Migrations and structure of the species range in ridge-scaled rattail Macrourus carinatus (Southwest Atlantic) and their application to fisheries management

Abstract

The biology, distribution and abundance of the ridge-scaled rattail (Macrourus carinatus) was studied in four seasonal bottom-trawl surveys in 2006-2009 using biological material collected on board different research and commercial fishing vessels. The species was found to exhibit ontogenetic and seasonal migrations. Upon switching to the demersal lifestyle, juveniles gradually move north with the Falkland Current. Adults return to the spawning areas (50-54{degrees}S) and remain there. They move seasonally along the slope from 54{degrees}S to 50{degrees}S between 500 m and 900 m, with males and females moving separately. The northernmost aggregations (at 50-51{degrees}S) occur in autumn, during the major spawning event. In winter, fish migrate south. During spring and summer the entire population gradually shifts north with ongoing minor off-season spawning. Females, which are the larger sex, tend to stay shallower than males. Such a sex-related migratory behaviour should be taken into account when the existence or absence of Heincke's law is considered for a particular species. A complicated migratory pattern should also be accounted for in fishery management.