MAIA JÚNIOR, W. M.; http://lattes.cnpq.br/0518480353490439; MAIA JÚNIOR, Walter Moreira.
Résumé:
The aim of this research was to evaluate the dynamics of the physical, chemical and
biological factors in the raise of tilapias in heavily organically polluted and not polluted
water, working experimentally during 120 days in fish ponds at the NUPPA/UFPB,
(João Pessoa/PB/Brazil). Four earthen fish pond (300m2 and average depth of 1,0m)
supplied with entrance and water exit systems opposing longitudinally received the
1.200 post reversion fry of Oreochromis niloticus, (Linnaeus, 1757), Chitralada strain,
originated from artificial incubation, had been stocked fish1:1m2 in each pond totaling
300 fish with 1,0g average weight and 3,0cm length. All fed with commercial feed using
a protocol recommended for the manufacturer. Two ponds were supplied with water
from a heavily organically polluted lagoon, and the other pair underwater filled, all of
them kept to the same level replacing the losses for evaporation and percolating. All
the water sample were collected, always at 07:00/08:00hours on the surface three
times week and weekly, and analyzed the parameters physical, chemical and
biological characteristics in the origin and use waters of the ponds- pH, dissolved
oxygen, temperature, transparency, total, fixed and volatile solids, color, electric
conductivity, turbidity, BD05, COD, chloride, alkalinity, total acidity, hardness, calcium,
magnesium, salinity, ammonia, nitrito, nitrate, total phosphorus, ortophosfate, sulfate,
pheofitina and chlorophyll a, structure of the plankton communities, the composition
and production of macroinvertebrates benthics biomass, and quantitative aspects of
the growth of tilapia with emphasis in the data of growth, length and weight, fillet and
residue, proximal chemical composition, and the relationship of the microbiological
quality of the water, the used feed and the fish skin. The nychthemeral dynamics of the
limnological variables the temperature, dissolved oxygen, pH, and transparency had
been realized each fourteen days. The main meteorological variables (temperature,
rainfall, insulation, solar radiation, photoperiod and winds speed) and physical,
chemical and fertility analyses of the pond soil were also analyzed. The results showed
that the values of pH in the four pond had been inside of range recommended as ideal
for the fish culture, exceeding a little at the superior limit. The increase in total and
volatile solid was observed with elapsing of the experiment, and the load of suspension
organic substance in the pond was greater than the inorganic, indicating that the
biological activity was more elevated. The measures of ammonia in the pond had
placed below of the concentration considered lethal to the tilapia and of the inadequate
value to the growth of the fish - 0,25mg, even so lethal concentration (LC50) either
equal 0,5mg/L. The average of phosphorous generated in the four ponds is improper to e received by the river that cross the experimental area. The results of the
nychthemeral dynamics of the limnological showed that the temperature of the pond
water is in accordance with the solar radiation and the days hours, being registered the
extreme temperatures on the afternoon and during the dawn. The diurnal variation of
the values of dissolved oxygen discloses a standard typical, with lesser concentrations
in the part of the morning and a gradual increase in the part of the afternoon. The
variation of pH values had the extreme after the introduction of the fish, reaching the
level of pH 10,0 remaining in this value for the first weeks, and as well as it occurred
with the OD, the largest variations of pH had occurred in the daylights. The
transparency of the pond water had became more reduced with the growing of the fish
and with development of phytoplankton. The phytoplanktonic community structure
(composition, specific richness, density, diversity, equitability, and dominance) found
the identification of 35 taxons in specific and the interspecific The class of Chlorophyta
was dominant in the community, with ample dispersion of the some species of
Scenedesmus equally distributed in all environments, followed by the Cyanophyta,
Bacyllariphyta, Euglenophyta and only one sort of Dinophyta. The results showed
greater presence of phytoplankton and concentration of chlorophyll a. principally in that
ones with minor SDV, explain therefore the plankton origin of the turbidity. The
zooplankton community presented low diversity, typical of continental water
characteristic, being rotifer+nauplius, more abundant in all the samples with cyclopoid
and calanoid contribution of copepod in some collects, and also a little of cladocerans.
The insects bentics reflects the littoral regions characteristics, being the Diptera
(Chironomidae) more abundant, followed by the Odonata, Coleoptera (Hydrophilidae,
Dytiscidae), Odonata (Gomphidae, Libellulidae), Hemiptera (Naucoridae),
Ephemeroptera. In the end of the experiment five units of each pond had the stomach
content analyzed, the results showed the more frequency of cianoficeas seaweed
debris and fragments of ration and Diatomaceae, verifying also the presence of items
of zooplancton, rotifers and eggs of Rotifera and vegetable remaining portions. The
processing results showed that the percentage of the rude skin, did not differ (P>0,05)
for the units created in different environments, what also is verified in relation to the
average percentage of residues, and the average percentages of fillets around 28,0%.
The bacteriology of the water indicates that counting of total viable bacteria was placed
below of the biosecurity reference, and the effluent generated had been inside of the
legislation for fecal coliformes/100ml_. The external surface of fish microbiology
presented the average values of total coliformes and fecal coliformes in the pond water
higher to the skin surface and, in terms of total counting of meshophilic bacteria, were evidenced that the fish raised in the pair of clean water pond had presented in washed
of the surface the counting ten times shorter to the water of these ponds, in
counterpoint the similarity observed in the pair of pond filled with water of the lagoon.
There was a significant difference of the growth of the fish between the pair of the
ponds 1 and 4 with underwater to the other pair 1 and 3 with water from na eutrophic
lagoon, otherwise there was an increase of population because some fish come
through from the lake. In the pond 1 and 4 the weight reach the average of 491,1 and
539,5g and 27,3 e 28,3cm of lenght. The fillet obtained was around of 28,0%, with,
total skin and residue between 60,2 and 72,0%. The proximal chemical composition
resulted 18,6-21,4% to protein, 78,5-78,8% to umid 0,9-1,5% to lipid ancH.1-1,3% to
minerals.