Distribution and Size of Crab (Portunus pelagicus) in Betahwalang Waters, Demak, Central JavaSex Ratio, Size Distribution and Length-Weight Relationship of Portunus pelagicus Linnaeus, 1758 (Malacostraca : Portunidae) in Betahwalang, Demak, Central Java

Abstract

Blue Swimming Crab (P. pelagicus, Linnaeus, 1758) is the main fisheries product from Betahwalang peoples. Fishing activity of Blue Swimming Crab by the fisherman almost every day in Betahwalang waters. Distribution and body size data of Blue Swimming Crab can be used for sustain management reference. The purpose of this study was to determine distribution pattern and body size of Blue Swimming Crab, started from July to November 2018 in Betahwalang waters, Demak. The data analyze consist of sex ratio, carapace width distribution and relationship between carapace width and body weight. 11790 samples Blue Swimming crab from Betahwalang waters consist of 7070 female crabs and 4720 male crabs. The result showed that sex-ratio between male and female crabs are balanced (1.0:1.37), with the most female crabs found at July and August. Body size distribution of male and female crabs are dominated in class 103-111 mm carapace width. Male and female crabs have a positive allometric on growth parameters, that means growth of the body weight is faster than carapace width. The result showed that Blue Swimming Crab in Betahwalang waters are support for sustainable fisheries.

Komposisi Hasil Tangkapan Utama Rajungan dan Tangkapan Samping Nelayan Desa Danasari, Pemalang

“…Perbedaan nilai sebaran lebar karapas pada rajungan di beberapa perairan tersebut menunjukkan adanya pengaruh yang signifikan dari berbagai faktor utama seperti faktor lingkungan dan tekanan akibat penangkapan (Kembaren dan Surahman, 2018). Analisis terhadap distribusi ukuran rajungan digunakan dalam upaya menggambarkan dan memperkirakan kondisi populasi rajungan di perairan (Redjeki et al, 2021). Menurut Hosseini et al (2012), menyebutkan rajungan muda umumnya ditemukan di daerah sekitar pantai (shoreline), sedangkan rajungan dewasa dan berukuran lebih besar ditemukan pada perairan yang lebih dalam dan salinitas yang lebih tinggi.…”

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

“…Rajungan betina matang gonad dan bertelur (TKG 2 dan 3) ditemukan dengan ukuran terkecil dibawah 100 mm atau dibawah kriteria minimum layak tangkap. Hal tersebut sesuai dengan Redjeki et al (2021) Nilai fekunditas telur menunjukkan estimasi jumlah butir telur yang dihasilkan oleh individu rajungan. Fekunditas rajungan paling rendah diperoleh yaitu pada kisaran 120.779 butir telur dengan lebar karapas rajungan betina berukuran 95 mm, sedangkan fekunditas paling besar diperoleh pada kisaran 738.673 butir telur dengan lebar karapas rajungan betina berukuran 143 mm.…”

The Composition of Portunus pelagicus on the Fishing Ground Area of Danasari Waters, Pemalang Regency

“…According to Kamrani et al (2010), crabs with positive allometric growth traits can be considered large and fat, while crabs with negative allometric growth properties have the same size but lighter body weight or can be considered skinny crabs. The different growth characteristics of blue swimming crabs from Danasari water to another, can be caused by environmental conditions such as currents, oceanographic conditions, and fishing pressure (Redjeki et al, 2021). According to Shukor et al (2008), the condition of water currents is related to the distribution and availability of food for fish, calm water currents make it easier to get food, conversely, fast water currents will make it more difficult for fish to find food.…”

“…According to Warner (1977), the composition of the size of the carapace width from one area to another caused several factors such as genetic factors and environmental factors. The analysis of size distribution of blue swimming crabs was used to describe and develop the condition of the blue swimming crab population in the sea waters (Redjeki et al, 2021). Regulation of the Minister of Maritime Affairs and Fisheries Number 16 of 2022 states that the minimum size of crabs that may be caught is 100 mm, however, small crabs are still found in fishing areas caught by fishermen.…”