Daniel Limbong

EMISSIONS AND ENVIRONMENTAL IMPLICATIONS OF MERCURY FROM ARTISANAL GOLD MINING IN NORTH SULAWESI, INDONESIA

In artisanal gold mining practiced in North Sulawesi Island, Indonesia, gold is separated from ore by the use of mercury, which forms an amalgam with gold. All related processes are undertaken with a low level of technical knowledge and skills, no regulation, and with disregard for the safety of human and environment health. The situation is generating serious potential health and environmental risks in the area. As part of an ongoing monitoring program, total mercury concentrations were examined in water, bottom sediment and fish samples from three main rivers in Talawaan Watershed, which receives drainage from gold mining practices. Monitoring began in May-June 2000, almost 2 years after artisanal gold mining had begun. At that time, the mercury concentration in the sediment was generally low, except in places close to the gold processing plants. In the present study, a more systematic sampling and analysis was conducted in May-June 2001. Bottom surface sediments, water, and fish samples were collected at 12 sites along the three main rivers in the watershed. In addition, one site outside the watershed was sampled to serve as a control. Sample collections were conducted in three phases in duplicate, with two-week intervals between each phase. The mercury concentration observed in this study indicated that an increase took place along the three main rivers in the watershed. Solutions to this problem must be formulated as soon as possible in order to avoid a major health, economic, and ecological disaster arising from the continuing discharge of Hg. The present study proposes that mercury dispersion occur downstream of the mining.

Morphological and physiological changes of female tropical eels, Anguilla celebesensis and Anguilla marmorata, in relation to downstream migration

The morphological and physiological characteristics of migrating and non-migrating female tropical eels, Anguilla celebesensis and Anguilla marmorata were examined in relation to their downstream migration on central Sulawesi Island, Indonesia. Migrating eels (64 A. celebesensis and 37 A. marmorata) were obtained from weirs set near the outlet area of Poso Lake and non-migrating eels (21 A. celebesensis and 21 A. marmorata) were sampled by set-lines and eel pots in Poso Lake, its inlet rivers, and in the La River system during February 2009 to October 2010. In both species, values of eye index, pectoral-fin length index, gonado-somatic index (I(G)), hepato-somatic index, swimbladder-somatic index and cardio-somatic index of migrating eels were significantly higher than those of non-migrating eels and the gut-somatic index values of the migrating eels were significantly lower than that of non-migrating eels. When silvering stages of eels were classified by the silvering index for Anguilla japonica, in A. celebesensis, all non-migrating eels were Y1 stage and the migrating eels consisted of Y2, S1 and S2 stages eels. In A. marmorata, the non-migrating eels consisted of Y1 and Y2 eels, and the migrating eels consisted of Y2 and S1 eels, but there were no S2 eels. Results of principal component analysis (PCA) of morphological and physiological variables suggested that these characteristics changed drastically between the Y1 and Y2 stages in A. celebesensis, while A. marmorata showed a gradual change with silvering, which differs from the temperate species A. japonica. The mean ±S.D. I(G) value of migrating A. celebesensis (6.9 ± 1.8, 3.3-11.4) was very high and that of A. marmorata (3.1 ± 0.8, 1.8-5.7) was comparatively low. The very different rates of maturation that were found between these two species provide support for the hypothesis that the reproductive characteristics of silver eels can reflect their migration scale.

Repeated vertical movements of mature anguillid eels in a lake

Reproductive migration is a critical phase in the life history of anguillid eels. Nevertheless, fine-scale behaviours of migrating eels remain unknown, primarily due to the difficulty in attaching high-resolution recording devices to, and recovering them from, these small-sized teleosts. We attached a small accelerometer with time-scheduled release system to mature Anguilla celebesensis and A. marmorata in Lake Poso, Indonesia, during the pre-migration period. The eels repeated up-and-down movements in the water column (maximum depth, 77m), with slower, less active descents at shallower pitch angles, followed by faster, more active ascents at steeper pitch angles. The asymmetric diving pattern indicates negative buoyancy of the eels, which was confirmed by the measurements of body densities. The repeated diving is unlikely to represent foraging or thermoregulation because mature eels are thought to fast and water temperature changed little with depth. We suggest that the repeated diving is a result of the eels’ internal motivation for continuous swimming in preparation for oceanic migration, and is possibly energetically more efficient than if they keep swimming at a certain depth. The swimming energetics of eels in nature might be more complicated than previously thought because of the effect of vertical movements and non-neutral buoyancy.

Age and growth of migrating tropical eels, Anguilla celebesensis and Anguilla marmorata : AGE AND GROWTH OF MIGRATING TROPICAL EELS

The age and growth of migrating tropical eels, Anguilla celebesensis and Anguilla marmorata from central Sulawesi, Indonesia, were examined. Migrating eels (63 A. celebesensis and 38 A. marmorata) were obtained from weirs near the Poso Lake outlet and non-migrating eels (35 A. celebesensis and 119 A. marmorata) were captured by baited hooks, eel pots, scoop net and electro-fishing in the Poso River system, Laa River system, Baluga River, Tongku River and Padapu River from February 2009 to October 2010. In both species, the proportion of eels with opaque otolith edges showed a single peak in July, suggesting that one annulus (a pair of translucent and opaque zones) was formed each year in their otoliths. Mean ± s.d. and range of total length (LT ) and age was 785·2 ± 114·9 (585-1083) mm and 7·5 ± 1·6 (5-11) years in migrating female A. celebesensis and 1132·2 ± 173·7 (800-1630) mm and 11·6 ± 3·3 (7-23) years in A. marmorata. The age of migrating female eels was negatively correlated with annual growth rate, 100·7 ± 17·2 (68·1-145·0) mm year-1 in A. celebesensis and 97·9 ± 19·3 (66·6-131·6) mm year-1 in A. marmorata, but there was no significant correlation between the LT and annual growth rate in either species. The annual growth rates of these female tropical eels were typically higher than those of temperate anguillid species, suggesting a latitudinal cline in growth rate in the genus Anguilla reflecting the environmental conditions of their growth habitat.

Interspecific and sexual differences in riverine distribution of tropical eels Anguilla spp.

A total of 261 individuals of the four tropical eel species, Anguilla celebesensis, Anguilla marmorata, Anguilla bicolor pacifica and Anguilla interioris, were collected from 12 locations around Sulawesi Island, Indonesia, to gain knowledge about the riverine distribution of tropical eels. Anguilla marmorata was predominant in the lower reaches of Poso River (94·4% of total eel catch in the sampling area), Poso Lake (93·3%), three small inlet rivers of Tomini Bay (100%) and Laa River (92·3%). Anguilla celebesensis occurred frequently in the inlet rivers of Poso Lake (63·5%). Anguilla bicolor pacifica and Anguilla interioris were rare (1.5 and 0.4%, respectively). Otolith Sr:Ca ratio electron-probe micro analysis (EPMA) for individual migratory histories revealed that 15 A. celebesensis caught in Poso Lake and its inlet rivers were categorized into 14 river eels (Sr:Ca < 2·5) showing upstream migration seemingly at their elver stage and only one sea eel (Sr:Ca ≥ 6·0) that stayed in the marine habitat for the majority of its life after recruiting to Sulawesi Island before its late upstream migration. In A. marmorata, 19 examined eels from Poso Lake and its inlet rivers were all river eels, while 17 eels from the lower reaches of Poso River were two river eels, six sea eels and nine estuarine eels (2·5 ≤ Sr:Ca < 6·0) that mostly lived in the brackish water. The sex ratio of A. celebesensis was highly skewed towards a dominance of females (99%). In A. marmorata, females were predominant in Poso Lake (95·2%), its inlet rivers (94·7%) and Laa River (100%), while males were more frequent in the lower reaches of Poso River (76·5%) and small inlet rivers of Tomini Bay (94·1%). These results indicate that the riverine distribution pattern of tropical eels differs among species and between sexes.

Interspecific difference in downstream migratory season between two tropical eels, Anguilla celebesensis and Anguilla marmorata

Downstream-migrating Anguilla celebesensis eels were predominant relative to Anguilla marmorata in October, November, December, January and February (75.9-92%), while no A. celebesensis occurred and A. marmorata were predominant in May and July (96-100%), at the outlet of Poso Lake, Sulawesi Island, Indonesia. Merging these results with those from published data suggests that most A. celebesensis start downstream migration during the early to middle rainy season, and A. marmorata migrate almost year-round with a peak from the late rainy to middle dry season.

MEKANISASI SISTEM PANEN PADA KULTUR MASSAL ROTIFER, Brachionus rotundiformis

Rotifer adalah salah satu jenis zooplankton yang populer dimanfaatkan sebagai pakan alami untuk pemeliharaan larva fauna air. Beberapa kajian dewasa ini juga mempromosikan rotifer sebagai sumber senyawa bioaktif seperti khitin. Salah satu permasalahan utama dalam upaya pemanfaatan rotifer untuk akuakultur maupun untuk memproduksi senyawa bioaktif, adalah ketidakberlanjutan dan rendahnya produksi rotifer. Berdasarkan eksperimen di laboratorium menyangkut biologi dan ekologi rotifer, kultur massal yang intensif telah berhasil dilakukan pada kolam beton berukuran panjang 5 m, lebar 1 m, dan dalam 1 m. Teknik panen dan hal lain yang terkait, dipandang sebagai faktor penting yang mempengaruhi keberhasilan sistem kultur massal tersebut. Mengacu pada beberapa aspek teknik yang sedang dijalankan, studi ini dilakukan untuk memperbaiki mekanisasi teknik pemanenan yang diharapkan akan meningkatkan efektivitas produksi biomassa rotifer yang bermutu baik. Beberapa uji penerapan dari hasil mekanisasi teknik pemanenan, menampilkan kapasitasnya dalam memperbaiki mutu produksi rotifer, mereduksi waktu panen dan tenaga kerja, serta mempertahankan kontinuitas siklus produksi.