Rancang Bangun Bubu Lipat Rajungan Ramah Lingkungan

Abstract

Rajungan merupakan komoditas perikanan bernilai ekonomi tinggi dengan permintaan kuat pada pasar domestik dan internasional. Peningkatan pemanfaatan sumber daya rajungan perlu diikuti penggunaan alat tangkap yang mampu menjaga efektivitas penangkapan sekaligus meningkatkan selektivitas ukuran. Bubu lipat memiliki keunggulan karena mempertahankan rajungan dalam kondisi hidup, tetapi konstruksi konvensional masih dapat menghambat rajungan saat memasuki perangkap dan belum menyediakan jalur pelolosan yang terintegrasi bagi rajungan tidak layak tangkap. Penelitian bertujuan mengembangkan rancangan pintu masuk bubu lipat yang sesuai dengan morfologi dan tingkah laku rajungan, sehingga berbagai ukuran rajungan dapat memasuki bubu, rajungan layak tangkap dapat dipertahankan, dan rajungan tidak layak tangkap memperoleh peluang untuk membebaskan diri. Penelitian dilaksanakan pada Oktober 2024-Oktober 2025 di SUPM Pariaman, Kabupaten Padang Pariaman, Sumatera Barat, melalui percobaan laboratorium terkontrol. Pengembangan konstruksi dilakukan secara bertahap melalui pengujian sudut dan ukuran mata jaring lintasan, bentuk celah, arah celah, bentuk dan ukuran kisi, serta posisi pintu masuk. Pengujian lintasan dan bentuk celah menggunakan 136 rajungan, pengujian arah celah dan kisi menggunakan 115 rajungan, sedangkan pengujian posisi pintu menggunakan 80 rajungan. Data dianalisis menggunakan regresi linier, analisis deskriptif, rancangan acak lengkap, analisis ragam dua arah, uji Tukey HSD, uji Chi-square, dan Wilcoxon Signed-Rank Test sesuai karakteristik setiap tahap percobaan. Pengujian lintasan menunjukkan bahwa sudut 20° dan mata jaring 0,125 inci memberikan kondisi paling mudah bagi rajungan untuk merayap menuju pintu masuk. Sudut 20°, 30°, dan 40° masing-masing dilewati 73, 59, dan 46 rajungan, sedangkan mata jaring 0,125; 0,75; dan 1,25 inci masing-masing dilewati 69, 59, dan 50 rajungan. Mata jaring berukuran besar meningkatkan risiko kaki jalan terperosok dan kaki renang tersangkut. Selanjutnya, celah persegi panjang lebih efektif daripada celah elips. Celah persegi panjang dilewati 369 rajungan, sedangkan celah elips dilewati 211 rajungan. Bukaan persegi panjang yang seragam lebih sesuai dengan bentuk karapas yang pipih dan melebar serta pola gerak lateral rajungan. Pengujian arah celah menunjukkan bahwa arah depan dan bawah lebih mudah dilewati dari sisi luar dibandingkan arah atas. Dari sisi belakang, arah bawah meloloskan 54 rajungan tidak layak tangkap dan hanya 24 rajungan layak tangkap. Pola hasil menunjukkan keseimbangan terbaik antara fungsi masuk, pelolosan, dan retensi. Berdasarkan morfometri rajungan, kisi dirancang dengan panjang 4,0 cm, jarak antarkisi 3,0 cm, dan diagonal 5,0 cm. Kisi batang dan kisi huruf U tidak berbeda nyata dalam kemudahan masuk dari sisi depan. Namun, kisi batang masih meloloskan 93 rajungan layak tangkap, sedangkan kisi huruf U menahan seluruh rajungan layak tangkap dan tetap meloloskan 203 rajungan tidak layak tangkap. Penempatan pintu pada sisi samping meningkatkan peluang rajungan menemukan jalur masuk dan jalur pelolosan. Pintu samping dilewati 472 rajungan, sedangkan pintu depan dilewati 386 rajungan. Sebanyak 314 rajungan tidak layak tangkap membebaskan diri melalui pintu samping dan 247 rajungan melalui pintu depan. Setelah dilengkapi kisi huruf U, rajungan layak tangkap tidak dapat membebaskan diri melalui kedua posisi pintu. Sintesis seluruh tahapan menghasilkan rancangan bubu lipat dengan lintasan 20°, mata jaring 0,125 inci, celah persegi panjang mengarah ke bawah, kisi huruf U berukuran 4,0 × 3,0 cm dengan diagonal 5,0 cm, dan pintu pada sisi samping. Kebaruan penelitian terletak pada integrasi fungsi pintu masuk dan celah pelolosan dalam satu konstruksi. Rancangan yang dihasilkan berpotensi meningkatkan efektivitas dan selektivitas penangkapan serta mendukung pemanfaatan sumber daya rajungan secara berkelanjutan.

Blue swimming crab is a high-value fishery commodity with strong demand in domestic and international markets. Increasing exploitation requires fishing gear that can maintain capture effectiveness while improving size selectivity. Collapsible traps are advantageous because crabs are retained alive; however, conventional entrance structures can hinder crab entry and generally lack an integrated escape route for undersized individuals. This study aimed to develop a collapsible-trap entrance design based on crab morphology and behavior so that crabs of various sizes can enter the trap, legal-sized crabs can be retained, and undersized crabs can escape. The study was conducted from October 2024 to October 2025 at SUPM Pariaman, Padang Pariaman Regency, West Sumatra, using controlled laboratory experiments. Trap development was performed sequentially by testing entrance-ramp inclination and mesh size, entrance-opening shape, opening orientation, escape-grid dimensions and configuration, and entrance position. Tests of the entrance ramp and opening shape used 136 crabs, tests of opening orientation and escape grid used 115 crabs, and tests of entrance position used 80 crabs. Data were analyzed using linear regression, descriptive analysis, a completely randomized design, two-way analysis of variance, Tukey's HSD test, Chi-square test, and Wilcoxon Signed-Rank Test according to the characteristics of each experimental stage. The entrance-ramp experiment showed that a 20° inclination and 0.125-inch mesh provided the easiest surface for crabs to crawl toward the entrance. Ramps inclined at 20°, 30°, and 40° were traversed by 73, 59, and 46 crabs, respectively, while mesh sizes of 0.125, 0.75, and 1.25 inches were traversed by 69, 59, and 50 crabs. Larger mesh increased the risk of walking legs slipping through the mesh and swimming legs becoming entangled. A rectangular opening was more effective than an elliptical opening. The rectangular opening was traversed by 369 crabs compared with 211 crabs through the elliptical opening. Its uniform aperture was better suited to the flattened, laterally expanded carapace and lateral movement of swimming crabs. Tests of opening orientation showed that forward- and downward-facing openings were easier to traverse from outside the trap than an upward-facing opening. From inside the trap, the downward-facing opening allowed 54 undersized crabs to escape while only 24 legal-sized crabs passed through, providing the best balance between entry, escape, and retention. Based on crab morphometrics, the escape grid was designed with a length of 4.0 cm, a spacing of 3.0 cm, and a diagonal dimension of 5.0 cm. The bar grid and U-shaped grid did not differ significantly in entry performance. However, the bar grid still allowed 93 legal-sized crabs to escape, whereas the U-shaped grid retained all legal-sized crabs and allowed 203 undersized crabs to escape. A side entrance increased the probability of crabs locating both entry and escape routes. The side entrance was traversed by 472 crabs compared with 386 crabs through the front entrance. A total of 314 undersized crabs escaped through the side entrance and 247 through the front entrance. After the entrances were equipped with U-shaped grids, legal-sized crabs were unable to escape through either entrance position. The final design integrated a 20° entrance ramp, 0.125-inch mesh, a downward-facing rectangular opening, a U-shaped grid measuring 4.0 × 3.0 cm with a 5.0-cm diagonal, and a side entrance. The principal novelty lies in integrating the entrance and escape functions into a single structure. The resulting design has the potential to improve capture effectiveness and size selectivity while supporting sustainable exploitation of swimming crab resources.