Sunday, December 6, 2009

grass carp & hydrilla di rawapening

berikut ini beberapa penelitian kuno yang sangat penting dan berguna, isinya tentang makanan ikan grass carp dan pemanfaatan ikan grass carp, sumber tulisan dari FAO Document Resipotary, judul ; Handbook of utilization of aquatic plants, dalam chapter; FOOD FOR FISH AND AQUATIC ANIMALS

Adams, A.E. and V. Tifolko, 1970 A progress report on the introduction of grass carp (Ctenopharyngodon idella) in Fiji. Fiji Agric.J., 32(2):43–6

Hydrilla verticillata is a serious weed in rivers in Fiji. Grass carp were imported from Malaysia as fingerlings and fed on the weed in a pond, and released into a netted portion of theRewa river. Weight increased from 9.75 g in December 1968 to 3 069 g (length 56 cm) in April 1970. This weight gain was noted as being much higher than those recorded in Malaysia, China, Russia and various European countries. It was concluded that grass carp are able to control H. vertioillata but that large-scale introduction of the fish to do this was dependent on the successful development in Fiji of induced breeding.

Ahling, B. and A. Jernelöv, 1971 Weed control with grass carp in Lake Osbysjön. Rep.Swed. Water Air pollut.Res.Lab., (B94a):24 p. Issued also in Vatten, 27(2):253–64

The authors describe an experiment to control Myriophyllum verticillatum in a lake in Sweden with grass carp. The area of the lake was 4.6 ha and contained about 16 tonnes (dry weight) of the weed. In May, 250 grass carp, average weight 380 g, were introduced. After 100 days they had increased in weight to about 1 kg average, and had consumed about half of the weed. At the same time some Potamogeton natans was eliminated, while Nymphaea alba, Typha angustifolia and phragmites sp. were largely unaffected. A curious feature was that the Myriophyllum reduction was uneven, some areas being cleared and others apparently unchanged. The clearance was more pronounced in deeper water. There was a slight increase in plankton but no effect on turbidity.

Blackburn, R.D. and D.L. Suton, 1971 Growth of white amur (Ctenopharyngodon idella) on selected species of aquatic plants. Proc.Eur.Weed Res.Counc.Int.Symp.Aquat. Weeds, 3:87–93

Tests with grass carp in tanks showed that the fish gained more weight on a diet of fresh Najas guadalupensis and Hydrilla verticillata than on a dried fish food diet. Contrary to the observations of other authors cited in this chapter grass carp were observed to eat water hyacinth. The small fish ate only the roots and did not grow so fast as the large fish which ate both leaves and roots. (From Weed Abstracts)

Chapman, V.J. and B.J. Coffey, 1971 Experiments with grass carp in controlling exotic Macrophytes in New Zealand. Hidrobiologia, Bucharest, 12:313–23

The authors review the introduction and spread in New Zealand of the submerged aquatic weeds Lagarosiphon major, Ceratophyllum demersum, Egeria densa and Elodea canadensis. Methods of control are discussed including possible utilization by harvesting for stock food. Though harvesting was considered practicable the use of the plants as fodder was believed to be unsuitable because of the content of arsenic accumulated by the plants from the thermal waters that enter the lakes. Arsenic in amounts of 35–75 ppm dry weight are common, and extreme values up to 2 000 ppm have been recorded. The alternative possibility of the use of grass carp was investigated as considered more promising, so a few fish were imported from Malaysia.

Mehta, I. and R.K. Sharma, 1972, Control of aquatic weeds by the white amur in Rajasthan, India. Hyacinth Control J., 10:16–9

Grass carp is reported as a voracious feeder of Najas foveolata, Chara sp., Vallisneria spiralis, Potamogeton nodosus, P. pectinatus, P. perfoliatus and Hydrilla verticillata. Fish weighing about 65 g preferred Chara sp., N. foveolata and V. spiralis. Larger fish (200 g) preferred P. pectinatus, P. nodosus, V. spiralis and N. foveolata, and only ate small amounts of Hydrilla sp., P. perfoliatus and Typha sp. However, large fish may flourish on these weeds and may be able to chew leaves of tough plants and fibrous grasses. The observations on grass carp to date are most favourable and show how useful they can be in place of herbicides. More information is needed on best stocking rates. (From author's summary)

Anon., 1971 Use grass carp for weed control. Indian Farming, 21(5):45–7

The paper reports the introduction in 1959 of grass carp and its successful induced breeding and distribution in India. “The fish from 25-mm size starts feeding on minute floating plants such as Wolffia and as it grows it feeds on Lemna, Spirodela and Azolla,and cut bits of submerged weeds such as Hydrilla, Najas, etc., as the size of its mouth increases. Fish of about 100 g size can be used to control most of the common water weeds in small farm ponds, if free from predators. Bigger fish of 0.5–1 kg can be employed to control weeds in larger waters.

The submerged weeds preferred by grass carp are Hydrilla, Najas, Ceratophyllum, Potamogeton, Utricularia and Myriophyllum. The fish will also control Ottelia, Nechamandra, Vallisneria, Trapa, Limnophila andSalvinia (to some extent). However, water hyacinthand Pistia are not completely consumed.

For control of floating weeds grass carp of about 10 cm length (about 15 g) are stocked at 1 000-2 000/ha according to weed density. For other weeds use fish of about 20–30 cm(100–250 g) and stocked at 200–1 000/ha. Regular inspections are needed to determine whether control is proceeding satisfactorily. If not more fish can be added. After the weed has been cleared the fish may be carefully netted out of the water and transferred for use elsewhere. As grass carp is good to eat, and easily caught by angling, precautions against poaching are necessary. If predatory fishes are present then the grass carp should be at least 1 kg in weight before being introduced.”

Point penting yang dapat di ambil untuk diaplikasikan dari hasil penelitian diatas adalah:
Ternak grass carp di rawapening, akan sangat menguntungkan, karena:

- telah terbukti ikan grass carp doyan banget dengan yang namanya hydrilla, yang jelas sangat melimpah ruah di rawapening, hampir 95% dasar rawa pening ditumbuhi hydrilla.

- budidaya grass carp merupakan budidaya yang sangat aplikatif di rawapening, karena pakan berlimpah, dan yang penting pakan gratis.... dan jelas keuntungan besar, dan jika budidaya grasscarp diaplikasikan di karamba rawapening, tentu saja akan menambah kesejahteraan nelayan di rawapening.

Daripada Ngrapah dijadikan sentra bibit patin dan lele yang jelas jelas peternak pembesaran pada gulung tikar karena pelet mahal, mending Ngrapah di jadikan sentra bibit grasscarp, tawes, dan Nilem yang lebih cocok dengan kondisi alam sekitarnya yang kaya pakan, melimpah ruah dan gratis untuk ketiga jenis ikan tersebut

No comments:

Post a Comment