Population dynamics of the king mackere (Scomberomorus cavalla) of the Campeche Bank, Mexico

Abstract

The king mackerel (Scomberomorus cavala) a migratory pelagic resource which is caught along the coasts of the Gulf of Mexico, where some hypothesis suggest the existence of at least two stocks. In this contribution, the population dynamics of the Campeche Bank stock is analyzed. It is a small scale fishery with limited access to the whole population. Several locations along the coast were sampled around the Peninsula of Yucatan. Size structure of catches indicates a spatial gradient with large fishes found on the northeastern coast of the Yucatan Peninsula, and smaller ones on the southern Gulf of Mexico. This behavior is associated with environmental factors; the southern region, with fluvial influence, probably acting as a nursery area; while in the northeastern region the population dynamics is in syncrony with a seasonal upwelling. The average population parameters estimated were as follows: growth parameters of the von Bertalanffy equation: L∞=140 cm; K=0.19 (l/year), and tz=0.54 years. Total mortality was estimated as Z=2.16, and natural mortality was estimated to be M=0.4. Length-structured-VPA was applied in order to estimate fishing mortality by size, which was more intensive on fishes ranging 60 cm to 80 cm; however, for Campeche, the small length at first catch (Lc) imposes large fishing mortalities on small sizes, and an increment to the Lc was recommended. The Thompson and Bell method suggests the stock is being exploited at the maximum biological production level. Results are discussed within the framework of ecological behavior, stock identity and fish accessibility. The emerging hypothesis is that a well defined stock occurs in the Campeche Bank, with a certain degree of mixing with other stocks from the Northern Gulf of Mexico.