Growth and Biometry Analysis of the Atlantic Bonito (Sarda sarda (Bloch, 1973)), in the Southern Coast of Morocco

Abstract

A total of 112 specimens were sampled from Southern Atlantic of Morocco in the period from April to June 2016. Sixty-two dorsal fin spines were analyzed for ageing and growth studies, and all samples (112) were used for biometric studies. The length of the aged individuals ranged from 440 to 704 mm. Fish ages ranged from 1 to 4 years old and the mean length by age were calculated for males and females. The standard von bertallanfy growth function was used to fit length at age data. The growth parameters are L∞= 73.01, K=0.3075 and to=-2.4469. Also, a biometry analysis of Atlantic bonito was conducted in this paper. Relative growth was studied by comparing changes in morphological characters with growth fork length. Length weight relationship is presented as well. Atlantic bonito (Sarda sarda (Bloch, 1793)) which is a member of Scombridae is distributed in both sides of the tropical and subtropical Atlantic Ocean, in the Gulf of Mexico, and in the Mediterranean and Black Seas. In the Eastern Atlantic, it is distributed from Oslo (Norway) to Port Elizabeth (South Africa), including the Mediterranean and Black Sea. In the western Atlantic off the east coast of the United States and Canada its usual northern limit is Cape Ann but also has been recorded along Nova Scotia [1]. Atlantic bonito is a small tuna species that feeds on small fishes, especially clupeoids such as anchovy, sardine, and sprat, and also on crustaceans [2]. Maximum length in the Atlantic is 91.4 cm fork length (LF) and 5.4 kg and in the Black Sea is 85 cm and 5 kg weight [3]. Common size is 50 cm fork length and about 2 kg. Maximum published weight is 11.0 kg [4]. In Morocco, this species is distributed along the Atlantic Coasts, especially in the southern part of the Atlantic coast [5]. Coastal fishing units, using gill net as the main gear, mainly exploit the Atlantic bonito. Knowledge of biometric variations is necessary in species descriptions. Collette., et al. 1975 [6], using a morphometric approach, described S. sarda from different areas. Pujolar., et al. (2001) and Vinas., et al. (2004) [7,8] studied the patterns of differentiation in two sub-populations of Atlantic bonito inhabiting the Mediterranean. In addition, the growth parameters studies are necessary for stock status and stock assessment. Also, determination of age is an important task in all studies population dynamics. In addition, knowledge of the age and growth process constitutes a