An analysis of biological characteristics
of Macrobrachium rosenbergii (de Man) in relation to pond production
and marketing in Thailand
C. Kwei Lin, Agricultural and Food Engineering Division, Asian Institute
of Technology, P.O. Box 2754, Bangkok, Thailand; Great Lakes Research Division,
The University of Michigan, Ann Arbor, Michigan 48109, USA
Mali Boonyaratpalin, National Inland Fisheries Institute, Bangkhen, Bangkok,
Thailand
14 February 1989, CRSP Research Report 89-16
Abstract Data on production and marketing of giant freshwater
prawn were collected over a seven-month, grow-out period through collaboration
with a medium-sized commercial prawn farm in central Thailand. Juvenile
prawns with an average weights of 4.2 g were stocked at a density of 6 prawns/m²
in three 0.5-ha earthen ponds. Average growth rate determined during the
first three months of the grow-out period was 0.4 g/ prawn per day; prawns
of marketable size were harvested selectively during the remaining four
months of the rearing period, resulting in a total accumulated yield of
1.3 tons/ha with an average prawn weight of 32 g and 60% survival. As different
sexes and sizes of prawns were sold at different prices, the harvests were
customarily sorted into several categories: large, medium, and small males,
long-clawed males "soft shells" females with eggs, females without eggs,
and terminal males. The total weight and number of prawns recorded for each
of these categories showed that the female to male ratios were 1.6:1 and
4:1 by weight and number, respectively, while the ratio of short-to long-clawed
males was 3:1 by weight and 4:1 by number. Four percent of the marketable
population was termed "soft shells" and 64% of the females bore
eggs. The ratio of head weight to tail weight of marketable prawns varied
substantially among the different categories: 1.0:1 for females, 2.5:1 for
long-clawed males, and 1.6:1 for short-clawed males. Females predominated
in the first and second 1.5-month harvest periods while males predominated
in the final 1.5 months of the harvest. The economic yield of prawn culture
was not only determined by the biomass, but also the population structure
of the various biological categories and the harvest season.
This paper was published in Aquaculture, 74: 205-215(1988).
Estimates of hypolimnetic oxygen deficits
in ponds
W.Y.B. Chang, Center for Great Lakes and Aquatic Sciences, University
of Michigan, Ann Arbor, Michigan 48109, USA
3 August 1989, CRSP Research Report 89-17
Abstract Shallow tropical integrated culture ponds in the Pearl
River Delta, China, have been found to stratify almost daily, with high
organic loadings and dense algal growth. The dissolved oxygen (DO) concentration
is super-saturated in the epilimnion and is under 2 mg/l in the hypolimnion
(>1 m). The compensation depth corresponds to twice the Secchi disk depth
ranging from 50 to 80 cm. As a result, little or no net oxygen is produced
in the hypolimnion (>1m). The low DO concentration in the hypolimnion
causes organic materials, such as unused organic wastes an senescent algae
cells, to be incompletely oxidized, since the rate of oxygen consumption
by oxidable matter in water is dependent on the dissolved oxygen concentration
in water. This material becomes the source of hypolimniotic oxygen deficits
(HOD) which can drive whole pond DO to a dangerously low level, should sudden
destratification occur. An improved estimate of hypolimnetic oxygen deficits
is introduced in this article, and the advantages of this method are discussed.
This paper was published in Aquaculture and Fisheries Management 1989,
20:167-172.
The effects of water exchange rate and
density on yield of the walking catfish, Clarias fuscus
James S. Diana, School of Natural Resources and Center for Great Lakes
and Aquatic Sciences, University of Michigan, Ann Arbor, Michigan 48109,
USA
Arlo W. Fast, Mariculture Research and Training Center, Hawaii Institute
of Marine Biology, University of Hawaii, Kaneohe, Hawaii 96744, USA
28 September 1989, CRSP Research Report 89-18
Abstract High stocking densities (600 fish/ m3) of walking catfish
resulted in slightly higher mortality rate, no difference in growth rate,
and a much higher yield than low density stocking (300 fish/ m3). Water
flow rate (10, 5, or 2.5 turnovers/day--turnover is defined as one diluted
replacement volume) had no effect on survival, growth, or yield. Fish were
cultured from an initial weight of 5.4 g for 90 days, and most mortality
occurred early in the cycle when the fish weighed <26 g. Growth also
was high initially and declined with time. Dissolved oxygen did not differ
between tanks of different density, but was altered by flow rate. Water
supply parameters, such as short-term BOD, strongly affected dissolved oxygen
content at all flow rates. Ammonia concentrations increased with density
and decreased with increased flow rate. Mortality rate of all fish was strongly
dependent on size, and mortality of small fish was correlated with short-term
BOD.
This paper was published in Aquaculture, 78: 267-276(1989).
Relationships between primary production
and yield of tilapia in ponds
James S. Diana and P.J. Schneeberger, Great Lakes Research Division and
School of Natural Resources, University of Michigan, Ann Arbor, Michigan
48109, USA
C. Kwei Lin, Division of Agricultural and Food Engineering, Asian Institute
of Technology, G.P.O. Box 2754, Bangkok 10501, Thailand
28 September 1989, CRSP Research Report 89-19
Abstract The purpose of this study was to determine relations
between physicochemical variables and primary productivity of fish yield
using multiple regression analysis.
In Thailand, 8-12 pond (250 m2) were stocked with male Oreochromis niloticus
(25-35 g) at a density of 1 fish/m3. Experiments were run for approximately
5 months during the wet season of 1984 and the wet and dry seasons of 1985.
Ponds received nutrient inputs according to three different management schemes:
(1) low input inorganic fertilizer (8 kg/ ha/month P2O5); (2) high input
organic ferilizer (500 kg/ha/week chicken manure); and (3) high input inorganic
fertilizer (100 kg/ha/week P2O5 and 30 kg/ha/week urea). Air and water temperature,
solar radiation, rainfall, dissolved oxygen (DO), total phosphorus, nitrate-nitrite,
ammonia, turbidity, chlorophyll a, primary productivity, fish weight,
and fish survival were measured regularly throughout each experiment. Data
were examined by regression analyses.
Ponds receiving high fertilizer inputs exhibited higher nutrient levels
in water, higher primary productivity, and higher fish production than ponds
treated with low inputs of fertilizer. Nitrogen and phosphorus appeared
to be limiting factors for primary productivity, although multiple regression
between these two factors and primary production indicated no significant
relationship. The availability of nutrients may have been related more closely
to regeneration rate than absolute concentration.
Fish yield was strongly correlated to rainfall, fish biomass, DO, water
temperature and solar radiation. The correlation between net yield and fish
biomass was a positive one, indicating that carrying capacity was not reached
in the ponds.
This paper was published in The Second International Symposium on Tilapia in Aquaculture.p.1-6, 1988.
R.S.V. Pullin, T. Bhukaswan, L. Tonguthai,and J.L. MacLean (eds.) ICLARM Conference Proceedings 15, Department of Fisheries, Bangkok,
Thailand, and International Center for Living Aquatic Resources Management, Manilla, Phillippines.
Biological nitrogen fixation as a source
of nitrogen input in fish ponds
C. Kwei Lin, Division of Agricultural and Food Engineering, Asian Institute
of Technology, G.P.O. Box 2754, Bangkok 10501, Thailand
V. Tansakul, Great Lakes Research Division and School of Natural Resources,
The University of Michigan, Ann Arbor, Michigan 48109, USA
C. Apinhapath, Soil Science Division, Royal Thai Department of Agriculture,
Bangkok, Thailand
9 November 1989, CRSP Research Report 89-20
Abstract The potential input of nitrogen derived from natural
biological fixation in water of fertilized tilapia grow-out ponds in Thailand
was determined by the acetylene reduction technique for 12 ponds over a
15-month period. On average, nitrogen fixation ranged from undetectable
levels of N to 105 µg/L/day in the water column, compared with 200µg/L/day
input of N from chicken manure loading at a rate of 500 kg/ha/week. Estimated
total nitrogen fixation in fishponds during a 5-month grow-out cycle ranged
from 8.8 to 85.7 kg N/ha. Nitrogen fixation primarily occurred in daylight;
it was inhibited in the dark and suppressed by elevated ammonium concentrations
present in pond water. Nitrogen-fixing blue-green algae commonly present
in the pond water were Anabaena, Cylindrospermum, and Nodularia.
This paper was published in The Second International Symposium on Tilapia in Aquaculture.p.1-6, 1988.
R.S.V. Pullin, T. Bhukaswan, L. Tonguthai,and J.L. MacLean (eds.) ICLARM Conference Proceedings 15, Department of Fisheries, Bangkok,
Thailand, and International Center for Living Aquatic Resources Management, Manilla, Phillippines.
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