Authored by Algrient Nana Towa
Abstract
In order to improve fish productivity, an essay on the evaluation of
the comparative effect of chicken and pig manure on the composition and
structure of Zooplankton was conducted at the Application and
Research farm from the University of Dschang (LN: 5º44’-5 °36 and LE:
10º06’-9 °
85’). For this purpose, 15 ponds (5.7 x 5.7 x 1m), three doses of 0
(control); 800 and 1000kg/ha of chicken manure as well as pig dung were
used. At
each of the randomly selected ponds was administered one of the
fertilizer doses every 7 days. Each of the doses and type of fertilizer
representing
a treatment was repeated three times. The physicochemical
characteristics of the water and the Zooplankton population were
measured every 14
days. With respect to the physicochemical characteristics of water, the
values of nitrites (7.92 ± 0.05mg/l), nitrates (8.03 ± 0.24mg/l),
phosphates
(4.68 ± 0, 05mg/l) were significantly (p <0.05) higher in ponds
fertilized at 1000kg/ha pig dung, the lowest being obtained in the
control treatment.
For Zooplankton, the highest specific (64.51% of total species), generics (87.87% of total genera) and families (82.35% of total) Zooplanktonic
abundances were obtained in ponds fertilized at the rate of 1000kg/ha of
chicken manure. The species of rotifers were the most diverse survived
those of cladocerans whatever the type or the dose of fertilizer. The
use of the 1000kg/ha dose of chicken droppings makes sense for a large
production of Zooplankton diversity.
In Africa and more specifically in Cameroon, the role of
aquaculture in the economy remains marginal. In fact, aquaculture
accounts for less than 0.1% of total fish inputs, despite the water
surface area covering nearly 3.5 million hectares, spread over 4
major river basins MINEPIA [1]. It should be noted that commercial
fish farming is 90% from fertilized ponds. However, one of the
constraints of development of pond production is attributable
to the fertilization technique associated with the mastery of the
operation of the interspecific, intraspecific biodiversity of the living
prey of the pond ecosystem.
Fertilization is an activity that makes it possible to optimize fish
production by improving the physicochemical parameters of water
and the densities of Zooplankton organisms [2], which are the living
prey for the most fishes. Zooplankton is by its specific diversity and
nutritional value the best fish about the plasticity of the diet of fish
species. Several studies have been carried out on the fertilization
of ponds from animal waste [3-5], at different doses. But none of
this work has focused on studying the diversity of Zooplankton
populations.
The objective of this work is to contribute to the improvement of
the production of Zooplankton intended for larval feeding through
a better fertilization. More specifically, the aim is to evaluate the
effect of pig manure doses on:
• The physicochemical characteristics of water
• The richness and distribution of Zooplankton populations
Area and period of the study
The trial was conducted from May 15 to November 15, 2016 at
the Dschang University Applied Research Farm (FAR) (LN: 5° 44’-5°
36’ and LE: 10° 06’ -9° 85’, altitude: 1392-1396m) in the Sudano-
Guinean agro-ecological zone characterized by a short dry season
(mid-November to mid-March) and a long rainy season (mid-March
to mid-March) November). The annual rainfall varies between 1500
and 2000mm and the temperatures oscillate between 14 °C (July-
August) and 25 °C (February).
Fertilizer
The slurry and droppings used in hens came from a pork farm
and egg layer layers fed a feed (feed). A sample of each fertilizer was
taken to determine the total dry matter, nitrogen and phosphorus
concentration. The average values of the characteristics of
the droppings were: dry matter (80.2±3.33%), total nitrogen
(2±0.14%) and total phosphorus (1.5±0.06%) and those of pig
slurry: dry matter (30.5±2.21%), total nitrogen (33±1.11%), total
phosphorus (9±2.30%).
Experimental ponds
The test was carried out in 15 identical by-pass ponds (5.7 x 5.7
x 1m and a water exchange rate of 0.05 l/s). The 15 ponds were fed
in water from an artificial lake located 100m away. A 1.5mm mesh
net was attached to the feed pipe of each pond to prevent intrusion
of fish from the artificial lake.
Conduct of the test and data collection
At each randomly selected pond, one of the 0kg/ha (control),
800; 1000kg/ha for both chicken manure and pig dung (weighed
with a 0.1g precision electronic balance) corresponding to T0, F800,
F1000, L800 and L1000, respectively. Fertilization was done every 7 days
on the surface of each pond according to Lacroix (2004).
The determination of the physicochemical characteristics of the
water was carried out parallel to that of Zooplankton every 14 days
between 6 and 8 o’clock in the morning according to Agadjihouédé
et al. [6] Dakwen et al. [7]. The sampling of Zooplankton was carried
out at twenty different points of the water column of each pond
using a calibrated polyethylene container of 1 liter capacity, ie a
total volume of 20 liters/pond filtered by means of a plankton
screen of 40μm mesh. A volume of 350ml Zooplankton concentrate
was recovered, fixed by addition of 5% formalin (¼ volume of
the concentrated sample) and stored in the plastic bottles for
quantitative and qualitative analyzes.
Determination of the physicochemical characteristics of water
a. The transparency of the dry disk, temperature, pH,
dissolved oxygen and electrical conductivity were directly
measured in the field with the help of a weighed dry disk
and attached to a graduated rope, Thermo-Conductivity
meter, Thermo pH-meter, pH meter, thermo-oximeter and
thermo-conductivity meter brand HANNA.
b. Total nitrite, nitrate and phosphate measurements were
carried out by spectrophotometry (HACH DR/2000
spectrophotometer) using Alpha techniques Greenberg
[8].
Determination of Zooplanktonic characteristics
Two types of analysis were carried out namely: qualitative
analysis and quantitative analysis.
Qualitative analysis
Only rigid integument species have been identified. Indeed,
all the samples are fixed with formalin which by these chemical
properties modifies the shape of the species with flexible
integument. After homogenization, 10ml of the sample were taken
by means of a calibrated pipette and introduced into a Petri dish
90mm in diameter. Species identification was performed using a
MOTIC brand binocular loupe.
Identification of rotifers: It was possible thanks to the use of
the keys of determinations and works of [9-12].
Identification of cladocerans: It was based on the observation
of morphological characters, such as the shape of the body, the
shape of the cephalic capsule ventral or dorsal view, the shape of
the rostrum and the detailed examination of appendages of the
abdomen. The observation of these characters was only possible
after dissection with the binocular loupe MOTIC using munities
mounted on pen or mandrel. The keys to determinations and works
were those of Rey & Saint Jean [12-15].
Identification of copepods: The copepods are identified
based on the body shape, the length of the antennules and
antennas, the lateral ornamentations of the segments of the
abdomen, the position of the ovigerous sacs, and the shape of the
rostrum. The identification was made after dissections with the
binocular magnifier MOTIC by means of the munities. The keys to
determinations and works were those of Dumont [12,15-17].
Quantitative analysis of Zooplankton
The counting of individuals was done simultaneously as
identification. The count was done in duplicate Legendre and Watt,
[18] under the binocular loupe brand MOTIC. Counts of at least 100
individuals per sample were conducted Frontier [19,20].
Statistical analyzes
The collected data were subjected to one-way analysis of
variance (ANOVA 1). In case of significant differences between
averages, the Duncan and Student tests were applied to separate
them at the 5% significance level. The SPSS 20.0 software (Statistical
Package for Social Sciences) was used for these analyzes.
Influence of types and doses of fertilizer on the physicochemical characteristics of water
The influence of fertilizer types and doses on the
physicochemical characteristics of water is summarized in Table
1 and illustrated in Figure 1. Evolution of the physicochemical
characteristics of water according to the types and doses of
fertilizer. The trend, the profile, and the pace of the evolution of all
the physicochemical characteristics of the water (Figure 1a-h) were
generally comparable between the treatments.
Transparency: The transparency as illustrated in (Figure 1a)
shows that whatever the period considered the highest values
significantly (p <0.05) are recorded in the control treatment and
the lowest values in the chicken manure (1000kg/ha). When
comparing the types of fertilizer at the same dose, the highest value
of transparency is recorded in pig manure. For the same type of
fertilizer, the lowest value of transparency is obtained in the largest
amount of chicken droppings (1000kg/ha), the opposite being
observed with pig manure. However, no significant differences
were observed between the types and between the fertilizer doses.
Temperature and pH: The evolution of temperature (Figure
1b) regardless of the period of the test was comparable between
the types and doses of fertilizers. However, the highest value of
the temperature at the end of the test is recorded in the control
treatment (T0) and the lowest value being that fertilized at the dose
of 800kg/ha.
Whatever the period of the test, the highest pH values (Figure
1d) are obtained in the treatment without fertilization (T0), followed
by the dose of 800kg/ha of chicken manure, the lowest being with
the smallest amount of pork slurry (800kg/ha). At the end of the
test, the pH values were comparable between the control treatment
and the two doses of chicken manure on the one hand and between
the highest dose of pig manure (1000kg/ha) on the other hand.
Electrical conductivity: The evolution of the conductivity as
illustrated in (Figure 1h) was comparable between the types and
doses of fertilizer regardless of the period of the test. However, the
highest value of the conductivity at the end of the test is obtained
in the treatment at the rate of 1000kg/ha of chicken droppings and
the lowest being in the unfertilized ponds (T0).
Dissolved oxygen trophy quotient: The evolution of dissolved
oxygen (Figure 1c) shows that the highest values are recorded in
the unfertilized ponds (control) and the lowest in pig manure.
When comparing the same-dose fertilizer types, the dissolved
oxygen values are lower in the chicken droppings at 1000 kg/ha, the
reverse being with the smaller dose (800kg/ha). Nevertheless, no
significant difference is observed between the types of fertilizers.
Nitrites, nitrates, phosphates and trophic state: Whatever
the period of the test, the lowest values for nitrites, nitrates and
phosphates (Figure 1e-1g) are obtained in the control treatment
without fertilization (T0) (Table 1). Regardless of the period, the
highest values for nitrite, nitrate and phosphates (p <0.05) were
observed in the 1000kg/ha pig dung, the lowest values being
obtained with the 800kg/ha dose of chicken manure. When
comparing the types of fertilizer at equal doses, the highest values
are significantly obtained in pig manure. As for the trophic quotient,
the values have inversely increased with the same type and doses
of fertilizer. The significantly lower value is obtained in the control
treatment, the highest being recorded in the pond fertilized at the
rate of 800kg/ha of pig manure (Figure 1).
Effects of fertilizer types and doses on species richness and distribution, Zooplankton genera and families
The influence of fertilizer types and doses on the species, genus,
and family richness of Zooplankton is summarized in Tables 2&3.
Regardless of treatments, a total of 93 species grouped into 33
genera and 17 families were identified.
Zooplankton species: The effect of fertilizer types and doses on
species richness (Table 2) shows that the highest value is obtained
in ponds fertilized with the 1000kg/ha dose of chicken manure.
The lowest value is recorded in the control treatment (T0). When
comparing the same-dose fertilizer types, the number of species
recorded in the treatment with hen’s droppings is higher compared
to that obtained in ponds fertilized with pig manure regardless of
the dose. With the same type of fertilizer, it appears that the species
richness has increased with the dose both in ponds fertilized with
pig manure and with chicken manure.
The distribution of Zooplankton species according to fertilizer
types and doses (Table 3) shows that of the 93 identified species
3, ie 3.22% (Euclanis triquetra, Lecane bulla, Polythra vulgaris), are
represented in all treatments. Only one of the 93 species recorded
(Lecane lunaris) is represented only in the control treatment. The
numbers of species represented specifically in the treatment with
pig slurry (6 species, Keratella mixta, Filinia mator, Trichocerca
insulana, etc.) are the lowest compared to those obtained in ponds
fertilized with chicken manure (35 species Cephalodella physalis,
Resticula melandocus, Lecane aguessi, etc.).
When comparing the same fertilizer type doses, the species
identified specifically in the 800kg/ha treatment are the lowest
(1 species Lecane hamata) compared to the 1000kg/ha treatment
of pig dung (4 species, Keratella mixta, Filinia mator, Trichocerca
insulana, etc.). The same trend is observed in lots fertilized with
chicken droppings where 12 species (Cephalodella physalis, Lecane
aguessi, L obtusa, etc.) are specifically identified in the treatment
with the smallest dose (800kg/ha) and 19 (Resticula melandocus,
Lecane blachei, L doryssa, etc.) in the largest dose (1000kg/ha)
(Table 2).
Zooplanktonic genera: The generic richness of Zooplankton
(Table 3) shows that the highest value is obtained in ponds
fertilized with the largest amount of chicken manure (1000kg/ha).
The lowest value is recorded in the treatment without fertilization
(control). At equal doses, the genera recorded in the treatment with
chicken manure are the most numerous compared to those ponds
fertilized with pig dung irrespective of the dose. When comparing
the doses to the same fertilizer type, it appears that the richness
of the genera enumerated increases with the dose both in ponds
fertilized with pig dung and with chicken manure.
Wealth of species by genera: The specific richness of the
genera according to the types and doses of fertilizer is grouped in
4 categories namely: low specific richness ≤ 2,5%; average> 2.5
and ≤ 5%; high> 5 and ≤ 7.5% and very high> 7.5% corresponding
to the number or percentage of species recorded by genus. Those
criteria show that of the 33 genera identified 25 or 75.75% of the total genera (Keratella, Plationus, Platyias, etc.), have low specific
wealth. Similarly, 4 genera or 12.12% of the 33 genera identified
(Brachionus, Cephalodella, Lepadella, etc.), 3 or 9.09% (Trichocerca,
Alona, Ceridaphnia) and one genus only (Lecane) have average
specific wealth respectively, high and very high.
The number of genera represented by low species richness
increased with the type and dose of fertilizer. Thus, the genera with
low species richness are higher in the ponds fertilized with the
highest dose of chicken manure (Brachionus, Keratella, Plationus,
etc.) and lower in the treatment without fertilization (Keratella,
Pliationus, Euchlanis, etc).
The Lecane genus with the highest species richness is recorded
only in ponds fertilized with hen droppings.
Distribution of Zooplanktonic genera according to types
and doses of fertilizer. The distribution of Zooplanktonic genera
is summarized in (Table 3). A total of 6 genera or 18.18% of the
33 identified (Brachionus, Euchlanis, Lecane, Polythra, etc.) are
represented in all treatments. Only one genus is specifically
identified for 1000 kg / ha pig dung (Bryocyclops) on the one hand
and ponds fertilized on the other with the lowest dose of chicken
manure (Moina). A total of 3 genera (Scaridium, Xenolepadella,
Resticula) are present in ponds fertilized with the largest dose of
chicken droppings (1000kg/ha).
Zooplanktonic families: The abundance of Zooplankton
families according to the types and doses of fertilizer as summarized
in Table 2 is highest (15 or 88.23% of total families) in ponds
fertilized with the lowest dose of chicken droppings (800kg/ha)
and the lowest (9 or 52.94% of the 17 families surveyed) in the
treatment without fertilization (control).
When comparing fertilizers at equal doses, the wealth of the
families surveyed is higher in the treatment with hen droppings
compared to ponds fertilized with pig manure regardless of the
dose. The distribution of Zooplankton families as summarized in
Table 3 shows that a total of 6 families are counted in all treatments.
The families represented specifically in ponds fertilized at 800
and 1000kg/ha of chicken droppings are those of Moinidae and
Scarididae respectively. (Table 3)
Results concerning the influence of fertilizer types and doses
on the physicochemical characteristics of water showed that
dissolved oxygen, transparency, nitrite, nitrate and phosphate
were significantly affected by fertilizer doses. Thus, concentrations
of nitrite ions (NO2-), nitrates (NO3-) and phosphates (PO4
3-) were
significantly higher in fertilized ponds.
The concentrations of nitrates and phosphates were comparable
to those obtained by Akodogbo et al. [21] in the production of
Zooplankton based on pig droppings in buckets. On the other hand,
they were higher than those recorded by Kumara et al. [3] in nursery
tanks fertilized with chicken droppings and cow dung. Such a
difference would be due to the absence of fry in our ponds that feed
on organic matter or phytoplankton in suspension, responsible for
the increase of mineral elements after decomposition.
The waters of the ponds fertilized with the greatest amount
of fertilizer were remarkable for their low transparency. This
observation is largely due to the distribution of seston elements in
the water column, including plankton swarming Njine et al. [22].
Dissolved oxygen was significantly lower with the largest
amount of fertilizer. On the other hand, results obtained in tanks
fertilized with cow dung and pig excrement showed that dissolved
oxygen was comparable between doses Agadjihouedé et al.
[21,23,24]. Such variation would be due to the dose and frequency
of fertilization of our ponds. The low value of oxygen obtained is
characteristic of eutrophic media (Moss, 1998). Deoxygenation
is the consequence of the oxidation of organic matter, carried out
biologically or chemically Njine et al. [22].
The temperature, conductivity and pH were relatively constant
and comparable between fertilizer types and doses. This trend was
reported by Agadjihouedé et al. [23,24] and by Akodogbo et al. [21]
in fermented bins based on animal waste. Observations show that
fertilization does not significantly affect temperature, conductivity
and pH whatever the fertilizer dose. Thus, the temperature and the
pH were in the range favorable to the development of plankton,
namely respectively 20-30 °C; 6.5 - 7.5; advocated by Cabrallo et
al. [25,26].
Results on the effect of fertilizer types and doses on Zooplankton
biodiversity have shown that Zooplankton species, species, and
species richness increased significantly with fertilizer types and
doses. The richness of the species identified independently of
the treatments was greater than 70 and 69 species respectively
obtained by Adedeji et al. [27] Dakwen et al. [7] in fish pond, as
well as 30 species identified by Elegbe et al. [28] in a traditional
aquaculture system, “Whedos”. The differences observed would be
due either to the types and doses of fertilizers, the sampling effort
(twice a month versus one), the size of the plankton net (40μm
versus 64μm) and the predation of the fish.
The specific richness of Zooplankton in fertilized ponds was
significantly higher compared to that of the control ponds. This
trend corroborates that reported by Adedeji et al. [27,28]. This
observation confirms the hypothesis that the contribution of
biogenic elements in a body of water influences its planktonic
richness, especially Zooplankton. Indeed, in the Lake Municipal of
Yaoundé qualified hypertrophe the specific wealth (131 species
and subspecies) recorded by Zébazé [12] was greater than that
obtained in our pond.
The distribution of species richness of Zooplankton groups
showed that rotifers were more dominant, followed by cladocerans
regardless of treatment. The same trend was obtained by Dakwen
et al. [7] in fish pond. Our results are dissimilar to those reported
by Elegbe et al. [28] who achieved the dominance of cladocerans.
The dominance of rotifers was previously mentioned in eutrophic and
mesotrophic media by Shiel [29,30]. In fact, the dominance of
rotifers is linked to the fact that they are the organisms whose mode
of reproduction is the fastest of all the metazoans Nogrady et al.
[31] and therefore rapidly settle the available niches.
At the end of the test on the influence of hog droppings and
pig slurry on the physicochemical characteristics of water and
the composition and structure of Zooplankton populations in
ponds, the main conclusions are as follows. The physicochemical
characteristics of water were significantly affected by fertilizer
types and doses. The nitrite, nitrate and phosphate concentrations
as well as the conductivity were significantly higher in hog manure
ponds at a rate of 1000kg/ha. The higher trophic quotient in
fertilized ponds showed that fertilization improved the quality of
the water from the oligotrophic state to the mesotrophic control
pond in a fertilized pond.
The distribution composition of species as well as Zooplankton
genera and families were affected by fertilizer types and doses.
Indeed, the highest Zooplankton species and genera richness was
recorded in the treatment at 1000 kg / ha of chicken droppings.
The species of rotifers were the most diverse survived those of
cladocerans whatever the type or the dose of fertilizer. For a better
production of the Zooplankton diversity, it is preferable to use the
dose of 1000kg/ha of chicken manure.
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