# Age and Growth Based on the Scale Readings of the Two Scarid Species *Hipposcarus harid* and *Chlorurus sordidus* from Hurgada Fishing Area, Red Sea, Egypt

2. Faculty of Science, Port Said University, Egypt

Author Correspondence author

International Journal of Marine Science, 2014, Vol. 4, No. 31 doi: 10.5376/ijms.2014.04.0031

Received: 17 Feb., 2014 Accepted: 15 Apr., 2014 Published: 11 Jun., 2014

Mehanna et al., 2014, Age and Growth Based on the Scale Readings of the Two Scarid Species *Hipposcarus harid* and *Chlorurus sordidus *from Hurgada Fishing Area, Red Sea, Egypt, International Journal of Marine Science, Vol.4, No.31 (doi: 10.5376/ijms.2014.04.0031)

*Hipposcarus harid*and

*Chlorurus sordidus*from Egyptian Red Sea, Hurgada region were studied based on the scale readings using a non-linear back-calculation method. A total of 1000

*H. harid*(17.0 – 50.0 cm TL)and 700

*C*

*. sordidus*(16.0–33.5 cm TL) were aged and their maximum life span was 8 and 5 years respectively. The most dominant age group in the catch is the second age group for

*H. harid*(34.7%)and the fourth one for

*C. sordidus*(45.6%). The von Bertalanffy growth parameters obtained by using the back-calculated lengths were L∞ = 57.16 cm TL, K= 0.23 year

^{−1}, and t

_{0}= −0.65 years for

*H. harid*and L∞ = 40.27 cm TL, K= 0.28 year

^{−1}and t

_{0}= -0.17 years for

*C. sordidus*. These data are needed to assist in the wise management of this potential fishery. It is also clear that more information about the scarid biology and dynamics is needed to establish bases for a responsible fishery development of the Egyptian Red Sea.

Age determination and growth modeling are critical aspects needed to assess different fish stocks (Hilborn & Walters, 1992; Dwyer et al., 2003). Assessment of age and growth is also essential for estimating the biological and physiological aspects of fishes such as stock age structure, age-at-50% maturity, yield- per-recruit and adaptation of stock to changes in habitat, exploitation and productivity (Morales-Nin, 1992; Francis et al., 1998 & 2000; Campana, 2001; Welcomme, 2001; Robinson & Motta, 2002; Kanyerere, 2003; Sulikowski et al., 2007; Simon and Mazlan, 2010). Also, understanding the life history of fishes is fundamental for the scientific protection of fish species and the sustainable use of natural fishery resources (Jia and Chen 2011; Mehanna, 2013).

*Hipposcarus harid*and

*Chlorurus sordidus*) which could serve as a guide for their future management.

**1 Material and Methods**

**1.1 Study area**

Figure 1 Egyptian Red Sea map showing the study area |

**1.2 Collection of samples**

**1.3 Biological measurements**

**1.4 Age determination**

_{n}= a + (L - a) R

_{n}/R where L

_{n}is the length at the formation of the n

^{th}annulus, a is the intercept in the L-R linear function, and R

_{n}is the scale radius of the n

^{th}annulus.

**1.5 Length-weight relationship**

^{b}was fitted to the data. Confidence intervals (CI) were calculated for the slope to see if it was statistically different from 3.

**1.6 Growth**

_{t}= L∞ (1 - e

^{-K (t - t0)}), where L

_{t}is the predicted length at age t, L∞ is the mean theoretical maximum length, K is the Brody’s growth coefficient, and t

_{0}is the theoretical age at 0 length.

_{0}was estimated from the following rearranged formula of the von Bertalanffy equation:

_{0}+ Kt

**2 Results and Discussion**

**2.1 Age composition**

*H. harid*and

*C. sordidus*from Hurgada fishing area. Scales as a reliable and valid method for ageing these species have been proven. Body length – scale radius relationship (Figure 3) showed a strong correlation between the body length and scale radius. Also, the increase of fish size is accompanied by an increase in the number of annuli on the scales. On the other hand, back-calculated lengths are accord with the observed lengths for the different age groups.

Figure 2 Scales of |

Figure 3 Body lengths – scale radius relationship of |

Based on the number of annuli on the scales, the oldest individuals were 8 and 5 years old for

*H. harid*and

*C. sordidus*respectively (Figure 4). It is found that the age group two was the most dominant age group for

*H. harid*forming 34.7 % of the total collected samples, while for

*C. sordidus*the fourth age group was the most frequent one representing 45.6 % of the total catch. The other age groups were represented by relatively very low percentage for both species. Age readings indicated that the both species attain their highest growth rate in length during the first year of life, after which a gradual decrease in growth increment was observed with further increase in age (Figure 5).

Figure 4 Age composition of |

Figure 5 Growth in length and growth increment of |

**2.2 Total length–scale radius relationship**

*H. harid*and

*C. sordidus*was found to be linear (Figure 3) and represented by the following equations:

*H. harid:*L = 2.6019 R + 1.8501 (r

^{2}= 0.94, n = 1000)

*C. sordidus:*L = 1.1463 R + 9.2601 (r

^{2}= 0.92, n = 700).

**2.3 Length – weight relationship and growth in weight**

*H. harid*and 700 specimens of

*C. sordidus*were used for the estimation of length weight relationship.

*H. harid*varied in total length from 17 to 50 cm and in weight from 70 and 2100 g, while

*C. sordidus*ranged between 16 and 33.5 cm in total length and between 60 and 710 g in weight. The estimated length - weight equations for the investigated species (Figure 6) are:

Figure 6 Length – Weight Relationship of |

*H. harid*: W= 0.0182 L

^{2.9323}

*C. sordidus*: W= 0.0182 L

^{3.0169}

*H.harid*and the third year of life for

*C. sordidus*then decreasing with further increasing in age (Figure 7).

Figure 7 Growth in weight and growth increment of |

**2.4 Growth parameters**

_{o}) were as follows:

*H. harid*

_{t}= 57.16 (1 - e

^{-0.23 (t +0.69)})

^{ -0.23 (t +0.69)})

^{2.9323}

*C. sordidus*

_{t}= 40.27 (1 - e

^{-0.28 (t +0.17)})

^{ -0.28 (t +0.17)})

^{3.0169}

_{0}= −6.92 and −4.6 year, for

*H. harid*and

*C. sordidus*, respectively from the Red Sea, Saudi Arabia. This difference may be due to the difference in specimens maximum size or their samples not representative sample as

*H. harid*K value was too low for a species has L∞ = 43.9 cm.

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