1 BIOLOGI DAN HARVEST STRATEGY PERIKANAN RAJUNGAN DI LAUT JAWAOleh TRI ERNAWATI (Peneliti BPPL-P4KSI) Seminar dan Lokakarya Perikanan Rajungan di Indonesia dan Kajian Peraturan Menteri Kelautan dan Perikanan No.1 dan No. 2. Kerjasama APRI dan Pusat Penelitian Pengelolaan Perikanan dan Konservasi Sumberdaya Ikan (P4KSI), IPB CONVENTION CENTER Bogor 25 Februari 2015

2 BACKGROUND Blue Swimming Crab(BSC) in Java Sea is one of small scale fishery harvest since 1970s. BSC production in Java sea is about 40 % of national BSC production (2012) National export of BSC in 2012 is about tons and value about US$ 368 milion Many kinds of gear are used to exploitate BSC in Java Sea.

3 PROBLEM High demand of BSC commodities tend to exploited intensivelyPopulation decline was indcated by decline of crab production and sizes of crab especially in Java Sea Many fishing gears that is not environmental friendly to utilize the BSC Data on catch effort and biology of BSC is scarce

4 DATA COLLECTION OF BSC Data Recorded :From January – December 2014 at 6 sampling sites (Jakarta, Cirebon, Demak, Rembang, Sumenep dan Sampit), 400 samples per month Biology data : size (carapace width), weight, sex and gonad Gonad stage female immature, Mature and berried (enumerator)

5 RESULT

6 LENGTH-WEIGTH RELATIONSHIPSex Variabel Length-Weight Relationship (W = aLb) Jakarta Cirebon Demak Rembang Sumenep Sampit Male a 7.00E-05 4.00E-05 8.00E-06 2.00E-05 3.10E-03 b 2.9953 3.1058 3.4489 3.2800 2.2200 3.3100 R2 0.9217 0.8653 0.9630 0.9320 0.8303 0.8830 Female 1.20E-04 6.00E-05 1.80E-05 1.00E-05 3.23E-02 5.00E-05 2.8803 3.0234 3.2695 3.394 1.7118 3.0722 0.8714 0.8668 0.935 0.947 0.8311 0.81 ALL 1.00E-04 1.07E-02 2.9304 3.1019 3.3474 3.201 1.9532 3.2211 0.8955 0.8678 0.9443 0.928 0.8092 0.8512 Male is heavier than female, indicated by b(male)>b(female), except in Rembang

7 SIZE COMPOSITION Location Male Female min max mean Jakarta 73.4 152.095.3±10.73 69.1 122 94.5±11.43 Cirebon 71.1 151.3 111.60±11.64 60.0 152.6 108.08±14.66 Demak 58.8 168.4 110.35±18.06 40.4 166.1 112.56±18.21 Rembang 70.4 159.2 115.29±15.45 75.4 165.6 116.41±15.81 Sumenep 75.6 148.0 115.98±15.62 77.2 143.8 114.87±17.00 Sampit 87.0 165.0 134.63±14.73 90.0 183 131.96±14.32

8 SIZE BY GEARS is determined by where the fishing ground are?

9 GROWTH Location Growth parameters L∞ (mm) k (per year) to t max (year)Cirebon 168.60 1.05 2.86 Demak 179.35 1.11 2.70 Rembang 178.80 1.18 2.54 Sumenep 161.40 1.21 2.48

10 Length (CW) frequency & von Bertalanffy GrowthCIREBON DEMAK

11 Length (CW) frequency & von Bertalanffy GrowthREMBANG SUMENEP (MADURA)

12 LENGTH AT FIRST CAPTURE (Lc)Location Mean Length at first capture (Lc/L50) Bubu lipat (Collapsible trap) Jaring (Gill Net) Arad (Mini bottom trawl) Garuk (Dredge Net) Jakarta 100.21 93.64 - Cirebon 109.01 107.22 108.52 99.38 Demak 123.32 101.34 105.43 Rembang 115.72 108.84 Sumenep 114.13 Sampit 130.96

13 LENGTH AT FIRST MATURITY (LM)Lokasi Rata-rata ukuran pertama kali matang gonad (Lm/L50) Location Mean length at first maturity (Lm/L50) Jakarta - Cirebon 99.23 Demak 104.89 Rembang 101.06 Sumenep 101.32 Sampit 123.89 Mean ± 10.11

14 SPAWNING SEASON

15 STATUS STOCK BY LENGTH-CONVERTED CATCH CURVELokasi Parameter mortalitas & Tingkat pemanfaatan Location Mortality parameters & Exploitation Rate Z (Total mortality) M (Natural mortality) F (Fishing mortality) E (Exploitation Rate) Cirebon 6.24 1.15 5.09 0.82 Demak 5.41 1.17 4.24 0.78 Rembang 5.49 1.23 4.26 Sumenep 4.65 1.26 3.36 0.72 IT IS INDICATED THAT THE FISHING PRESSURE ON BSC POPULATION IS AT A HEAVILY EXPLOITED LEVEL

16 SPAWNING POTENTIAL RATIO (SPR)Lm = 99 mm CW

17 SPAWNING POTENTIAL RATIO (SPR)Lm = mm CW

18 SPAWNING POTENTIAL RATIO (SPR)Lm = 101 mm CW

19 SPAWNING POTENTIAL RATIO (SPR)Lm = 101,86 mm CW

20 HARVEST STRATEGY & HARVEST CONTROL RULERegulation of BSC fishing zone that not allowed to fishing in nursery ground area (as preservation stock) – Clossed Area Regulation Apply a minimum legal size of crab (10 cm < ) Clossed season regulation Use gears enviromental friendly (collabsible trap and gill net) Not to catch berried/ovegerous female – If caught, return to the sea Recovery Habitats

21 THANK YOU