MONITORING OF CHANGES IN FISHPOND ECOSYSTEMS
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© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
MONITORING OF CHANGES IN FISHPOND
ECOSYSTEMS
Jan Pokorny, Günther Schiott, Karin Schiott, Libor Pechar &
Jana Koutnikovä
Abstract
The fishponds in Central Europe are shallow, man-made water bodies of different size. Management of fishponds
did not change over several centuries since the 15th and 16th centuries, when most of the fishponds were built. In the
20th century, the changes in fishpond management resulted in an increase of fish production from about 50 kg/ha to
more than 500 kg/ha. The long-term development of eutrophication of Czech fishponds is shown. The amount of
fertilizers (N, P) applied, average concentration of total P and N, NQ, NH4, PO4 and pH values from the 1930s until
now are given. An increase in N and P results in an increase in chlorophyll concentration and decrease in light
transparency. On the other hand, no substantial rise in nutrient concentration has been observed. In particular a high
load of N does not result in an increase in total N concentration in the water. Dominance of blue-green algae appears
to be more correlated with the ratio of N/P than with a lack of CQ. A model experiment on the relationship between
fish stock, size of Daphnia sp. and water quality is described. The experiment in several fishponds in Lower Austria
shows how a fish stocking level estimated according to natural food supply may improve water quality in fish ponds.
Pokorny, J., G. Schlott, K. Schlott, L. Pechar & J. Koutnikovä: Monitoring von
Veränderungen in Fischteich-Ökosytemen
Die Fischteiche in Zentraleuropa sind seichte künstliche Gewässer unterschiedlicher Größe. Seit dem 15. und 16.
Jahrhundert, als die meisten Teiche angelegt worden waren, hat sich die Bewirtschaftungsform nicht geändert. Im
20. Jahrhundert stieg die Fischproduktion durch Veränderungen in der Teichwirtschaft von 50 kg/ha auf 500 kg/ha
an. Die langfristige Entwicklung der Eutrophierung tschechischer Fischteiche wird gezeigt. Menge der Düngung (N,
P), durchschnittliche Konzentration von Gesamt-P und N, Werte von NQ, NH4, PO4 und pH seit 1930 werden
angeführt. Zunahme von N und P führt zur Zunahme der Chlorophyllkonzentration und zur Abnahme der
Lichtdurchlässigkeit. Es konnte aber keine bedeutende Erhöhung der Nährstoffkonzentration beobachtet werden.
Besonders hohe Stickstofffrachten ergeben keinen Anstieg des Gesamt-N im Wasser. Die Dominanz von Blaualgen
scheint mehr mit dem Verhätlnis N/P zu korrelieren als mit fehlendem CQ. Ein Modellexperiment über die
Zusammenhänge zwischen Fischbestand, Daphnia sp.-Größen und Wasserqualität werden beschrieben. Das an
Fischteichen in Niederösterreich durchgeführte Experiment zeigt, wie Fischbestände, gemessen am natürlichen
Nahrungsangebot, die Wasserqualität in Fischteichen verbessern könnten.
Pokorny, J., G. Schlott, K. Schlott, L. Pechar & J. Koutnikovä: Monitoroväni zmen
rybnicnich ekosystemü
Rybnfky ve stfednf Evrope jsou melke vodnf nädrze o plose jeden az nekolik set hektarä. Zpflsob obhospodarovänf
rybnfkü se nemenil nekolik stoletf od 15., 16. stoletf, kdy byla vetsina rybnfkü postavena. Ve dvacätem stoletf se
zpüsob obhospodarovänf rybnfkü zmenil natolik, ze produkce ryb se zvysila z cca 50 kg/ha na vfce nez 500 kg/ha. V
präci jsou uvedena mnozstvf aplikovanych hnojiv, prümeme koncentrace celkoveho dusfku, celkoveho fosforu, NO3,
NH4, PO4 a hodnot pH od 30tych let tohoto stoletf do soucästnosti. Zvysene davky hnojiv vedou ke zvysenf
koncentrace chlorofylu a sn'zenf propustnosti svetla, naproti tomu nebylo pozoro\dno podstatne zvysenf koncentrace
zivin. Zejmena vysoke dävky dusfkatych hnojiv nevedou ke zvysenf koncentrace dusfku ve vode. Dominance sinic se
zda byt vfce korelovana s pomerem N/P nezli s nedostatkem anorganickeho uhlfku. Popsän je modelovy experiment
zamefeny na Studium vztahu velikosti rybf obsädky, velikosti dafhif a kvality vody. Tento experiment pro\ödeny v
nekolika mensich rybnfcich v Dolnfm Rakousku prokazal jak volbou vhodns rybf obsädky zalozene na nabfdce
prirozene potravy lze zlepsit kvalitu vody v rybn'ce.
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INTRODUCTION The fishstock influences plankton structure,
and therefore it influences indirectly other
The management of fishponds in Bohemia parameters of water quality, including
did not change for several hundred years abiotic parameters such as transparency and
since the 15th and 16th centuries, when water chemistry (FOTT et al., 1980). The
most of the fishponds on the present nutrient input both from fertilizers applied
territory of the Czech Republic were built. directly to fishponds and from the
However, management practices changed in catchment increase the trophic level of
the second half of the 19th century. The fishponds. Changes in nutrient input and in
basis of modern management of Bohemian the fish stock take place simultaneously and
fishponds aimed at an increase in fish their individual roles in changes in water
production, according to SUSTA (1898). In quality are very difficult to distinguish.
the 20th century, the changes in fishpond The aim of this study was to compare data
management resulted in an increase in fish on amount of fertilizers used from the
production of an order of magnitude - from 1930's until present with the amount of
about 50 kg/ha to more than 500 kg/ha. nutrients, pH, transparency and chlorophyll
Reliable information on fish production found in the water. In this way we aimed to
from the 15th century can be found in the evaluate the relationship between the
State and town archives. amount of nutrients applied (load) and the
Long term changes in fishpond ecosystems water quality (i.e., the concentration of
caused by different management practices nutrients in the water etc.).
for fishponds and their catchments may be For one season, we evaluated the
studied from records of fisheries. Since the relationship between pH and chlorophyll a,
1930s the results of hydrobiological studies and also the relationship among NO3, NH4
and hydrochemical data are also available. and PO4 and blue green algae (cyanophytes),
The relationship between fertilizing and fish in order to test whether the development of
production has been studied by HRBÄCEK blue green algae is controlled by lack of
(1969), KUBÜ (1975) and BUDEBA (1992). inorganic carbon or by the N/P ratio.
They showed relationships between fish An example of a comparative study on
production and the amount of fertilizers fishpond management from Lower Austria
used (for some of the figures, see POKORNY is also given in order to demonstrate how
et al. (1993)). The high correlation between optimalisation of fish stock may improve
the amount of fertilizers applied and the fish water quality.
production is evident from the 1930's to the
1960's. In the past decades, the changes in METHODS
nutrient load has not resulted in any changes
in fish production. Recently, there is no The data from the 1930's, 1950's, etc., on
correlation between the amount of fertilizers the amount of fertilizers used (load) and on
applied and the fish production. The high the nutrient content in the water were taken
nutrient load brings about deterioration of from JIROVEC & Ji'ROVCOVÄ (1938) and
water quality which negatively influences from the State Fisheries. Since the 1950's,
the fish stock and the stability of the whole standard methods of hydrobiological and
pond ecosystem. hydrochemical analysis were recommended
The changes in management practices may and mostly used for fish pond study. The
be considered as a long term ecosystem methods used during that time are known
experiment. During this century, similar and may be repeated, and the results from
management practices, i.e. fishstocking and the 1950's and later may be compared in
fertilizing, were used in a large number of this way with recent results.
fishponds.
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The recent data on pH, chlorophyll a, Table 2 shows average concentrations of
nutrient content in the water and cyanophyte total nitrogen and total phosphorus,
biomass were collected from 90 ponds in transparency (Secchi disc depth) and
TfEBOri Biosphere Reserve 5 times during chlorophyll a concentration in two regions
the season of 1992 (March 19, April 29, of the Czech Republic from 1954 to 1993.
June 1, June 24, August 19). NH4, NO3 Blatnä is located in the Southwest and
and PO4 were estimated by Flow Injection Tfebon Biosphere Reserve is in the South of
Analysis using Tecator (RLJZICKA & the Czech Republic. The number of ponds
HANSEN, 1981). Chlorophyll a was evaluated is given under No. loc. (number
estimated in acetone + methanol ( 5 : 1 ) of localities).
extract using a Turner fluorometer (10 - Table 2 shows an increase in total nitrogen
OOR). One sample from each pond was of about 2.5 times from the 195O's to 1992
taken for determination of the main - 1993. The changes in the concentration of
phytoplankton groups. total phosphorus correspond to the decrease
In Waldviertel fish ponds (Lower Austria), in the amount of mineral fertilizers applied
the species, amount and size of Zooplankton in the 1970's. The rise of total phosphorus
were monitored during a season in order to concentration in the 1990's results from the
optimalize amount of food and fertilizers higher load of organic fertilizers. The
applied. The water chemistry was also transparency decreased from 1.7m to 0.52m,
studied. and a corresponding increase in the
concentration of chlorophyll a (from 35 to
RESULTS AND DISCUSSION 95 ug/1) is also shown in Table 2.
Table 3 shows average values of pH and
Table 1 shows long term development of average concentrations of NO3, NH4, PO4
eutrophication of the Czech fishponds. The from 1954 to 1993 again in Tfebon and
load means the amount of fertilizers applied Blatnä regions. Except for the value of NH4
(1973-78, Tfebon), the concentrations
Year LoadN loadP N:P oscillate around the values which are
(kg/ha) (kg/ha) relatively low regarding the high nitrogen
1930 0,3 load increase from the 1950's to the 1990's
0,1 0,2
and regarding the high chlorophyll content.
1950 5,8 12,0 0,5
The load of nitrogen has increased 10 times
1960 5,0 4,8 1,0
from the 1950's to the 1990's, although no
1974 39,7 7,4 5,4 rise in mineral nitrogen can be seen.
1979 12,2 4,0 3,1 Figures la and lb show relationships
1984 36,8 7,6 4,8 between the nitrogen (phosphorus) load and
1990 41,0 8,3 4,9 mean concentrations of total nitrogen (total
1991 51,9 5,3 9,9 phosphorus). It is evident from Figure la
that an increasing load of nitrogen does not
Table 1: Czech fishponds. Long-term result in a proportional rise in total nitrogen
development of eutrophication concentration. On the other hand, an
increasing load of phosphorus brings about
by fishpond managers per hectare per year. a proportional rise in phosphorus
The data were compiled from the records concentrations as evident in Figure lb.
and documents of the State Fishery Blatna High pH caused by photosynthetic activity
and represent the means from several of autotrophs can bring about fish-kills,
decades of fish ponds. An increasing load of particularly in late spring when higher
nitrogen (except 1979) and increasing N : P concentrations of NH4 occur. High pH is a
ratio are evident.
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Period Total N Total P Transparency Chl-a No. loc. Region
(mg/1) (mg/1) (m) (ng/i)
1954-1958 1,00 0,20 1,70 35 9 Blatna
1973 -1978 1,27 0,11 1,27 66 10 Tfebon
1979-1980 1,55 0,12 0,97 48 33 Blatnä
1990-1991 2,60 0,29 0,45 121 35 Tfebon
1992-1993 2,48 0,24 0,52 95 89 Tfebon
Table 2: Czech fishponds: Long-term development of eutrophication
Period pH NO 3 -N NH 4 -N PO4-P No. loc. Region
(mg/1) (mg/1) (mg/1)
1954-1958 8,3 0,07 0,09 9 Blatnä
1973 -1978 8,2 0,13 0,39 0,05 10 Tfebon
1979-1980 8,3 0,11 0,11 0,04 33 Blatnä
1990-1991 8,5 0,12 0,12 0,05 35 Tfebon
1992 -1993 8,2 0,14 0,23 0,09 89 Tfebon
Table 3: Czech fishponds. Long-term development of eutrophication
CZECH FISHPONDS CZECH FISHPONDS
Dependence of the annual mean of TN on N load Dependence of the annual mean TP on P load
20 40 60 80 100 120 140 0 5 10 15 20 25 30 35
Load N [kg. ha1] Load P [kg.ha1]
Fig.la: Dependence of the annual mean Fig.lb: Dependence of the annual mean
total nitrogen concentration (TN) on the total phosphorus concentration (TP) on
annual load of nitrogen (N) the annual load of phosphorus (P)
consequence of intense inorganic carbon phytoplankton groups. Therefore, the
uptake by phytoplankton. concentrations of chlorophyll a and pH
There are hypotheses which explain the values were measured in 91 ponds five
dominance of blue green algae in eutrophic times during the period March 19 to August
waters by the higher affinity of blue green 19, 1992. Figure 2 shows that pH does not
algae to inorganic carbon. SHAPIRO (1990) follow the pattern of chlorophyll a
explains the increasing portion of blue concentrations. The highest pH values
greens by their higher ability to take up caused by photosynthesis have been found
inorganic carbon at higher pH than other in spring.
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CZECH FISHPONDS CZECH FISHPONDS
Seasonal course (mean data from 91 localities, 1992) Seasonal course (mean data from 91 localities, 1992)
T© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
bring about a corresponding increase in total b) the fishponds in Tfebon Biosphere
nitrogen concentration. The losses of Reserve can be considered as
nitrogen (in the form of NH3 and N2) and the hypertrophic water bodies.
accumulation of phosphorus in the bottom
sediments bring about convenient The next part of this article deals with the
conditions for the development of results of a model experiment on the
planktonic blue green algae. This trend is relationship between fish stock, cladoceran
shown in Fig. 3. The NO3 concentration is number and size, and water quality.
highest in spring. Later, nitrate is The monitoring of fishponds must be
denitrificated or directly metabolized. The closely connected to knowledge of fishpond
increase in NH4 and PO4 may be explained management. Ahead of this conclusion,
by their release from sediments. there is the hypothesis that proper
Figure 4 demonstrates the dramatic change functioning of ponds is possible only with a
in the percentage of ponds in which the proper fish stock. The size of the fish stock
cyanophytes dominated (i.e. more than 4/5 should be balanced with the amount of
of phytoplankton biomass consists of blue- nutrients and amount of natural food.
green algae). It is evident from Figures 2 The number of large cladocerans is a
and 4 that the development of cyanophytes representative parameter for the amount of
is more closely related to the decrease in the natural food. Therefore the control of the
ratio of dissolved inorganic nitrogen to Daphnia population and its interpretation
dissolved reactive phosphorus than to the regarding the ecological circumstances
lack of inorganic carbon. Despite no should be an essential point of monitoring.
increase in pH during the season, Figures 5 - 9 show results of the modelling
cyanophytes are becoming more successful experiment in which five fishponds were
and their ratio rises from several percent in studied during one season. Number of large
March to more than 40 % in August. These cladocerans {Daphnia larger than 1 mm)
data show that in the case of our study, the and total phosphorus content in the water
N/P ratio is more important for the were analysed during the season. The
development of blue greens than the annual production of fish, the amount of
deficiency of CO2 Fish stock is another food applied and feed conversion ratio were
reason of the higher ratio of cyanophytes - also estimated. Table 4 shows that a large
the high biomass of fish eliminates the large fish stock and a large amount of food
filter-feeding Zooplankton {Daphnia spp.), applied brings about high values of total
allowing the development of dense phosphorus (635 ug/1). Figure 8 shows the
phytoplankton. This massive development situation when the size of the fish stock was
of phytoplankton results in further lowering balanced with natural food supply. The
of the N:P ratio and in further deterioration consumption of large Daphnia by fish was
of the underwater light conditions. The high balanced in this case with the growth and
stock density of carp can thus stimulate natality rate of Daphnia, and the
development of shade-adapted blue-green concentration of total phosphorus was
algae in the phytoplankton community. lowest of all the ponds studied.
The crucial point for the sustainable use of
fishponds in the future is to find the most
The presented results show that effective way of transforming nutrients to
fish production. The use of additional food
a) the seasonal development of has to be harmonised with the amount of
phytoplankton and concentration of natural food. Figure 7 shows another
nutrients differ from those described example - feeding was stopped when the
earlier by KofiNEK et al. (1987) number of Daphnia was rather high in July.
42© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
Clad. > I mm
Clad. > 1 am
ind./l
ind./l
AWT 2-92
8oo 8oo
ISO ISO
.700 .700
• 600 -600
100. 500 100. 500
400 . 400
300 300
SO 50
. 200 . 200
100 100
10
Clad. > 1 mm Clad. > 1
ind./l ind./1
B-1, 93/HT-2
800 0. F. 92/HT-3 800
ISO ISO
700 700
600 600
500 100. 500
/i
400 A 1
t
1
\
\
\
400
Ar
' » /
• / » *
' * /
•300 300
50 SO.
• 200
/ V/
. 200
• 100 100
10 10-
7
Clad. > 1 mm
ind./l
NZ, 93/HT-1 800
150-
700
600
100 500
400
300
50
. 200
100
Figs. 5-9: Comparison of the number of large Cladocera ( ) and concentration of total
phosphorus ( ). For fish production, additional feeding etc., see Table 4.
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Pond Annual Amount of food Food conversion Total
production (grain, pellets) ratio phosphorus
kg/ha kg/ha ug/1
mean value
May-Sept.
AWT 2 / 1992 1560 2540 1,62 635
AWT 1 / 1992 650 1350 2,08 445
B-l,93/HT-2 760 1090 1,44 367
NZ.93/HT-1 140 - 178
(natural prod.)
O.F. 92 / HT-3 no fish stock - - 219
Table 4: Annual fish production, amount of food, FCR and total phosphorus content.
An immediate decrease in Daphnia is with the DIN/DRP (dissolved inorganic
evident and a reduction in the concentration nitrogen/ dissolved reactive phosphorus)
of total phosphorus followed. The feed ratio which decreases markedly during
conversion coefficient and the concentration the season.
of total phosphorus were lower than in the 4)The size of fishstock in fishponds should
previous two cases, and the total annual be taken into account when interpreting
production was even higher than in the any monitoring data for fish ponds. It has
second case. been demonstrated how optimal use of
natural food by fish results in a reduction
CONCLUSIONS in total phosphorus.
The data and results presented in this paper
represent survey not monitoring. The REFERENCES
following conclusions may be made from
these data: BUDEBA, Y.L. (1991): Relationship of
fertilizers and food to fish production in
1) No marked changes in dissolved Tfebon Biosphere Region. Manuscript,
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44© Biologiezentrum Linz/Austria; download unter www.biologiezentrum.at
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