INFORMATION ABOUT THE BIOLOGY AND CULTURE OF THE RED CRAWFISH, PROCAMBARUS CLARKII (GIRARD, 1852) (DECAPODA, CAMBARIDAE) FOR FISHERIES MANAGERS IN LATIN AMERICA

Trabajo recibido el 5 de octubre de 1979 y aceptado para su publicación el 21 de agosto de 1980.

RESUMEN

INTRODUCCIÓN

Crawfish are freshwater, decapod crustaceans that closely resemble small marine northern lobsters (Homarus spp.). With few exceptions, maximum sizes are 7.5-12.5 cm. They are closely related to marine shrimps (Camaron), freshwater prawns (Lagonstino), crabs (Cangrejo), and lobsters (Langosta). One species,Procambarus clarkii(Girard, 1852 Decapoda, Cambaridae), also referred to as the red crawfish, is native to northeastern Mexico and the southcentral U.S.A. It has been successfully introduced into the western U.S.A. (California), Africa (Kenya and Uganda), Spain, Japan, Hawaii, Mexico (Sonora), Costa Rica, and Santo Domingo (Hobbs, 1972; Huner and Avault, 1979). In southern Louisiana as many as 25 million kg are harvested annually for food from natural swamps and marshes as well as from 20,000+ ha of culture ponds. In California, Africa, Japan, and Hawaii, however, it is considered an agricultural pest because its extensive burrowing destroys irrigation systems (Huner, 1977). Harvesting which would reduce numbers and problems is not done because inhabitants have a cultural aversion to eating the red crawfish. The population densities in Costa Rica and Santo Domingo are not yet high enough to create such problems.

Recently, private individuals and goverment agencies from Latin America have expressed interest in the culture of the red crawfish in that region. This short article is designed to provide pertinent facts about the biology and culture of this species for fisheries managers contemplating introductions. Additionally, other species of North American, European, and Australian crawfish that are valuable food animals and might be considered for introduction in Latin America are listed.

Most English speaking peoples use the common namecrayfish rather thancrawfish. However, the word crawfish in the accepted vernacular in Louisiana, the area where this group assumes the greatest socio-economic importance. Latin Americans often call crawfishLangostinos whereas the Spanish call themCangrejo del Río.

The red crawfish is an animal that is normally found in areas that periodically dry up during the year (temporary lentic habitats) (Penn, 1943 1956). It survives by building simple burrows that may extend 1.0-1.5 meters from the surface to the water table below. Egg laying takes place in the burrow with the female attaching the eggs to the underside of her abdomen. Number layed depends largely on the size of the female with a small animal of 6.5 cm laying about 100 eggs and a larger animal of 9.0 cm laying about 300 eggs. Eggs hatch in 2-3 weeks when temperatures exceed 20-22ºC. Young molt (shed their shells) twice during the next 2-3 weeks and are ready to leave the mother at that time. The young crawfish are about 1.0 cm long. They will shed their shells at least 9 more times before reaching sexual maturity. This is achieved in 2½-6 months depending on temperatures and the availability of water at the surface. Temperatures below 12ºC severely curtail growth. Molting does not take place in burrows. Size at maturity ranges from 5.5-12.5 cm (Huner and Romaire, 1979). This depends on several factors including habitat stability-availability of water at the surface, food availability, and population densities. Males can be differentiated from females by the presence of enlarged abdominal appendages called gonopodia. These are situated on the first two abdominal segments behind the cephalothorax (or head). Mature males (called form I) also have enlarged claws and distinct hooks at the bases of the 2nd and 3rd pairs of walking legs. These features are absent in immature males and females. Females also have a sperm receptacle located between their walking legs.

Once sexual maturity is achieved, gowth stops until the reproductive cycle is complete, usually 2-6 months. Crawfish will then molt to a sexually inactive (called form II in males) growth state. The next molt will again produce a sexually active state. Life span for red crawfish in subtropical and warm temperate climates is 12-18 months. In cold temperate climates, the life span may be 36 months or longer.

The red crawfish can produce one to three generations per year depending largely on the availability of surface waters in which to live and grow and the presence of warm temperatures (over 20ºC) (Huner, 1975, 1977). Temperature is largely a function of latitude and altitude. Thus, populations found near the equator may produce as many as three generations per year while those found around 40º north latitude are restricted to roughly one generation per year.

The red crawfish normally occupies semipermanent lentic habitats although some populations have been able to establish themselves in permanent lotic habitats. Populations are know to survive from the vicinity of the equator to roughly 40º north latitudes (Huner, 1977). These have been found at altitudes as high as 1500 meters although they are more commonly found near sea level. Red crawfish populations are not well adapted to withstand predation pressure from carnivorous fishes. Therefore, semi-permanent habitats are very important to the red crawfish. It survives in a burrow while surface waters evaporate. At such times most predatory fishes die. Thus, when rains or floods replenish the habitats with water, few, if any, fishes are present to prey on the crawfish and its progeny.

Red crawfish populations are found in waters with pH's as low as 6.0 and as high as 10.0 (Huner, 1978). The species can thrive in waters with virtually no dissolved calcium as long as modest alkalinity, 50 parts per million (ppm), occurs and calcium is available from its food. Reproductive populations occur in estuarine areas with salinities ranging from 5-10 parts per thousand.

The red crawfish can tolerate periods of no measurable dissolved oxygen for several days because its gills are contained in branchial chambers on the sides of the cephalothorax. As long as these chambers are moist, a crawfish can utilize atomospheric oxygen. When dissolved levels fall below 2.0 ppm, a crawfish will climb to the surface on plant stalks or limbs or will move to the water's edge to obtain atmospheric oxygen. A crawfish will not molt under such conditions and it is extremely vulnerable to terrestrial predators, but it will not suffocate.

The principal food of the red crawfish is organic plant detritus (Black and Huner, 1978; Lorman and Magnuson, 1978). That is, when plants die and are submerged in water, they quickly become covered with a living layer of bacteria and fungi that use the dead plant material as food. That dead plant material itself is of little value to a red crawfish as a food, but when it eats it, it digests the protein rich layer of bacteria and fungi. A red crawfish will also eat any insects, crustaceans, mollusks (especially snails), and annelid worms that it can catch. Animal matter is much more important in the diets of young, rapidly growing juveniles than adults. Since it cannot float, most of its foraging, is done on the bottom, or benthic region. However, some individuals, especially young ones, can catch planktonic organims with filters on the mouth parts. A red crawfish will also eat living green plant material, an important source of dietary carotenoids.

The red crawfish is considered to be a pest species in most areas where it has become well established California (U.S.A.), Hawaii (U.S.A.), Japan, and Kenya (Huner, 1977). It is well accepted in Spain were, although it is not widely distributed yet, it replaces a native crawfish that disappeared some years ago. It is too localized in Costa Rica and Santo Domingo to cause troubles at this time.

In areas where the red crawfish has become a pest, it has few natural predators. This coupled with high reproductive potential leads to large numbers of animals. Populations as high as 2000 kg per hectare have been noted in Japanese rice fields and one investigator noted that a fisherman with a dip net caught 200 kg of red crawfish in one hour in a Kenyan lake. The initial introduction in Spain was less than 200 kg of brood animals in 1973. In 1978, over 80,000 kg were haversted according to official records. Such large populations will burrow extensively, often destroying irrigation systems. Whether or not actual crop damage occurs is questionable; however, food limited populations of red crawfish will eat virtually any vegetation available. This could cause crop damage.

Large red crawfish populations may also interfere with fishing. They may damage fish in nets or become trapped in the nets necessitating extra time to remove them.

The problems related above could occur in the southeastern U.S.A. (Louisiana and Texas) and Spain but do not. The reason is that the inhabitants of the two regions harvest and consume most of the surplus production, reducing the damages associated with large populations of red crawfish in other areas. Since the animal is of great commercial value, damage done by remaining crawfish it tolerated.

A red crawfish may be used for several purposes. It may serve as a specimen for basic taxonomic studies by biology students or for ecology or physiology studies by basic and applied workers. It is an excellent natural fish bait used by both sports and commercial fisherman in fresh and salt waters. Finally, it is an excellent food.

The red crawfish is commonly prepared in two manners, boiled whole, alive in spicy, salted water or cooked in perpared dishes made from peeled abdominal meat. Abdomens are hand peeled. This is a labor intensive process and quite expensive (Huner and Barr, 1981). A problem in processing crawfish meat, is the fact that yield ranges from 15-25% of live weight. The large percentage of waster reduces profits and increases the cost of the commercial products. The wastes can be used in fertilizers and as lime substitutes, or they can be reduced to high quality meals. However, the profitability of these uses has yet to be demonstrated in the U.S.A. The value of the wastes may be much greater in nations with less developed economies.

Large numbers of red crawfish may be held alive for several days after capture in loose mesh vegetable sacks (20-25 kg per sack) as long as the crawfish are cool (510ºC) and moist.

Aquaculture of the red crawfish is limited largely to southern Louisiana (20,000+ hectares) and southeastern Texas, (1000+hectares) (Huner and Barr, 1981). It is cultured exclusively in earthen ponds. Sustaining populations are established by stocking sexually mature adults in mid-late spring. Stocking rates may very from 50/200 kg her hectare depending on the amount of protective cover present and the presence or absence of native populations of red crawfish in the area. Pond waters are then gradually lowered so that the pond will be dry by early summer. Mated crawfish survive in burrows and reproductive activies commence. Vegetation is permitted to grow in the pond bottoni during the summer. This can include annual volunteer grasses (Graminaeae) and sedges (Cyperaceae) as weIl as semiaquatic plants such as primroses (Onagraceae,Ludwigiaspp.). smartweeds (Polygonaceae,Polygonurn spp.), and alligator weed (Amaranthaceae,AIternanthera philoxeroides). Rice and millet may be intentionally planted. A pond is refilled in late summer or early fall. The annual vegetation begins to die and form microbially enriched detritus used by the crawfish as food. Stalks of dead and living plants serve to provide crawfish with access to, the surface when oxygen is low and as a means for crawfish to segregate themselves when populations are high. All young are not produced at once and several groups are released during the fall and winter. The provides for sustained production beginning as early as late fall but no later than late winter and continuing through the spring.

Crawfish are harvested exclusively with traps (20-40 traps per hectare). Seine cannot be used in vegetation choked ponds. Traps are made of 1.6-1.9 cm mesh wire chicken netting and retain crawfish 6.5-7.5 cm or longer. Traps are barrelshaped and are 1 meter long by 0.5 meters in diameter. Traps have funnel-shaped entrances.

Ponds are drained slowly in late spring. Surviving crawfish burrow and the cycle is repeated.

The major problems in this type of crawfish culture include: 1) oxygen depletion, 2) predaceous fishes, 3) stunting, and 4) poor reproduction. When submerged vegetation dies, a great biological oxygen demand is created as it decomposes. Vegetation loads in excess of 1 kg of dry matter per square meter normally exceed the assimilation capacity of most ponds. Recirculation of water with pumps is necessary to add oxygen if assimilation capacity is exceeded. Predaceous fishes can decimate a crop. These must be controlled by use of fish poisons in waters that remain after summer dewatering and by placing screens on pump intakes if water comes from surface sources with fish populations. Stunting normally results from underharvesting and consumption of available foods by the crawfish present. Here intensive harvesting must be practiced. There is no economically feasible method to stock egg bearing female crawfish or young crawfish if reproductive failure occurs.

Yields in well managed ponds consistently exceed 500 kg per hectare with 1000 kg per hectare being commonly mentioned. When all conditions are favorable, yields of 2500 kg per hectare are not out of the question.

Rotation of rice, crawfish, and cattle or soybeans is practiced in Louisiana. Adult crawfish are stocked after rice is planted in the spring. Watres are shallow and they burrow during the hot summer. Water is removed in mid-summer prior to rice harvest. Following rice harvest, ponds are refilled for crawfish. They are drained for soybean cultivation or ponds are left fallow for catlle pasture in late spring of the following year. The cycle is resumed the following spring with rice planting and crawfish stocking.

A problem with rotation of crawfish and field crops it that extreme care must be exercised in the application of pesticides. Where the value of crawfish is great, it is preferable to use no pesticides and sustain a lower yield of rice rather than risk damage to the crawfish crop.

An excellent reference detailing crawfish culture techniques is that of LaCaze (1976).

There are only two other species of North American crawfishes (family Cambaridae) that have shown goods results in earthen pond culture. These are Procambarus acutus acutus, found throughout the eastern U.S.A., overlapping most of P. clarkii's range, and Orconectes immunis, found throughout the north-central U.S.A. Both are residents of temporary lentic habitats and burrowers. P.a. acutus is a large, edible crawfish. O immunis is commercially valuable as a fish bait but has little food value since size rarely exceeds 6.0 cm.

Several other species of North American crawfishes might do well if introduced into natural Latin American ecosystems but techniques have not been clearly established for their culture. These species are found in permanent lentic and lotic habitats. Those that reach sizes comparable to the red crawfish include Orconecies limosus, Orconetes virilis,and Orconectes rusticus from the north-central U.S.A. There are several species ofProcambarus from the south-central U.S.A. that might do well under pond culture situations or comparable natural conditions. However, not enough is known about them to make accurate predictions about their suitability for culture at this time.

The American Pacific Northwest crawfish, Pacifastacus leniusculus, belongs to the family Astacidae. This is a cool water species associated with permanent lentic and lotic habitats. It reaches maximum sizes in the 7.5-15.0 cm range. It has been successfully introduced into Europe to replace stocks of the natíveAstacus spp. decimated by disease and pollution.

Astacus astacus and Astacus leptodactylus might do well in natural temperate ecosystems in Latin America. They are European species (family Astacidae) that reach sizes of 7.5-15.0 cm. They are highly susceptible to the crawfish plague, a fungal disease, that is transmitted by, but is rarely fatal to, virtually all North American crawfishes. Astacusspp. along with the introducedP. leniusculus are frequently held in heated areas during the winter in Europe in order to speed up the egg laying and incubating processes. However, the young crawfish are normally stocked into natural habitats rather than culture systems.

The Australian crawfishes (family Parastacidae) are larger (12.5-50.0 cm) than their North American or European counterparts. Species such as the Yabbie, Cherax destructor, and the Marron, Cherax tenuimanus,should do well in carthern ponds in both temperate and tropical regions of Latin America. Both species reach sizes of 15-20 cm. A problem is, however, that they have no resistence to the crawfish plague. The huge (to 4 kg) Tasmanian crawfishes of the genus Astacopsis,inhabit flowing streams and appear to have little culture potential. They, too, are not resistant to the crawfish plague.

Introductions of any non-native crawfish could result in an ecological nightmare unless they occupied a wholly unused niche. This is, of course, high1y unlikely. They would compete with native decapod crustaceans including freshwater crawfishes, crabs, and prawns. If competition were successful, those species could be eliminated. Introduced species could change neutral aquatic vegetation profiles leading to drastic changes in all associated invertebrate and vertebrate faunas. This could be acceptable from a socio-economic standpoint if the newly established populations were exploited. However, there is some reason to question their acceptability based on experience in other parts of the world. Non-native disease organisms including human pathogens, specifically parasites, might also be established by such introductions. Damage to agriculture has been covered above.

Serious thought must be given by all regulatory agencies before any introductions are made. It is imperative that the Fisheries Division of the Food and Agriculture Organization of the United Nations and the Transplantations Committee of the International Association of Astacology be contacted before final action is taken to make such introductions.

The seriousness of the matter is that successful introductions of the red crawfish in Hawaii, Japan, Keyna, and Spain originated from 1000 or less individuals (perhaps as few as 100) (Huner, 1977; Huner and Avault, 1979). Several mature females of any species with eggs could be readily transported to any country in the world in a hand held bag by unscrupulous, misguided, and/or ignorant individuals. In any species does, however, become established it, is critically important that the residents of that geographic area be thoroughly educated as to their value. Failure to do so would rob those peoples of a valuable food source with unlimited commercial potential. Otherwise, the presence of the crawfishes may well precipitate the problems discussed above.

Several species ofProcambarus occur naturally in southern Mexico, Guatemala, Honduras, and Cuba (Hobbs, 1972). None seems to have culture potential.

Small, isolated populations of red crawfish are present in Costa Rica and Santo Domingo (Huner and Avault, 1979). Some work has been done with the red crawfish in Venezuela but it is not know if it, has been released from laboratory facilities. Rumors of red crawfish introductions have come from Guatemala and Nicaragua.

Two genera of Parastacid crawfishes are native to South America (Hobbs, 1974). These areParastacus in Chile, Argentina, Uruguay, and southern Brazil and Samastacus in Chile. Little is known about their biology or culture potential.

Most of the literature concerning the culture and biology of the red crawfish has originated in Louisiana where the animal assumes unparalled cultural and economic importance. Two references are available: LaCaze, Cecil G., 1976 (revised). Crawfishe Farming,Louisiana Wild Life and Fisheries Commission, Fisheries Bulletin Number 7. 27 p. (Obtain from. the Louisiana Department of Wildlife and Fisheries, P.O. Box 44095, Capitol Station, Baton Rouge, Louisiana 70804 U.S.A.). Huner, J. V. and J. F. Barr, 1981; Red swamp crawfish: biology and exploitation, Louisiana State University Sea Grant Program BulletinNo. LSU-T-80-001, 148 p.

An extensive list of technical and semitechnical publications dealing with red crawfish biology and culture is available from Louisiana State University. This list may be obtained from: Publications Clerk, Fisheries Section, 249 Ag Center, Louisiana State University, Baton Rouge, Louisiana 70803 U.S.A.

There is much technical literature available about other potentially valuable crawfishes including North American, European, and Australian species. Good sources of information are the four publications of the International Association of Astacology.

The accepted citation for these volumes is: Papers from the Int. Symp. on Freshwater Crayfish.

1. Freshwater Crayfish, Papers from the First International Symposium on Freshwater Crayfish., Austria 1972. Published 1973. Edited by Sture Abrahamsson, Obtain from Stud enlitteratur, AB, Fack, S-221 01 LUND 1, Sweden.

2.Freshwater Crayfish, Papers from the Sec. ond International Symposium on Freshwater Crayfish, Baton Rouge, Louisiana, USA, 1974.Published 1975. Edited by J. W. Avault, Jr. Obtain from Division of Continuing Education, Louisiana State University, Baton Rouge, Louisiana 70803 USA.

3. Freshwater Crayfish, Papers from the Third International Symposium on Freshwater Crayfish, Kuopio, Finland, 1976. Published 1977. Edited by Ossi V. Lindqvist. Obtain from Dr. Ossi V. Lindqvist, University of Kuopio, P.O. Box 140, 70101 Kuopio, Finland.

4. Freshwater Crayfish, Papers from- the Fourth International Symposium on Freshwater Crayfish, Thonon-les-Bains, France, 1978.Published 1979. Edited by Pierre-J. Laurent. Obtain from Dr. Pierre-J. Laurent, Institut National de la Recherce Agronomique. F 74203, Thonon-les-Bains, France.

The International Association of Astacology was established in 1972 to foster international exchange of information about crawfish biology, p. Since the organization has no permanent officers, questions concerning the organization should be forwarded to the author of this article.

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