Background. Striped seabream, Lithognathus mormyrus (Linnaeus, 1758), is a bony fish, which has a high economic value on the Algerian coast. Because of the increasing fishing pressure, however, a close monitoring is recommended. The information about the biology of this species, occurring in the south-western Mediterranean Sea and especially in the north African coast, is very limited. The presently reported study provides new estimated data on age and growth parameters of striped seabream in Algeria.
Materials and methods. A total of 449 specimens of L. mormyrus were sampled for 2 years (January 2013 to December 2014) from the commercial fishery in the central part of the Algerian coast. The samples were collected monthly. The fish ranged in size from 11.5 cm to 34.5 cm and weighed between 21.6 g and 540.3 g. We analysed the sagittal otolith morphology and morphometry to determine a relation with the fish ontogeny. Fish age was determined from the sagittal otoliths to identify growth structures based on digitally processed otolith images aided by the TNPC software.
Results. No significant difference between the two otoliths (left and right) was detected (ANCOVA, P . 0.05). The correlation between each biometric parameter of the otolith (length and width) and fish length (TL) was significant (ANCOVA, P < 0.05). The evolution of marginal increment analysis (MI) showed that the annual periodicity of the growth ring was between July and December. The growth parameters of the von Bertalanffy model were estimated for each sex separately. In females they assumed the following values: TL8 = 35.44 cm, K = 0.27 yr–1, and t0 = -1.25 yr, while in males—TL8 = 26.94 cm and K = 0.6 yr–1, t0 = -0.45 yr. The asymptotic length was higher in females than in males. Males were represented only by small specimens and less than or equal to four years of age.
Conclusion. The presently reported results are the first ones on the age and growth of L. mormyrus off the Algerian coast. They will hopefully improve future stock management to get a sustainable fishery