AGE, GROWTH AND REPRODUCTIVE BIOLOGY OF SPANGLED EMPEROR, LETHRINUS NEBULOSUS (FORSSKÅL, 1775), FROM THE ARABIAN SEA, OMAN

AGE, GROWTH AND REPRODUCTIVE BIOLOGY OF
SPANGLED EMPEROR, LETHRINUS NEBULOSUS
(FORSSKÅL, 1775), FROM THE ARABIAN SEA, OMAN
AL MAMRY, J. M1
; A.A. EL GANAINY2 I. MCCARTHY3
; C. RICHARDSON3
; AND
S. BEN MERIEM4
1
Marine Science and Fisheries Center, Ministry of Agriculture and Fisheries, P O Box 467 code
113, Muscat. Sultanate of Oman. 2
National Institute of Oceanography and Fisheries, P O Box 182, Suez, Egypt. 3
School of Ocean Sciences, University of Wales, Bangor, Menai Bridge, Anglesey, LL59 5AB.
United Kingdom. 4
Institute National des Sciences et Technologie de la Mer (INSTM), 2016 Salammbo, Tunisia.
[email protected]
Keywords: Spangled emperor; reproductive biology; age and growth; Omani waters.
ABSTRACT
Spangled emperor, Lethrinus nebulosus (N=2306) were caught off at Doqum and
Salalah in the Arabian Sea, Oman from January 2001 to December 2002. Total length (LT)
ranged from 11 to 70 cm. Sagittal otoliths of 363 L. nebulosus were pretreated and
examined for age determination. Growth rings in the otoliths of different sizes were read
and the marginal increments of selected otoliths were measured using light microscopy.
The estimated parameters from the VBG equation were (L∞ = 72.2 cm LT, k = 0.086, t0 = –
3.041) were estimated using observed age. A significant linear relationship was found
between otolith weight and age (P<0.05). Growth parameters were then calculated using estimated age from otolith weight, the values were comparable to those calculated using the observed age. The maximum age recorded was 29 years old and the largest fish in the sample was 70 cm LT. Seasonal changes in gonado-somatic index (GSI) demonstrated that the spawning season of L. nebulosus occurred between September and December. The estimated length and age at 50% of maturation was 33.7 cm LT and 4.2 yrs. Chi squared test of variance showed no significant different between the distributions of mature males and females amongst the different size classes. Sex ratio study showed that male-female distributed by 1.09:1 proportion in the L. nebulosus population.