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Morphometric Relationships Between Length-weight and Length-length and Condition Factor of Four Small Indigenous Fishes from the Payra River, Southern Bangladesh

Newton Saha
Department of Fisheries Management, Patuakhali Science and Technology University, Dumki, Patuakhali-8602

Md. Rahamat Ullah
Department of Fisheries Biology and Genetics, Patuakhali Science and Technology University, Dumki, Patuakhali-8602

Md. Samiul Islam
Department of Fisheries Biology and Genetics, Patuakhali Science and Technology University, Dumki, Patuakhali-8602

Md. Belal Hossain
Department of Fisheries Biology and Genetics, Patuakhali Science and Technology University, Dumki, Patuakhali-8602

Abstract/ Executive Summary:

The present study describes the length–weight (LWR) relationship, length– length (LLR) relationship, and condition factor (K) of four small indigenous fish species from the Payra River, southern Bangladesh, namely Mastacembelus pancalus, Lepidocephalus guntea, Salmostoma bacaila and Mystus vittatus. A total of 867 specimens, representing 4 species of 4 families used for this study were caught by traditional fishing gear from July to October 2018. Standard length (SL) and total length (TL) for each specimen were measured by digital slide calipers and each body weight (BW) was taken by a digital balance. The allometric coefficient b of the LWR was close to the isometric value (b=3.078 and 3.028) in M. pancalus and L. guntea respectively, although it suggested negative allometric growth in M. vittatus (b < 3.00), whilst positive allometric growth in S. bacaila (b > 3.00). All the LWRs were highly significant (P < 0.05) and most of the coefficients of determination values were ≥ 0.857. The results further indicated that the LLRs were highly correlated (r² ≥ 0.939; P < 0.05). Fulton’s condition factor (K) by month basis ranged from 0.52 (in M. pancalus) through 1.89 (in M. vittatus). The results of this study can be very effective for stock assessment of this four species in Payra River as well as in the surrounding ecosystems.

Keywords: Morphometric Relationships, Length-weight relationship, Length-length relationship, Indigenous species

Location: Payra River, southern Bangladesh

Start Date: 00-07-2018

End Date: 00-11-2018

Program Area: Animal Health and Management

Commodity: Fish

Objectives:

The present study was carried out to study the length- weight relationship, length-length relationship, and condition factor of these four species from the Payra River, southern Bangladesh.

Methodology:

The present study was conducted in the Payra River, southern Bangladesh. The Payra River is a body of running water moving to a lower level in a channel on land in the country of Bangladesh and the river finally fall into the Bay of Bengal by the name of Burishwar River. It’s center lies at a latitude of 22º 35´ N and longitude of 90º 26´ E and it has an elevation of 1 meter above sea level. The Payra River is the suitable habitat for fresh water species especially fresh water SIS species are available in this River. Samples were collected using different types of traditional fishing gears including cast net (mesh size 1.0 to 2.0 cm), seine net (mesh size 1.5 to 2.5 cm) and square lift net (mesh size ~1.0 cm) from the Payra River in late July to early October, 2018. During collection of fish, care was taken that individuals of all size groups of every population were proportionately available in the sample. After collection, the specimens were chilled immediately in ice and preserved in 10% formalin upon arrival at the laboratory to prevent their decomposition. Preserved samples were taken out from the formalin solution and kept on a plastic tray. The tray was placed under running tap water to eliminate dirt, odour of formalin and surplus water from fishes for half an hour. Then fishes were kept in the room temperature for gentle air dry. The each individual’s standard length (SL) and total length (TL) was measured to the nearest 0.1 mm using a digital slide caliper (Mitutoyo, CD-6″ CSX). The TL was measured from the tip of the snout to the posterior end of the caudal fin. The SL was measured from the tip of the snout to the base of the caudal fin. The individual body weight (BW) was measured using a digital balance (AND, FSH, Korea) to 0.01 g accuracy. All estimations were done using combined sex. Data were input in on the spread sheet of the computer software, Microsoft Excel. The length-weight relationship was estimated by linear regression analysis based on natural logarithms: ln (W) = ln (a) + b ln (L), where W is the body weight (BW, g), L is the total length (TL, cm), and a and b are the regression parameters. Furthermore, SL vs. TL was estimated by linear regression using combined sex. According to Froese (2006), all extreme outliers were excluded from the analyses. A t-test was applied to determine significant differences from the isometric value (b= 3.0 for length-weight relationship and b = 1.0 for length-length relationship) (Sokal and Rohlf, 1981). Deviation of the b value from the theoretical isometric value indicates either positive (b > isometric value) or negative (b < isometric value) allometric growth. Fulton’s condition factor (K) was estimated using the equation: K = (BW ⁄ SL³) × 100, for monthly basis. The statistical analyses were performed using GRAPHPAD PRISM 8 software (GraphPad Software, Inc., San Diego, CA) and Microsoft Office Excel software (version 2010). Analysis of co- variance (ANCOVA) (Zar, 1984) was used to test for significant differences in slopes and intercepts between the relationships. All the statistical analyses were considered significant at 5% (P < 0.05) level of significance.

Source of Information: Archives of Agriculture and Environmental Science 4(2): 230-234 (2019)

Article Link (Online Journal): DOI: 10.26832/24566632.2019.0402016

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Based on the results, all the LWRs were highly significant (P < 0.05) and most of the coefficients of determination values were ≥ 0.857. The results further indicated that the LLRs were highly correlated (r² ≥ 0.939; P < 0.05). The value of K was <1 for M. pancalus and S. bacaila showing no proper environmental conditions of habitat for this two species in Payra River, where- as, K values of the rest of two species were >1 showing suitable conditions of this river for them. These results will be helpful for stock assessment of these fishes in the Payra River and the surrounding ecosystem and also would be an important baseline for future studies. However, further and more detailed researches are necessary for future assessment.

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