Volumen 42 - Número 3: 345-356 | 2007
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Spatial variations of the Argentine hake (Merluccius hubbsi (Marini, 1933)) spawning shoals in the Patagonian area during a reproductive season  

Gustavo J. Macchi^1,2*, Marcelo Pájaro² and Claudia Dato²

¹Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Rivadavia 1917 (1033), Buenos Aires, Argentina
²Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), Paseo Victoria Ocampo N° 1, CC. 175, Mar del Plata (7600), Argentina

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Displacements of Argentine hake Merluccius hubbsi shoals in the spawning area of Patagonia before and during a reproductive season were analyzed. In particular, monthly changes in fish density, sex composition, size structure and spawning location were described for this stock. During October-November, hake shoals moved from deeper waters to the coast at about 44°S, where spawning took place in December. During January the main reproductive aggregations stayed near the coast (50 m depth) but displaced to the southern area (45°S); in February spawning activity diminished and spent females began to return to deeper waters. In general, this process was first completed by young spawners (35-45 cm TL), which have a breeding season shorter than the old females. We observed that males arrived at the spawning area first and remained there for a longer period than females. During the reproductive period skewed sex ratios in different sampling sites were observed. These differences in sex composition were attributable to: 1) local segregation produced by the reproductive behavior of hake, in which males form groups with a single female, and 2) migration of spent females to deeper waters, which causes male-biased samplings in coastal areas.

Key words: Merlucciidae, southwest Atlantic Ocean, reproduction, migration