404
Aquaculture of Cypnids
trammel nets and gills nets, in surface and bottom waters at seven different
points in each reservoir. The common carp is usually among the most abundant
species of the community of both reservoirs (19.32 in Arrocampo R. and 27.5Z
in Torrejon
,
as
percentages of the total number of all fishes taken du—
ring the sampling period. For the life history study, out of the total of
fish caught, 262 species of the Torrejon R. and 315 of the Arrocampo R. were
taken.
Principally, four phenomena were studied : length—weight relationship,
reproduction, food habits and spatial distribution. Lenght—weigbt relation—
ship of carp in the Arrocampo R. is represented by W = 0.000016 L2'95]; and
in Torrejon R. by W = 0.000024 L2'855. The differences between the two popu—
lations are not significant (95%). Carp begin spawning in the Torrejon R. as
early as June and continue until July. In the Arrocampo R., the spawning sea—
son
begins in May and continues until July; the results show a second peak
of activity during the winter period (January—February). Thus, the spawning
season
may be described as spring—summer with the possibility of other peaks
depending of the reservoir's characteristics. Food habits were analyzed in
terms
of frequency of ocurrence and a food importance index. In the Torrejon
R., the prefered foods of carp were cladocerans copepods, detritus and algae
all year around, but there were marked variations in certain foods items due
to
seasonal variations in he abundance of the preys.
In
the Arrocampo R., carp
is a markedly benthic feeder (chironomid larvae, nematodes and larvae of the
other
diptera) and secondarily planktophagus. According to our results, the
carp
in mediterranean aquatic ecosystems are versatile omnivores which utili—
ze
whatever food is available
(without competition processes). The spatial
distribution in both reservoirs is similar. The carp exhibits definitive ho—
ming tendencies; except for movements toward shallow water with vegetation
associated with spawning, the carp is highly sedentary; the water depth where
carp were
located ranged from 1 m. to 6 m.
INPUT—OUTPUT RELATIONSHIPS OF INDIAN COMPOSITE FISH CULTURE. M. RANADHIR and
V.R.P. SINHA,
Aquacwüîu}œ Ruewœh and TaæémÇng Cc…c, P.O. KauAa£yagang, vm Bhubanœwa& 751002, ()…/SCL, INDIA.
Composite fish culture involving six Asiatic major carps like Catla catla
Labeo rghita, Cirrhinus mrigala, Hypophthalmichthys molitrix, Etëh6phäfÿhgo—
Êgn_idella and Cyprinus carpio appears very
study is based on 156 case studies of composite fish culture undertaken in
different parts of India during several years, wherein input—output relation—
ship for total fish production and also the contribution for six individual
species separately have been established. The model thus evolved explained
842 of variation in total output, 632 for catla, 812 for rohu, 602 for mrigal,
for silver carp,
822 for grass carp and 67% for common carp. The product—
ion
function exhibited increasing returns to scale. Production elasticities
were
also computed and feed was found to be the most dominant explanatory
variable with output elasticity 0.433. As the marginal physical product
feed
Ç233.644)
is greater than price ration (2.00/0.012), increasing use of
feed 15 recommended. However, the mahua oil cake (Bassia latifolia), a pisc1c1de
cum
fertilizer showed the value of marginal product as Indian Rs.0.88
which was less than marginal cost thus the use of mahua oil cake need to be
rev1ewed.
Production functions can also possibly indicate in quantitative
terms, the interspecies competition in Composite fish culture, such as silver
carp affecting catla and rohu and common carp affecting mrigal.
Aquaculture of Cypnids
trammel nets and gills nets, in surface and bottom waters at seven different
points in each reservoir. The common carp is usually among the most abundant
species of the community of both reservoirs (19.32 in Arrocampo R. and 27.5Z
in Torrejon
,
as
percentages of the total number of all fishes taken du—
ring the sampling period. For the life history study, out of the total of
fish caught, 262 species of the Torrejon R. and 315 of the Arrocampo R. were
taken.
Principally, four phenomena were studied : length—weight relationship,
reproduction, food habits and spatial distribution. Lenght—weigbt relation—
ship of carp in the Arrocampo R. is represented by W = 0.000016 L2'95]; and
in Torrejon R. by W = 0.000024 L2'855. The differences between the two popu—
lations are not significant (95%). Carp begin spawning in the Torrejon R. as
early as June and continue until July. In the Arrocampo R., the spawning sea—
son
begins in May and continues until July; the results show a second peak
of activity during the winter period (January—February). Thus, the spawning
season
may be described as spring—summer with the possibility of other peaks
depending of the reservoir's characteristics. Food habits were analyzed in
terms
of frequency of ocurrence and a food importance index. In the Torrejon
R., the prefered foods of carp were cladocerans copepods, detritus and algae
all year around, but there were marked variations in certain foods items due
to
seasonal variations in he abundance of the preys.
In
the Arrocampo R., carp
is a markedly benthic feeder (chironomid larvae, nematodes and larvae of the
other
diptera) and secondarily planktophagus. According to our results, the
carp
in mediterranean aquatic ecosystems are versatile omnivores which utili—
ze
whatever food is available
(without competition processes). The spatial
distribution in both reservoirs is similar. The carp exhibits definitive ho—
ming tendencies; except for movements toward shallow water with vegetation
associated with spawning, the carp is highly sedentary; the water depth where
carp were
located ranged from 1 m. to 6 m.
INPUT—OUTPUT RELATIONSHIPS OF INDIAN COMPOSITE FISH CULTURE. M. RANADHIR and
V.R.P. SINHA,
Aquacwüîu}œ Ruewœh and TaæémÇng Cc…c, P.O. KauAa£yagang, vm Bhubanœwa& 751002, ()…/SCL, INDIA.
Composite fish culture involving six Asiatic major carps like Catla catla
Labeo rghita, Cirrhinus mrigala, Hypophthalmichthys molitrix, Etëh6phäfÿhgo—
Êgn_idella and Cyprinus carpio appears very
study is based on 156 case studies of composite fish culture undertaken in
different parts of India during several years, wherein input—output relation—
ship for total fish production and also the contribution for six individual
species separately have been established. The model thus evolved explained
842 of variation in total output, 632 for catla, 812 for rohu, 602 for mrigal,
for silver carp,
822 for grass carp and 67% for common carp. The product—
ion
function exhibited increasing returns to scale. Production elasticities
were
also computed and feed was found to be the most dominant explanatory
variable with output elasticity 0.433. As the marginal physical product
feed
Ç233.644)
is greater than price ration (2.00/0.012), increasing use of
feed 15 recommended. However, the mahua oil cake (Bassia latifolia), a pisc1c1de
cum
fertilizer showed the value of marginal product as Indian Rs.0.88
which was less than marginal cost thus the use of mahua oil cake need to be
rev1ewed.
Production functions can also possibly indicate in quantitative
terms, the interspecies competition in Composite fish culture, such as silver
carp affecting catla and rohu and common carp affecting mrigal.