GROWTH AND EXPLOITATION STATUS ( Channastriata Bloch , 1793 ) IN LUBUK LAMPAM FLOODPLAINS , SOUTH SUMATERA

Due to the economic importance of C. striatain Lubuk Lampam floodplains (Indonesia), this study is aimed to estimate the biological and population parameters required for proposing a future plan to sustain and manage this valuable fish resource. The growth, mortality and explotation ratio of Channa striata estimated by employing FiSATProgramme are reported. The parameters of Von Bertalanffy growth model of 1,529 sample fishes were estimated as K= 0.36/ year, L” = 72.98 cm and to = -0.52 year. The coefficients of total mortality (Z), natural mortality (M) and fishing mortality (F) were 1.72, 0.73 and 0.99 year respectively. Relative yield per recruit analysis shows that the presentexploitation rate (E) was 0.58. Yield per recruit can be maximized at the exploitation ratio of 0.5 and Lc/Linf values of 0.3. The Yield per recruit and biomass per recruit models indicated that, the fisheries status of C. striatain Lubuk Lampam floodplains exceed the limit reference point (Fmax), thus stock of this species in Lubuk Lampam floodplains is indicated being driving down.Reduction in fishing effort and increase number of selective fishing gears are suggested to sustain the fishery of Channa striata in Lubuk Lampam floodplains.


INTRODUCTION
Channa striata is commonly found in swamps, freshwater plains and also occurs in the lowland rivers, usually caught in bathymetric range of 1-2 m (Allington, 2002in Makmur, 2004).The fish is widely distributed in the Southern Asia, Central Asia and along the South Eastern Asia from Thailand to Indonesia including Papua New Guinea (FAO, 2000in Muflikhah, 2007).
There have been few studies published on C. striata in different areas of Indonesia, so it's biological aspect has been little described from several literatures.It is summarized that the maximum length of C. striatareportedly can reach about 100 cm, while in several lake and dams in Indonesia asymptotic length of C. striata ranged 457 and 722 mm (Kartamihardja, 1994;2000, Makmur, 2004)).Spawning season of C. striata occurs in the rainy season with the peak period occurred from February to April.In the floodplains ecosystem, spawning occurs throughout the year, while the peak frequency of spawning occurs in the rainy season, it is seen from the observed diameter of the eggs contained at least 3 of the population size of the eggs in each month (Muflikhah et al., 2005;Makmur, 2003).
The species of Channa striata is commercially important freshwater fish and one of the major fish species in Lubuk Lampam floodplains.This area is a shallow basin located at about 60 km southeast of Palembang, South Sumatera.Due to high demand of this fish and habitat degradation, it is necessary to evaluate the population of this fish to ensure the proper management of this fishery.
Hence, the present study was design to provide a review preliminary assessment and management of the species of C. striata in Lubuk Lampam fishery.It is aimed to estimate the biological and population parameters required for proposing a future plan to sustain and manage this valuable fish resource.

MATERIALS AND METHODS
Random samples of C.striata were collected for nine months from the commercial catch in the landing site, in Lubuk Lampam floodplains during the period from April to November 2011 (Fig. 1).From each collected fish sample, total length and total weight were recorded to the nearest centimeters and gram, respectively.Length weight relationship was estimated for 1,529 fish of C. striata according to Le Cren (1951).The condition factor was calculated according to Hile (1936).
Growth parameter of C. striata was estimated using Von Bertalanffy growth model (1938) by fitting the Ford-Walford plot (Lt vs L(t+Δt), while t 0 was estimated by inverse Von Bertalanffy growth equation and W inf was Performance of length and weight were estimated according to Moreau et al. (1986).The maximum age was determined according to Pauly & David (1981), and the massive maturity age was obtained using Richter-Evanov methods (1972).
The instantaneous total mortality coefficient (Z) of C.striatain Lubuk Lampam floodplains was obtained by using length-converted catch curve method (Gayanilo et al., 1994).The natural mortality (M) was calculated using Pauly empirical formula (1980): Log M= -0.0066 -0.279 log L inf +0.6543 log K +0.4634 log T,where, L inf & K are VBGF parameters and T is the annual mean temperature ( o C).Instantaneous fishing mortality(F) was calculatedbysubtractingthenatural mortalitycoefficient (M) from the total mortality coefficient (Z).
The estimation of survival rates (S) was estimated by the equation S = e -z (Ricker, 1975).The exploitation ratio (E) was calculated for C.striata according to Baranov (1918) formula.Length at first capture and Length at recruitment (Lc&Lr) were investigated from the equation of Beverton andHolt (1956 &1957).While Age at first capture and Age at recruitment (tc&tr) were estimated by applying back calculation of growth equation of Von Bertalanffy.
The relative yield per recruit (Y'/R) and biomass per recruit (B'/R) were estimated by Beverton and Holt models (1957).The biological reference points values of fishing mortality such as E max and E 0.1 were investigated together with various relationships between the yield per recruit, fishing mortality, age at first capture and natural mortality.

Length-Weight Relationship and Condition Factor
The examined sample of C. striata varied in length between 5.1 and 70.0 cm and from 7 to 2,997 gram in weight.The condition factor (q) value of C.striata in Lubuk Lampam floodplains was found to be 0.9, where length weight relationship equation was found to be: environment and food aviability in those area (Makmur, 2004).While growth pattern of C. striata showed isometric pattern in April and September, and allometric pattern in May-August and October-November (Table 1).

Growth Performance and Maximum Age
The growth parameters using Von Bertalanffy equation were estimated as K= 0.36/year, L" = 72.98 cm and t 0 = -0.52 year.Values of W" obtained from length-weight relationship was estimated 3,049 gram.Thegrowth performance values in length (ÔL) and in weight (ÔW) of this species were 3.283 and 1.879 respectively.Growth performance values showed that C. striata growth rapidly in length than weight scales.According to the present data, it was found that maximum age (longevity) and age of massive maturity of C. striata in Lubuk Lampam floodplainsare 11.5 year and 2.60 year respectively.Monthly length frequency distribution of C. striata is showed in Figure 3.

Mortality and Exploitation rate
The length converted catch curve analysis for C. striata in Lubuk Lampam floodplains produced total mortality estimates of Z = 1.72 ± 0.09 (Figure 4).The natural mortality M = 0.73 is calculated using Pauly's empirical formula, with annual temperature about 29 o C (Pauly, 1980).The fishing mortality (F) is therefore 0.99/year.The survival rate value of C. striata in Lubuk Lampam floodplains was found to be 0.57, while the exploitation ratio (E) was 0.58.Length and age at first capture (Lcand tc) as obtained in the present study were found to be 21.44 cm and 0.70 year, while length at recruitment (Lr) was 19.18 cm and the corresponding age at recruitment (tr) was 0.3 year.

Recruitment Pattern
Plot of the percentage recruitment of C. striata into the fishery in the portions of the floodplains showed continues recruitment from January to November with three pulses were recorded in March (14.2%),April (9.5%) and October (14.7%) with average recruitment in one year was 8.3% (Figure 5).

Relatif Yield Per Recruit (Y'/R) and Biomass Per Recruit (B'/R)
Using knife edge selection of Beverton and Holt, the yield per recruit for C. striata in Lubuk Lampam floodplains with input parameter M/K and Lc/Linf, and the optimum exploitation rates were calculated.The E max , E 0.1 and E 0.5 values for relative yield per recruit analysis were 0.52, 0.41 and 0.30 respectively (Figure 6).Relative yield per recruit analysis showed that the present exploitation rate (E) was 0.58.Yield per recruit can be maximized at the exploitation ratio of 0.5 and Lc/Linf values of 0.3.The exploitation rate (E) in Lubuk Lampam floodplains was slightly higher than maximum acceptable limit and the position present exploitation value was on the right side of yield per recruit curve (E present (0.58) >E max (0.52)).

DISCUSSION
In the present study, the value of the exponent "b" was found to be 2.8785 which indicated negative allometry.This value compared with previous study was higher than values of "b" of C. striata which was estimated by Kartamihardja (1994) in Kedungombo dams (2.743) and Makmur (2004) in Talang Fatima floodplains, South Sumatera, but still within the range of values in Banjaran River (2.77-3.123)(Table 2).In fisheries studies; the condition factor is an essential biological parameter needed to understand the suitability of the environment for good living of fish (Le Cren, 1951;Mahmoud et al., 2010).The condition factor (k) was estimated 0.9, compared with previous authors (Makmur, 2004) gave different values (0.51 -1.81).This controversy was explained to be due to the variations in the environmental conditions (Hernandez, 1986).The condition factor fluctuated monthly, affected by differences of age, gonad maturity and food suitability in their habitat (Makmur, 2004).

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The growth performance index is considered to be a convenient and robust tool for the comparison of growth parameters from different data sets (Moreau et al., 1986& Pauly, 1980).The growth performance of C. striata in the present study, (ÔL= 3.283), which is lower than that observed by Kartamihardja, (1994) (ÔL = 5.253) in Kedungombo dams and Tondano Lake (2000) (ÔL = 5.36) and Makmur (2004) in Talang Fatima floodplains (ÔL = 5.85).Variationsinthevalues of the parameter of growth performance might suggest variations in the growth rate (Moreau et al., 1986).The value of growth performance index in the present study compared with Makmur (2004) which has the same type of habitat and near geographic location has only half performance due to adaption flexibility on change of environmental condition.
Maximum age of C. striata in Lubuk Lampam floodplain scould live 11.50 years in the present study.The longevity of fish species might be affected by the environmental conditions under which a fish lives (Wootton, 1990;Mahmoud et al., 2010).C. striata is highly predacious species, ambush feeders on other fishes.In addition, their adaptability to living in turbid or clear waters, their apparent ability to tolerate extreme water temperature change were considered affected maximum age of this species.
The recruitment pattern established in this study revealed an all year around recruitment with three pulses in March, April, and October.This observation agreed to the assertion of Makmur et al., (2003) that C. striata in South Sumatera floodplains spawned along the year with length at recruitment (Lr) 15.4-18.0cm while in the present study value of Lr was 19.18cm respectively.Species C. striata in the present study estimated, that exploitation rate E = 0.58 showed that fishing mortality was higher than natural mortality.The implication is that C. striata died more due to human exploitation than natural death (e.g disease, predation etc).For an optimally exploited stock, natural and fishing mortalities should be equal or E = 0.5 (Gulland, 1971;Abowei et al., 2010).The maximum exploitation rate (Emax), which gives maximum relative yield-perrecruit, is estimated at 0.52 and slightly differs from the exploitation rate (0.58) estimated in this study.This further indicated that the stock of C. striata is driving the stock down into overfished condition.

CONCLUSIONS
Channa striata in Lubuk Lampam floodplains shows a negative allometric growth.Although this species recruits along the year, the stock has slightly reached an overfished phase (E present >E max ).This was due to the fishing mortality for C. striata is higher than the natural mortality.Therefore, it is necessary to reduce fishing effort tand applied selective fishing gears to maintain fish stocks sustainably.

ACKNOLEDGEMENTS
This study is based on the data collected from the project of implication climate change on fish resources in Musi River funded by Research Institute for Inland Fisheries, Palembang.We thank to the Director of RIIF for the funding support.

Figure 3 .
Figure 3. Length frequency distribution of C. striata

Table 2 .
Von Bertalanffy growth parameters for C. striata in different places.