Judul: Population dynamics and stock assesment of blue swimmer crab (Portunus pelagicus Linnaeus) resource in Pati and Adjacent Waters
Abstrak: Blue swimmer crab ( P.pelagicus ) resource have been exploited continuously in Pati regency waters for two decades. The main fishing gear were used by portable traps. It was indicated crab catches decline. It’s caused by decline of crab population that have been fishing continuously. That is a problem to manage the crab resource . This study aims to assess: 1) the distribution and stock abundance of crab and it’s environmental factors, 2) aspects of crab reproduction, 3) the mean width at first capture (Lc) and mean width at the first maturity (Lm), 4) population dynamics such as size distribution, growth, mortality and age, 5) status and exploitation rate of crab resource and 6) management options for sustainable crab resource. Research has been carried out from January 2012 to March 2013. It was divided into three parts, consisting of: observations at the landing base, observations at the sea and observations in the laboratory. Study area were divided into three zones which are crab fishermen fishing ground based in Alasdowo, Pati regency, Central Java. The data consists of environment parameters, biology ( size, weight, sex and TKG ) and the catch ( buku bakul and experimental fishing). Marine environmental conditions were quite optimum for the growth of crab in East and West season, so the distribution of crab catches by season and different substrate are relatively similar (p < 0.05). Crab catch per unit effort ( CPUE ) in fishing zone 1, 2 and 3 are influenced by the lunar cycle (p <0.05). CPUE in zones 1 and 3 was relatively similar (p > 0.05) in the west and east season. While CPUE in West season was higher than east season ( p < 0.05 ). Sex ratio is relatively balanced (p > 0.05) in West season. But sex ratio was not balanced in East season, it’s tendency that females more than males (p<0.05 ). Crab reproduction occured throughout the year in Pati waters. The mean carapace width at first maturity (Lm) of females were 107 mm. The fecundity of crab was ranged between 351 214 to 1 347 029 grains with an average at 957 196 grain. The mean carapace width of the crab caught in zone 2 was smaller (105.2 mm for males and 106.8 mm for females) than the crab caught in the waters of the middle zone 1 and 3 ( p <0.05 ). The average crab in January and February are smaller than in other months due to decreased salinity waters. It made adult crabs which generally maturring were migrated to deeper waters. Crab size between September and November are relatively higher than in other months, alleged that the crabs generally have entered the mature phase and has matured gonad. The mean width at first capture (Lc) of crabs by portable trap was 108 mm . Carapace width and weight relationship of male and female crab were allometric positive (p<0.05). Monthly condition factor of males and females are relatively similar, the females are influenced by gonadal maturation process. The growth rate of males were faster than females, showed
Keyword: population dynamics, Portunus pelagicus, management, Pati waters

Judul: Analysis of Morphometric Characters and Habitat of Blue Swimming Crab (Portunus pelagicus Linnaeus, 1758) in Pamekasan Regency, Madura
Abstrak: Rajungan (Portunus pelagicus Linnaeus, 1758) termasuk dalam sumberdaya laut penting dan bernilai ekonomis tinggi. Kondisi habitat alami yang menurun dapat menyebabkan rajungan stress, terkena penyakit, sehingga kematian. Perlu adanya analisis karakter morfometrik dan habitat rajungan pada Kabupaten Pamekasan, Madura. Penelitian dilaksanakan selama tiga kali sampling yaitu Agustus 2022, Oktober 2022, dan Januari 2023. Hasil menunjukkan rajungan yang tertangkap memiliki distribusi lebar karapas pada 62,5-152,5 mm. Rajungan jantan memiliki pola pertumbuhan allometrik, sedangkan rajungan betina memiliki pola pertumbuhan isometrik. Nilai slope pada ANCOVA menunjukkan laju pertumbuhan lebar karapas dan panjang karapas tiap bulan sama/tidak memiliki perbedaan nyata (p>0,05). Analisis Kruskal Wallis menunjukkan sebagian besar karakter morfometrik rajungan tiap bulan berbeda nyata (p<0,05). Analisis diskriminan menunjukkan persebaran karakter morfometrik tiap bulan tidak berbeda jauh dan berhubungan erat. Sebagian besar parameter fisika kimia telah memenuhi baku mutu serta tiap parameter saling memiliki korelasi. Komposisi bycatch yang tertangkap sebesar 45,60% dan didominasi famili Portunidae., Blue swimming crab (Portunus pelagicus Linnaeus, 1758) is an important marine resource and has high economic value. Decreasing natural habitat conditions can cause crab stress, disease, and even death. There is a need to analyze the morphometric characters and habitat of blue crabs in Pamekasan Regency, Madura. The research was carried out with three sampling sessions in August 2022, October 2022, and January 2023. The results showed that the crabs caught had a carapace width distribution of 62.5-152.5 mm. Male crabs have an allometric growth pattern, while female crabs have an isometric growth pattern. The slope value in ANCOVA shows that the growth rate of carapace width and carapace length each month is the same/no significant difference (p>0.05). Kruskal Wallis analysis showed that most of the crab morphometric characters were significantly different each month (p<0.05). Discriminant analysis showed that the distribution of morphometric characters for each month is not much different and is closely related. Most of the physicochemical parameters have met quality standards and each parameter has a correlation with each other. The composition of bycatch caught was 45.60% and was dominated by the Portunidae family.
Keyword: morphomertric characters, habitat characteristic, blue swimming crab, Pamekasan, physicochemical parameters, bycatch

Judul: Dekomposisi Nilai Singular pada Matriks Kompleks Toeplitz Bidiagonal Atas.
Abstrak: Dekomposisi nilai singular merupakan salah satu metode faktorisasi matriks berdasarkan nilai singular dan vektor singularnya. Dekomposisi nilai singular bertujuan untuk memfaktorisasi suatu matriks �������� berukuran �������� × �������� menjadi bentuk �������������������������������� dengan �������� merupakan matriks berukuran �������� × �������� , �������� merupakan matriks berukuran �������� × �������� dan �������� merupakan matriks berukuran �������� × ��������. Pada karya ilmiah ini, dibahas dekomposisi nilai singular pada matriks kompleks Toeplitz bidiagonal atas berukuran �������� × (�������� + 1).
Keyword: dekomposisi nilai singular, matriks Toeplitz, matriks bidiagonal atas, matriks kompleks