Chemical profiles in otoliths from 3 fish species along the Moroccan coast: accumulation and migration patterns

Abstract

International audienceThe Canary Current Large Ecosystem is characterized by a major, nutrient-rich up-welling of deep, cold oceanic waters, which stimulates high biological productivity that results in an abundance of both pelagic and demersal fishery resources. In this area, the Moroccan coast is also under direct anthropogenic activities influences such as phosphates industries. Several observations indicate that variations of the upwelling activities observed in the recent years would generate the remobilization of the contaminants. Our study deals with the metallic concentrations in the otoliths of 3 fish species of economic interest ( Merlucius merlucius, Pagellus acarne, Sardina pilchardus) along the Moroccan coast. The fishes were collected in markets in june 2012 for the northern part of Morocco (during the maximum of the upwelling activity) and in November 2012 for the southern part. Concentrations were measured by ICP-MS on transects from nucleus to the edge of otoliths to characterize environmental variations or accumulations linked to ecophases and growth. For each species, 5 fishes were analyzed in 7 locations from North to south of the Moroccan Atlantic coast. First results indicate that the concentrations are highly variable in hake transects, and on the other hand, transects in seabreams seem very stable regardless of location. Transects in sardines indicate different patterns depending on the locations and, some of them, clearly show the upwelling signature