International Journal of Fisheries and Aquatic Studies 2015; 3(2): 283-286
ISSN: 2347-5129
(ICV-Poland) Impact Value: 5.62
(GIF) Impact Factor: 0.352
IJFAS 2015; 3(2): 283-286
© 2015 IJFAS
www.fisheriesjournal.com
Received: 18-08-2015
Accepted: 20-09-2015
Konan Amenan Marie Madeleine
22 Bp 584 Abidjan 22,
University Felix Houphouet
Boigny, Hydrobiology
laboratory.
N’ZI Konan Gervais
22 Bp 584 Abidjan 22,
University Felix Houphouet
Boigny, Hydrobiology
laboratory.
Goore Bi Gouli
22 Bp 584 Abidjan 22,
University Felix Houphouet
Boigny, Hydrobiology
laboratory.
Correspondence
N’ZI Konan Gervais
22 Bp 584 Abidjan 22,
University Felix Houphouet
Boigny, Hydrobiology
laboratory.
Weight-length relationships and condition factor of
Atya gabonensis Giebel, 1875 in Bandama River – Côte
d’Ivoire
Konan Amenan Marie Madeleine, N’ZI Konan Gervais, Goore Bi Gouli
Abstract
Growth characteristics for length and weight of Atya gabonensis Giebel, 1875 were calculated for a
sample of 817 specimens collected along the Bandama River during 12 sampling surveys from August
2014 to July 2015. The relations between total length and weight of the females are determined by W =
0.0483TL2.7338 for the dry season and by W = 0.1315 TL2.29 for the rainy season; for males W = 0.0102
TL3.4341 for the dry season and W = 0.0181TL3.2089 for the rainy season. Allometric coefficient “b”
according to Student t-test, and Condition Factor (k), males of A. gabonensis (b > 3; k = 3.05 ± 0.62) are
in better condition than females (b < 3; k = 2.67 ± 0.35).
Keywords: Atya gabonensis, Allometric growth, Condition factor, Bandama River, Cote d’Ivoire
1. Introduction
In the studies on artisanal fisheries, particularly those conducted in West Africa, survey
systems have largely favored the acquisition of information on sizes of species captured to the
detriment of data on weight and biomass. However, fisheries management and research often
require the use of biometric relationships in order to transform data collected in the field into
appropriate indexes [1-5]. One of the most commonly used in any analysis of fishery data is the
length – weight relationship (W = aLb) and Condition Factor (k). According [8], length and
weight data are essential for estimating growth rates, age structure; calculate the standing
stocks biomass [10], condition indices [19] and several other aspects of species population
dynamics [12]. This is particularly important to be investigated in species that might profitably
be used for aquacultural purposes, where the main objective is to rapidly produce organisms
with an optimal size at a reasonable cost [18].
In Côte d’Ivoire, the freshwater decapod Atya gabonensis Giebel, 1875, was first reported in
Gabon and it inhabits is in clean waters, burrows on root masses, crevices and rocky bottoms
[16]
, is heavily exploited. However, despite its ecological importance, basic aspects regarding
the relative growth and condition factor of this species have not been satisfactorily evaluated.
For stock assessment and fisheries management, the present work, aimed to study weightlength relationships and condition factor (k) parameters of Atya gabonensis caught in
Bandama River (Cote d’Ivoire) using shrimps nets and traps of various mesh sizes.
2. Material and methods
2.1. Sampling area
Bandama River has a main channel stretching over a distance of 1.050 km and a catchment
area of 97.500 km². This river is located between 3°50′ - 7°00′W and 5°00′ - 10°20′ N, and
rises in the north of the country, between Korhogo and Boundiali, and enters the sea at GrandLahou lagoon. It is two tributaries are Marahoue (550 km length) and N’zi (725 km length).
Two hydroelectric dams, Kossou lake (drainage area: 900 km2) and Taabo lake (drainage area:
69 km2) were built on the main course of the river [9]. Data were collected in N’douci locality
located between 5°50’ - 6°00’ W and 5°00′ - 10°20′ N where an artisanal exploitation of
shrimp Atya gabonensis exists (Figure 1).
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International Journal of Fisheries and Aquatic Studies
For males, in rainy season length - weight relationships was W
= 0.0181TL3,2089 with a significant correlation (r = 0.90, p ˂
0.001) whereas in the dry season this relation was W = 0.0102
TL3.4341 (r = 0.95 ; p ˂ 0.05). The allometric indices b was
3.2089 during the rainy season and 3.4341 during dry season
(Figure 2).
In females, the corresponding relationship between length weight was W = 0.1315 TL2.29 in rainy season and W =
0.0483TL2.7338 during dry season. The allometric indices b was
2.29 during rainy season and 2.7338 during dry season (Figure
3).
In both season, t-value test revealed a significant difference
between calculated b and it was superior of 3. This positive
allometric, indicates that the weight of Atya gabonensis males
grew at a faster rate than their total length (TL). However, in
all season, population of females had a negative allometric (b
˂ 3). Females increase in size than in weight.
2
1
3
BANDAMA RIVER
SAMPLING SITE
Fig 1: Sampling area of Atya gabonensis in the Bandama River (Cote
d’Ivoire)
2.2. Data collection and analysis procedure
Shrimps were collected during 12 sampling campaigns from
August 2014 to July 2015 using shrimps nets and traps of
various mesh sizes. Species were identified according [16] and
[17]
. Data on Total Length (TL) in cm was measured to the
nearest 0.01 cm for each shrimps using digital slide calipers
(Mitutoyo, CD-15PS), and total weight (W) in g were recorded
with a top loading Sartorius balance model BP 310S with 0.01
g accuracy.
The length-weight relationship was estimated using the
equation W = aLTb. The value of constants “a” or intercept
and “b” or slope [21] were computed from the log transformed
values of length and weight using the following formula Log
W = Log a + b Log LT; where W = Weight of shrimps (g) and
LT= Total length of shrimps (cm).
The condition factor (K) was calculated using Fulton’s
condition factor, to determine the well-being of the shrimps
according [15]:
K
W
102
3
LT
In order to verify if calculated “b” was significantly different
from 3, the Student’s t-test for independent samples was
employed [20]. Differences in the condition factor were
examined between males and females, and among different
populations in rainy and dry season with a one-way ANOVA.
All statistical procedures were performed using STATISTICA
software version 7.1.
3. Results
3.1 Length weight relationships
In this study, length of Atya gabonensis ranged from 7.3 cm to
12.9 cm and weight ranged between 11.35 g and 47.5 g with a
mean of 23.79 ± 5.62 g for females. For males, length ranged
from 8.1 cm and 13.8 cm, weight varies between 11.68 g and
86.8 g with a mean of 40.89 ± 15.47 g. The total length-weight
relationships of Atya gabonensis are presented in figure 2 and
3. The r2 values ranged from 0.6426, for females in rainy
season (March to July and September to November) to 0.8935
for males in dry season (December to February and August),
and all regression were found to be highly significant at p <
0.01.
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Fig 2: Total length and Weight relationships for Atya gabonensis
males captured in the Bandama River during August 2014 to July
2015. (A) = Dry season; (B) Rainy season
International Journal of Fisheries and Aquatic Studies
Fig 3: Total length and Weight relationships for Atya gabonensis
females captured in the Bandama River during August 2014 to July
2015. (A) = Dry season; (B) Rainy season
3.2 Condition factor
Values of the condition factor (k) (Table 1) show that for
females, in rainy season k ranged from 1.8 to 4.79 with a mean
of 2.67 ± 0.42. In dry season value of k is between 1.9 and
3.75 with an average of 2.67 ± 0.29. For male’s populations, k
calculated in rainy season (March to July and September to
November) varies between 1.58 and 4.72 with an average of
3.16 ± 0.80. During the dry season (December to February and
August), this value is between 1.96 and 4.53 with a mean of
2.94 ± 1.43. The one-way ANOVA showed a significant
difference in k (F = 25.58 and p = 0.00001) among season and
sexes.
A Newman-Keuls test showed a significant difference between
males and females during dry season (p = 0.0002) and rainy
season (p = 0.0001). Monthly variation of the Fulton condition
showed that k of males is always higher than those of females
(Figure 4).
Table 1: Values of Condition Factor k by sex and by season of Atya
gabonensis caught in the Bandama River during August 2014 to July
2015.
Condition factor (k)
Min
Max
Mean
SD
Rainy season
1,82
4,77
2,67
0,42
Females
Dry season
1,90
3,75
2,67
0,29
Rainy season
1,58
4,72
3,17
0,80
Males
Dry season
1,96
4,53
2,94
0,43
Min = minimum; Max = maximum and SD = Standard deviation
4. Discussion
In the present study, the smallest individuals of Atya
gabonensis were having size of 7.3 cm in females and 8.1 cm
for males. A maximum size recorded, was 12.9 cm for females
and 13.8 for males. Atya gabonensis exhibit a sexual
dimorphism which means the male’s length size is always
superior to females. This difference in size between the sexes
was also observed in Atya scabra [4].
The results of the relation between total length-weight
revealed positive allometric growth for males, and negative in
females, according to the t-test. Males grew faster than size.
This observation contrasts with females which increase in size
than in weight. For [6], several factors could affect relationship
between length–weight, habitat, seasonal effects, degree of
stomach fullness, gonad maturity, sex, health, preservation
techniques, differences in the observed length of specimens
and ontogeny aspect.
Allometry for the growth relation between Total Length and
Weight was also observed in West African shrimp,
Macrobrachium vollenhovenii [7]. The males and females of
Macrobrachium vollenhovenii exhibited negative allometry
thus contradicts the present findings. Okayi and Iorkyaa [13]
reported isometric growth for A. gabonensis with “b” value of
2.989 in River Mu. This difference could be the result of
availability of food and sufficient space to support the biomass
as reported [2].
In the present study, the condition factor varies significantly
between males and females in all season. These results suggest
that males are in a better condition than females. Also, this
difference between males and females could be explained by
the competition for food. This food competition was a factor
that inhibits growth and therefore affecting the value of “b” in
the length-weight relationship of any species as noted by [14].
Similar results have been observed in Macrobrachium dux [3]
in Niger Delta (Nigeria).
Current study demonstrated that condition factor is higher, in
both sexes and in all season, than those reported for Atya
gabonensis (k = 1.014) [13] in Mu River. The difference could
be attributed probably to difference in habitats prospected,
selective capture by local people for human consumption as
reported [11].
5. Conclusion
This study provides the basic information on Atya gabonensis
in a lotic Bandama River. More research is needed to
understand their reproductive biology so as to enhance their
candidacy for aquaculture. Also, a regular monitoring of
catches will be necessary to better assess fishing pressure on
this species.
6. Acknowledgement
The authors would like to thank the staff of the Hydrobiology
Laboratory of university Felix Houphouet Boigny (Cote
d’Ivoire).
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