Distribution of Mullus barbatus and M. surmuletus (Osteichthyes: Perciformes) in the Mediterranean continental shelf: implications for management

Abstract

The present work attempts to study the spatio-temporal distribution of Mullus barbatus and M. surmuletus in the Mediterranean Sea by using a time series of data from an international bottom trawl survey that covered a wide area of the Mediterranean Sea. The experimental surveys were accomplished annually from 1994 to 2000 on approximately 1000 pre-defined sampling stations distributed in 15 major areas. Selection of stations was based on a depth-stratified random sampling scheme that included five depth strata: 10-50, 50-100, 100-200, 200-500 and 500-800 m. The examined species were found throughout the studied region, mostly in depths down to 200 m. Abundance differences among major areas were found to be statistically significant and were attributed to the different exploitation patterns, as well as the different abiotic and biotic conditions prevailing in each area. Although both species undergo high fishing pressure, results did not demonstrate any decreasing trends in their abundance indices suggesting the existence of a good stock-recruitment relationship over the studied period. However, the dominance of young fish that has been found, makes the stocks highly vulnerable to recruitment changes; hence protection of spawning and nursery areas seems to be essential for their conservation.