Length-weight Relationship and Condition Factor of Four Catfish Species (Actinopterygii: Siluriformes) from the Stanley Reservoir, Tamil Nadu, Southeast India

The length-weight relationship is a key metric that offers essential insights into the condition of fish stocks. Accurate data on body weight aids fisheries management and conservation efforts in regulating catches and estimating biomass (Rao et al., 2024). Data on the length-weight relationship of fish species are crucial for biologists to assess fish stocks, manage populations effectively, make morphological comparisons across species and populations, evaluate life history patterns across regions and support species conservation efforts (Ozaydin et al., 2007). The length-weight relationship (LWR) is a key tool for biologists to assess the well-being of fish populations as well as offers information regarding the growth rates of fish, estimation of biomass, genetic variations and condition factors (Froese, 2006; Jafari-Patcan  et al., 2018; Qadri et al., 2017; Kop et al., 2019; Eagderi et al., 2020; Phromthep et al., 2024). The condition factor is a significant factor in determining the overall productivity and physiological condition of the fish population (Richter, 2007). It can be utilized for assessing the potential differences within the stocks (Froese, 2006).
       
The order Siluriformes includes freshwater catfishes and occurs all over the world (Malabarba et al., 2020). Catfish species form one of the most diverse and species-rich groups in freshwater and marine environments, holding significant commercial value. Their name comes from the prominent tactile barbels (whiskers) near their mouths, resembling those of a cat (Muhammad et al., 2016). Catfish have scaleless body, fleshy adipose fins without fin rays and sharp spines in their dorsal and pectoral fins, which serve as a defense mechanism (Wang et al., 2016). They also exhibit various sizes, reflecting their adaptability and ecological versatility (Muhammad et al., 2016).
       
Over the past decade, scientific interest in the length-weight relationship in fish has grown significantly (Froese et al. 2011). Most research has focused on the length-weight relationships of common fish species from various aquatic habitats worldwide (Miranda et al. 2009). However, studies on the length-weight relationship of catfish species in Southern India’s reservoirs have been limited (Gupta et al. 2011). In particular, length-weight relationships for fish species in Stanley Reservoir have not been previously documented. Therefore, this study aims to evaluate the length- weight relationships of four catfish species collected from the Stanley Reservoir of the Cauvery River in Southeast India.

Samples were taken from sampling stations (S1) Masilapalayam (S2) Keeraikaranoor (S3) Kottaiyur (Fig 1) and transferred to laboratory facility at Erode Centre for Sustainable Aquaculture (ECeSA), TNJFU, Bhavanisagar. Fish samples were collected from the reservoir by using a coracle and gillnet with mesh sizes ranging from 50-200 mm for catching fish of different sizes from December 2021 to November 2022. Fish samples were identified up to the species level, followed by standard fish identification books/manuals/literature (Talwar and Jhingran, 1991; Jayaram, 1999). The length and weight were measured from the freshly collected specimens. Total length (TL) was measured to the nearest millimeter (from the tip of the snout to the tip of the lower caudal lobe) and weight was measured by a digital top pan scale with an accuracy of 0.01 g. The weight was taken after wiping off the moisture from the fish body. The relationship between length and weight was determined according to a linear regression model using the formula:
 

TW = a TL^b

 
Where,
W = Total body weight in grams.
L = Total length of fish.
a = Intersection of regression curve or slope (coefficient related to body shape).
b = Growth coefficient.


       
The b value denotes information on the type of fish growth of fish i.e., isometric growth b=3 (no change in fish body shape as it grows), if the b value is less than 3 i.e.,  b<3 shows negative allometric (as the fish grows body shape becomes more slender), if fish b value is greater than 3 i.e., b>3 it shows positive allometric growth (as fish grows body shape becomes relatively stouter or deeper-bodied ) (Bagenal and Tesch, 1978). The extreme outliers were found and removed before regression analysis (Froese, 2006). Also, the coefficient of determination (r2) and 95% confidence limit of ‘a’ and ‘b’ were evaluated using linear regression. Fulton’s condition factor (KF), calculated using the formula below was employed to evaluate the health of the subjects.

KF = (W/L³) x 100

 
The relative condition factor (KR) was determined using the equation below to account for variations in form or condition with length.

A total of 465 specimens of Siluriformes catfish species belonging to four genera were involved in the present analysis. Descriptive statistics and the length-weight relationship of the species are presented in Fig 2 and Table 1. During this study period, the intercept value ranged from 0.0005 (Pangasius icaria) to 0.0341 (Wallago attu). The slope b value ranged from 2.5 (W. attu) to 3.77 (P. icaria).




       
The results of the b value for P. icaria was 3.77 which indicates positive allometric growth. It is a new catfish species, described from the river Cauvery (Ayyathurai et al., 2022). The findings of the present study were concurrent with the earlier reports by Kumar et al. (2020) who also concluded the positive allometric growth for its congener P. silasi.  The b value for Mystus vittatus was 3.71 which shows positive allometric growth in the present findings. Hossain et al. (2009) and Chetia and Chutia et al. (2020) also concluded positive allometric growth in M. vittatus. However, Hossain et al. (2006) and Victor et al. (2014) concluded negative allometric growth in the same species. The b value of Sperata aoroides (3.01) was close to the isometric growth. The b value for W. attu observed during the present study recorded was 2.5 which indicates negative allometric growth. Similarly, many researchers (Sani et al. 2010; Sarkar et al. 2011) also reported that the value of b was significantly b<3.0 in W. attu, which shows agreement with the present finding. However, Khan et al. (2011) stated the isometric growth in W. attu. In contrast, several researchers (Yousaf et al. 2009; Achakzai et al. 2013; Rufus et al. 2015) observed positive allometric growth (b > 3) in W. attu across different water bodies. Kumar et al. (2023) concluded that W. attu showed negative allometric growth in Ganga, Yamuna and Yamuna whereas positive allometric growth in Hoogly and Pampa rivers. There are several reasons which were been suggested to influence the b value such as sex, age, season, feeding behaviour, variation in the number of specimens examined, anthropogenic activities, ontogenic changes, variation in the length of the specimen caught and gonad weight variation during different stages of sexual maturity (Moutopoulos et al. 2002; Peck et al. 2005, Winfield et al., 2012). The lower r2 value was observed in M. vittatus (0.843) and S. aoroides (0.874) may be due to the overrepresentation of same size range groups in the specimens examined (Gupta et al., 2011).
       
Condition factor (K) is the parameter which indicates fish health (Bagenal and Tesch, 1978) and is strongly influenced by both the biotic and abiotic environmental variables such as feeding habits, feeding intensity, age, growth rate and the reproductive cycle (Le Cren, 1951). The values for KR and KF ranged from S. aoroides (0.57) to W. attu (2.11) and S. aoroides (0.22) to M. vittatus (1.54) respectively. Clark (1928) identified a link between the condition factor (KF) and the parameters of the length-weight relationship (LWR), illustrating that if the b value approximates 3, KF can be directly compared. KR, on the other hand, measures an individual’s deviation from the average weight for a given length within the sample (Le-Cren, 1951). KF indicates the influence of biotic and abiotic factors on fish physiology (Çiçek et al. 2022) and assesses the health of the aquatic ecosystems they inhabit (Anene, 2005). Hence, the present analysis of KF indicates positive health and favourable environmental condition for all catfishes.

This pioneering study will offer essential baseline information for effectively conserving and managing catfish species in their natural habitats, such as the Stanley Reservoir. This reservoir is already experiencing significant anthropogenic pressures, leading to the rapid decline of endangered species like Hemibagrus punctatus (and commercially valuable catfish species like P. icaria in the reservoir and the River Cauvery. This present study provides length-weight information of catfishes around the Stanley Reservoir alone, which can be useful in future research with several other biological and environmental parameters and extensive sampling along the entire river will provide suitable exploitation and conservation management of fishery resources along the Stanley Reservoir.

The authors are very grateful to the Dean, Dr. MGR Fisheries College and Research Institute, Ponneri for support and encouragement.
 
Disclaimers
 
The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.
 
Informed consent
 
All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.
 

All authors declares no conflict of interest. No funding or sponsorship influenced the design of the study, data collection, analysis, decision to publish, or preparation of the manuscript.