This research was conducted in February-March 2018 at Banten Bay. The purpose of research is to determine to presence of growth overfishing of crab (Portunus pelagicus), to cover width-weight relationships, sex ratio, Gonad Maturity Rate (GMR), Length at First Capture (Lc) and Length at first maturity (Lm). The method used is market survey (observation on crab collectors). Temporary research result showed that width-weight relationships are allometrically positive. Sex ratio show a balance value. GMR is the dominant GMR III. Lc 11,26 cm male; 11,38 cm female and Lm 11,82 cm male; 9,30 cm female. Based on the data, it can be seen that the population of the male crabs more quickly decreased compared to the females. If these fishing conditions continue to happen in the long time. It will cause the growth overfishing, result the temporary loss of population and change the food chain.
Ikan selar bentong (Selar crumenophthalmus) merupakan salah satu jenis ikan pelagis kecil yang cukup dominan tertangkap di perairan Natuna, Laut Cina Selatan. Pemanfaatan yang semakin intensif oleh perikanan pukat cincin dikhawatirkan akan mengakibatkan penurunan populasinya. Pengetahuan tentang biologi ikan selar bentong penting sebagai dasar pertimbangan pengelolaannya. Penelitian ini bertujuan menganalisis karakter biologi reproduksi ikan selar bentong di perairan Natuna, meliputi nisbah kelamin, ukuran rata-rata pertama kali matang gonad, ukuran rata-rata tertangkap (L50%), tingkat kematangan gonad dan dugaaan musim pemijahan. Penelitian dilakukan dengan mengumpulkan ikan contoh hasil tangkapan pukat cincin yang didaratkan di PPN Pemangkat Kalimantan Barat selama 5 tahun (2012-2016). Hasil penelitian menunjukkan Nisbah kelamin ikan jantan dan betina adalah 1:1.05. Sebagian besar ikan dalam stadium pematangan (ripening, TKG 3). Ikan bentong mengalami dua musim pemijahan yakni pada awalmusim timur (Juni-Juli) dan awal musim barat (Desember-Januari). Ukuran rata-rata tertangkap (L50%) sebesar 18 cm FL lebih kecil dari nilai pertama kali matang gonad (Lm) yakni 20,2 cm FL. Nilai Lc yang lebih kecil daripada nilai Lm mengindikasikan terjadinya growth overfishing.Bigeye scad (Selar crumenophthalmus) dominantly caught by fishers in the Natuna watersof South China Sea. The intensive exploitation rate of this species by purse seiner led to population decrease. The understanding on biological aspect of bigeye scad is important as a consideration on arranging a proper management. This study aims to analyze biological reproduction of bigeye scad in the Natuna waters, such as sex ratio, length at first maturity, length at first capture, gonad maturity stage and the estimation of spawning season. This research is conducted by sampling the fishes that caught by purse seine fleets which is landed in AFP Pemangkat, West Borneo for 5 years (2012 to 2016). The result showed that sex ratio of males and females were balance by 1:1,05. It dominated by fish that are ripening stage. Spawning season happens twice per year which are in the beginning of east season on June to July and at the beginning of west season on December to January. Length at first capture (L50%) is 18 cmFL lower than length at first maturity (Lm = 20,2 cmFL) this condition indicated growth overfishing occurred in this fishery.
Studies on the exploitation and catch fluctuations of pelagic fishes have been undertaken in order to understand the fishery systems, annual and seasonal change of fishing effort and catches, as well as species composition. The study was based on the daily monitoring data of the purse seiners. The results showed that generally the fishing activities is one day fishing, the increase of fishing effort reflected in the number of fishing units and the number of trip, while the trend of production and catch rate were fluctuated by either annual or seasonal; the peak of catch rate was occurred in 2007, 2008 and 2012 periods, during December to June were low catches, and are going in the peak season in September-October. The lowest catch rate is about 100kg/trip and the maximum of 4.3 tons/trip (the average of 1.3 tons/trip), however the fail of fishing was often occurs and reached 30% of the total number of trips; the failed fishing was decline from year to year. The catch rate (kg/trip/day) was showed a pattern fluctuations; the small pelagic fish mainly the scads (Decapterus spp.) and clupeids (Bali sardine, Sardinella lemuru), respectively 33% and17%, whereas the dominan large pelagic fish is 'tongkol'/frigate tuna (Auxis thazzard). The changes of species domination was occurred either in annually or seasonally
The waters Kwandang are one of the main fishing grounds for small pelagic fisheries in Sulawesi Sea in where the Indian mackerel (Rastrelliger kanagurta) has been exploited. The objective of the research was to estimate population parameters of indian mackerel that included: growth, mortality, gonad maturity and exploitation rate. Length frequency data were collected from Coastal Fishing Port of Kwandang, from January to November 2012. Estimation of population parameters of Indian mackerel was done using FISAT II software. The results show that growth rate were as follows (K) = 0.80 year -1 , L =27.3 cm. Total mortality rate (Z) was 2.72 year -1 , with natural mortality (M) = 1.29 year -1 and consequently, fishing mortality (F) was 1.43 year -1 and exploitation rate (E) = 0.53. This indicates the exploitation of Indian mackerel in Kwandang waters has reached its optimum level. The sex ratio of Indian mackerel was balance. The most common specimens is found at immature stage of I. Based on the results, it is suggested that precautionary approach through responsible management should be applied through several possibilities such as increasing of the mesh size of the gears, restricting additional lift net, restricting fishing for certain seasons, declaring fish sanctuaries in certain areas, especially in spawning grounds to protect the Indian mackerel.
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