1 DECEMBER 1999
From: Peter Larkins <plarkins@manta.ecua.net.ec>
To: <shrimp@onelist.com>
QUESTION:
Does anyone have an equation or graph showing the relationship of egg production as function of broodstock weight in Penaeid shrimp?
Peter Larkins
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COMMENTS 1:
Have you looked at Emmerson 1980 Marine Ecology Progress Series 2: 121-131, Ottogali et al. 1988 J Aquacult Tropics 3: 111-125, Hansford and Marsden 1995 J World Aquacult Soc 26: 396-405, Beard et al. 1977 Aquaculture 10: 275-289, Menasveta et al. 1993 Aquaculture 116: 191-198 or Wyban et al. 1987 J World Aquacult. Soc. 18: 198-200? They have all seen higher egg/nauplii production with larger females. I do not remember them having a graph, but you may be able to put one together yourself. At the Oceanic Institute with
50-75 gram female vannamei, we did not see size having an affect on number of nauplii produced (r=0.05; P = 0.6) (but we did not look at egg production).
Brad Argue
The Oceanic Institute
41-202 Kalanianaole Hwy.
Waimanalo, HI 96795
USA
Tel: (808) 259-3185
E-mail : bargue@teligentmail.com
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COMMENTS 2:
I have data from wild P. vannamei spawners at the Ecuadorian coast. The following equation is calculated from 612 spawns (some of them are repeat spawns) from spawners with weights that ranged from 27 to 80 g:
y = 3665 x + 22660 with R-squared = 0.1892
The biggest spawn in this group is of 621.000 eggs from a 45 g female.
Pond shrimp (n=51) gave similar results.
Hansford and Marsden (1995) report data for P. monodon in JWAS, Vol. 26, No. 4
Roeland Wouters
E-mail: rwouters@cenaim.espol.edu.ec
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COMMENTS 3 :
The following are commercial data from various stocks of P. vannamei I have worked with (weights are means):
Domesticated Stocks:
Colombian Wt 37g eggs/Female 105,000 (n=25)
Wild Stocks:
Panamanian (pond raised from wild nauplii kept in maturation tanks) Wt 29.5g > eggs/female 116,000 (n=25)
Ecuadorian (wild broodstock kept in maturation tanks) Wt 60g eggs/female 230,000 (n=130)
Peter Larkins
E-mail: plarkins@manta.ecua.net.ec
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COMMENTS 4:
In most batches of wild P. vannamei spawners that we received, there was a significant positive correlation between fecundity and spawner weight (p<0.05; p<0.001). When filling in Peter's data in my previously reported equation (eggs per spawn = (3665 x spawner weight in grams) + 22660) it can be noticed that this equation is OK for wild broodstock, while domesticated animals produce 30% less as expected. Of course, this latter observation is only based on 25 data, which is too little to draw conclusions, but I read/hear similar data elsewhere.
This could indicate that lower fecundity of domesticated broodstock is not only due to lower spawner weight, but that other factors are involved as well. For example, Medina et al. (1996) detected an absence of fully mature oocytes in pond P. kerathurus, Tan-Fermin (1991) reports smaller oocytes in pond ablated P. monodon. Browdy et al. (1986) reported lower eggs per spawn but equal egg production per day for P1 P. semisculatus as compared to P0. I suspect that in many occasions pond broodstock is not fed adequately, and results in an inferior nutritional status as compared to wild broodstock. We have experienced this ourselves. Some managers feed their animals with excellent feeds in the ponds (artificial broodstock diets and fresh diets), and seem to overcome this problem. Also, from what I hear, in the domestication process it takes three to four generations to obtain pond broodstock of equal or better quality than wild broodstock. Keep in mind that egg quality and larval quality are mostly equal or even better with domesticated broodstock (for example Palacios and Racotta (1999) with P. vannamei), and as such lower fecundity alone should not discourage the use of domesticated broodstock. All of us depending on wild broodstock should start serious breeding programs as soon as possible, and over time the benefits will be more than clear. Fecundity could be just one more on the list of traits to select for... .
Roeland Wouters
E-mail: rwouters@cenaim.espol.edu.ec