POPULATION DYNAMIC OF ENDEAVOUR SHRIMP ( Metapenaeus elegansl IN THE WATERS OF SOUTH COAST OF JAVA

Study on the population dynamic of endeavour shrimp (M. etegans) was conducted in the south coast of Java baied on data collected during a period of November 2002to october 2003. The purpose of the study is to identify biological and population parameters of the endeavour shrimp.


INTRODUCTION
Endeavour shrimp (M.elegans) is one of penaeid shrimp species, dominantly caught in the waters of south coast of Java.Catch of endeavour shrimp may reach the third highest after others small size shrimp (Parapenaeopsls stylifera) and brown shrimp (Metapenaeus ensis) (Suman, 2004).
Exploitation of the endeavour shrimp in the water of south coast of Java has been carried out for years (Van   Zalinge & Naamin, 1975) and become more intensive in the recent years due to an increase of local and or foreign market demand.lf this situation continues to occul, sustainability of the shrimp stock would be disturbed in the future.Therefore comprehensive research is needed to reach rational utilization in order to maintain sustainability of the stock for prosperity purposes in the future (Naamin et al',1992)' This paper discussed population dynamic of the endeavour shrimp (M' etegans) in the south coast of Java.lt hopes that the result can be used as basic and important information for other endeavour shrimp studies and sustainable exploitation of the endeavour shrimp in the waters of the south coast of Java'

MATERIALS AND METHODS
Samples of the endeavour shrimp were taken from field research in south coast waters of Java (Figure 1) from N ovem ber 20o2to October 2003' Biometric stud ies (carapace length, sex, and gonad maturity identifications) were done for 872 samples.Spearman & Karber method (Udupa, 19BO) was applied to identify the size at first maturity with assumption that average size of first maturity occurs when 50% of the endeavour shrimp is already mature.Logarithmic size of the first sex mature (m) was calculated based on equation below:

m=xk+X2-(XIpi)
where: m = logarithmic size of first sex mature xk= logarithmic size of mean value of 100% mature X = logarithmic different of mean value pi = comparison of sex maturityof each length class lnd.Fish Res.J. Vol.13 No.l Juni-2007: 49-54 Figure 1.
Shrimp fishing ground in the waters of south coast of Java.
In this classification, gonad maturity (stage) I and ll are classified as immature while stage lll, lV, and V are mature.The morphologically identified sex maturity stages of the shrimp (Tuma,196T in Naamin,19ga) ari as follows | = quiescent or undeveloped; ll = developing; lll = early maturity; lV = ripe; and V = spent.While chi square method was used to identify sex comparison (Sudjana, 1975).

RESULTS AND DISCUSSIONS
Size at First Maturity -Shrimp age and size at first maturity are important for management purposes.
The size at first maturity of endeavour shrimp in the waters of south coast of Java was 32.6 mm in carapace length with confidence limits of 31.g to 33.g mm.

Martosubroto (1978) reported that M. ensis in Tanjung
Krawang waters reached first maturity when they groi to about 20 mm in carapace length.This differenie in reaching first maturity might be influenced by the availability of food and environment condition such as temperature and salinity.
Maturity percentage frequencies distribution of the endeavour shrimp female can be seen in Table 1.Table 1 also illuskated that the longer the size of carapace length, the higher the maturity percentage of shrimp.
Frequency distribution of mature female shrimp (M, elegans) in various size of carapace tength in the waters of south coast of Java Data on sex and maturity of fish or shrimp stock are important as basic information for reproduction biology of the stock (Suhendrata & Merta, 1986).Homogenity test informs that value of male and female was imbalance, it was also identified that sex ratio of the endeavour shrimp in south coast waters of Java was found to be 't.0:1.7.This ratio is significantly different with those reported in previous researchs (Suman ef  al., 1987i Suman, 1991).That first authors found the value of 1.0:1.2 in Pangandaran waters, while the later found 1.0:2.5 in Kotabaru waters (South Kalimantan).
The measured carapace length of 318 male of endeavour shrimp ranged from 20 to 40 mm and of 554 female ranged from 20 to 44 mm.Suman et al. (1987'1   illustrated that in Pangandaran waters, range of carapace length of male endeavour shrimp was 12.2to 24.3 mmand of female was 13.3 to 31.9 mm.Meanwhile in Kotabaru, South Kalimantan, it were found that carapace length of male and female endeavour shrimp ranged from21.2to32.6 mm (Suman, 1991).
This data informs that range of carapace length of female was higher than that of male.This phenomenon might be influenced by difference in growth type of female and male.The growth of female was fasterthan male so that carapace length of female was always longer than male in the same age (Naamin, 1984).
Population Dynamic of... in the Water of South Coast of Java (Suman, A. et al.)   Spawning Season Spawning season of shrimp in a certain waters can be studied by identifying distribution of egg density or shrimp maturity in that waters (Martosubroto, 1978).
The observation shows that the number of immature and mature female endeavour shrimp were 331 (60%) and 223 (40o/o), respectively.lt could be concluded that number of immature endeavour shrimp was higher than mature endeavour shrimp.lt mean that on the biological aspects, status of the shrimp stock was likely in danger zone because fishing activity exploited more young shrimp than adult shrimp.
The distribution frequency of female endeavour shrimp in two maturity stages from November 2002 to October 2003 can be seen in Table 2.
Table 2 shows that the highest number of mature female shrimp occurred in January and August.lt shows that peaks of spawning seasons of endeavour shrimp in the waters south coast of Java took place twice, in January and August.In Tanjung Krawang waters, peak of spawning season of endeavour shrimp occurred in March and December (Martosubroto, 1978) while in Kotabaru waters, South Kalimantan, peak of spawning season occurred happened in June only (Suman, 1991).
Value of K and L. was greater than 1, showing that growth type of endeavour shrimp in the south coast Mortality Rate and Exploitation Rate Value of total mortality (Z) represented by value of slope (b) between Ln N/t and relative age (Figure 3) was 4.53 per year.Meanwhile value of natural mortality (M) and fishing mortali$ (F) were 1.15 peryearand 3,38 year, respectively, Pauly ef a/. (1984)reported that values of Z and F of lndian shrimp (Metapenaeus affinis) in Versoba waters, were 5.29 and 3.0 per year respectively.While values of Z and F of Metapenaeus kutchensis were 5.83 and 2.20 per year, respectively.lt was also reported that the differences in value of shrimp mortality rates in several waters were caused by different level of effort, predator, and environ mental conditions.
By usjng the exploitation rate equation (E)=F/Z, it obtained that the value E of endeavour shrimp in the waters of the south coast of Java was 0.75 per year.
Based on Pauly criterion (Pauly ef a/., 1984), it concluds that over fishing of the shrimp stock occurred in this location waters of Java, because rational the fishing of waters of Java was fast growth (Sparre & Venema).Eventhough care must be taken into account when planning the amount of effort allowed to be applied each year for exploiting the shrimp stock in order to obtain rational management of the stock.lf value of recommended effortwas lower, uncapture shrimp stock would be useless or number of natural mortality would be high because the growth type of the stock was fast.It means that the stock had short life span.In contrast,   if value of recommended effort was higher, the stock would be disturbed or even jeopardized because there was not enough time for population to grow the recruitment number and amount of next year stock will decrease.fish or shrimp stock can be gained if the value E in that waters equals 0.5.lf the value E is more than 0.5, the stockwould endangered thus effort has to be decreased in order to sustain the stock.Phenomenon of the endeavour shrimp stock in the south coast waters of Java suggests that fishing effort of the endeavour shrimp stock should be deducted until 50% of the present status.
CONGLUSION AND RECOMMENDATION 1.The endeavour shrimp (M.elegans) reached at for maturity at the carapace length of 32.4 mm.
2. Sex ratio of male and female of endeavour shrimp (M.elegans) was 1 .0:1.7.lt called in imbalance condition.
3. Spawning season of endeavour shrimp (M.elegans) occured throughout the year with two peaks in January (west monsoon) and August (east monsoon).The value of total mortality (Z) of endeavour shrimp (M.etegans) in south coast waters of Java.
4. Values of growth rate (K) and maximum carapace length (L") of endeavour shrimp (M.elegans) in the south coast waters of Java were 1.5 per year and 51.5 mm, resPectivelY.
5. Values of totral mortality (Z), natural mortality (M)' and fishing mortality (F) of endeavour shrimp (M' elegans) were 4.53: 1.15; and 3'38 per year respectively' 6. Exploitation rate (E) of endeavour shrimp stock in south coast waters of Java was quite high; 0'75 per year.
7, ln order to keep sustainability of endeavour shrimp stock, it suggests biolog ically that fi shing effort shou ld be deducted until 50% of present status' 8.In order to perform sustainability management of the endeavour shrimp (M.elegans) stock' comprehensive research in biology, economic, and social aspects are recessary to be conducted' Figure 3.
, ELEFAN program is applied to interprete carapace length in time series data adjusted with von Bertalanffy growth curve.Growth pattern is indicated by curve which crosses highest number of modes(Sparre  & Venema, 1992).