Caracterización de agregaciones de merluza de cola (Macruronus magellanicus) en la zona centro-sur de Chile

A monthly characterization of Chilean hoki aggregations was done using acoustic records ob- tained with SIMRAD EK60 and ES60 devices aboard three multipurpose vessels that operated in the central- southern fishery unit during 2003; this considered morphological and bathymetric descriptors. The wide mor- phological variation of the aggregations was explained by their cohesion level and tendency to form large horizontal aggregations whereas, bathymetrically, 90% of the aggregations were located between 300 and 450 m. Evidence of associations between various descriptors was found, and these were, in turn, associated with other factors such as mean size, water temperature, latitude, and month, allowing an adequate description of the shape of the aggregations and their location in the water column. The relevant relationships were: aggrega- tion depth with regard to bottom depth (r = 0.55), aggregation altitude with regard to bottom depth (r = 0.72), aggregation altitude with respect to the relative depth index (r = -0.98), and aggregation depth with respect to mean size (r = 0.66).