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| Pond Dynamics/Aquaculture CRSP Fourteenth Annual Administrative Report |
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The objective of this study was to evaluate the effect of diet protein
level and feeding rate on shrimp yields, food conversion ratio (FCR), and
nitrogen effluents. Earthen ponds ranging in area from 0.7 ha to 2 ha were
stocked with Penaeus vannamei post larvae at 24/m2. The
larvae were fed high or low rates of a commercially formulated pellet containing
20% or 40% crude protein, respectively. Protein level or feeding rate did
not significantly effect gross shrimp yield or mean shrimp size. Feeding
rate, but not protein level, significantly affected FCR, which was higher
at the higher feeding rate. No interaction was detected between protein
level and feeding rate for yield, mean shrimp size, or FCR. A high protein
diet fed at a low rate did not influence production any more than a low
protein diet fed at a low rate. Mean material exchange in treatment ponds
was negative (greater mass discharge than mass intake) for total nitrogen,
total phosphorus, chlorophyll-a, and BOD2, and positive
for dissolved inorganic nitrogen. There waa net discharge of filterable
phosphate at the high feeding rate and a net accumulation at the low feeding
rate. More total nitrogen was introduced into ponds by shrimp, water, and
feed than was removed from ponds as harvested shrimp and discharge water.
The mean treatment difference between input and output nitrogen was significantly
higher at the high feeding rate than the low feeding rate. Protein level
had no significant effect on the nitrogen balance.
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Delia Martinez and Eneida Ramirez
Laboratorio de Calidad de Agua
La Lujosa, Choluteca, Honduras
Results of previous research in Honduras have demonstrated that shrimp
production is similar at feed protein levels ranging from 20% to 40%, when
shrimp are stocked at densities ranging from 5 to 11/m2. Additionally,
a 50% reduction in the feeding rate did not affect dry-season shrimp production.
The objective of this experiment was to determine the effect of dietary
protein and feeding rate on feed conversion and nitrogen discharge in semi-intensive
production of Penaeus vannamei. Twelve 1.67-ha earthen ponds located
on a commercial shrimp farm were used in a completely randomized study
design. Three treatments, with four replicates per treatment, were tested:
a 20% and 30% protein feed applied at 50% of the feeding curve, and a 20%
protein feed applied at 75% of the feeding curve. Ponds were stocked with
hatchery-produced post-larval (PL) Penaeus vannamei to achieve a
final stocking rate of approximately 80,000 shrimp/ha. Ponds were harvested
87 days after stocking. Gross yields of head-on shrimp ranged from 412
to 534 kg/ha for the 87-day production period. Feed protein content did
not affect gross shrimp yields significantly; however, gross yield of whole
shrimp fed the 20% protein feed was significantly greater at the 75% feed
curve rate compared to 50% feed curve rate. Feed conversion ratios (FCR)
were close to one, and were significantly lower with the 30% protein feed
and at the 50% feed rate. Nitrogen and phosphorus additions to ponds as
feed were significantly greater with the high-protein feed and with the
low-protein feed at the higher feed rate. Significant differences in nitrogen
or phosphorus concentrations in water discharged from ponds were not detected
among treatments.
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The objective of this study was to monitor estuarine water quality in
order to detect trends over time, and evaluate the impact of shrimp farming
on water quality. Water samples were collected at intake pumps of shrimp
farms. Samples were taken every 1 to 2 weeks from at least 12 sampling
sites distributed over six estuaries in the shrimp farming area of southern
Honduras. Water samples were analyzed and summarized according to estuarine
type, location, season, month, and year for total settleable solids, total
ammonia nitrogen, filterable reactive phosphate, chlorophyll-a,
total alkalinity, salinity, and BOD7. Data collection and analyses
are in progress. A preliminary analysis of total nitrogen was completed
for El Pedregal estuary. Nitrogen input as feed was greatest during the
rainy season due to increased shrimp growth in this season; however, there
was no accumulation of nitrogen from heavy feeding because of flushing
by runoff. During the dry season, a period of relatively light feeding,
nitrogen concentrations tended to increase, because of insignificant freshwater
input and low exchange with bay water. Overall total nitrogen concentration
did not increase with time, primarily because runoff from rainfall flushes
the estuaries yearly.
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Sex reversal of newly hatched tilapia generally is accomplished via
oral administration of 17a-methyltestosterone
(MT), which has been incorporated
into a starter fish feed at 60 mg MT/kg feed. Other investigators have
reported sex reversal of tilapia at dose rates less than 60 mg MT/kg feed;
however results from some of these studies are inconsistent, and it is
difficult to separate treatment environment effects. Naturally occurring
sources of testosterone may be an alternative to using a synthetic androgen,
which also is an anabolic steroid, for tilapia sex reversal. Bull testes
are a by-product of the beef industry in the US, and are a potential source
of dietary testosterone for tilapia sex reversal. The objectives of this
research were: 1.) to determine the efficacy of different dosage rates
of MT for sex reversal of fish treated in different environments, and 2.)
to evaluate the potential of freeze-dried bull testes as a dietary source
of testosterone for tilapia sex reversal. Newly hatched Nile tilapia (Oreochromis
niloticus) were stocked at 8 fry/l into 80-l glass aquaria located
inside a hatchery building or into hapas suspended in 20-m3
outdoor concrete tanks. Trout chow was the carrier for MT, which was incorporated
into the feed at 0, 10, 20, 30 and 40 mg MT/kg of feed. Frozen bull testes,
obtained from a meat packing plant, were freeze-dried, ground, and mixed
with trout chow either in a 1:1 or 1:3 freeze-dried testes: trout chow
ratio. The use of freeze-dried bull testes (BT) as a source of testosterone
was not effective in producing tilapia populations of 95% or greater males.
The percentage of males ( 54%) in populations fed a ration containing 25%
BT did not differ from non-treated populations (52.4%). The percentage
males (64.8%) obtained when BT composed half of the ration was significantly
greater than non-treated populations. Indoor and outdoor treatments did
not affect the ability of 17a-methyltestosterone to alter the sex ratio
of tilapia. Greater than 97% male populations were obtained at dose rates
of 15 mg,
30 mg, 45 mg and 60 mg MT/kg feed when fish were treated in indoor aquaria
or outdoor hapas.
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Abstract (Printed as submitted)
Two major shrimp producing estuaries, El Pedregal and the San Bernardo, were sampled weekly at high and low tides for five weeks during the rainy season of 1995. The sampling period spanned a lunar cycle when tidal levels fluctuated. Water samples were collected from the surface, mid depth, and near the bottom. Samples were taken at four stations along a longitudinal transact of each estuary that discharges into the Gulf of Fonseca. Water was analyzed for BOD5, total phosphorus, filterable phosphate, nitrate nitrogen, total nitrogen, total ammonia, chlorophyll-a, and total suspended solids. El Pedregal estuary had significantly higher concentrations of organic material and more nutrients than the San Bernardo. Mean nutrient concentrations were significantly higher at low tide than at high tide, probably because estuarine water was diluted with relatively pristine gulf water during the high tide. Nutrient concentrations were not predictably stratified along the lengths of estuaries. There was no apparent pattern between nutrient concentrations and lunar phase in either estuary. High freshwater inflow from rainfall probably masked lunar and longitudinal effects of estuarine hydrology. There were few water quality differences between the surface and bottom of estuaries, except for total settleable solids which tended to be higher at the bottom. Otherwise, high tidal fluctuation kept water vertically mixed in the main estuarine channels.
(This thesis was in partial fulfillment of the Ingeniero Agrónomo degree, Escuela Agricola Panamericana, Zamorano, Honduras. Abstract translation by David Teichert-Coddington)
Two major shrimp producing estuaries, El Pedregal and the San Bernardo, were sampled weekly at high and low tides for five weeks during the rainy season of 1995. The sampling period spanned a lunar cycle when tidal levels fluctuated. Dissolved oxygen, temperature, and salinity were recorded at 50-cm intervals from surface to bottom. Measurements were taken at seven stations in El Pedregal and six stations in the San Bernardo. The stations were located along a longitudinal transect of each estuary that discharges into the Gulf of Fonseca. Both estuaries are influenced by rivers. The Black River (Rio Negro) enters the San Bernardo at its head, and the Choluteca River enters the El Pedregal near its mouth. Salinity of the San Bernardo was less than that of the El Pedregal due to river flow through the estuary. In both estuaries, but particularly in the San Bernardo, salinity increased closer to the gulf because of intrusion by higher salinity gulf water. Mean estuarine salinity was significantly higher during high tide. The distance upstream that gulf water exchanged with estuarine water could be demonstrated from the change in salinity at various depths during tidal exchange. Dissolved oxygen concentrations of estuarine water increased with greater influence of the gulf. In both estuaries, dissolved oxygen concentrations were significantly higher near the gulf than upstream. Dissolved oxygen was also significantly higher during the high tide, and during the new moon.
(This thesis was in partial fulfillment of the Ingeniero Agrónomo degree, Escuela Agricola Panamericana, Zamorano, Honduras. Abstract translation by DavidTeichert-Coddington)
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The Pond Dynamics/Aquaculture CRSP is funded under USAID Grant No. LAG-G-00-96-90015-00
and by
the participating US and Host Country institutions.
Questions for or about the Aquaculture CRSP? Comments about this site? Email ACRSP@oregonstate.edu.
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