THE LARVAL HATCH FECUNDITY OF A STOCK OF THE GIANT FRESH WATER PRAWN Macrobrachium rosenbergii

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THE LARVAL HATCH FECUNDITY OF A STOCK OF THE
GIANT FRESH WATER PRAWN Macrobrachium rosenbergii

• By. George B. Brooks, Jr. Ph.D.
• Environmental Coordinator/Aquatic Scientist
• Gila River Indian Community
• Adjunct Assistant Professor Wildlife and
  Fisheries Resources
• University of Arizona, Tucson

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Introduction

• With few major Macrobrachium hatcheries in the
  continental U.S., shortages of available seed
  could occur if there were a sudden increase in
  demand for postlarvae.
• Therefore to support a viable local prawn
  industry, local seed sources (hatcheries) must be
  developed.
• Successful hatchery management requires a
  knowledge of the number of brood stock required
  to produce a defined number of postlarvae.

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Larval Hatch Fecundity (LHF)

• In Macrobrachium rosenbergii, fecundity is a
  function of body weight. Larval Hatch Fecundity
  (LHF) is defined as the number of larvae released
  from the egg mass following incubation (Malecha
  1983).
• The literature reports two average LHF values for
  M. rosenbergii.
• 1,000 larvae per gram (New and Singholka (1982)
  and DAbramo et al 1995)
• 405 larvae per gram (Malecha 1983)

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Purpose of Study

• The purpose of this study is to determine the
  larval hatch fecundity of one stock of M.
  rosenbergii available in the United States in
  comparison to reported LHF values.

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Materials and Methods

• In March of 1998, 6 females with dark near ripe
  eggs, were captured as part of periodic sampling
  from an Arizona fish farm were, weighed and
  individually isolated in 37 liter (10 gallon)
  tanks until their eggs hatched. The newly hatched
  larvae were counted volumetrically (New 1990).

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Materials and Methods Cont.

• Larval Hatch Fecundity is the number of larvae
  hatched, divided by the after hatching mass of
  the female M. rosenbergii as measured in grams
  (Malecha 1983). The LHF value for this stock of
  prawns was defined as the average of the
  individual LHF values from the reproductive
  females.

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ResultsFigure 1. Average of Larvae produced
per gram of female weight
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Discussion

• As seen in Figure 1, The average number of
  viable larvae per female was 430 per gram of body
  weight 220 gram. Though preliminary, these
  results suggest the LHF value is far nearer the
  405 larvae/g value than the 1,000.
• Possible Reasons for the differences
• Stocks within the native range for the species
  (Anuenue (Hawaii), Australian A, Australian B,
  and Palau. demonstrate differences in larval
  development rate (Malecha 1983, Sandifer and
  Smith 1985). This suggests the possibility of
  genetic divergence. Genetic divergence could also
  be responsible for differences in LHF.
• The literature and communications with prawn
  producers suggest the parental prawns used in
  this study probably originated with Anuenue stock
  from Hawaii, the same stock used by Malecha
  (Malecha 1983, Sandifer and Smith, 1985, Craig
  Upstrom, owner Aquaculture of Texas, Personal
  Communication). Origination from the same stock
  could in part account for the similarities in
  LHF.

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Discussion (Cont.)

• An additional possibility accounting for
  differences and similarities in LHF are regional
  culture conditions. Growth rates, survival and
  other biological factors can be affected by how
  the animals are cultured. Placing genetically
  similar animals under similar conditions may
  produce similar results. If the growout
  conditions and spawning conditions provided by
  Malecha (1983) were similar to those in this
  study, then similar results could be expected.

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Literature Cited

• DAbramo, L. R., Daniels, W. H., Fondren, M. W.
  and M. W. Brunson. 1995. Management practices
  for culture of freshwater prawn (Macrobrachium
  rosenbergii) in temperate climates. Mississippi
  Agricultural and Forestry Experiment Station
  Bulletin 1030. September. 12pp
• Malecha, S. 1983. Commercial seed production of
  the freshwater prawn, Macrobrachium rosenbergii,
  in Hawaii.Pages 203-230. in J.P. McVey eds, CRC
  Handbook of Mariculture, Vol.I, Crustacean
  Aquaculture. CRC Press, Inc., Boca Raton, FL.
• New, M.B. and S. Singholka. 1982. Freshwater
  prawn farming. A manual for the culture of
  Macrobrachium rosenbergii. FAO Fisheries
  Technical Paper No.225.
• Sandifer, P.A., and T. I. J. Smith. 1985.
  Freshwater prawns. Pages 63-125. in J. V. Huner
  and E.E. Brown eds Crustacean and mollusk
  aquaculture in the United States. AVI Publishing
  Company Inc. Westport, Connecticut.