Spatial variations of the Argentine hake (Merluccius hubbsi (Marini, 1933)) spawning shoals in the Patagonian area during a reproductive season

Resumen

Displacements of Argentine hake Merluccius\nhubbsi shoals in the spawning area of Patagonia before and\nduring a reproductive season were analyzed. In particular,\nmonthly changes in fish density, sex composition, size\nstructure and spawning location were described for this stock.\nDuring October¿November, hake shoals moved from deeper\nwaters to the coast at about 44°S, where spawning took place\nin December. During January the main reproductive\naggregations stayed near the coast (50 m depth) but displaced\nto the southern area (45°S); in February spawning activity\ndiminished and spent females began to return to deeper\nwaters. In general, this process was first completed by young\nspawners (35¿45 cm TL), which have a breeding season\nshorter than the old females. We observed that males arrived\nat the spawning area first and remained there for a longer\nperiod than females. During the reproductive period skewed\nsex ratios in different sampling sites were observed. These\ndifferences in sex composition were attributable to: 1) local\nsegregation produced by the reproductive behavior of hake, in\nwhich males form groups with a single female, and 2)\nmigration of spent females to deeper waters, which causes\nmale-biased samplings in coastal areas.