Biology Aspect of Blue Swimming Crabs (Portunus pelagicus) In Jakarta Bay Waters, Indonesia

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1 AUSTRALIAN JOURNAL OF BASIC AND APPLIED SCIENCES ISSN: EISSN: Journal home page: Biology Aspect of Blue Swimming Crabs (Portunus pelagicus) In Jakarta Bay Waters, Indonesia 1 M. Hikmat Jayawiguna, 2 Mugi Mulyono, 2 Erick Nugraha, 2 Hari Prayitno, 2 Abdul Basith 1 Agency of Marine Affairs and Fisheries Research and Development, Jakarta 2 Jakarta Fisheries University of Jakarta. Pasar Minggu, Jakarta. Address For Correspondence: Mugi Mulyono, Jakarta Fisheries University of Jakarta. Pasar Minggu, Jakarta. mugimulyono@kkp.go.id A R T I C L E I N F O Article history: Received 10 August 2017 Accepted 1 October 2017 Available online 18 October 2017 Keywords: Biology Aspect, Portunus pelagicus, Blue Swimming Crabs, Jakarta Bay, Indonesia A B S T R A C T Blue swimming crab (Portunus pelagicus) is one of exported comodities with high economic value. The objective of the research were to examine biological and habitat characteristic of blue swimming crabs as base of sustainable fisheries management. The research was conducted from December 2014 to March 2015 in the Jakarta Bay. Samples were collected by gillnet and collapsible traps. The crabs were measured the carapace width (CW) and its weighted (W). Ecological data also were recorded such as substrate type, temperature, salinity and depth. The carapace lengths for all crabs were 62 mm to mm, generally, male have bigger size than female. The growth pattern showed allometric positive. The value of sex ratio was 1,3:1. In every single month, we found female with mature gonad. Size at first capture for all crabs is smaller than size at first maturity (98,91 mm < 105,45), its indicated that exploitation rate was overfishing. The legal size of blue swimming crab based on size at first maturity is about more than 105 mm. INTRODUCTION Jakarta bays is one of the biggest fishing ground of Blue Swimming Crabs (Portunus pelagicus) in Java Sea with its small scale fishery. In 2013 Java sea has noted as the biggest contributor for Blue Swimming Crabs (BSC) with 47,4% of natioanal BSC Productions (Capture Fisheries Statistic 2013, MMAF). Height demand of BSC comodities was made BSC in Java Sea tend to exploited intensively. It could be shown with the increasement of effort number with many kinds of gear was tags as destructive gear to be used. The trend has shown that there were some indications of population degradations. It was indicated by the decline of crab production and its sizes especially in Jakarta Bay. Data about biological and habitat characteristics very important to give predictions about the trend but its scarce. Therefore the aims of this study is to collect data about biological and habitat characteristics of BSC in Jakarta bays in order to know the existing condition for sustainable fisheries management plan. MATERIALS AND METHODS The research was conducted from December 2014 to March 2015 in the Jakarta Bay. Samples were collected by fishing gear that called gillnet and collapsible traps with survey methods. The crabs were measured carapace width (CW) and its weighted (W). CW was measured to the nearest millimeter across the tips of the epibranchial spines while individual wet weight were recorded at the nearest gram (Hartnoll, 1982). Up to 250 Portunus pelagicus were collected monthly for 4 (four) month from Kali Adem Jakarta Bays. Biological data were collected in situ and analyzed descriptively. The carapace width-weight relationship was estimated using the log form of the allometric growth equation W = a L b (Rickter, 1973). Where W= Open Access Journal Published BY AENSI Publication 2017 AENSI Publisher All rights reserved This work is licensed under the Creative Commons Attribution International License (CC BY). To Cite This Article: M. Hikmat Jayawiguna, Mugi Mulyono, Erick Nugraha, Hari Prayitno, Abdul Basith., Biology Aspect of Blue Swimming Crabs (Portunus pelagicus) In Jakarta Bay Waters, Indonesia. Aust. J. Basic & Appl. Sci., 11(13): 63-67, 2017

2 64 M. Hikmat Jayawiguna et al, 2017 expected weigght, L= total carapace width, a = initial growth (y-intercept) and b = growth coefficient (slope). The values of constants of a and b were calculated by the least squares method. The values of the correlation coefficient (r) were calculated to know the pattern of association between abdomen and carapace dimension. Sex ratio was differentiated by the abdominal shape. The abdomen is narrow and interved V shaped in males while it is triangular to semicircular in females. The overall sex ratio were tested using chi square. Fig. 1: Location of sampling sites for Portunus pelagicus in in Jakarta Bays RESULTS AND DISCUSSION Size Composition: Carapace width (CW) for all crabs sampled ranged from 62,5 mm to 152,5 mm and the CW of the smallest ovigerous female was 95 mm. Generally, male have bigger size than female. It might be the adult female was moving to the offshore waters at the same time. While in Java Sea the trend of catching BSC for all showed the same result as generally, male have bigger size than female. In Jakarta Bay there is no organized fishing port for the blue swimming crab (BSC) that makes the data of catch and effort is scarce. Therefore it is very difficult to give information and prediction about existing condition of BSC population in Jakarta Bay because of the unreported data production. Therefore biological, morphological and environtmental aspect become very important to studied in order to give alternative options in the sustainable fisheries management program. Width-Weight Relationship: The result showed the values of constant b for all crabs were 3,12. The values are different both male and female. For male it range from 3,12-3,20 while in female range from 2,83 to 2,99. In general for all crabs the values of b is more than 3 (b>3) its means that the growth pattern showed Allometric Positive. The values of the correlation coefficient (R 2 ) for all crabs were 0,927 (92,7%). Based on the coefficient (R 2 ) means that there were strong associations between abdomen and carapace dimension both in male and female. Tabel 1: Size composition of Blue Swimming Crabs in several fishing base in Java Sea Spesies N W = al b R 2 Pola Pertumbuhan BSC (Male) 571 W = L 3,203 0,949 Allometric Positive BSC (Female) 450 W = L 2,947 0,886 Allometric Negative BSC (All) 1021 W = L 3,122 0,927 Allometric Positive Our results have shown that the size composition of blue swimming crabs (BSC) caught in Jakarta Bay was proven as the smallest size of all crabs caught in Java Sea. It indicates that the possibility rate of capture was overfishing (Safaie et al., 2013). The study has also shown that there were significantly more male than females in the sampled population (1 1). (Table 2). The small number of female caught caused by the movement of Mature Female to the deeper offshore waters to get more salinity and more pressure for spawning. Sienes et al., (2014); Smith et al., (2004) has reported that the low of females caught in estuary was caused by migrations of adult females to deeper waters for spawning. Sex ratio: The value of sex ratio between male and female were 1,3 : 1. There were significantly more male than females in the sampled population. It can be proof with the result of chi-square analysis

3 65 M. Hikmat Jayawiguna et al, 2017 Tabel 2: Sex Ratio of Blue Swimming Crabs in Jakarta bay Month Sex Ratio χ2 Count. (n) Male (n) Female Male : Female December ,32 : 1 4,73 January ,39 : 1 8,15 February ,14 : 1 1,44 March ,19 : 1 1,73 χ2 Count (total) 16,077 χ2 Table 5,991 Gonosomatic Indices: In every single month, we found female with mature gonad in significant number. The proportion of females which were both had mature and immature gonad throught out the month are present in Table 3. Tabel 3: Proportion of mature and immature female of BSC in every single month TKG Proportion (%) Des-14 Jan-15 Feb-15 Mar-15 Rate (%) Maturing 42,11 37,31 41,35 52,94 43,43 Immature 57,89 62,69 58,65 47,06 56,57 Berried females were also found in every single month. The peaked season can be predicted is during on Desember-January. Males are marginally heavier than females. We assume that female needs nutrition both for growth and reproduction while in male tends to use nutrision for it growth. The tendency of males tobe heavier than females in portunids is in accordance with the observations of Sumpton (1994); Xiao and Kumar et.al. (2003). Meanwhile In every single month, we found female with maturing gonads in significant number and also to the proportions of berried females (Table 3.). We predict that the area of sampling site is the matting ground for the crabs. If there is no ban on fishing berried female by the government, in the long term it will give impact to the lost potention numbers of recruitment and be the main causes of recruitment overfishing. Lc, Lm and Minimum legal size: Size at first capture (Lc) for all crabs is smaller than size at first maturity (Lm)(98,91 mm < 105,45), its indicated that exploitation rate was overfishing. The legal size of blue swimming crab based on size at first maturity is about more than 105 mm. (a) (b) Fig. 2: (a) Proportion of mature immature and berried female; (b) Berried female caught

4 66 M. Hikmat Jayawiguna et al, 2017 Lm total (a) (b) Fig. 3: Size at first capture-lc (a) and size at first maturity-lm (b) In Jakarta bay waters, we also found there were so many fishing gear operated in shallow waters (coastal area) which was uncontrolled. It caused almost all young fishes (include crabs) was caught intensively. (Carmona and Conde, 2002) In the long term if there is no ban on fishing in coastal area there will be no big fish because of over exploitations on young fishes (growth overfishing). Size at first capture (Lc) for all crabs were found smaller than size at first maturity (Lc<Lm ; 98,91 mm < 105,45), its indicated that exploitation rate was overfishing (Campbell & Eagles, 1983). In fact it Should be Lc > Lm to give chance for the crabs hatching at least for the first time. so it should be implemented the regulation about minimum legal size of blue swimming crab to caught (Tito&Alanano, 1998). That could be based on the size at first maturity. From this research the legal size is about more than 105 mm. Conclusion: Blue Swimming Crabs (Portunus pelagicus) in Java Sea with its small scale fishery, we also found there were so many fishing gear operated in shallow waters (coastal area) which was uncontrolled. It caused almost all young fishes (include crabs) was caught intensively. The study has also shown that there were significantly more male than females in the sampled population (1 1). The small number of female caught caused by the movement of Mature Female to the deeper offshore waters to get more salinity and more pressure for spawning. The prediction that the area of sampling site is the matting ground for the crabs. If there is no ban on fishing berried female by the government, in the long term it will give impact to the lost potention numbers of recruitment and be the main causes of recruitment overfishing. ACKNOWLEDGMENTS The authors wish to express sincere gratitude to the director of Indonesian blue swimming crabs association and the director of fisheries management and conservation riset center for the permiting and providing facilities needed for the riset. This study was largely sponsored by Indonesian blue swimming crabs association (APRI) and under supervisory by P4KSI- Balitbang KP. REFERENCES Campbell, A., D.M. Eagles, Size at Maturity and Fecundity of Rock Crabs, Cancer Irroratus, From The Bay of Fundy and Southwestern Nova Scotia Fishery Bulletin, 81(2): Carmona, S.C., E. Conde, Local distribution and abundance of swimming crab (Callineste spp. And Arenaeus cribrarius) on tropical and beach, Ensenada de la vela, Venezuela Fisheries Bull., 100: Chan, T.Y., M. Osawa, C.B. Boyko, S.T. Ahyong, E. Macpherson, Crustacean Fauna of Taiwan: Crab-Like Anomurans (Hippoidea, Lithodoidea, and Porcellanidae). National Taiwan Ocean University, Keelung (TW). Corgos, A., F. Juan, Morphometric and Gonad Maturity In The Spider Crab Maja brachydactyla : A Comparison of Methods for Estimating Size at Maturity in Species with Determinate Growth ICES J Mar Sci., 63(5): De Lestang, S., N.G. Hall, I.C. Potter, Influence of a deep artificial entrance channel on the biological characteristics of the blue swimmer crab Portunus pelagicus in a large microtidal estuary. J Exp Mar Biol Ecol., 295: Froese, R., Cube Law, Condition Factor and Length-Weight Relationships: History, Meta-Analysis and Recommendations. JAI., pp:

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