Judul: Dampak penangkapan rajungan  ( Portunus pelagicus) terhadap target dan non target di perairan Demak dan sekitarnya
Abstrak: Penangkapan berlebih merupakan penyebab utama penurunan populasi rajungan di alam. Alat tangkap dengan selektivitas rendah, dapat menimbulkan hasil tangkapan sampingan lebih banyak dari hasil tangkapan utama. Penelitian ini bertujuan mendeskripsikan unit perikanan rajungan di lokasi studi, mengidentifikasi dampak penangkapan terhadap target (rajungan), dan mengevaluasi dampak ekologis penangkapan terhadap non target. Analisis yang digunakan yaitu analisis ukuran dan jenis, analisis kelayak tangkapan dan analisis komposisi. Hasil penelitian menunjukkan unit perikanan rajungan yaitu armada, nelayan, dan alat tangkap di lokasi studi yaitu arad 252, bubu 114, dan gillnet 38 unit. Porsi hasil tangkapan utama arad, bubu, dan gillnet masing-masing sebanyak 12%, 25% dan 37%, dan hasil tangkapan sampingan arad 88%, bubu 75%, dan gillnet 63%. Komposisi rajungan layak tangkap oleh arad 43%, bubu 80%, dan gillnet 65%. Ukuran bycatch alat tangkap arad, bubu, dan gillnet rata-rata masih di bawah ukuran layak tangkap (lenght at first maturity). Indeks keragaman (H’) tangkapan arad sebesar 3.40, bubu 3.05, dan gillnet 2.74. Alat tangkap arad, bubu, dan gillnet didominasi trophic level (TL) 2 dan TL 3. Untuk mengatasi dampak tersebut perlu dilakukan perbaikan teknologi penangkapan agar ramah lingkungan terhadap target dan non target, serta tidak merusak struktur dan fungsi ekosistem.
Keyword: fishing impact, Betahwalang waters, bycatch, target blue swimming crab

Judul: Dampak Penangkapan Rajungan (Portunus pelagicus) terhadap Target dan Non Target Spesies di Perairan Cirebon dan Sekitarnya
Abstrak: Kondisi tangkap lebih mengancam keberlanjutan stok rajungan di perairan. Rendahnya selektivitas alat tangkap mengakibatkan tertangkapnya hasil tangkapan sampingan (bycatch) dalam jumlah cukup besar. Penelitian ini bertujuan: (1) mendeskripsikan unit penangkapan rajungan yang berbasis di Desa Gebang Mekar Kabupaten Cirebon; (2) mengevaluasi status stok rajungan; dan (3) mengevaluasi dampak penangkapan rajungan, khususnya terhadap sumber daya ikan non target tangkapan. Data dianalisis dengan beberapa metode yakni analisis mortalitas dan laju eksploitasi, ukuran layak tangkap, serta jenis dan proporsi hasil tangkapan. Hasil penelitian menunjukkan unit penangkapan rajungan di lokasi studi yaitu jaring kejer sebanyak 102 unit, bubu lipat 25 unit, jaring arad 100 unit, dan garuk 100 unit. Laju eksploitasi (E) rajungan jantan 0,66 dan betina 0,60 per tahun. Rajungan ukuran boleh ditangkap (legal size) oleh jaring kejer berjumlah 97%, bubu lipat 97%, jaring arad 83%, dan garuk 19%. Bycatch jaring kejer, bubu lipat, jaring arad, dan garuk sebagian besar belum memenuhi ukuran layak tangkap. Proporsi hasil tangkapan sampingan jaring kejer 51%, bubu lipat 55%, jaring arad 95%, dan garuk 59%. Indeks keragaman Shannon – wiener (H’) hasil tangkapan jaring arad sebesar 3,52, jaring kejer 3,37, bubu lipat 1,82, dan garuk 1,52. Pemerintah perlu meningkatkan penyadaran nelayan agar tidak menggunakan alat tangkap jaring arad dan garuk karena melanggar hukum dan berdampak negatif terhadap sumber daya ikan., Over fishing threatens the sustainability of crab stocks in the waters. The low selectivity fishing gears resulted in a relatively large number of caught bycatch species. This study aims to describe the blue swimming crab fishing unit based in Gebang Mekar Village, Cirebon District; to evaluate the status of the crab stock, and to evaluate the impact of crab fishing, especially on non-target species. The analyses of mortality and exploitation rate, allowable (legal) catch size, and catch composition were conducted. The results showed that the fishing units of blue swimming crab at the study site were 102 units of kejer nets, 25 units of collapsible traps, 100 units of arad nets, and 100 units of dredged nets. The exploitation rate (E) of male crabs was 0.66 and for females was 0.59 per year. For the kejer nets 97% of the crabs caught were in the legal size, 97% for collapsible traps, 83% for arad nets, and 19% for dredged nets. Most of the bycatch of kejer nets, collapsible traps, arad nets, and dredged nets did not meet the allowable catch size. The proportion of the bycatch for kejer nets was 51%, collapsible traps was 55%, arad nets was 95%, and dredged nets were 59%. Shannon – wiener diversity index (H’) of arad nets catches were 3.52, kejer nets (3.37), collapsible traps (1.82), and dredged nets (1.52). Government should disseminate to fishers not to used arad, and dredged nets for crabs fishery due to illegal fishing gears and negative impact on the fish resources.
Keyword: blue swimming crab, bycatch, Cirebon waters, Gebang Mekar, fishing impact, dampak penangkapan, rajungan, perairan Cirebon

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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