Population Dynamics of Some Important Fish Species from Pakistani Waters.pdf

1、This study has estimated the growth and mortality parameters of some important fishspecies including Croaker Atrobucca alcocki，Tiger toothed croaker Otolithes cuvieri，andRibbon fish Lepturacanthus savala using the length

2、-frequency data in Pakistani waters.However the length-weight relationship (LWR)，biological reference points (BRPs) were alsoestimated.The length-frequency data were collected from the fishery resources survey ofPakistan

3、 during the year 2009-2010.The Maximum sustainable yield were also estimated ofBarramundi，Lates calcarifer and Black Pomfret Parastromateus niger using the catch andeftort data taken from the fisheries statistics book of

4、 Pakistan complied by Marine FisheriesDepartment (MFD) Government of Pakistan，Karachi.
　　Atrobucca alcocki
　　The fisheries statistics book of Pakistan is evident that prior to the fishery resourcessurvey of Pakista

5、n during the year 2009-2010，the Atrobucca alcocki were not observed inthat abundance as observed in surveys during 2009-2010.The species was observed in auniform abundance during the four demersal trawl surveys and it wa

6、s the main objective ofour study to estimate the growth and mortality parameters of this specie.In this connection atotal of 819 (n =819) length weight and 7240 (n=7240) length frequency of Atrobuccaalcocki were observed

7、，the minimum length were 10cm and maximum length were 44cmwith the dominant length group ranges from 19 to 29cm.The total weight ranges from 14 to928g.The length-weight relationship parameters were estimated as a =0.012，

8、b =2.925andR2 =0.972.Applying FiSAT computer software package using ELEFAN method the length-frequency distribution data were analyzed.The calculated von Bertalanffy growth functionparameters were L∞=47.25cm，K=0.180 yr-1

9、.Total mortality (Z) were computed using thelength-converted catch curve analysis at Z=1.07yr-1.Natural mortality using Pauly's equationwere computed as M=0.494 yr-1 at an annual average sea surface temperature of 26 0℃，

10、hencethe fishing mortality were computed as F=Z-M=0.576 yr-1.Yield per recruit analysis revealedthat when tc was assumed to be 2，F(xiàn)max was calculated at 0.75 and F0.1 at 0.6.When tc wasassumed to be 1，F(xiàn)max was calculated

11、at 0.55 and F0.1 at 0.45.Current age at first capture isabout 1 year and Fcurrent was 0.576 therefore Fcurrent was larger than F0.1 and Fmax whichshows that the fishery ofAtrobucca alcocki may not be in a sustainable sta

12、te in the region.Hence it is recommended that fishing effort may be reduced for the rational exploitation ofthe species in the region.
　　Otolithes cuvieri
　　Although 66 genera and 284 species belonging to the famil

13、y Sciaenidae aredistributed worldwide but in Pakistani waters 18 species belongs to family Sciaenidae arewell known，but the catch in such abundance of Otolithes cuvieri were observed first timeduring the fisheries resour

14、ces survey of Pakistani waters during the year 2009-2010.Keepingthis in view we had put an attempt to estimate the growth and mortality parameters of theOtolithes cuvieri using the length-frequency data.Four demersal tra

15、wl surveys were carriedout in Pakistani marine waters for the collection of length-frequency data of the species.Thedata used in present study for the combined sexes of the species were based on 3219 length-frequency (n=

16、3219) and 671 length-weight (n=671) pairs.The length ranges from 3-35cmand weight ranges from l-208g.The dominant length of Otolithes cuvieri ranges from 4-18cm.The length weight relationship parameters were computed as

17、a=0.014，b=2.870 andR2 =0.952.Using the ELEFAN routine of the FiSAT computer package，the calculated vonBertalanffy growth function parameters were L∞ =36.75cm，K=0.300year-1.Total mortalityrate (Z) were computed using leng

18、th-converted catch curve analysis at Z=1.26 year-1.Following the Pauly's equation natural mortality rate were computed as M=0.740year-1，atan average sea surface temperature of 260 ℃，fishing mortality rate were computed a

19、s F=Z-M=0.52 year-1.The yield per recruit analysis showed that when tc was 1，F(xiàn)max wascalculated at 0.5 and F0.1 at 0.4.When biological reference point of Fopt was M (0.740),current fishing mortality rate of 0.52 is small

20、er than the target biological reference point.Thisindicates that the fishery is in a safe condition.
　　Lepturacanthus savala
　　Lepturacanthus savala (Cuvier，1829) is a commercial fish species distributed in thecoas

21、tal waters of Indo-west Pacific and Indian Ocean.In present study Length-frequency datawere analyzed.The length-frequency data of Lepturacanthus savala (Cuvier 1829) werecollected by the four demersal trawl surveys in th

22、e Pakistani waters in 2009-2010.A total of4035 pairs of lengths and 1391 pairs of length-weight were measured.The length ranges from1 to 121cm with average length of 44.23cm (± 19.75cm) while weight ranges from 1 to1942g

23、 with average weight of 110.81 g (±229.57g).The estimated values of length-weightrelationship for L.savala were W =0.0001*L？191 (R2 =0.960).The calculated yon Bertalanffygrowth function parameters using ELEFAN method in

24、FiSAT computer package ofL.savalawere L∞ =133.35 cm and k =0.130year-1，t0 were estimated at-0.877.The estimated rate oftotal mortality Z applying the length-converted catch curve analysis method for L.savala wasZ =0.49ye

25、ar-1，natural mortality M were estimated as M=0.304year-1 at an annualaverage sea surface temperature of 26 ℃ while the rates of fishing mortality F was calculatedas F=0.185year-1.Hence exploitation ratio (E=F/Z) were cal

26、culated as 0.377 yr-1.Yield perrecruit contour map reveals that when tc was assumed to be 1，F(xiàn)max was estimated at 0.6 andF0.1 at 0.45.Current age at first capture was about 1 year and Fcurrent was 0.185 thereforeFcurent

27、was smaller than Fo1 and Fmax.When biological reference point Fopt was equal to M(0.304)，current fishing mortality rate of 0.185 is smaller than the target biological referencepoint.The estimated values of growth perform

28、ance index for the L.savala from Pakistaniwaters wereφ' =3.364year-1.The estimated value of MSY was 26983t with the estimatedbiomass of 110135t.Again the obtained results of maximum sustainable yield (MSY) of26983t for L

29、.savala from Pakistani waters were larger than recent catch of 20375t; thereforewe may indicate that the L.savala fishery in Pakistani may be in a sustainable state.
　　Lates calcarifer (MSY)
　　This chapter was to e

30、stimate the maximum sustainable yield of the Barramundi Latescalcarifer because it is a commercially important fish species and was fished in abundance in1980s from the southern part of the Indus delta but in recent year

31、s it is caught not in thatabundance as in 1980s.Maximum Sustainable Yield (MSY) of Barramundi Lares calcarifer(Bloch，1790) fishery of Pakistan were estimated based on catch and effort data from 1995-2009.Two computer sof

32、tware packages CEDA (catch effort data analysis) and ASPIC (asurplus production model incorporating covariates) were applied.Three surplus productionmodels including Fox，Schaefer and Pell-Tomlinson with three error assum

33、ptions of normal,log-normal and gamma were used by applying CEDA and two surplus production modelsincluding Fox and Schaefer were used by applying ASPIC computer software package.InCEDA initial proportion (IP) was used r

34、anging from 0.1-09.The obtained MSY results using1P 0.8 (because the initial catch was roughly 80％ of the maximum catch) in normal，log-normal and gamma error assumptions from Fox，Schaefer and Pella-Tomlinson models werea

35、bout 107-117t (± 8.131-15.260)t and estimated R2 for three models with three errorassumptions were about 0.61-0.67.The estimated MSY results of Fox and Schaefer modelsusing ASPIC computer software package were 118t (±10.

36、856)t and 109t (± 10.384)t andestimated R2 for Fox and Schaefer models were 0.803 and 0.794 respectively.The estimatedvalues of MSY are smaller than the recent catch which indicates that the fishery of L.calcarifer in Pa

37、kistani waters is over-exploited.Hence it is recommended to the fisherymanagers that for the sustainable exploitation of the species in Pakistani waters fishing effortshould be reduced.
　　Parastromateus niger (MSY)

38、>　　Parastromateus niger is among the most important commercial fish species in thePakistan.The main emphasis of this chapter was to evaluate the MSY maximum sustainableyield of Parastromateus niger fishery based on the c

39、atch and effort data from 1992-2009.The computer software package CEDA (catch effort data analysis) was used to analyze thecatch and effort data for the estimation of maximum sustainable yield (MSY) ofParastromateus nige

40、r fishery from Pakistani waters.An initial proportion IP of 0.4 (becausethe initial catch was roughly 40％ of the maximum catch) were applied，the estimatedmaximum sustainable yield (MSY) were about 2000-2300t，the correlat

41、ion coefficient R2 wereabout 0.20-0.31.Gamma error assumption often showed minimization failure.The estimatedMSY from CEDA is smaller than most recent catch of the data which indicates that the fisheryof Black Pomfret P

42、niger in Pakistani waters may not be in a sustainable condition.Hence itis suggested that，for the well being and sustainable utilization of the fishery，the fisherymanagement authorities and other stack holder may take so