General trends in carp farming
461
that the pond area to be analysed must always be specified since the results
and conclusions may be totally different. This point is very important since
the four types of pond area (item 5 of Material) are frequently used (or
miused) by authors.
Differences between the trends of total carp production and the actually
used pond area reveal that the increase of carp production in Poland is mainly
due to
intensification.
It
is known that feeding is a radical measure commonly
used to intensify pond fish production. ln most cases, feeds are also the main
cost
item.
The trend
in feed use
(y3) (Fig. 1) indicates that there was an
increased use of feeds
in pond culture during the period under study (3.31 %
annually compared to the multi—year average), whereas carp production increa—
sed by only 2.12 %. It can be concluded that the effectiveness of feeding
decreased. Moreover, there was a strict correlation between the use of feeds
and carp production (r = 0.8993, P > 0.001). These results constitute one of
the basic problems of carp farming. Increasing the use of feeds (at decreasing
feed effectiveness) is related with the increasing cost of feeds but also with
other cost
items such as labour, transportation and storage.
However, the decreasing effectiveness of feeding might be (and probably
is) connected with the effect(s) of some other factor(s), independent of the
manager.
Total carp production included two fractions (see item 1 in Material),
the production of table fish and that of carp stocking material. Is it possi—
ble to assess feed use for these two fractions of carp production ? No direct
data are available for the State Pond Fish Farms and their computation from
basic records in particular farms would be very difficult and excessively
labour—demanding. However, as mentioned, there was a strict
correlation bet—
ween
carp production and feed use, so the opposite should also be true. If
data is available on total feed use on the one hand and on the two fractions
of carp production in the other, multiple regression between the use of feeds
and the fractions of carp production can be computed. Partial determination
Of each fraction will show how much each determined the use of feeds.
Thus,
the effect of feed use on these fractions can be estimated, while the coeffi—
cients of partial regression can be used to compute unit feed use for carp
production in both fractions.
Respective calculations reveal that table carp production accounted for
about 27 % of the variation in feed use and the production of stocking mate—
rial about 60 %, whereas the two fractions represent, respectively, 63.2 and
32.8 % of the total carp production. The coefficients of partial regression
indicate that 1.47 unit
of
feeds were used to produce one unit of table carp,
Whereas 3.92 units were needed to produce one unit of carp stocking material.
These results suggest that table carp was somewhat "underfed" and that State
Pond Fish Farms seemed to be more concerned with the production of carp sto—
cking material than with table carp.
The latter observation is reflected by trends in table carp and stocking
material productions (Fig. 1). The production of the stocking material (y4)
is characterized by a growing trend, with an annual increment of 4.35 %
pared to the multi—year average. Linear approximation of table carp production
(ÿ5) is not statistically significant (broken line of Fig. 1)- On the other
hand, parabolic approximation of this production is significant (P > 0:02)
and the parabola reaches a maximum in the 12th year of the period studied
(about 1975, Fig. 1). In spite of this, the linear trend will probably fit
the real data better in the future.
This is because in recent years
1984), which have not considered, table carp production increased
again.
In
any case, both trends indicate that the effectiveness of stock1ng decreased
461
that the pond area to be analysed must always be specified since the results
and conclusions may be totally different. This point is very important since
the four types of pond area (item 5 of Material) are frequently used (or
miused) by authors.
Differences between the trends of total carp production and the actually
used pond area reveal that the increase of carp production in Poland is mainly
due to
intensification.
It
is known that feeding is a radical measure commonly
used to intensify pond fish production. ln most cases, feeds are also the main
cost
item.
The trend
in feed use
(y3) (Fig. 1) indicates that there was an
increased use of feeds
in pond culture during the period under study (3.31 %
annually compared to the multi—year average), whereas carp production increa—
sed by only 2.12 %. It can be concluded that the effectiveness of feeding
decreased. Moreover, there was a strict correlation between the use of feeds
and carp production (r = 0.8993, P > 0.001). These results constitute one of
the basic problems of carp farming. Increasing the use of feeds (at decreasing
feed effectiveness) is related with the increasing cost of feeds but also with
other cost
items such as labour, transportation and storage.
However, the decreasing effectiveness of feeding might be (and probably
is) connected with the effect(s) of some other factor(s), independent of the
manager.
Total carp production included two fractions (see item 1 in Material),
the production of table fish and that of carp stocking material. Is it possi—
ble to assess feed use for these two fractions of carp production ? No direct
data are available for the State Pond Fish Farms and their computation from
basic records in particular farms would be very difficult and excessively
labour—demanding. However, as mentioned, there was a strict
correlation bet—
ween
carp production and feed use, so the opposite should also be true. If
data is available on total feed use on the one hand and on the two fractions
of carp production in the other, multiple regression between the use of feeds
and the fractions of carp production can be computed. Partial determination
Of each fraction will show how much each determined the use of feeds.
Thus,
the effect of feed use on these fractions can be estimated, while the coeffi—
cients of partial regression can be used to compute unit feed use for carp
production in both fractions.
Respective calculations reveal that table carp production accounted for
about 27 % of the variation in feed use and the production of stocking mate—
rial about 60 %, whereas the two fractions represent, respectively, 63.2 and
32.8 % of the total carp production. The coefficients of partial regression
indicate that 1.47 unit
of
feeds were used to produce one unit of table carp,
Whereas 3.92 units were needed to produce one unit of carp stocking material.
These results suggest that table carp was somewhat "underfed" and that State
Pond Fish Farms seemed to be more concerned with the production of carp sto—
cking material than with table carp.
The latter observation is reflected by trends in table carp and stocking
material productions (Fig. 1). The production of the stocking material (y4)
is characterized by a growing trend, with an annual increment of 4.35 %
pared to the multi—year average. Linear approximation of table carp production
(ÿ5) is not statistically significant (broken line of Fig. 1)- On the other
hand, parabolic approximation of this production is significant (P > 0:02)
and the parabola reaches a maximum in the 12th year of the period studied
(about 1975, Fig. 1). In spite of this, the linear trend will probably fit
the real data better in the future.
This is because in recent years
1984), which have not considered, table carp production increased
again.
In
any case, both trends indicate that the effectiveness of stock1ng decreased