*Correspondence author: Jega Ibrahim Shehu, Department of Forestry and Fisheries, Kebbi State University of Science and Technology, P.M.B. 1144, Aliero, Nigeria
How to cite this article:Jega Ibrahim S, Daramola Ismail M, Rasaq I. Length-Weight Relationship and Spawning Season of Bagrus bayad (Forsskal, 1775)
002 in Yamama Lake Kebbi State, Nigeria. Oceanogr Fish Open Access J. 2020; 12(4): 555841: 10.19080/OFOAJ.2020.12.555841
The study was conducted to investigate the Length-weight relationship and spawning season of Bagrus bayad from Yamama Lake, Kebbi State Nigeria. Fresh fish catches of B. bayad were collected in batches from the fish landing site of Yamama Lake for a period of six (6) months, from April 2019 to September 2019. The parameter of Length-weight relationship of sampled fish was evaluated using the equation W = aLb. The Gonadosomatic Index (GSI) was determined using the formula, (Gonad weight/ Total body weight) x 100. The regression analysis of Length-weight relationship for the male fishes was estimated as W= 0.006 L3.25 indicating positive allometric growth pattern. For the females, the regression analysis was found as W= 0.009 L3.077 also indicating positive allometric growth pattern. Monthly mean GSI values for female were highest in June (2.79), indicating the peak spawning season. For increased spawning of B. bayad in Yamama lake, it was recommended that fishing should be restricted in June.
Keywords: Bagrus bayad; Length-weight relationship; Gonadosomatic index; Yamama lake
High production capacity of members of Bagridae family in the wild has prompted many attempts by fisheries scientists to culture them. Chrysichthys nigrodigitatus have been cultured along with Tilapia melanoplura and Cyprinus carpio in Buguma, Nigeria, with encouraging results . Bagrus docmac have been cultured with Tilapia in Uganda and being carnivorous, they were found to be effective in controlling Tilapia population. Many catfishes do not readily breed under captivity because they are not able to exhibit their natural spawning behavior in artificial ponds and this constitutes a limiting factor to their culture and mass production . Bagrus bayad, also called bayad with local (Hausa) name Shambani is a member of Bagridae family which are commonly referred to as a naked catfish. They are commercially important species found in Nigeria fresh waters especially in Rivers and Lakes such as Niger, Kaduna, Benue, Lake Chad, and other inland waters . The length-weight relationship (LWR) of fishes are important in fisheries biology and the study of natural history of fishes because they allow the estimation of the average weight of fish of a given length group by creating a mathematical relationship
between them [4,5]. LWR can also be used to calculate condition indices, to compare life history and morphology of population belonging to different region and to study oncogenic allometric changes [6,7]. LWR is also an important factor in fish ecology and in the biological study of fishes, being of prime importance in parameterizing fish yield equation in stock assessment and management .
Studies on B. bayad had been limited to the growth, food and feeding habits and culture of its wild species [9,10]. No reported breeding program for B. bayad till date. The gonadosomatic index (GSI) is the calculation of the gonad mass as a proportion of the total body mass. It is a tool for measuring the sexual maturity of animals in correlation to ovary development and testes development. GSI is one of the important parameters of fish biology, which gives the detailed idea regarding the fish reproduction and reproductive status of the species particularly in identifying seasons of spawning [11,12]. The aim of the study was to provide information on the species gonadosomatic index and in the study area which might assist in the culture and breeding of the fish in captivity.
The study area is in Yamama village, Kalgo Local Government
Area of Kebbi State, Nigeria. The people of Yamama are
predominantly fisher folks and farmers. Yamama Lake is a lake
created from the Shella River, which sometimes floods into the
lake. The lake, which is situated between latitude 11020’ – 120 N
and longitude 04020’ – 060 East, stretches some 900 m in length
and is 195 m wide giving a surface area of 17.5 hectares. The five
fishing communities bordering Yamama are Rungumi, Nguwar
Nenu, Janbaki and Yamama Ketare (Figure 1).
Collection of samples
Fresh fish catches of B. bayad were collected in batches from
the fish landing site of Yamama Lake for a period of six (6) months.
Identification of the Species and data Collection
The species was identified by counting of the barbells, fin
rays and the position of the lateral line, using fish identification
manual . Total length (TL) was measured using a meter rule
from the tip of the snout to the end of the caudal fin, Standard
length (SL) was measured from the tip of the snout to the caudal
peduncle, Fork length (FL) was measured from the tip of the snout
to the separation of the tail. Body weight and gonad weight of the
samples (g) were taken using an electric digital weighing balance.
Determination of sex was done by dissection method as
described by .
Determination of Length-weight Relationship
The total length (TL) of each fish was measured from the tip
of the snout (mouth closed) to end of the caudal fin using a meter
rule. The body weight was measured using electric digital balance.
The parameter of length-weight relationship of sampled fish was
evaluated using the equation. 
W = aLb
Where, W = weight of fish (g), L = length of the fish, a = the
intercept, and b the slope. The values of constants a and b were
estimated after logarithmic transformation of W = aLb
Determination of Gonadosomatic Index (GSI)
The weight of the individual fish was taken, the female fish
gonads were removed carefully, weighed on a sensitive weighing
balance after removing the excess of moisture using a blotting
paper and the length of the gonad were also taken. The GSI was
determined using the formula: 
The standard length of the collected samples ranged from
23.00 – 32.90 cm and 22.10 – 34.40 cm for female and male fishes,
respectively (Table 1). The weight of the fishes ranged from 135.0
– 472.0g and 117.0 – 482.0 g for females and males, respectively.
Length – weight relationships
The Length weight relationship of both sexes of B. bayad was
used to describe the growth pattern of the fish. The graphical
representations of the Length - weight relationship of both the
male and female B. bayad are shown in Figure 2 and 3, respectively.
The regression analysis of Length-weight relationship for the
male fishes was estimated as W= 0.006 L3.25 (Figure 2), indicating
positive allometric growth pattern (b = 3.25) while r2 = 0.912. For
the females, the regression analysis was found as W= 0.009 L3.077
(Figure 3), also indicating positive allometric growth pattern (b =
3.07) with r2= 0.524. The values of “a”, “b” and r2 were estimated.
The relationship showed that the weight increases as the length
increased as shown by positive b value and high correlation (r2)
Gonadosomatic Index (GSI)
The mean monthly changes in GSI in female Bagrus bayad
during the study period ranged from 0.14 – 2.79. Plotting the
average relative GSI against months (Figure 4), the values rises
from 0.27 in April to 0.72 in May and the peak value of GSI was
observed in June (2.79), indicating one spawning period within
the period of April to September. The GSI then abruptly decreased
from July to September. Results indicated that monthly mean GSI
values for female were highest in June. Based on this, spawning
season of B. bayad was found to be in June over the study period.
The size ranges recorded in this study for Bagrus bayad
indicated a rare phenomenon whereby the males were larger
than the females in the waterbody. This agrees with Lewis
 and Tsadu et al.  who reported that males of B. bayad
recorded higher mean standard length and body weight than
the females. The length weight relationship of fish is crucial in
fisheries biology and their stock assessment because they help
in estimating the fish’s average weight of a given length category
by estimating a mathematical relation between the two . The
values of “b” for both the male (3.077) and female (3.25) showed
positive allometric growth pattern in Yamama lake. Nwabueze
and Garba  reported positive allometric growth for Bagrus
bayad from River Niger at Asaba and River Adofi at Ossissa in
Southern Nigeria with b values of 12.864 and 14.637, respectively.
Ogbe and Fagade  also found positive allometric growth for B.
bayad from lower River Benue. Similar results were also reported
for B. Bayad (b = 3.1) and B. docmac (b = 3.05) from Muess
Channel, Sharkia Province, Egypt . In contrast to this study, El-
Badawy  found negative allometric growth for Bagrus bayad
(b = 2.8802) and Bagrus docmac (b = 2.7858). Musa et al. 
reported negative allometric growth for Bagrus bayad (b = 2.364
male; 2.714 female) and Clarias gariepinus (2.621 male; 2.676
female) in Thomas Lake, Kano State, Nigeria.
The differences in the reported b values and the values from
this study could be due to factors such as food availability in the
waterbodies, prevailing weather conditions and difference in
latitude. Gonadosomatic index (GSI) is a metric that represents the
relative weight of the gonad to the fish weight. GSI has been widely
used to evaluate reproduction timing . The onset of spawning
season is also defined by GSI. The highest value of GSI obtained in
June (2.79) during the study period indicates the peak occurrence
of mature individuals of Bagrus bayad. This was similar with Vinci
 who recorded the peak values of GSI in female Silonia chidreni.
Shaheena et al.  observed that GSI fluctuates from a minimum
of 2.3 in June to 11.3 in March with decrease being indication of
completion of spawning. This is in contrast with what Elsayed and
Mohammad  reported that monthly variation in GSI for both
sexes of Mormyrus rume followed nearly the same pattern and GSI
showed higher values during the period from June to September
with a peak in July, while the lower ones occur during the period
from October to February. This is not in the case in this present
study since the sampling period was not all year round.
This study revealed that the length-weight relationship
of Bagrus bayad in Yamama lake showed a positive allometric
growth which implies that this species grows fatter as the length
of the fish increases. It is evident from the present study that
the gonadosomatic index of freshwater B. bayad was higher in
June, indicating that the spawning season of the fish is in June.
To encourage increased spawning by B. bayad in the Yamama
lake, fishing should be restricted in June. This information will be
useful in formulation of more conservation strategies and policies
for the species in the waterbody.
Bardarch KH, John HR and William OM (1972) Aquaculture: The Farming and Husbandry of Freshwater and Marine Organisms. John Wiley and Sons Inc. 244-255.
Lamai S L (1993) Aspects of the Applied Biology of Clariasgaripepinus, Aquacultural Techniques and Deldrin toxicity. PhD Thesis. Department of Pure and Applied Zoology, University of Reading, UK, Pp. 204.
Holden M and Reed W (1972) West African Freshwater Fish. In: West African Nature Handbook. Longmans, UK, P.45.
Sarker O M (2008) Length – weight relationship and condition factor of two Bagrid fish (Bagrusbayad and Bagrusdocmac).Journal of Fish Biology45:33-39.
Ogbe FG and Fagade SO (2002) Distribution, abundance, and dimensional features of Claroteslaticep (Rupell) in lower River Benue, Makurdi, Nigeria. Journal of Prospects in Science6:18-23.
El-Badawy A A (1991) Biological Study on Some Fishes of High Dam Lake.
Musa H, Mahmud U, Safiyanu I, Bashir S I and Kutama AS (2016) Some Ecological Aspects of Bagrusbayadand Clariasgariepinusin Thomas Lake, Kano State, Nigeria. Global Advanced Research Journal of Agricultural Science 5(5):165-174.