Aspek Biologi Rajungan (Portunus pelagicus) Linnaeus, 1758 (Malacostraca : Portunidae) Ditinjau dari Morfometri dan Tingkat Kematangan Gonad di TPI Bulu, Jepara

Abstract

Rajungan (P. pelagicus, Linnaeus, 1758) merupakan salah satu komiditas perikanan yang memiliki nilai ekonomi yang penting sehingga banyak diminati dalam negeri maupun luar negeri. Permintaan rajungan yang terus meningkat berbanding lurus dengan penangkapan yang semakin meningkat. Tingkat pemanfaatan rajungan masih ditemukan ukuran yang masih under size tanpa memperhatikan ukuran dan kondisi habitat sehingga akan berpotensi mengurangi stok rajungan di perairan. Penelitian ini bertujuan untuk mengetahui morfometri dan tingkat kematangan gonad rajungan yang dilaksanakan bulan Oktober – November 2020 selama 30 hari di TPI Bulu, Jepara. Penelitian ini menggunakan metode survey yg bersifat deskriptif dengan pengambilan sampel secara random sampling. Hasil dari penelitian diketahui rasio kelimpahan rajungan jantan sebesar 51% (2.297 ekor); rajungan betina 49% (2.203 ekor) dari 4.500 ekor sampel rajungan. Distribusi lebar karapas rajungan selama penelitian berkisar antara 64 – 164 mm dan berat tubuh kisaran sebesar 23 – 333 gram. Data menunjukkan bahwa pola pertumbuhan rajungan yang ada di perairan TPI Bulu adalah allometrik positif yaitu pertumbuhan berat tubuh lebih cepat dibandingkan dengan lebar karapas. Hasil nilai b sebesar pada rajungan jantan 3,51 dan rajungan betina sebesar 3,33 serta nilai b sebesar 3,41 pada keseluruhan rajungan. Rajungan betina diduga mengalami pertama kali matang gonad pada selang kelas ukuran lebar karapas 61 – 70 mm. Distribusi tingkat kematangan gonad rajungan betina pada perairan TPI Bulu adalah 44% (961 ekor) pada TKG 1; 28% (626 ekor) pada TKG 2; dan 28% (616 ekor) pada TKG 3, yang berarti nelayan Jepara belum sepenuhnya menerapkan kriteria dan ukuran layak tangkap dengan peraturan yang diberlakukan.

Blue swimming crab (P. pelagicus, Linnaeus, 1758) is a fishery commodity and is in great demand both domestically and abroad. The demand for crabs that continues to increase is directly proportional to the increasing catch. The utilization rate of the size is still undersize without paying attention to the size and condition of the crab so that it has the potential to reduce the crab stock in the waters. This study aims to determine the morphometry and maturity level of the small crab gonads which were conducted from October to November 2020 for 30 days in Bulu Fish Port, Jepara. This study used a descriptive survey method where the sample was taken by random sampling. The results of the study revealed that the abudance of male blue swimming crab was 51% (2.297 male blue swimming crabs) and the abudance of the female blue swimming crabs was 49% (2.203 female blue swimming crabs) of 4.500 blue swimming crab samples. The distribution of crab carapace width during the study ranged from 64 – 164 mm and body weight ranged from 23 – 333 gram. The data shows of blue swimming crab growth pattern in Bulu Fish Port waters was positive allometric both male and female blue swimming crab, meaning that bodyweight growth is faster than the size of the carapace width. The result of the b value of 3,51 male crabs and the female crabs was 3,33 and the b value was 3,41 on the whole crab. The female crab is thought to have experienced gonad maturity for the first time in the class sizes of carapace 61 – 70 mm. The distribution of gonad maturity level female blue swimming crabs in the waters Bulu is 44% (961 individual) at TKG 1; 28% (626 individual) at TKG 2; and 28% (616 individual) at TKG 3, which means that Jepara fishermen have not fully implemented the criteria and sizes for catching fish with the applicable regulations.