Morphometric Characteristics, Length-Weight Relationships, and Condition Factors of Five Indigenous Fish Species from the River Ganga in Bihar, India

Morphometric characteristics, length-weight relationships (LWRs), and condition factors ( K ) were studied for fve indigenous fsh species belonging to fve diferent families ( Barilius barila Hamilton, Cirrhinus reba Hamilton, Chanda nama Hamilton, Mystus bleekeri Day, and Clupisoma garua Hamilton), from the River Ganga in Bihar, India. A total of 557 fsh individuals were collected seasonally from September 2021 to August 2022 using a monoflament drift gill net and a conical trap net Khairel jal. In morphometric analysis, the highest degree of correlation was observed between the total length and the standard length for all species (except C. garua ). Te estimated exponent value b varies from 2.920 to 3.214, where the slopes of regression lines among the species have signifcant diferences ( p < 0 . 0001). Te b value indicated that three species ( B. barila , C. nama, and C. garua ) follow positive allometric growth, whereas M. bleekeri shows isometric growth and C. reba exhibits negative allometric growth. Te condition factor value for these fshes ranged from 0.67 to 0.98, which indicated that the population of C. reba was robust compared to all other species ( p < 0 . 0001). A new maximum length (146.8mm) was obtained for B. barila from India. Te present study gives baseline biological information on fve commercially important indigenous fsh species found in the River Ganga, Bihar. As the population of these species has been dwindling in recent times, these data will be important for the conservation and sustainable utilization of these important species in the long run.


Introduction
Ganga is the largest river system in India and is home to around 300 freshwater fsh species that support 10-13 million riverine fshers' livelihoods and nutritional security [1]. Many freshwater fsh species have become critically endangered as a result of human interventions, including the building of multipurpose dams and barrages, overfshing, pollution, invasions of exotic species, climatic changes, and soil erosion [2][3][4]. Approximately 480 kilometers of the River Ganga fow through Bihar, and fsh were caught using traditional fshing gear (monoflament drift gill nets and Khairel jal). Annual fsh landings from the Patna stretch of this river were 7.4 tons [5], while Bihar's total fsh production was 0.64 metric tons with an annual per capita fsh consumptions rate of 8.82 kg [6]. In local fsh markets, catfsh sell for 300-400 rupees per kilogram (US$ 3.67-4.89), while minor carps sell for 100-150 rupees per kilogram (US$ 1.22-1.83), but this depends on availability and season. Te study of the biological parameters of fsh species provides valuable information for management and sustainable use. Morphometric characters are frequently used to identify fsh species [7] and determine whether a stock is heterogeneous or homogeneous [8]. Te length-weight relationship of fsh is a useful index for evaluating growth, survival, maturity, reproduction, and general well-being [9]. It explains the change in weight of fsh with respect to length and vice versa [10]. It is often used to estimate fsh biomass when the length-frequency distribution is known [11], to determine possible diferences between separate unit stocks of the same species [12] and to estimate the mean weight of fsh based on known length [13]. It also serves as a tool to assess the life history characteristics of fsh populations, such as stock composition, age at sexual maturity, and lifespan and provides important insights into resource conservation [14,15]. Similarly, the condition factor provides information on the health status of species and the community as a whole [16] and can be used to compare the physiological robustness of fsh on a numerical basis [17]. In recent times, increased pollution, reduced water fow, and the use of nonscientifc fshing methods have had an impact on the morphological and physiological statuses of fsh species. In spite of their commercial and ecological importance, there is still a scarcity of information on morphometric characteristics, length-weight relationship, and condition factors, for numerous fsh species from the River Ganga. Terefore, the present study aimed to generate baseline data on these parameters of fve indigenous fsh species, the Barilius barila Hamilton, Cirrhinus reba Hamilton, Chanda nama Hamilton, Mystus bleekeri Day, and Clupisoma garua Hamilton, belonging to the families, Danionidae, Cyprinidae, Ambassidae, Bagridae, and Schilbeidae, respectively.

Study Area.
Fish were collected at seasonal intervals from Digha Ghat Patipul (25°40′8.4″N; 85°0′18″E), a fsh landing site of the River Ganga in Bihar, India ( Figure 1). A total of 557 specimens of fve indigenous fsh species were collected from September 2021 to August 2022. Tese fourseason samples were pooled for statistical analysis. Fish specimens were caught using a monoflament drift gill net (100-200 m length, 1.5-2 m width, 10-30 mm mesh size, and 4-6 hours" of operational time) and a conical trap net/ Khairel jal (7-8 m length, 10 m mouth width, 1 m cod end width, and cod end mesh size 5-10 mm). Freshly caught fsh specimens were kept in an ice box and brought to the laboratory. Fish specimens were identifed to the species level using the standard manuals/taxonomic literature [18,19]. Te total length of specimens was measured from the tip of the snout to the tip of the caudal fn to the nearest 1 mm using a digital Vernier caliper (Insize -0/150 mm), and wet weight was recorded to the nearest 1 g using a digital balance (WENSAR TM-MAB 220).

Length-Weight Relationships (LWRs).
Te length-weight relationships were established separately for each species using the equation W � aL b [9], where W � body weight (g) of the fsh specimens, L � total length (mm), a � intercept, and b � slope of the regression line. Furthermore, the relationship was expressed in the logarithmic form log W � log a + b log L. A T-test was applied to determine whether the regression coefcients difer signifcantly from the isometric value of 3 (p < 0.05). Te isometric growth is considered for a fsh species when the estimated regression coefcient value is close to 3. In contrast, if it deviates from 3, fsh growth becomes either negative allometric (b < 3) or positive isometric (b > 3).

Condition
Factor. Condition factor (K) of the studied fsh species was determined as per Fulton's index K � W/L 3 * 100 [23]. Here, "K" is the condition factor, "W" is the total body weight (g) of fsh specimens, and "L" is the total length of specimens (mm).

Data Analysis.
A statistical analysis of all the data was performed using Graph Pad Prism software. Tese fsh's length and weight parameters are recorded in millimeters (mm) and grams (g). Te data were presented as mean ± SD. Table 1 shows the regression of total length (TL) on standard length (SL), predorsal length (PDL), prepectoral length (PPL), preventral length (PVL), preanal length (PAL), caudal peduncle depth (CPD), head length (HL), snout length (SNL), eye diameter (ED), postorbital length (POL), interorbital length (IOL), caudal fn length (CFL), and body depth (BD). For B. barila, C. reba, C. nama, and M. bleekeri, the correlation coefcient shows the highest degree of correlation between the total length and standard length, while for C. garua, it shows the highest correlation between the total length and head length. Te correlation coefcient reveals the lowest degree of correlation between the total length and caudal fn length, snout length, and postorbital length for B. barila, C. nama, and C. garua. Descriptive statistics for meristic counts are shown in Table 2. For each species, the gill rakers had the highest coefcient of variation, while the caudal fn ray, ventral fn ray, and pectoral fn rays of B. barila, C. reba, and C. nama had the lowest coefcient of variation. Based on the Kruskal-Wallis multiple comparison tests, the mean values of the gill rakers of B. barila were statistically diferent from those of C. garua (p � 0.0438). Te mean of C. reba is signifcantly diferent from C. nama (p � 0.0168) and C. garua (p < 0.0001), while M. bleekeri is also signifcantly different from C. nama (p � 0.0101) and C. garua (p < 0.0001). Te mean value of gill rakers in C. reba and M. bleekeri is not statistically signifcant (p > 0.99). Te results indicate that there are no signifcant diferences in morphological characters and meristic counts of these species within their populations, indicating that the stocks of these fsh that occur along the Ganga River are homogeneous. Terefore, the fn formula based on meristic counts can be written as follows: D08-10 P11-15 V08-10 A10-13 C18-24 GR19-26 for B. barila; D09-11 P13-16 V09-10 A07-09 C21-24 GR24-39 for C. reba;  Journal of Applied Ichthyology Table  2: Descriptive statistics of DFR, PFR, VFR, AFR, CFR, and GR of fve fsh species from the River Ganga, Bihar, India.

27)
Min. Max.  , whereas M. bleekeri shows isometric growth (b � 3.013) and C. reba exhibits negative allometric growth. Te observation confrms that the exponent value b is species-specifc, and each fsh species has a specifc growth rate.

Discussion
Te morphometric data revealed that the regression coefcient has a varying strength relationship between the total length and other characters for each species. Tese variations are species-specifc and depend on the ontogenetic development of the species. In meristic counts, the number of rays in the dorsal, pectoral, ventral, caudal, and anal fns varies within the size range of B. barila (97-123), C. reba (102-152), C. nama (74-83), M. bleekeri (77-119), and C. garua (138-216), confrming that meristic counts depend on body size and vary with fsh growth. Gill rakers are signifcantly more numerous in planktivorous fsh (C. reba) compared to carnivorous fsh (C. garua and C. nama), confrming that gill rakers depend on the feeding habits and food preferences of the species. Morphometric plasticity tends to respond to local environmental vitiations related to niche patterns of resource use [24] and physical characteristics of habitats that determine biological, evolutionary, and ecological changes in morphological traits of fsh populations [25].
Te length-weight relationship is important for understanding fsh's growth rate and the pattern. Te estimated b values for these indigenous fshes (2.92-3.24) were consistent with the expected range of 2.5-3.5 [10]. C. reba has a relatively slow growth rate and tends to be thinner (almost all specimens are in the juvenile stage), whereas estimates for B. barila are signifcantly better. 24.53% of individuals in the entire population of B. barila are sexually mature, and these mature specimens range in length from 73 to 123 with a mean length of 108.35 ± 10.55 mm (mean ± SD). In mature specimens, two-thirds of the entire body cavity are occupied by mature ovaries. Furthermore, recorded mean values for the length and weight of these ovaries are 45.90 ± 3.64 and 1.74 ± 0.69, respectively (mean ± SD). Fish fecundity and egg diameter (mm) were calculated to be 3150 ± 1452.62 and 0.77 ± 0.05, respectively. Te maximum length observed for B. barila (146.8 mm) was higher than previously recorded for this fsh (139.5 mm) from the Manas River in Assam, India [26]. Te condition factor K is an important factor to explain the relative robustness of fsh. Te largest variation in K was found in C. reba, whereas the least variation was found in C. garua. Despite their dissimilar food preferences and diferent physical forms in the juvenile and adult life stages, the species showed variation in K. In addition, size composition, seasonal sampling, and a limited number of specimens afect the K value of fsh. Furthermore, it is also infuenced by reproductive status, seasonality of natural diet, and age of fsh [10,27]. In conclusion, the present study on these parameters is perhaps the frst detailed report on these fve indigenous fsh species from River Ganga, Bihar, India. Tese fndings will provide valuable information to the fsheries biologists of the region to study their population parameters and formulate appropriate management measures for the sustainable exploitation of these resources.

Data Availability
Te data used to support the fndings of this study are available from the corresponding author upon reasonable request.

Conflicts of Interest
Te authors declare that they have no conficts of interest.  Journal of Applied Ichthyology