Spawning Migration and Some Biological Aspects of Labeobarbus species
in Infranz River, Lake Tana Sub Basin, Ethiopia
The main aim of the study is to investigate the spawning migration and some
biological aspects of Labeobarbus species. Fish were sampled monthly
in the non-peak spawning season and twice in the peak spawning season using
gillnets and Monofilament. A total of 832 Labeobarbus specimens were
collected from all sampling sites. Out of the total catch of Labeobarbus,
the four dominant species contributed 83.0%. Labeobarbus intermedius
was the most dominant species in all sites but L. nedgia was the second
in site 2 and 3. However, L. tsanensis and L. brevicephalus were
the second dominant species in site 1 and 4, respectively. The peak spawning
months for Labeobarbus species was from August to October. Length-weight
relationship for all of the dominant species was curvilinear and statistically
significant (p<0.05). The chi-square test showed that there was significant
difference between the number of females and males for L. intermedius
and L. tsanensis. The average number of eggs for L. intermedius
and L. brevicephalus was 9055 and 4312, respectively and the relationship
of absolute fecundity with FL, was curvilinear, however, with TW and GW of the
two species was linear and statistically significant (p<0.05). Labeobarbus
intermedius and L. tsanensis were the first species to aggregate
in the river mouth. However, Labeobarbus brevicephalus was the last species
to aggregate. The first and the last migrant to upstream sites were L. intermedius
and L. brevicephalus, respectively. Closing season should be strictly
implemented during the spawning season from July to November.
April 27, 2013; Accepted: May 21, 2013;
Published: September 10, 2013
In Lake Tana there are three commercially important families of fish: Cichlidae, Clariidae and Cyprinidae.
According to Nelson (1994), Cyprinidae is one of the
widespread and diverse family from all freshwater fish families and vertebrates.
Labeobarbus species of Lake Tana are the only species in the world (Kornfield
and Carpenter, 1984; Nagelkerke et al., 1994;
Nagelkerke and Sibbing, 2000). Some Labeobarbus
species migrates to the upstream of the tributaries to get suitable environment
for spawning like gravel beds, fast flowing water with adequate oxygen.
In Lake Tana there are 15 Labeobarbus species which are biologically
distinct and forms a unique species flock (Nagelkerke and
The common evidences for the species status of Labeobarbus of Lake Tana
are: their distinct morphometrics (Nagelkerke et al.,
1994; Nagelkerke, 1997; Nagelkerke
and Sibbing, 2000); their segregation in food niches (Nagelkerke
et al., 1994; Nagelkerke, 1997; Sibbing
and Nagelkerke, 2001; De Graaf et al., 2008);
their spatial distribution patterns (Nagelkerke et
al., 1994; De Graaf et al., 2008); the
maximal body size they attain (Nagelkerke and Sibbing,
1996); different immuno-genetics (Dixon et al.,
1996; Kruiswijk et al., 2002); and indications
of spawning segregation (Nagelkerke and Sibbing, 1996;
De Graaf, 2003; Palstra et al.,
2004; De Graaf et al., 2005; Anteneh
et al., 2008; Gebremedhin et al., 2012).
Different studies conducted in some tributary rivers of Lake Tana such as Gelgel
Abay, Gelda and Gumara Rivers (Nagelkerke and Sibbing,
1996; Palstra et al., 2004; De
Graaf et al., 2005) and Ribb, Dirma and Megech, Arno-Garno Rivers
(Anteneh et al., 2008; Getahun
et al., 2008; Gebremedhin et al., 2012)
showed the upstream spawning migration of some Labeobarbus species. At
least nine Labeobarbus species (L. acutirostris, L. brevicephalus,
L. intermedius, L. macrophtalmus, L. megastoma, L. platydorsus,
L. truttiformis L. tsanensis and L. nedgia) were reported as riverine spawners.
But the remaining six L. dainellii, L. surkis, L. gorgorensis,
L. crassibarbis, L. gorguari and L. longissimus) were reported
as missing. The probable assumptions are either they migrate to spawn in other
unstudied tributary of Lake Tana such as Infraz River, or they might be lacustrine
spawners (Nagelkerke and Sibbing, 1996; Palstra
et al., 2004; De Graaf et al., 2005;
Anteneh et al., 2008; Gebremedhin
et al., 2012). However, which species of the Labeobarbus species
migrate and at what time or seasons of the year do they migrate to Infranz River
is not clearly known.
On the other hand Labeobarbus species are vulnerable to fishing activities
as a result of their aggregation at the river mouths (De
Graaf et al., 2004; De Graaf et al.,
2006). The upstream spawning migrations of Lake Tana Labeobarbus
species is highly influenced by the commercial gillnet fishery as gillnets are
set near the river mouths. Hence, there is a dramatic decline (>75% in number)
of the riverine spawners (De Graaf et al., 2004).
Poisoning of the spawning stock using the crushed seeds of Birbira (Ameha,
2004) and alteration of the breeding and nursery grounds are the possible
explanations for the decline of Labeobarbus stock. Infranz River is one
of the unstudied rivers flowing into Lake Tana. Therefore, investigation of
the Labeobarbus species migrating to Infranz River is very important
for the rational exploitation and conservation of the unique species flock.
Thus, the aim of this study was to investigate the spawning migration and some
biological aspects of Labeobarbus species in Infranz River.
MATERIALS AND METHODS
Study area description: Lake Tana is the largest lake in Ethiopia with
an area of about 3200 km2 and is situated in the north-western highlands
at an altitude of about 1800 m. The Lake is believed to have originated two
million years ago by volcanic blocking of the Blue Nile River and it is the
headwater of the Blue Nile River. It is shallow lake with an average depth of
8 m and maximum depth of 14 m and it is turbid, well-mixed and has no thermocline
(Vijverberg et al., 2012) and it has a catchment
area of 16,500 km2. Infranz River which is the tributary of Lake Tana is situated
North west of Bahir Dar town, in the southern part of Lake Tana watershed in
the district of Bahir Dar zuria woreda and western Gojam zone of the Amhara
region (Fig. 1). At local level, this river is surrounded
by three villages, namely: Yibab from the South, Waramit from the North and
Chercher Wegelsa from the West and its source of water is ground water (Gebrekidane,
|| Map of the study area
The mean monthly temperature of this river is 17.5oC, mean annual rainfall
of 1437 mm with heavy rains during July-September and dry season during December-April
Data collection and sampling
Field sampling: Four sampling sites based on the nature, velocity
of the flowing river, human interference, suitability for fish spawning and
availability of fishes were selected by preliminary assessment/survey and sampling
sites were fixed using GPS. Fish samples were collected monthly in July and
November, 2011. However, samples were collected twice per month from August
to October 2011 at all selected sites of Infranz River. Gill nets of 6, 8, 10
and 14 cm stretched bar mesh, having a length of 25 m and depth of 1.5 m and
monofilament were used to sample fish. Gill nets were set in the river mouth
at a depth of 2.5-3.5 m overnight.
But in the upstream fish were sampled during day time since it is difficult
to set gill nets overnight due to the usual heavy rainfall in the afternoon
in the area. Fish were identified to species level using keys developed by Nagelkerke
and Sibbing (2000). Some fish samples from each species were preserved in
5% formalin solution and put in plastic jar and transported to the laboratory
to serve as reference specimens. Then, fork length (0.1 cm), total weight (0.1
g) and gonad weight (0.01 g) of each specimen of Labeobarbus species
were measured at the sampling sites. After dissection, gonad maturity of each
fish specimen was identified using a seven-point maturity scale (Nagelkerke,
1997) and at the same time each fish was sexed. Samples of eggs from some
ripe female Labeobarbus species having different fork lengths were preserved
using 5% formalin solution for fecundity estimation.
Abiotic factors: The physico-chemical parameters (water temperature, pH, total dissolved solutes and conductivity) were measured in all sampling sites and time using conductivity meter. Water transparency (Secchi-depth) was measured using Secchi-disc.
Relative abundance: An Index of Relative Importance (IRI) was used to
evaluate relative abundance. IRI is a measure of the relative abundance or commonness
of the species based on number and weight of individuals in catches, as well
as their frequency of occurrence (Kolding, 1989 and 1999).
IRI was used to find the most important species in terms of number, weight and
frequency of occurrence in the catches from the different sampling localities.
IRI gives a better representation of the ecological importance of species rather
than the weight, numbers or frequency of occurrence alone (Sanyanga,
1996). Percent of IRI was calculated as follows:
where, Wi and Ni% are percentage weight and number of each species of total catch respectively; Fi% is percentage frequency of occurrence of each species in total number of settings. Wj and Nj % are percentage weight and number of total species of total catch, respectively. % Fj is percentage frequency of occurrence of total species in total number of settings.
Length-weight relationship: The relationship between fork length and
total weight of the dominant Labeobarbus species of the Infranz River
were calculated using power function of Tw = aFLb as in Bagenal
and Tesch (1978). Where; Tw total weight (g), FL- fork length (cm),
a and b are intercept and slope of regression line, respectively. The line fitted
to the data was described by the regression equation for each species.
Condition Factor (Fultons factor): The well-being of each dominant
Labeobarbus species of the Infranz River was studied by using Fultons
condition factor (Bagenal and Tesch, 1978). Fultons
condition factor (%) was calculated as:
where, Tw- total weight (g) and FL- fork length (cm).
Sex-ratio: Sex ratio, is the proportion of females to males, was determined using this formula:
Chi-square (χ2) was used to test significant difference in
Gonado-somatic index (GSI): GSI is the ratio of fish gonad weight to
body weight. The GSI was determined using the following formula Bagenal
Fecundity: Fecundity is the number of eggs in ovary before spawning
and it was estimated using gravimetric method (MacGregor,
1957) by weighing all the eggs from each of the ovaries of gravid fish species.
Samples of eggs were taken from different size classes of each fish species
on various ovary areas. These eggs were preserved in a labeled plastic bag containing
5% formalin solution for fecundity estimation (Bagenal, 1978).
After ovarian membranes were removed mechanically using tap water from the preserved
ovaries, eggs were counted. Three sub-samples of 1 g eggs were taken from different
parts of ovary and counted and the average was calculated.
The total number of eggs per ovary was calculated by extrapolation from the
mean calculated. The correlation of fecundity with total length, total weight
and ovary weight were done to determine the relationship of fecundity with morphometrics
measurements. This was done according to this formula:
where, F-Fecundity; FL-Fork length (cm); Tw- Total weight (g); GW- Gonad weight; a- constant and b- exponent.
Data analysis: SPSS version 16 software and Microsoft office Excel 2007 were used to analyze and manage the data. One-way ANOVA was used to analyze length weight relationship, Fultons condition factor, abiotic parameters and spatial and temporal segregation.
RESULTS AND DISCUSSION
Physico-chemical parameters: Physical and chemical parameters such as temperature, pH, TDS, conductivity and water transparency (secchi depth) from all sampling sites were analyzed using one way ANOVA and there was no significant difference (p>0.05) except for secchi depth (64.65±9.09) at all sampling sites (Table 1). However, water transparency (secchi depth) showed significant variation (p<0.05) between the sampling sites. As it is tested using LSD the mean of secchi depth of site 1 (17.44±6.33) showed significant variation (p<0.01) with means of site 3 (82.56±20.02) and 4 (109.59±13.36). Aquatic populations are highly dependent upon the characteristics of the aquatic habitat, which supports all their biological functions (reproduction, growth, feeding and sexual maturation).
Thus, abiotic factors are the controlling factors for the aquatic life, since
they shape most of the biological functions of aquatic life (Murdoch
and Martha, 1999).
|| Mean±Std. error of the abiotic parameters in all of
the sampling sites
|*Significant at p = 0.001, ns: Not significant, Values are
presented as Mean±EE. Number of observation for all of the parameter
Cyprinids (e.g., Labeobarbus) as they lack parental care, fast flowing,
clear and highly oxygenated water and gravel-bed streams or rivers are generally
their spawning ground requirements. The gravel or pebble beds protect their
eggs from being washed away by riffle and clear water will not cover their eggs
with a film of sediment obstructing the diffusion of oxygen (Lowe-McConnell,
Infranz River serves as a best spawning area for Labeobarbus species
since it has fast flowing, clear and gravel beds and absence of clear waterfalls
that affect fish migration. The variation in mean secchi depth of site1 with
site 3 and 4 might be due to the fact that the river mouth gets more turbid
due to sediment deposition from various sources. The pH value of the River was
almost neutral at all sampling sites. A similar observation was made by Anteneh
et al. (2008) in Megech and Dirma Rivers and Gebremedhin
et al., 2012 in Arno-Garno River which are thought to be ideal breeding
ground for the Labeobarbus species of Lake Tana. The average conductivity
and TDS of Infranz River were in line with Gebremedhin
et al. (2012) in Arno-Garno River.
Relative abundance: Relative abundance is a measure of the relative
commonness of the species based on number and weight of individuals in catches,
as well as their frequency of occurrence (Kolding, 1989,
1999). Hence, the species composition of gillnet catch
from all of the sampling sites at Infranz River were ranked based on the Index
of Relative Importance (IRI) (Table 2). Labeobarbus intermedius
was the most abundant species at all sampling sites (i.e., 47, 67, 48 and 70%
in site 1 to 4, respectively). Except at site one (31%) and four (14%), in which
L. tsanensis and L. brevicephalus were abundant, L. nedgia
was the second most abundant species at site 2 (19%) and site 3 (25%). For L.
intermedius similar results were reported by Gebremedhin
et al. (2012) in Arno-Garno River and Anteneh
et al. (2008) in Dirma and Megech Rivers.
|| Percentage IRI of Labeobarbus species in Infranz River
in all of the sampling sites
Length-weight relationship: Total Weight of the four dominant Labeobarbus species showed curvilinear relationship with Fork Length (FL) and was statistically significant (p<0.001) (one-way ANOVA) and the line fitted to the data was described by the regression equation (Fig. 2). The regression coefficients for most of the dominant species were near to the cube value (b = 3).
In agreement with Anteneh et al. (2008) at
Megech and Dirma Rivers, Nagelkerke et al., 1994
in Lake Tana and Gebremedhin et al. (2012) at
Arno-Garno River, most of the dominant Labeobarbus species showed nearly
Fultons condition factor: Fultons condition factor for the
dominant Labeobarbus species (L. intermedius, L. brevicephalus,
L. nedgia and L. tsanensis) both by sex and spawning season in Infranz
River was done. The mean Fultons Condition Factor for L. intermedius
and L. brevicephalus, was higher during the peak spawning months (August
to October) than the non-peak spawning months (July and November), however,
it was lower for L. nedgia and L. tsanensis. Fultons condition
factor for L. intermedius, L. brevicephalus, L. nedgia
and L. tsanensis migrating to Infranz River was not showed significant
variation during the peak spawning months (August to October) and non-peak spawning
months (July and November) with an average of 1.27±.008, 0.13±.010,
1.26±.013 and 1.35±.014 mean and standard error, respectively
(one way ANOVA, p>0.05), (Table 3). Similar result was
reported by Gebremedhin et al. (2012) for L.
brevicephalus at Arno-Garno River. However, results obtained in Megech and
Dirma Rivers (Anteneh et al., 2008) and Gebremedhin
et al. (2012) indicated FCF was significantly different during the
peak spawning months and non-peak spawning months. This difference might be
due to the difference in size and source of water between the rivers.
Fulton conditions factor of those females and males of L. intermedius,
L. brevicephalus, L. nedgia and L. tsanensis migrating
to Infranz River with average mean and standard error of 1.27±.007, 1.22±0.010,
1.26±.014 and 1.35±.015, respectively didnt show significant
variation during the spawning season July to November (p>0.05) (Table
||Length-weight relationship of the four dominant Labeobarbus
species migrating to Infranz River
||Mean±SE of Fultons condition factor for the most
dominant Labeobarbus species migrating to Infranz River by season,
N is sample size, (one way ANOVA)
||Mean±SE of Fultons condition factor for the most
dominant Labeobarbus species in Infranz River by sex. N is sample
size (one way ANOVA)
However, results obtained in Megech and Dirma Rivers by Anteneh
et al. (2008) and in Arno-Garno River Gebremedhin
et al. (2012) showed significant variation of Fultons condition
factor between females and males of the dominant Labeobarbus species.
Sex ratio: From the total catch of 832 Labeobarbus species migrating to Infranz River in the study period, 50% were females and 35% were males, whereas the remaining 15% were unsexed. Generally, females were more numerous than males and the variation was higher during peak spawning season. The chi-square test showed that there was significant difference between the number of females and males for L. intermedius (1.6:1) and L. tsanensis (1.7:1) in Infranz River (χ2, p<0.05), however, it was not significantly different for L. brevicephalus and L. nedgia (χ2, p>0.05) from the theoretical 1:1 ratio (Table 5).
There are different reasons for the difference in sex ratio. For example, different
biological mechanisms such as differential maturity rates, differential mortality
rates and differential migratory rates between the male and female sexes may
cause unequal sex ratios (Sadovy and Shapiro, 1987; Matsuyama
et al., 1988). In addition to this, Al-kholy (1972)
reported females of cyprinid Putius barberinus in Lake Lanao live longer
time in the spawning areas than males.
||Number of males, females,χ2 values and the
corresponding sex ratios of the Labeobarbus species in infranz river
(pooled data from all sampling sites)
|ns: Not significant: *significant: ***very strongly significant
||Proportion of gonad maturity stages (I to VII) of the most
dominant Labeobarbus species during peak spawning season (July to
November) in the (a) River mouth (b) Upstream areas in Infranz River
Hence, living longer time in spawning areas and increased ovarian development
as suggested by Taylor and Villoso (1994) may also
cause the deviation from 1:1 sex ratio. Similar results were obtained for other
cyprinid fishes like Labeo horie in Lake Chamo (Dadebo
et al., 2003), Carassius carassius in Lake Ziway (Hirpo,
2012), Labeobarbus species in Megech and Dirma Rivers (Anteneh
et al., 2008) and Gebremedhin et al.
(2012) for those Labeobarbus species migrating to Arno-Garno River.
Therefore, some of the above factors or combination of them might be the cause
for the sex ratio variations of Labeobarbus species migrating to Infranz
Gonado somatic index (GSI): The gonad proportion of mature dominant Labeobarbus species in Infranz River (gonad stage IV and V), running (gonad stage VI) and spent (gonad stage VII) together was higher (about 64%) than the immature gonads (gonad stages I-III, 36%) in the samples collected during the spawning season (August to November) (Fig. 3).
From the total catch of the dominant Labeobarbus species in Infranz River, nineteen were caught with spent gonads (3 in river mouth i.e. one male and 2 female and 16 in upstream sites i.e. 2 male and 14 female) and they were numerous at the end of October. From the total catch of specimens with spent gonad L. intermedius and L. brevicephalus were represented by 11 and 5 specimens each, 1 and 2 in the river mouth and 10 and 4 in the upstream sites, respectively. Labeobarbus nedgia was represented by 3 specimens all in the upstream areas. As it is clearly illustrated in Fig. 3, in the river mouth fish specimens with gonad stage V was dominant, whereas, in the upstream areas gonad stage VI was the dominant. Hence this is a good indication for the species aggregation in the river mouth as well as their migration to the upstream areas.
Fecundity: Information about fecundity of Barbus species in Africa
is limited (Marshal, 1995). The few data on the fecundity
of Labeobarbus species in Lake Tana and its tributaries are from the
recent studies by Alekseyev et al. (1996), Anteneh
et al. (2008) and Gebremedhin et al.
(2012). Fecundity of the most dominant Labeobarbus species (L.
intermedius and L. brevicephalus) was done from the total sample
taken from Infranz River. Labeobarbus intermedius with fork length of
18.2 to 34.2 cm, Mean±SE of 22.95±0.68 had absolute (total) fecundity
ranged from 1122 to 24506 and average fecundity was about 9055. Labeobarbus
brevicephalus with fork length of 18.3 to 27.3 cm, Mean±SE of 22.39±0.58
had absolute fecundity ranged from 574 to 16073 and average fecundity was about
4312. Many researchers Anteneh et al. (2008)
in Megech and Dirma Rivers, Tessema et al. (2012)
in Borkena and Mille Rivers and Gebremedhin et al.,
2012 was reported the average fecundity for L. intermedius. The result
from this study was relatively higher than these reports. This difference might
be due to the difference in size at maturity stages or the difference in environment.
Skelton et al. (1991) also reported the fecundity
of Labeobarbus in other African lakes and it is moderately higher than
from the reports in Lake Tana. For example, a female Labeo aeneus with
30 cm fork length in Vaal-orange River drainage system carries about 30,000
eggs on average (Berie, 2007) whereas L. intermedius
in Infranz River with fork length of 34.2 cm carries about 9055 eggs on average.
This might be related to environmental problems. Oliva-Paterna
et al. (2002) also reported that fast growth, high fecundity and
early maturity are the characteristics of unstable environments.
The relationship of Absolute Fecundity (AF) with FL, was curvilinear, however,
AF with TW and GW of the two species was linear (Fig. 4, 5).
There was strong relationship between AF and FL, TW and GW in both the L.
intermedius and L. brevicephalus species (one way ANOVA, p<0.05).
in line with studies conducted in Gelda and Gumara Rivers Alekseyev
et al. (1996), Borkena and Mille Rivers (Tessema
et al., 2012) and Arno-Garno River, the fecundity of L. intermedius
was strongly and positively correlated with its gonad weight, fork length and
Segregation of Labeobarbus spp. in Infranz River
Spatial segregation: All of the abundant Labeobarbus species migrating
to Infranz River were found in the entire sampling site, though there is difference
in proportion. The relative contribution of the most dominant Labeobarbus
species within the sampling site is illustrated in Fig. 6
Labeobarbus intermedius was equally abundant in site, 1, 2 and 3 but it
was relatively higher in site 4. Labeobarbus brevicephalus was abundant
in site 3 and it was less abundant in site 1. Labeobarbus nedgia was
almost all equally abundant in all sites. However, L. tsanensis was similarly
distributed in site 2, 3, 4 and it was higher in site 1. There was no significant
difference in the distribution patterns of the four most abundant species of
Labeobarbus over the four sampling sites in Infranz River (one-way ANOVA,
||Relationship between absolute (total) fecundity and fork length,
total weight and gonad weight of L. intermedius in Infranz River
||Relationship between absolute (total) fecundity and fork length,
total weight and gonad weight of L. brevicephalus in Infranz
Temporal segregation: Temporally the aggregation of the dominant Labeobarbus species migrating to Infranz river varies on the spawning season (July to November) in all sampling sites (Fig. 7). For instance L. brevicephalus was not found in all sampling sites during July. Labeobarbus nedgia was also found very rarely during July in site 3 and 4. On the other hand, L. intermedius was absent in site 4 during November and L. tsanensis was not found in site 1, 2, 3 during November and in site 2 and 3 during July.
||Contribution of Labeobarbus species at different sampling
sites in Infranz River during the sampling months (July-November)
||Proportions of Labeobarbus species during the peak
spawning season in all sampling sites as a function of time
Migration of the tropical freshwater fish to breeding grounds is mainly triggered
by rainfall patterns and water level variations (Lowe-McConnell,
1975). The Labeobarbus species in Lake Tana also aggregate at river
mouths to spawn in the rainy season (Nagelkerke and Sibbing,
1996; Dgebuadze et al., 1999; Palstra
et al., 2004; De Graaf et al., 2005;
Anteneh et al., 2008 and Gebremedhin
et al., 2012). In this study, four Labeobarbus species (L.
intermedius, L. brevicephalus, L. nedgia and L. tsanensis)
aggregated at the river mouth of Infranz River starting from July to the end
The aggregation patterns in the river mouth and migration patterns in the upstream
sites during the spawning months are given in Fig. 8. Labeobarbus
intermedius and L. tsanensis were the first species to aggregate
in the river mouth starting from July and reached their peak in September (Fig.
||Temporal variation in abundance of Labeobarbus species
during the breeding season (July to November) in the (a) River mouth and
(b) Upstream sites
Labeobarbus nedgia starts to aggregate in the river mouth in the late
July and reached its peak in August. Labeobarbus brevicephalus was the
last species to aggregate in the river mouth starting from August and reached
its peak in September (Fig. 8a).
The first migrant to upstream sites were L. intermedius and L. tsanensis which start to ascend at the end of July, but their catch was higher in September and October, respectively (Fig. 8b). The last migrant was L. brevicephalus starting from end of August. Catch of L. brevicephalus reached its peak on October. All Labeobarbus species showed a declining pattern in catch from October to November which is the indication of the end of spawning period (Fig. 8b). The temporal segregation of the dominant Labeobarbus species migrating to Infranz River showed statistically significant difference (p<0.001, one way ANOVA).
Out of the total 952 fish specimens collected during the study period from all sampling sites, 8 species were belonging to the genus Labeobarbus and the other species were O. niloticus, C. gariepinus and V. beso. From the index of relative importance, L. intermedius was the most dominant species in all of the sampling sites in the river and the relationship between fork length and total weight of the dominant Labeobarbus species in Infranz River was curvilinear. Fultons condition factor didnt significant variation for all of the dominant species during the peak and non-peak spawning season and by sex. Females were most numerous than males for the Labeobarbus species migrating to Infranz River and this is high in the peak spawning season. The chi-square test showed that there was significant difference between the number of females and males for L. intermedius and L. tsanensis however, it was not significantly different for L. brevicephalus and L. nedgia from the theoretical 1:1 ratio in Infranz River. From their monthly Gonado somatic index the peak spawning month was August to October.
Labeobarbus intermedius had both high number of eggs than L. brevicephalus
and the relationship of the total eggs with fork length was curvilinear, but
it was linear with total weight and gonad weight of the two species. Mainly
four species (L. intermedius, L. brevicephalus, L. nedgia
and L. tsanensis) aggregated at the river mouth. L. intermedius
and L. tsanensis were the first species to aggregate at the river mouth
however; L. brevicephalus was the last to aggregate in the river mouth.
The first species to migrate to the upstream sites was L. intermedius
and followed by L. tsanensis but the last migrant was L. brevicephalus.
First and foremost our praise goes to God, who has supported us to finish this study. Our warmest appreciation goes to Bahir Dar University (BDU) Graduate Program, Research and Community Service for all-round financial support, which was very fundamental to carry out this study without suffering. Thus, this work is not only the work of researchers, but also the funding agency i.e. Bahir Dar University too. We would like to express our gratitude to Asratu Wondie who assisted us in collecting the data.
Al-Kholy, A.A., 1972. Aquatic resources of Arab countries: Alesco science monograph series. Arab League Education Cultural and Scientific Organization (ALECSO), Pages: 452.
Alekseyev, S.S., Dgebuadze, Y. Yu, M.V. Mina and A.N. Mironovsky, 1996. Small large barbs spawning in tributaries of Lake Tana: What are they? Folia Zool., 45: 85-96.
Ameha, A., 2004. The effect of birbira, Milletia ferruginea (Hochst.) Baker on some Barbus sp. (Cyprinidae, Teleostei) in Gumara river (Lake Tana), Ethiopia. M.Sc. Thesis, Addis Ababa University.
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