An analysis of the length - frequency data of Lethrinus mahsena (Sky emperor) on Saya de Malha fishing bank, Republic of Mauritius

Abstract

Abstract by author:

The results obtained were consistent for the five years under study. However, the values obtained for growth parameters and total and fishing mortality rates were somewhat higher in 1997 than for the four following years. It was clear that large numbers of fish in the range of 30-34 cm were landed during the study period. The average size of fish landed varied between 31 cm in 1997 and 38 cm in 2001. The length-frequency relationship for the 1998 period was estimated to be W = 0. 021L2. 9819 with an R2 value of 0. 9778. The estimates for the asymptotic length (L8) ranged between 60. 0 cm in 2001 and 71. 2 cm in 1997. The total mortality (Z) estimates were found to be 1. 16 in 1997, 0. 60 in 1998, 0. 73 in 1999, 0. 85 in 2000 and 0. 76 in 2001. Natural mortality rates (M) ranged from 0. 40 in 1997 to 0. 47 in 2001 whilst fishing mortality (F) was lowest in 1998 and highest in 1997. The length - at - first capture (L50) varied from 25. 9 cm to 31. 8 cm. The growth curves obtained were quite similar from one year to another (1998-2001) except for 1997 when higher values were obtained. The trend in the growth parameters, length - at - first capture and mortality rates suggest that the management strategy currently in force is effective, although there are some gaps in relative growth of separate sexes