Salinity and temperature as factors controlling the spawning and catch of Parapenaeus longirostris along the Moroccan Atlantic Ocean

The deep-water rose shrimp, Parapenaeus longirostris (Lucas 1846, Decapoda: Penaeidae) is one of the main target species of the demersal fishery in the Moroccan Atlantic region. However, in the last decade, there is a severe decline of shrimp fisheries in the area without the existence of any management plan. The purpose of this article is to investigate the relationships between the spawning of the deep-water rose shrimp and environmental factors in order to provide basic information for any future management measure. The spatial distribution of mature females is investigated through statistical techniques on data collected in the Moroccan Atlantic Ocean from bottom trawl surveys during 1981-2004. The geographic distribution of mature females is jointly analyzed in association to the spatial distribution of salinity and temperature at the depth of species catch. The study reveals a strong relationship between locations of spawning females and high salinity. Most spawning occurrences are observed in high salinity 'islands' (35.6-36.5 psu) or in the boundaries of higher-lower salinity patterns in the specific range of 36.2-36.4 psu in shallower (75-200 m) and deeper zones (250-500 m). Spawning occurs mostly in the shallower zone from spring to summer while during winter, it occurs in both depth zones. Temperature seems to be important on catch levels of the species.