done on T. ilisha form an important part of the marine fishery stock assessment of this species in Iraq by Jabir [20], production of Iraq and are traditionally caught by Mohamed et al. [21] and Mutlak [22]. artisanal fishermen and most of the catches are made by The decline in the catch of T. ilisha punctuated by dhow boats and speedboats using drifting gillnets. fluctuating catch trends during recent years necessitated The percentage of T. ilisha landings during this study. The study deals with estimating the basic constituted 90.2% of total landings and this decreased to parameters required for assessing the status of T. ilisha 52.9% during and to 41.8% and 30.7% during in Iraqi marine water, northwest Arabian Gulf and make and , respectively [3]. Similar findings appropriate management recommendations. Corresponding Author: Razak Mohamed, Department of Fisheries and Marine Resources, College of Agriculture, Basrah University, Iraq. 201 Fig. 1: Study area in the Iraqi marine water, northwest Arabian Gulf MATERIALS AND METHODS log (M) = log (L8) log (K) log (T) Fish samples were collected monthly basis from Iraqi territorial water, northwest Arabian Gulf during November where T is mean annual environmental temperature 2012 to October 2013 (Fig. 1). Fishing operations were which is 21 C. Fishing mortality rate (F) was calculated carried out by steel fishing dhow Zainab, 21.5m from F=Z-M [27] and the exploitation rate (E) from length, 7m width and 2.5m draft with inboard engine of E = F/Z [28]. 240hp. Samples of fish were captured by drift gill nets The recruitment pattern was obtained by backward ( m long and 7m height) with different mesh sizes projection on the length axis of a set of length-frequency (42x42, 48x48 and 57x57mm). Additional random samples data as described in the FiSAT routine. The probability of were collected from artisanal fishermen at fish landings capture was estimated for gill net selectivity and the mean site in Fao city. A total of 3523 fish were collected size at first capture (L c) was derived by plotting the throughout the study period. Total length and weight of cumulative probability of capture against mid-length. the specimens were measured in 'cm' and 'g', respectively. From the resultant curve, L c was taken as corresponding Samples taken to the laboratory were used for estimation to the cumulative probability at 50%. of the length-weight relationship [23]: W=aL, where Relative yield-per-recruit model of Beverton and Holt W is weight (g) and L total length (cm). The length [29] as modified by Pauly and Soriano [30] and frequency data were pooled into groups with 2cm length incorporated in the FiSAT software, was used to estimate intervals. Then the data were analyzed using the FiSAT II the current state of the stock and the yield and biomass, (FAO-ICLARM Stock Assessment Tools) software as using selective ogive procedure. The yield isopleth explained in detailed by Gayanilo et al. [24]. diagram was used to assess the impact on yield created Bhattacharya's modal progression analysis was by changes of exploitation rate E and the ratio of length at applied to identify different cohorts in the monthly length first capture to asymptotic length (L c/l ) in relation to distributions and to estimate the mean length for each changes in mesh size to recommend adequate cohort. Means were then involved in the estimation of the management regimes. growth parameters (L 8 and K) using Fabens method integrated in FiSAT software package. The growth RESULTS performance index (ø) was computed according to the formula of Pauly and Munro (1984) as ø = Log K + Length Frequency Distribution: The monthly samples of 2LogL fish were pooled to produce a single length The total mortality rate (Z) was estimated using the frequency distribution (Fig. 2). No juveniles or young length-converted catch curve [25]. Z was estimated from ( 12cm) were captured throughout the year. The smallest the slope b (with sign changed) of the descending right fish was 12.2cm caught during January, whereas the arm of the curve. Natural mortality rate (M) was estimated largest one was 48.0 cm caught during June. The major following Pauly s empirical formula [26]: peak was at length 30cm and formed 8.1% from the 202 Fig. 2: Length frequency distribution and Bhattacharya's method of separating the cohorts of T. ilisha Fig. 3: Growth curve of T. ilisha by Faben s method Fig. 5: The selection curve for probability of capture of T. ilisha parameters. The asymptotic growth (L ) was 61.47cm and 8 the growth rate (K) was Length of the species at the end of age 1, 2, 3, 4 and 5 was found to be 16.3, 27.1, 35.5, 41.3 and 46.1cm, respectively (Fig. 3). The growth performance index (ø) of T. ilisha was computed as Mortality: The annual instantaneous rate of total mortality derived from the length converted catch curve (Fig. 4) was 1.66 and the natural and fishing mortality were 0.55 and 1.11, respectively. Exploitation rate (E) was Fig. 4: Length converted catch curve of T. ilisha calculated as species population. Fish lengths from 26 to 44cm were Probability of Capture: The selection length of L 25 (25%) dominated T. ilisha population in the region comprising was 26.9 cm, L 50 (50%) was 27.8 cm and L 75 (75 %) was 28.8 93% of the species catch. cm (Fig. 5). Therefore, the length at first capture was 33.74cm (L c) was 27.8 cm. Growth: The length weight relationship of T. ilisha was W= L, r = , TL= cm. The b Recruitment Pattern: The recruitment pattern (Fig. 6) value is significantly differing from value 3 (t= 14.91, shows double annual peak recruitment per year, the first P 0.05), which indicates allometric growth. peak in April (10.74%) is probably due to peak recruitment The mean lengths obtained by Bhattacharya s in migrant breeding stock while the July peak (16.61%) method (Fig. 2) in FiSAT program were linked using modal may be associated with the recruitment of juveniles bred progression method and used to estimate the growth the previous year into the adult stock. 203 The population structure of T. ilisha in Iraqi marine waters indicates that over 93% of the catch was between 26 and 44cm of length, these fish are in the way to breeding grounds or back to the sea after spawning with their progenies. The spawning migrations of the species to Shatt Al-Arab River, east Hammar marsh and other rivers in south Iran have been documented by several Fig. 6: Recruitment pattern of T. ilisha in Iraqi marine authors viz. Hussein et al. [31, 32], Jabir [20], Al-Noor [33], water Al-Hassan [34] and Roomiani and Jamili [19]. Al-Noor [33] stated that only mature individuals of T. ilisha ascend Shatt Al-Arab River during spawning season and larvae and juveniles of the species were available along Shatt Al-Arab River. Also, Mohamed et al. [35] collected larvae of the species from the northern part of Shatt Al-Arab River (Al-Sindibad Island) from March to September. Mutlak [22] mentioned that the increasing of salinity in Shatt Al-Arab River during the last years pushing adult individuals of T. ilisha to enter east Hammar marsh for spawning, after it has been exploited by the species for nursery and feeding activities during [36]. Fig. 7: Relative yield per recruit and biomass per recruit For comparison the published results of estimated curves growth and mortality parameters of T. ilisha derived from length frequency studies, are summarized in Table 1. It can be seen that estimated L obtained in this study is comparable to those in other waters, although is lower than the value recorded for females in Bangladesh waters by Haldar and Nurul Amin [11] and the value reported by Al-Sabbagh and Dashti [37]. The growth performance index (ø) was observed to be within the values mentioned by Al-Baz and Grove [17], Mohamed et al. [21] and Mutlak [22] and lower than those reported by other authors. The natural mortality rate (M) of the species is quite higher than the value mentioned by Al-Baz and Grove [17] and lower than those reported in other waters. Fig. 8: Yield isopleth diagram of T. ilisha The level of the fishing mortality rate (F) was considerably higher than those stated by Al-Baz and Grove [17], Yield-Per-Recruit and Biomass-Per-Recruit: The Mohamed et al. [21], Mutlak [22] and Dutta et al. [15], but Beverton-Holt relative yield per recruit (Y'/R) and relative lower than the values reported in other waters. Clearly, the biomass per recruit (B'/R) estimated using selective ogive exploitation rate (E) estimated in the present study agrees procedure are given in Fig. 7, the maximum catch (E max) can well with the values reported by Al-Baz and Grove [17] be obtained when exploitation ratio is 0.72, whereas the and Haldar and Nurul Amin [11] and higher than those current exploitation ratio is The exploitation level recorded by Mohamed et al. [21], Ahmed et al. [12], which will result in a reduction of the unexploited biomass Mutlak [22] and Dutta et al. [15]. However, it is slightly by 50% (E ), was equaled The yield isopleths are lower than the values estimated by Hashemi et al. [18] and 0.5 shown in Fig. 8, the yield contours predict the response of relative yield-per-recruit of the fish to changes in L c and E; Lc/L8 = 0.50 and E= DISCUSSION 204 Table 1: Growth, mortality and population parameters of T. ilisha from different regions Region Fish length (cm L8 (cm) K ø Z F M E Source North Arabian Gulf, Kuwait Al-Baz and Grove [17] Northwest Arabian Gulf, Iraq Mohamed et al [21] Bangladesh waters Haldar and Nurul Amin [11] = = Bangladesh waters Ahmed et al. [12] North Arabian Gulf, Kuwait Al-Sabbagh and Dashti [37] Northwest Arabian Gulf, Iran Hashemi, et al. [18] Northwest Arabian Gulf, Iran Roomiani and Jamili [19] Bay of Bengal, India Dutta et al. [15] East Hammar marsh, Iraq Mutlak [22] Northwest Arabian Gulf, Iraq Present study Roomiani and Jamili [19]. The ecological differences, The present assessment shows that the marine physiological conditions of fish, feeding variability, T. ilisha stock is already heavily exploited and the current fishing pressure and data resources may be the reasons exploitation rate is very close to optimal exploitation that for the variation in these values in different regions [38]. gives maximum yield per recruit and that increases in The bimodal recruitment pattern observed for T. ilisha fishing effort and changes in size at entry were unlikely to was also found for the same species in Shatt Al-Arab increase the yield. Thus, either fishing effort should be River by Jabir [20] and in northwest Arabian Gulf by reduced or size at first capture (L c) should be increased, Mohamed et al. [21]. because L cis already higher than size at first maturity (L m). So it is clear that the fishing mortality rate of T. ilisha Morgan [41] indicated that the sheim (Acanthopagrus was more than twice the natural mortality, which latus) fishery in Kuwait waters is producing the maximum indicates that this species is now under intense yield per recruit at the current size at first capture and fishing pressure. If the natural mortality and fishing fishing mortality and any changes in the existing situation mortality are equal, then the stock is supposed to be will most likely result in a reduction in yield per recruit. in a healthy state and an optimally exploited stock Comparing the yield isopleths diagram in this study [28, 39].This statement is also supported with the with that of Pauly and Soriano [30] quadrants rule, the obtained relative yield-per-recruit (Y'/R) and relative L c/l of 0.50 and exploitation rate of 0.72 falls within biomass-per-recruit (B'/R) values. Both estimates quadrant D which implies that the smaller fish are caught indicated that the present level of exploitation rate at higher effort level. Taxonomic studies confirmed that (E=0.67) lower slightly than the maximum allowable limit the T. ilisha in the marine waters and those enter Shatt based on the yield-per-recruit calculation (E max), which was Al-Arab River and its ramifications to breeding and calculated to be These findings suggest that the nursery are one population [33, 42]. Therefore, the exploitation of this stock has approached from the management policy must be taken in consideration the maximum fishing level and thereby the present level of status of T. ilisha stock in Shatt Al-Arab River and to the fishing mortality should be a great concern for the stock. upper stretches. For management purposes, T. ilisha stock (s) in the According to Jaber [20] who carried out a preliminary north Arabian Gulf is certainly shared among Iraq, Iran stock analysis for T. ilisha in Shatt Al-Arab River found and Kuwait [5]. Therefore, any actions on this stock by heavy exploited for the species during their reproductive any country fleet may affect the landings in other migration which was 0.8 and fishing mortality rates were countries [40]. T. ilisha stock from all countries is being 3.5 for males and 5.5 for females. Also, the stock was exploited at a higher level than the optimum. Information exposed to high exploitation rate, as 0.52 in their about status of the species in Iranian waters indicated that spawning and nursery grounds in east Hammar marsh the stock is overexploited, as E= 0.72 [19, 18]. Also, the [22]. He stated that illegal fishing methods employed stock in Kuwaiti water suffer from heavy exploitation, include, use of explosives, poisons and small mesh sized E= 0.67 [17]. Therefore, the regional co-ordination and co- nets. Added to this, small T. ilisha (Called Milat) are operation in fisheries management is essential between caught in large amount from north Shatt Al-Arab River these countries. and east Hammar marsh using small mesh nets during 205 nursery period by artisanal fishers. These fish are sold 4. AL-Husaini, M., Fishery of shared stock of cheaply on the local fish markets in Basrah Province the silver pomfret, Pampus argenteus, in the together with large quantity of egg carrying females. northern Gulf; a case study. In: FAO. Papers Similarly, Nurul Amin et al. [10] mentioned that 19,000 t of presented at the Norway-FAO Expert small T. ilisha (Jatka) were captured in inland rivers in Consultation on the Management of Shared Bangladesh in early 2000s. The harvesting of these Fish Stocks. Bergen, Norway, 7-10 valuable resources at a stage when the individuals have October FAO Fisheries Report. No. 695, Rome, reached only a small part of their growth potential seems FAO. to be a waste of biological resources and probably will 5. Morgan, G.R., Country review: Iraq. In: Review have a negative effect on the species population. of the state of world marine capture fisheries Therefore, have to focus on the management of management: Indian Ocean (ed. C. De Young). FAO T. ilisha stock in the areas of migration reproductive as Fisheries Technical Paper, No Rome, FAO, well as in nursery areas in the Shatt Al-Arab River, its pp: 458. branches and east Hammar marsh. We suggest the 6. Blabber, S.J.M., Socioeconomic and following administrative points to keep the species stock biopolitical linkages in the management of trophic at least in Iraqi waters: shads. American Fisheries Society Symposium, Closed areas to protect spawning as well as 69: recruitment of T. ilisha, these areas are Shatt Al-Arab 7. Rahman, M.A., S.M. Nurul Amin, G.C. Haldar and River and East Hammar marsh during breeding by M.A. Mazid, Population dynamics of imposed a 30-day ban during May to protect Tenualosa ilisha of Bangladesh water. Pakistan spawning biomass. Journal of Biological Science, 3(4): Small T. ilisha (Milat) (up to 23.0 cm size) catch, 8. Nurul Amin, S.M.N., M.A. Rahman, G.C. Haldar, transportation, marketing, selling and possessing M.A. Mazid and D.A. Milton, Population must be banned in the spawning and nursery areas. dynamics and stock assessment of hilsa shad, Pollution from domestic, industrial and agricultural Tenualosa ilisha in Bangladesh. Asian Fisheries sources continues to be a serious problem and Science, 15: several water quality parameters were seasonally 9. Nurul Amin, S.M.N., G.C. Haldar, M.A. Rahman, correlated with fish species catch. M.A. Mazid and D.A. Milton, Stock assessment Regional co-operation in fisheries management is and management of Tenualosa ilisha in Bangladesh. essential for Iraq, as well as for other countries in the Asian Fisheries Science, 17: region. 10. Nurul Amin, S.M.N., M.A. Rahman, M.A. Mazid, G.C. Haldar and D.A. Milton, Catch per unit In conclusion, evidence abound that T. ilisha is over effort, exploitation level and production of hilsa exploited in Iraqi waters, there is therefore urgent need to shad in Bangladesh waters. Asian Fisheries Science, protect the stock through the concerted effort of fishers, 21: communities and governmental agencies. 11. Haldar, G.C. and S.M. Nurul Amin, Population dynamics of male and female hilsa, Tenualosa ilisha REFERENCES of Bangladesh. Pakistan Journal of Biological Science, 8(2): Fischer, W. and G. Bianchi, FAO species 12. Ahmed, M.S., A.S.M. Sharif and G.A. Latifa, identification sheets for fishery purpose Western Age, growth and mortality of hilsa shad, Tenualosa Indian Ocean (Fishing Area 51). Danish Inter. ilisha in the River Meghna, Bangladesh. Asian Develop. Agency. Rome. FAO, 5: 1-6. Journal of Biological Science, 1: Pillay, S.R. and H.J. Rosa, Synopsis of 13. Rahman, M.J
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