Tag: crab

Lobster production- part 3

Maintaining the pen and managing stock

Stocking Density

Select stocks that weigh at least 200-300 g each. Lobsters are carnivorous, thus, select fingerlings of the same size. Stock the pen during high tide by gently dropping the fingerlings into the water. Do not mix healthy juveniles with those that are molting or have just molted. The following stocking densities are recommended for the different compartments:

-rearing area – 150 pieces;

-nursery area- 160 pieces; and

-transition are – 150 pieces

 

Sanitation and protection.  One month after constructing the pen, remove any fouling organisms, crabs or flotsam which can damage the net.  Clean then et at least twice a month. Using coconut husk or nylon  scrub, remove barnacles and other debris to allow water movement inside the pen. Install kerosene-fuelled lamps along the perimeter to warm fisher folks of the presence of the enclosure, especially at night.

 

Shelter for the stock

Arrange old tires, bamboo tubes or rock piles inside the pen to provide shelter for the lobsters. Use coconut fronds to filter out too much sunlight.

 

Feeding the stock

Feed the stock twice a day (early morning and late afternoon) at 15-20 % of the aggregate body weight of the stock. Some fisher folks from coastal communities in Guimaras (la Paz, Sabang and Pandaraonan0 have been using sea urchins, trash fish like rays and sharks and other animal-based feed with good results. Monitor the growth of the lobsters at least twice a month to determine feed requirement and for record purposes.

 

Monitoring

Keep a record of activities and financial concerns to determine the status of the project/

 

Harvesting

Harvest the lobster six months after the first stocking. Oversized lobster weighing 1.5-2 kg are rarely bought. Harvest those that weigh at least 1 kg each. Do not harvest lobster that have just molted because they cannot withstand stress during  transport. Survival is high at 90 percent for lobsters that weigh at least 250 g. harvesting can be done as early as four months and as late as seven months. Always keep a weighing scale to determine the weight  of the lobsters.  Succeeding harvest can be done every month thereafter. The ideal time for harvesting is between 6:00 am to 8:00 am, or when the weather is particularly cloudy. Do not harvest when it rains because lobsters die when exposed to freshwater.

Buyer prefer live lobsters; therefore lobsters must be handled with utmost care. Wear a pair of  goggles or snorkel while harvesting by hand or harvest using a scoop net. Always use a box (at least 2 cubic ft) made of plastic weave or netting partially buoyed by bamboo tubes. Styrofoam or any other floater to keep t the harvested lobster in the water while the collection is on going.

 

Marketing

Contact buyers before harvesting. Deliver the live harvest immediately to avoid stress. Wrap the lobsters in paper cloth pre-soaked in seawater and place them inside Styrofoam boxes.

 

Sustainability

A lobster pen operator must source for lobster juveniles and feeds to sustain this livelihood activity.

Lobster production- part 2

Constructing the pen

Layout- using bamboo poles or stakes, mark the corners of an area measuring 5 m x 5m. Drive the main post into these points.

 

Staking – Bamboo, ipl-ipil and bakawan are good staking materials.

-Sharpen the ends of the stakes and drive those 2-3 ft deep into the laid out area.

-Leave enough length to attach the net and 1-2 ft gap between stakes.

-Strengthen the hold of the stakes by attaching onto them a pole or piece of wood horizontal to the base at a height of 2-3 ft.

– Repeat the process every 2-3 ft above the last level depending on the desired height of the pen and the point for strengthening the whole structure.

 

Installing the screen.  Inside the pen, dig a 1 ft deep canal around the perimeter to bury the bottom part of the net and prevent burrowing a species from escaping. At least, two persons are needed to install the screen,  one inside the pen and the other outside it. From the inside, secure the net onto the wall framework with bamboo strips tied vertically onto the horizontal bars with nylon twine (80 lbs)

 

Dividing the pen into compartments.  Divide the pen into three compartments:

-rearing area (15 sq m.)

-transition area (6 sq. m)

-nursery area (4 sq. m)

Follow the process for the layout, staking and installing the screen mentioned earlier. Use nets of larger mesh or bamboo strips to secure an additional compartment of at least 2 m for the molting stock.

 

Constructing the caretaker’s shed . in one corner of the site, construct a shed for the caretaker and fro the harvested stock before the latter is transported to the market. Use local roofing material such as nipa or cogon.

 

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Lobster production- part 1

Lobster Culture

By; the Bureau of Fisheries and Aquatic Resources

 

Lobster (Family Homaridae) commands a higher price than other crustacean species such as shrimps and crabs. The common spiny lobsters are in demand both in the local and export market because of their delicate flesh. They are bought live and each weighs between 500 g – 1kg.

 

The spiny lobster has a hard shell, stalked eyes, four pairs of legs and a pair of antennae below the eyes. Unlike the common species, spiny lobsters do not have large claws. However, they have a pair of hand like appendages used to hold food. In guimaras, Philippines, the most common species are the ornate tropical rock lobster or tiger lobster (Panuliris ornatus); green lobster (Jasus verreauxi) and the Southern rock lobster or pulahan (Jasus novaehollandiae).

 

Fisher folks gather lobster from reefs at shallow  depths at nigh using kerosene-fueled lamps (lampara) and pole nets or gill nets. During the day, lobsters are speared or caught by air compressors. Fisher folks from Guimaras harvest tropical rock lobsters from wild stock. During the peak season, they could harvest about 50-80 kg per week valued at 800.00 pesos per kg. Lobsters are successfully cultured in Zamboanga and Guimaras, Philippines.

 

Lobster culture in Pens

Lobster culture has been done in cages, concrete ponds and sea farm pens in Singapore, Thailand, Australia and recently, in the southern Philippines. The most conventional design is the cubical pen measuring at least 5 m x 5 m x 4-6 m framed by wood or bamboo and strengthened at the corners by big poles.

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Alimango raising

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Introduction

Scylla serrata is the common mudcrab occurring in the estuarine and mangrove areas and is commonly called as “red crab” and it prefers to live in low saline waters. Male crabs of S. serrata grow to 700 to 800 gm at the maximum The export size of the crab is 500 g and above for males and 250 g and above for females.

Crab fattening is widely practiced in Thailand, Taiwan, Malaysia, Singapore and Indonesia. Gravid female mud crabs with full orange-red egg masses are in great demand in seafood restaurants of South East Asian countries. Due to its high price, people started to hold immature female crabs in some kind of enclosures and fed them until the gonads developed and filled the mantle cavity. This is how crab “fattening” spread, initially, throughout South East Asian countries. Subsequently, the practice of holding post-moult “water” crab of market size, in some enclosures, for short period of time and feeding them until they completely “flesh out” for getting quick returns also became popular. Cages, pens and small ponds with net are being used for holding crabs for a short period of 3-4 weeks.

The mud crab resource is a natural bounty for our country, which has a potential to change the socio-economic status of the coastal communities. The coastal poor fishermen and educated unemployed youths should realize this fact and take up crab culture or fattening in eco-friendly way to raise their economic status.

 

Culture

This is the process of stocking juvenile crabs (10 g to 250 g) and allowing them to moult and grow. Harvest is done after 3-8 months or once the crab reaches 400 g to 500 g size. Mud crab fattening is the most suitable method for small-scale aquaculture because:

  • Turnover is fast, hence, the period between investment and returns is short.
  • Fattened crabs can be stocked at higher densities (15 crabs/sq m) compared to grow-out systems (1 crab/sq m) as no molting occurs and therefore losses due to cannibalism are dramatically reduced.
  • Short production time reduces the risk of losing crabs to disease, thus, rendering a higher survival rate for fattening (>90%) compared to grow-out systems (40%).

 

Different Methods of Crab Culture

Four methods of oyster culture are practised in the Philippines; broadcast (sabong), stake (tulos), lattice and hanging (bitin, sampayan, horizontal, and tray) methods.

Pond Culture. Pond size of ½ to 1 acre is most suitable for crab culture. However, large size ponds of more than one acre can also be used for this purpose. Sandy soils with a mixture of 50% clay are ideal for culture of these crabs. A water inlet system and an outlet system to drain out water during water exchange should be constructed as in the case of shrimps. The pond should be constructed in such a way that it should hold 3 ½ to 4 feet of water towards the inlet and 4 ½ to 5 feet towards the outlet. A flow through mechanism of water exchange should be there in order to remove any left over organic food material and also to efficiently remove excretory material. A fencing of nylon net used for fishing can be placed on the dike to prevent the escape of the crabs during nighttime. In addition, about 1000 numbers of stone ware, pipes of 6 inch diameter and 1 ½ feet length, worn- out tyres, etc., should be kept at the bottom of the pond through out the dike. The nylon screen fencing should be supported with split bamboos of 1.5-meter height around the pond periphery for preventing the escape of the crabs from climbing over the bunds. The maximum stocking density should be 1crab per sq. metre.

Pen Culture in Ponds. Several units of pens of 4 X 4 X 2.5 m could be made inside the ponds using bamboo strips which are driven 1-1.5 m deep into the soil to prevent the escape of the crabs by burrowing. The pens could be made nearer to the dykes for easy stocking and monitoring.

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