Age, growth and mortality parameters of the Atlantic horse mackerel Trachurus trachurus (Linnaeus, 1758) in the North Atlantic Moroccan Sea

• Main Authors: KERKICH, Maha, AKSISSOU, Mustapha, TECHETACH, Mohamed, RAMDANI, Mohammed, FLOWER, Roger
• Format: Text
• Language: unknown
• Published: Station Biologique de Roscoff (SBR) 2017
• Subjects: North Atlantic
• Online Access: https://dx.doi.org/10.21411/cbm.a.11fb54af; http://application.sb-roscoff.fr/cbm/doi/10.21411/CBM.A.11FB54AF

Population parameters of the Atlantic horse mackerel Trachurus trachurus were investigated using size-at-age data derived from regular monthly samples comprising 962 individuals (488 males, 358 females and 116 undetermined). Samples were collected from the population living near the North Atlantic Moroccan coast (Larache area) between June 2005 and November 2006. The growth study was based on the interpretation of growth rings observable on 687 otoliths (Sagitta). The otoliths preserved two annual growth rings, one opaque and the other hyaline. The opaque ring is formed mainly in spring and summer, while the hyaline is formed in autumn and winter. Total fish length varied between 12.8 to 38.4 cm and total weight from 15.0 to 528.7 g; the calculated length-weight relationship was W = 0.005 L3.171. Parameters estimated by the Von Bertalanffy growth equation (using all captured individuals) were L∞ = 44.67 cm, K = 0.14 year-1 and t0 = -0.46 year. The maximum observed age was 9 years. Relationships between otolith weight, age, and fish length were examined to present evidence to support a rapid and inexpensive method for ageing individuals of horse mackerel. The determined values are total mortality Z = 0.39 year-1, natural mortality M = 0.14 year-1 and fishing mortality F = 0.26 year-1. The stock exploitation rate (E) was estimated to be 0.65 indicating over exploitation. The results obtained were compared with those from other horse mackerel growth studies made in different areas.