^{1}

^{*}

^{2}

^{3}

Length-weight relationship is an essential biological parameter needed to appreciate the suitability of the environment for any fish species. That is why many fishery biological studies give an importance to it. The relationships between total length and body depth and girth are very important in estimating the allowable catch and appropriate mesh size to be used in a fishery. Length-weight and some morphometric relationships (depth-total length, girth-total length and dorsal fin length and anal fin length-total length) of
Valamugil
seheli
(local name Arabi) (
Mugilidae
) were calculated from the commercial catches landed at Port Sudan Fish Market from February 2010 to January 2011. The length-weight relationship was found to be stronger in females (W = 0.0073L
^{3.1047}
, R
^{2}
= 0.966) than in males (W = 0.0074L
^{3.0954}
, R
^{2}
= 0.926). But for sexes combined it was y = 0.007x
^{3.114}
, R
^{2}
= 0.961. Values of R
^{2}
were high in all cases. The length-weight relationship indicated the cube law (W = aL
^{3}
) for males, females and the sexes combined relationships. The power equations for the relationship between total length and body depth, and total length and girth, for the two sexes have higher R
^{2}
than the strait line equations and hence better describe the two relationships. The two relations were stronger in females than in males. The relationships between total length and the first dorsal fin length and anal fin length of
sexes combined of
V. seheli
were not as strong as the total length-total weight relationship.

The relationship between the length and weight of a fish is used by fisheries researchers and managers for two main purposes (Le Cren, 1951) [

According to the Marine Fisheries Administration records in Sudan, Valamugil seheli constitutes high percent of the total fish landings and is available all the year round. It is the best local marine fish for preparing “Fasseikh” (wet-salted fishes) because of its good taste and texture (Faragalla, 2009) [

In practice, the use of morphometric measurements (body length, body girth, head length, fins length, eye diameter and jaw length) and meristics (fin ray, scale, teeth, gill raker and lateral line pore counts) to identify and classify fish is common. Morphometric measurements are generally presented as a proportion of total, standard and fork length, body weight and condition factor (Naeem et al., 2010 [

1) length-weight relationship of Valamugil seheli;

2) body depth-total length relationship of Valamugil seheli;

3) body girth-total length relationship of Valamugil seheli;

4) dorsal and anal fins-total length relationship of Valamugil seheli.

Random samples of about 30 fish of Valamugil seheli were collected monthly from the commercial catches landed at Port Sudan Fish Market from February 2010 to January 2011. Total length was measured to the nearest mm and total weight to the nearest 0.1 gm, then the data was entered to Excel package and the curve of the relationship between them was plotted. Values of the constants (a) and (b) were obtained from the relationship according to Abd El Razik (1987) [

W = aLb

where:

W = total weight in grams;

L = total length in cm;

b = a constant of the relationship represents the slope of the equation;

a = a constant of the relationship represents the intersect part of the “y” axis.

Total length, body depth, body girth, dorsal fin length and anal fin length of Valamugil seheli were measured to the nearest mm then the data was entered to Excel package and the curve of the relationships between each one the four later parameters and total length were plotted. Values of the constants (a) and (b) for each relationship separately were obtained using power and linear equations as follow:

B = aL^{b} (power equation)

B = aL + b (linear equation)

where:

B = one of these parameters body depth, body girth, dorsal fin length or anal fin length in cm;

L = total length in cm.

The length-weight relationship was very strong, but there was a little difference between males and females (for males R^{2} = 0.926 and for females R^{2} = 0.966) (^{2} = 0.958).

The relationship between total length and body depth, and total length and girth, for the two sexes are shown in ^{2} value than the strait line equations and hence better describe the two relationships.

The relationship between total length and the first dorsal fin length and anal fin length, are shown in ^{2} value (R^{2} = 0.6045) than the power equation (R^{2} = 0.584) and are therefore more appropriate. The opposite is true for the relationship between total length and anal fin length where the power equation is a little bit stronger (R^{2} = 0.653) than the linear equation (R^{2} = 0.6382).

Relationships | Sex | Equation | Equations | R^{2} |
---|---|---|---|---|

Total length vs. body depth | Male | Power | y = 0.174x^{1.032} | 0.779 |

Straight line | y = 0.204x − 0.282 | 0.764 | ||

Female | Power | y = 0.204x^{0.997} | 0.837 | |

Straight line | y = 0.204x − 0.046 | 0.824 |

Relationships | Sex | Equation | Equations | R^{2} |
---|---|---|---|---|

Total length vs. body girth | Male | Power | y = 0.642x^{0.933} | 0.811 |

Straight line | y = 0.485x + 0.813 | 0.795 | ||

Female | Power | y = 0.537x^{0.992} | 0.889 | |

Straight line | y = 0.522x + 0.044 | 0.876 |

Relationships | Equation | Equations | R^{2} |
---|---|---|---|

Total length vs. first dorsal fin length | Power | y = 0.083x^{0.962} | 0.584 |

Straight line | y = 0.0774x − 0.101 | 0.6045 | |

Total length vs. anal fin length | Power | y = 0.225x^{0.711} | 0.653 |

Straight line | y = 0.0583x + 0.7946 | 0.6382 |

The length-weight relationship of Valamugil seheli was found to be a little bit stronger in females (W = 0.0073L^{3.1047}, R^{2} = 0.966) than in males (W = 0.0074L^{3.0954}, R^{2} =^{ }0.926), but there was no significant difference between sexes. Khalifa (2007) [^{2.6294} for males and W = 0.0502L^{2.5283} for females. Comparing with the present study the variations may be due to the different environmental conditions of the two localities. Borafy and Soliman (1988) [^{3} as proper representation of the length-weight relationship for V. seheli inhabiting Sudanese Red Sea coast. Renjini and Bijoy (2009) [

The relationships of total length-body depth and total length-body girth for V. seheli were closely related for the two sexes. However, they were stronger in females (R^{2} = 0.824 and 0.876 respectively) than in males (R^{2} =^{ }0.764 and 0.795 respectively). These parameters are very important in estimating the allowable catch and appropriate mesh size to be used. The values of body depth and body girth of this fish increase with increasing in total length. The average values of depth and girth for males and females of V. seheli were 5.93 cm, 6.31 cm, 15.55 cm and 16.30 cm respectively. Khalifa (2007) [

In the present study the relationships between total length and the first dorsal fin length and anal fin length of sexes combined of V. seheli (R^{2} = 0.60 and 0.63 respectively) were not as strong as the total length-total weight relationship (R^{2} = 0.926 for males and 0.966 for females). This may be due to the differences of growth rhythm of the different parameters in each relationship. The relation between total length and anal fin length (R^{2} = 0.6382) was stronger than the relation between total length and first dorsal fin length (R^{2} = 0.6045). Renjini and Bijoy (2009) [^{2} for the relationship between total length and anal fin length of the mullet Liza parsia from the Champakkara region of Cochin estuary, India, as 0.452 and for the relationship between total length and first dorsal fin length as 0.476. They reported that these two relationships were positively correlated.

Both power and linear equations used in the present study to describe morphometric relationships of V. seheli have equal strength. The power equations however, had slightly higher R^{2}.

Motasim Ali Mokhtar,Osman Mohammed Farah,Sayed Mohammed Ali, (2015) Length-Weight and Some Morphometric Relationships of Valamugil seheli from Sudanese Red Sea Coast. Open Access Library Journal,02,1-7. doi: 10.4236/oalib.1101621