Kajian Komposisi Ukuran Rajungan Betina (Portunus pelagicus) di Fishing Ground Perairan Pemalang

Abstract

Rajungan betina memiliki peranan penting dalam keberlanjutan stok sumber daya rajungan di alam. Maraknya rajungan betina yang masih ditangkap oleh nelayan menjadi salah satu ancaman besar terhadap keberlanjutan sumber daya rajungan. Tujuan penelitian ini untuk mengetahui komposisi rajungan betina berdasarkan kelas lebar karapas, hubungan lebar karapas dan berat tubuh, komposisi tingkat kematangan gonad (TKG), nilai fekunditas dan persentase egg berried female (EBF) pada 20 titik area fishing ground yang dilaksanakan selama bulan Mei – Agustus 2022 di perairan Pemalang. Pengambilan sampel dan penentuan titik fishing ground dilakukan secara purposive sampling dengan menyesuaikan area penangkapan nelayan rajungan Desa Danasari, Pemalang. Distribusi ukuran lebar karapas rajungan menunjukkan modus kelas lebar karapas pada 101 – 110 mm, dimana kondisi tersebut tergolong kurang baik mengingat ukuran minimum rajungan yang boleh ditangkap adalah >100 mm. Hubungan lebar karapas dan berat tubuh menunjukkan pertumbuhan rajungan betina bersifat allometrik negatif, yang berarti pertambahan lebar karapas lebih cepat dibandingkan pertambahan berat tubuh. Komposisi TKG rajungan betina didominasi pada kondisi kematangan tingkat 2 (TKG 2) dengan persentase 78%. Nilai fekunditas rajungan betina bertelur dengan rata-rata pada kisaran 301.202±131.949 butir telur. Nilai EBF tertinggi ditemukan pada titik 12 dengan persentase 1,09% dengan rajungan betina bertelur sebanyak 7 ekor. Keberadaan rajungan betina di perairan menjadi salah satu faktor kunci keberlanjutan sumber daya rajungan, sehingga diharapkan dapat dijadikan acuan dalam penentuan area perlindungan dan kawasan potensial reproduksi rajungan di perairan Pemalang dan perairan lainnya.

Female blue swimming crabs have an important role in the sustainability of crab populations of natural resources. The large number of female crabs that are still caught by fishermen is one of the major threats to the sustainability of crab resources. The purpose of this study was to determine the composition of female crab based on carapace width class, carapace width and body weight relationship, composition of gonad maturity level (TKG), fecundity value and percentage of egg berried female (EBF) at 20 spots of fishing ground area during May - August 2022 in Pemalang waters. Sampling and selection of fishing ground points were carried out by purposive sampling by adjusting the fishing area of crab fishermen in Danasari Village, Pemalang Regency. The distribution of carapace width size of crab showed the mode of carapace width class at 101 - 110 mm, where the condition is not quite good considering the minimum size of crab that can be caught is >100 mm. The relationship between carapace width and body weight shows that the growth of female crabs is negative allometric, which means that the increase in carapace width is faster than the increase in body weight. The TKG composition of female crabs is dominated by the condition of 2nd maturity level (TKG 2) with a percentage of 78%. The fecundity value of egg laying female crabs with an average in the range of 301,202±131,949 eggs. The highest EBF value was found at spot 12 with a percentage of 1,09%, with the number of egg berried female crabs are 7 individuals. The presence of female crabs in the waters is one of the key factors for the sustainability of crab resources, so it is expected to be used as a reference in determining protection and potential reproduction areas of blue swimming crabs in Pemalang waters and other waters.