Many factors must be considered when a farmer is deciding which species of shrimp he should culture. Due to its large size and high price, P. monodon is generally considered the most desirable. However, if fry are not available, or are too expensive, it might be worthwhile to grow another species. In an area subject to flooding from typhoons, it might be advantageous to minimize risk by culturing a species with a short growing period. It may be desirable to consider growing different species during different seasons depending on the variations of the environment or availability of wild fry.
Of the species of shrimp occurring within the region, the following are the ones most commonly cultured:
|Penaeus monodon||Metapenaeus ensis|
|P. merguiensis||M. monoceros|
|P. indicus||M. brevicornis|
While not cultured in large numbers now, the following are thought to have commercial potential. That is, they grow to a suitable size and have a good market value.
|P. semisulcatus||M. affinis|
|P. latisulcatus||M. elegans|
|P. japonicus||M. burkenroadii - M. mastersii|
|P. orientalis||M. tenuipes|
|P. penicillatus||M. conjunctus|
As an aid in choosing which species to culture, some advantages and disadvantages of the most common or well-known species are given below. The material presented is necessarily incomplete as there is little data available for most species.
It attains a large size. Shrimp with a size of 10 to 12 pieces/kg are common, and sizes of 5 to 7 pieces/kg have been grown in ponds.
It is the fastest growing of all shrimp tested for culture. In ponds, fry of 3 cm in length have been grown to a size of 75 to 100 g in only five to six months. Forster (1974) was able to grow them to 25 g in 16 weeks in a tank stocked at 15/m2; Liao (1977) was able to grow them to 35 g in three months in a tank stocked at 15/m2.
Due to its large size, it brings a high price to the farmer. Over US$ 7 per kg of shrimp weighing 15/kg has been reported in Indonesia.
It can tolerate a wide range of salinity, 0.2 to 70 ppt. Salinity within the range of 10 to 25 ppt has no appreciable effect on growth when food is sufficient. Growth is reported to be slower at very low salinities.
It can tolerate temperatures up to at least 37.5°C. Mortalities occur at temperatures below 12°C.
It grows rapidly when fed either with animal or vegetable protein.
Food conversion ratios are favourable. Values as low as 1.8:1 have been reported from Taiwan (Liao, personal communication).
It is hardy and not greatly disturbed by handling.
There is a sparse supply of wild seed for stocking.
Wild fry are usually expensive.
Gravid females are difficult to obtain from the wild in sufficient numbers to support a large hatchery.
Females are more difficult to mature in captivity than many other species. Excellent progress is being made in this area, however, and reliable techniques for maturation are being developed.
It takes a long growing period to reach the large size which commands the best price. This increases risk of heavy losses from typhoons and other natural disasters.
It is difficult to harvest because it does not have a pond with discharged water as readily as other species.
It is not suited for polyculture with milkfish in the progress on method of culture because of the difficulty in transferring it from pond to pond and its long growing period.
The head to tail ratio is not as good as that of some other species. This could have an adverse effect on sales to the export market where only tails are desired.
The exoskeleton is rather thick and processors find it harder to remove than that of most other species.
P. indicus and P. merguiensis supposedly can be differentiated by five separate characteristics, but based on actual field surveys there are many individuals which do not have any clear distinction on these five points. Consequently, they were put into one group as indicus-merguiensis complex by Fujinaga and Kurata (1967). As these shrimp are difficult to distinguish, they have been grouped together in this paper unless one of the species is specifically identified.
In spite of the taxonomic confusion, there are indications of behavioural differences between the two species. In the Philippines, for instance, “P. indicus” is difficult to harvest by draining ponds, but in Thailand, “P. merguiensis” moves out of ponds readily when water is drained. In addition, P. indicus prefers sandy substrates and P. merguiensis is found most frequently on mud bottoms.
This shrimp grows to a fairly large size and brings a good price.
It is fairly fast growing, especially when young. Cultured in tanks at a density of 15/m2, it reached a size of 14 g in 16 weeks (Forster, 1974). In polyculture with milkfish in earthen ponds, females grew to about 28 g and males to about 12 g in 160 days (Gundermann and Popper, 1975).
Survival is high during the first three months of growth or up to a size of about 10 cm.
Wild fry are usually abundant in estuaries near areas where the adults are present.
Gravid females are relatively easy to obtain from the wild in numbers sufficient to operate a hatchery.
Females can be matured in captivity with relative ease.
This shrimp moves out of a pond with water discharge, making harvesting easy.
Good growth has been obtained in intensive culture with a feed having 40 percent protein, which is lower than that required for some other species.
The exoskeleton is relatively thin, giving greater portion of edible meat to total weight.
Relatively high salinity (20–30 ppt) is required for best growth. It has a wide tolerance to short-term exposure to salinity extremes, but dies with long exposure at salinities below 5 ppt and above 40 ppt.
Mortalities occur at temperatures above 34°C.
There is a significant size difference between sexes.
It can not stand rough handling as either a juvenile or an adult. Fry are weaker than those of P. monodon during transport.
Wild fry are more difficult to identify than most other species of Penaeus or Metapenaeus.
With present technology, great difficulty has been encountered in culturing this shrimp for longer than three months without heavy mortalities.
Artificial propagation of larvae is relatively easy.
This shrimp reaches a large size and brings a good price.
This species has not been successfully cultured to marketable size despite numerous attempts. In ponds, growth is slow and mortality has been high. It requires high salinity water.
Spawners are readily obtained from the wild.
Fry can be supplied in large quantities from artificial propagation.
It can tolerate cold weather.
It is hardy and can withstand handling. Survival rate for long distance transport of live adult shrimp is high.
The price of live edible size shrimp is high in Japan.
It has less tolerance to low salinity than some other species, 15–30 ppt is optimum.
It is not very tolerant to high temperature.
High protein (about 60%) feed is required for best growth.
In grow-out ponds a clean sand bottom is required for best growth.
Growth is fairly fast during the first three months.
Growth is relatively fast in cool weather and in Taiwan the shrimp can be cultured during the winter season.
Gravid females are easy to obtain from the wild. Ovarian maturation of females in captivity is relatively easy.
The head to tail ratio is favourable when compared to other species.
The red colour of the body after cooking is preferred by consumers.
Relatively high salinity and dissolved oxygen are required.
It is not tolerant to handling.
It is difficult to grow this shrimp to a large size.
These shrimps are very tolerant of low salinity and high temperature.
They require a relatively short growing period, only two to three months, to attain marketable size.
Wild postlarvae are abundant in most areas.
Survival in ponds is usually high.
Harvesting can be accomplished easily by catching them as water is drained from a pond.
Sexual size disparity is not as great as in some other species of Metapenaeus.
M. monoceros has been known to spawn in ponds.
They are easy to mature in captivity and larval culture is relatively easy.
They are tolerant of handling.
They are well-suited for polyculture.
These shrimps do not grow to a large size. In the wild, M. ensis reaches a maximum size of about 18 cm, but shrimp over 14 cm are not common. They bring a low price because of their small size.
It is tolerant of low salinity and high temperature.
Wild seed is abundant.
Survival in ponds is high.
The growing period is short.
This shrimp has been known to spawn in ponds.
It grows only to a small size. Full growth is about 12.5 cm for females and 7.5 cm for males. This great size disparity between sexes is not desirable in culture.
Due to its size the price is low.