AGRICULTURE – Page 72 – Philippine Tambayan

Apahap production in floating net cages

Efforts to raise the seabass or apahap are starting to bear fruit,

A study by Nestor D. Demenden, senior agriculturist of DA-Region 1, concentrated on culturing apahap.

The trial as conducted in Sto. Tomas, La Union. Water depth ranged from 1.5 to 2.5 meters during low and high tides, respectively.

Temperature and salinity ranged from 24.2 to 34.8 degrees centigrade and 32 to 36 percent respectively.

Bamboo was used to construct the platform where the net cages were suspended. Three bamboos (bayog) were arranged to form the raft-like structures needed to complete the platform. Four bamboo poles were arranged parallel with each other at two meters distances. They were fixed perpendicularly above it, forming six square holes for the net cages. Styrofoam floaters were fixed on the corners and inner joining of the platform. Anchors prevented it from drifting.

The net cages are square net walls (inverted mosquito netlike0 measuring 1.5 meters x 1.5 meters x 1.5 meters. A fine meashed net 9B net) was used for the juvenile cages where the fish was raised from two months.

The seabass were later transferred to the production cages, which was made of polyethylene net measuring 400/12 x k 12.

The fish were fed with cropped trash fish at 10 percent of biomass for the first two months. This was gradually reduced o seven percent on the third and fourth months, and five percent on the fifth month onwards. Feed was broadcast to the fish in the morning and afternoon daily.

Results showed that from an initial weight of 20.5 to 21.56 grams, the fish reached 282.3 to 302.4 grams in 180 days – or had a production of 10.73 kilograms per cubic meter mean net bodyweight gain. The project had an ROI of 67 percent from a food conversion ratio (FCR) of 6.93. The survival rate of the fish was 70 percent.

The trial also indicates that municipal waters can be used as both fishing ground and aquaculture area. – Wilhelmina Puyaban (Mariano Marcos State University)

Soruce: Greenfields, 1993

Rabbitfish can be grown in seacages

Rabbitfish or siganid, Siganus guttatus – locally known as “danggit” in Visayan and Samaral in Tagalog – can now be grown in seacages.

This was recently proven by Cefegrino F. Toledo of he Pangasinan State University – College of Fisheries in Binmaley Pangasinan. His studies showed that siganid can be grown to market size in floating net cages measuring 1 x 1 x 1.3 meters each with 20-millimeter mesh.

Toledo stocked siganid fingerlings weighing 8.6 to 12 grams each in the cages at a density of 50fish per square meter. The fish were cultured for 122 days using four experimental fields namely: commercially formulated feeds (CFF) containing 25% crude protein (Treatment 1), CFF containing 30% crude protein (treatment 2), combination of 50% CFF containing 30% crude protein and 50 percent filamentous green alaga, Chaetomorpha linum or “lumot” (treatment 3) and lumot only (treatment 4).

Result indicated that commercial feeds had significantly better effects on growth and production of S. guttatus than the combination of 50 percent CFF and 50 percent lumot and lumot only. The highest mean weight gain of 77.7 grams per fish and production of 4.18 kilograms per meter cage were obtained with treatment 2 but did not differ significantly from the weight gain of 70.1 grams per fish and production of 3.86 kilograms per meter cage in treatment 1. Lowest growth of 40.8 grams per fish and production of 2.26 kilograms per meter cage were obtained with treatment 4. The result in treatment 3 ranked third, but did not differ significantly from growth and production of 44.9 grams per fish and 2.56 kilogram per meter cages, respectively. The mean rate of survival of the fish ranged from 89 to 98 percent.

Commercial feeds with 25 percent and 30 percent crude protein appeared to be economically feasible as feed for S. guttatus in cages . A net income of 104.10 pesos per square meter per cage and a benefit cost ratio of 1.422 were obtained from from fish fed with the CFF containing 30 percent CP.

The project was funded by the DOST and coordinated by the Philippine Council for Aquatic and Marine Reserch and Dvelopment – Manuel P. Garcia (Mariano Marcos State University).

Source Greenfields, 1993

Cases of Marine Fish Poisoning

Cases of Marine Fish Poisoning

By Rafael D. Guerrero III

Some marine fish become poisonous after feeding on toxin-producing organisms.

With the frequent occurrence of red tide on Philippines waters, the public has become wary and discriminating in its choice of seafood. The red tide renders bivalves like mussels, oysters and clams in affected coastal areas unsafe for human consumption. Fishes are generally not problematic as long as people remove their gills and entails before they are cooked and eaten.

There are instances, however, when marine fish poisonings do occur and lead to sickness or even death. Cases of ciguatera, pufferfish poisoning and goby fish poisoning have occurred in the country.

Ciguatera is a disease caused by the eating of toxic fishes that inhabit like red snappers, groupers and eels become poisonous when they prey on plant-eating fishes like the surgeonfish (“labahita”). These have, in turn, eaten blue-green algae present in coral reefs producing the poisonous substance.

The symptoms of ciguatera are prickling of lips, tongue and throat; numbness, nausea and vomiting. The victim may also experience dryness of mouth, abdominal cramps and insomnia. While the death rate for the disease is usually low, recovery is slow and may take several months.

The poison causing ciguatera is known as ciguatoxin. Although there is no known antidote for the disease, the intravenous administration of mannitol reportedly alleviates symptoms. The disease is common in the South Pacific where the incidence is estimated to be as high as 500 cases per 100,000 inhabitants. The fatality rate is a low 0.1 percent.

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Oyster and Mussels in Western Visayas

Oyster and Mussels in Western Visayas

By Giselle PB. Samonte

Research should focus on increasing production and preventing red tides.

The slipper oyster (talaba) and the green mussel (tahong) are the only mollusk species being farmed in the Philippines.

The Western Visayas region in the central Philippines is one of the major sources of oysters and mussels, which are farmed for their meat. Production is mainly for the domestic market.

The need of the people in the region to augment their income from fishing has led to the proliferation of oyster and mussel farms.

The farms started operations as early as the 1950s. There are today an estimated 2,000 coastal families in the region which are engaged in the mollusk farming. Oysters are farmed along rivers using the bottom, stake, rack-hanging and raft-hanging methods.

In the bottom method, oyster shells or large stones are scattered on the sea bottom for oyster spat fall.

In the stake method, whole or halved bamboo poles are used as substrates for oysters.

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