<abstract xmlns="http://www.w3.org/1999/xhtml"><p>In this study, the pattern and magnitude of sexual dimorphic differences have been investigated in black jaw tilapia (<italic>Sarotherodon melanotheron</italic>) (n = 160; 74 males and 86 females) and banded jewelfish (<italic>Hemichromis fasciatus</italic>) (n = 120; 42 males and 78 females) from the Great Kwa River, Calabar, Nigeria. Fish samples were collected between July and December 2015. Fourteen morphometric variables, including body weight, total length, standard length, body depth, cheek depth, pre-orbital length, postorbital length, pectoral fin length (right and left), pelvic fin length (right and left), head length, gonad weight, eye diameter and four meristic variables, including number of pectoral fins (right and left) and number of pelvic fins (right and left), were taken using standard methods. Size-adjusted morphometric measurements subjected to step-wise discriminant function analysis were used to determine predictor variables to morphologically differentiate sexes for both species; magnitude of dimorphism between sexes was estimated using percentage classification accuracy of the discriminant function analysis. From the discriminant function analysis, the pectoral fin length and gonad weight positively contributed significantly to morphometric dimorphism (magnitude=69.2%) in male and female <italic>S. melanotheron</italic> suggesting adaptation for reproductive function; while for <italic>H. fasciatus</italic> the body depth and standard length were important contributors to sexual dimorphism (magnitude=84.2%) suggesting size dimorphism for aggressiveness, territorial behavior and improving swimming performance. Overall, our results indicate that the different magnitude of sexual dimorphism between the two species could be attributable to the type and functional role of sexual dimorphic traits.</p></abstract>

In this study, the pattern and magnitude of sexual dimorphic differences have been investigated in black jaw tilapia (Sarotherodon melanotheron) (n = 160; 74 males and 86 females) and banded jewelfish (Hemichromis fasciatus) (n = 120; 42 males and 78 females) from the Great Kwa River, Calabar, Nigeria. Fish samples were collected between July and December 2015. Fourteen morphometric variables, including body weight, total length, standard length, body depth, cheek depth, pre-orbital length, postorbital length, pectoral fin length (right and left), pelvic fin length (right and left), head length, gonad weight, eye diameter and four meristic variables, including number of pectoral fins (right and left) and number of pelvic fins (right and left), were taken using standard methods. Size-adjusted morphometric measurements subjected to step-wise discriminant function analysis were used to determine predictor variables to morphologically differentiate sexes for both species; magnitude of dimorphism between sexes was estimated using percentage classification accuracy of the discriminant function analysis. From the discriminant function analysis, the pectoral fin length and gonad weight positively contributed significantly to morphometric dimorphism (magnitude=69.2%) in male and female S. melanotheron suggesting adaptation for reproductive function; while for H. fasciatus the body depth and standard length were important contributors to sexual dimorphism (magnitude=84.2%) suggesting size dimorphism for aggressiveness, territorial behavior and improving swimming performance. Overall, our results indicate that the different magnitude of sexual dimorphism between the two species could be attributable to the type and functional role of sexual dimorphic traits.

Sexual Dimorphism in Black Jaw Tiliapia (<italic>Sarotherodon melanotheron</italic>) and Banded Jewelfish (<italic>Hemichromis fasciatus</italic>) from the Great KWA River, Calabar, Nigeria

Department of Zoology and Environmental Biology

Croatian Journal of Fisheries

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Sexual Dimorphism in Black Jaw Tiliapia () and Banded Jewelfish () from the Great KWA River, Calabar, Nigeria

In this study, the pattern and magnitude of sexual dimorphic differences have been investigated in black jaw tilapia (Sarotherodon melanotheron) (n = 160; 74...

Sexual Dimorphism in Black Jaw Tiliapia (Sarotherodon melanotheron) and Banded Jewelfish (Hemichromis fasciatus) from the Great KWA River, Calabar, Nigeria

Published Online: Oct 10, 2017

Page range: 122 - 131

Received: Nov 05, 2016

Accepted: Jun 14, 2017

DOI: https://doi.org/10.1515/cjf-2017-0016

Keywords
Morphometric measurement, Sexual dimorphism, Cichlids, Great Kwa River, Nigeria

© 2017 Oju Richard Ibor et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Sexual Dimorphism in Black Jaw Tiliapia (Sarotherodon melanotheron) and Banded Jewelfish (Hemichromis fasciatus) from the Great KWA River, Calabar, Nigeria

Published Online: Oct 10, 2017

Page range: 122 - 131

Received: Nov 05, 2016

Accepted: Jun 14, 2017

DOI: https://doi.org/10.1515/cjf-2017-0016

KeywordsMorphometric measurement, Sexual dimorphism, Cichlids, Great Kwa River, Nigeria

© 2017 Oju Richard Ibor et al., published by De Gruyter Open

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Keywords
Morphometric measurement, Sexual dimorphism, Cichlids, Great Kwa River, Nigeria