Timing and location of spawning of Blue Grenadier, Macruronus novaezelandiae (Teleostei: Merlucciidae), In Australian Coastal Waters

Abstract

The geographical distribution and ages of larvae of the blue grenadier, Macruronus novaezelandiae, based on ichthyoplankton surveys in southern Australian waters in 1984 and 1985, indicate that the species spawns primarily off the west coast of Tasmania in winter, and may spawn on a lunar cycle. Winter spawning off Tasmania is also suggested by adult gonad morphology: gonado-somatic indices peaked in winter, and mature and spent individuals were collected off the west coast of Tasmania. Small numbers of larval blue grenadier were also collected off north-eastern Tasmania, suggesting the occurrence of small-scale and sporadic spawning in that area. The date of first spawning differed by a month between 1984 and 1985, and was apparently related to broad-scale interannual differences in the oceanography of southern Australian waters. Use of oceanographic features to retrocast spawning dates for blue grenadier suggests that shifts in the date of first spawning of approximately one month are common in this species.