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Landmark Based Shape Variation of Normal Male, Female and Sex-reversed Tilapia (oreochromis Niloticus) in Bangladesh

R Moushomi
Department of Fisheries and Marine Science, Noakhali Science and Technology University, Sonapur,Noakhali 3814

S Saha
Department of Fisheries and Marine Science, Noakhali Science and Technology University, Sonapur,Noakhali 3814

Abstract/ Executive Summary:

The truss network systems constructed with the help of landmark were evaluated to infer the shape of normal male, female and monosex male tilapia. A total of sixty (60) individuals from different sources (Subarna Agro Based Initiative and Bismillah Agro Production) were collected during September-December, 2013. All the data of the studied characteristics were obtained using the digital photograph of the samples which were analyzed through professional image measurement software. Nine morphometric and eight meristic characters were considered along with twenty six truss network measurements. Highly significant difference (P<0.05) was observed in six (SL, HL, PrDL, MBH, EL and PL) of eight morphometric measurements. In case of truss measurements 7 of 26 measurements showed highly significant differences among the groups. For both morphometric and landmark measurements the first DF accounted for 98.9% and 85.7% and the second DF accounted for 1.1% and 14.3% respectively. With truss network system 100% monosex male samples, 85.5% of normal male samples, 100% of female samples were correctly classified. In both cases, plotting discriminant functions revealed high isolation of the groups especially between the monosex groups with the other two groups. The results showed that the shape of the tested tilapia groups significantly differed from each other depending on the truss measurements. that could be explained by the genetic sex related reasons.

Keywords: Landmark, Tilapia, Morphometric, Meristic

Location:

Start Date: 00-09-2013

End Date: 00-12-2013

Program Area: Animal Health and Management

Commodity: Tilapia

Objectives:

To evaluate the variation in morphometric and meristic characters of Nile tilapia among three groups (monosex male, normal male and normal female) collected from the hatchery and to assess and describe the shape variation of among the group of collected fishes.

Methodology:

Sixty Nile tilapia of different size was collected in live condition from two stocks. Ten morphometric characters (Total length (TL), Standard length (SL), Fork length (FL), Head length (HL), Maximum body height (MBH), Eye length (EL), Pre orbital length (PrOL), Post orbital length (POL), Peduncle length (PL), Pre dorsal length (PrDL) of the fish were measured respectively. A total of eight meristic characters (Dorsal fin rays, Pectoral fin rays, Pelvic fin rays, Anal fin rays, Caudal fin rays, Lateral line scale, Scale above lateral line, Scale below lateral line) were analyzed in the study. Twelve landmarks determining twenty six distances were measured on the body. For the need of the proper way of analysis, it was necessary to eliminate any size effect from the data set. It was necessary to remove size-dependent variation for all the characters. An allometric formula given by Elliott et al. (1995) was used to remove the size effect from the collected data set: M_adj = M (L_s/L_o)^b, Where, M: original measurement, M_adj: size adjusted measurement, L_o is the total length of fish and L_s is overall mean of total length for all fish from all samples.

Parameter b was estimated for each character from the observed data as the slope of the regression of log M on log L_o,using all fish in all groups. The efficiency of size adjustment transformations was assessed by testing the significance of the correlation between transformed variable and total length.

Univariate analysis of variance (ANOVA) was carried out to test the significance of morphological differences. In addition, size adjusted data were standardized and submitted to discriminant function analysis (DFA) using SPSS v 16.0. Comparison of meristic characters was done using non-parametric statistical test (Kruskal-Wallis test) also by SPSS v 16.0.

Source of Information: Progressive Agriculture 26: 168-172, 2015, ISSN: 1017 - 8139

Article Link (Online Journal): http://www.banglajol.info/index.php/PA/article/view/25978

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The truss network system can be effectively used to distinguish between the monosex groups, normal male groups and normal female groups. From the conducted analysis it is expected to get more significant differences because of different groups with different feeding conditions. From the analysis through Canonical Discriminant functions depending on the truss measurements it is found that there was no overlapping among the groups that indicates that the three fish group samples are different from the point of landmark counts also. The findings of the present study would significantly contribute towards designing of such a detailed study in future.

Knowledge Management: Journal