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: Pengelolaan Berkelanjutan Perikanan Rajungan (Portunus pelagicus) di Lampung Timur.
Abstrak: Increasing demand for crab meat export and followed by good prices have been increased fisher preference for capturing the blue swimming crab, Portunus pelagicus (Linnaeus, 1758) in Indonesia. One of potential area for wild catch production of this species in Indonesia was at the East Lampung coastal waters, which is an open coast type with generally slight slope of marine topography. However, biological information of this species was rare. Catches productivity as well as caught crabs sizes tend also to be decreased and might be related to high exploitation rate; so this fishery is required to be managed properly. This study aimed to: (1) describe life history characteristics in reproductive biology; (2) distinguish spatial temporal variation of stock structure; (3) describe population dynamic parameters; (4) evaluate of crab exploitation pattern; (5) arrange management measure options for sustainable management of this crab fishery in East Lampung coastal waters. A comprehensive reproductive biology parameters were analysed based on representative samples, which were collected at landing site and conducted monthly from June 2011−Mei 2012. Spatio-temporal of stock structure was analysed based on sampling at three stratifications area from March 2012−February 2013. These stratification areas consist of S1 (water depth <5 m and <4 nautical mile from the shore line), S2 (water depth about 5−10 m and 4−10 nautical mile from the shore line), S3 was offshore direction, whiles fourth sub-areas (A1−A4) at each stratification. Those sub-areas were decided based on morphological characteristics of shore and coastal land coverage. Thus, the unit area of sampling was noted as S1A1−S3A4. Those above samples were also used for population dynamic parameter analysis. Crab exploitation pattern was investigated by interviewing the fishers and guided by questionnaire during December 2012−February 2013 and June−September 2013. Life history characteristics of this species in this area indicated by: (a) the size of males and females reach gonad maturity 50% (Lm50)were at 98 mm and 103 mm carapace width (CW); (b) female’s Lm75 and Lm95 were at the size 111.6 mm and 126.0 mm CW, while reproductive maturity (Lr50) was at 115 mm CW; (c) berried females (BEF) ovaries have dominated by gonad development stage of III; (d) gonad somatic indexes of nonberried female (NBF) were higher than BEF in each month, except in August, November, and February, indicating multiple spawning in the year; (e) females became double breeding or more in the year as well as high potential for spawning and the value of relative percentage of BEF/NBF above 30% at the size larger than 111 mm CW; (f) the potentially reproductive females at the size 111−170.99 mm and reproductively females at 111−155.99 mm CW. Reproductive pattern was partially spawner and spawning occurred thorough in the year, but it was seasonal-continuous with two peaks season. The first peak of spawning season tends during April−June and the second peak was during September− October/November. Both peaks of spawning seasons vary in BEF abundance and fecundity. Fecundity at the 1st stage of embryonic development with BEF’s size between 91.58−168.00 mm CW was between 229,4682,236,355 eggs (mean ± SE = 926,638 ± 30,975 eggs), linearly and positive
Keyword: East Lampung, Blue swimming crab, harvest strategy, population biology, sustainable management

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