LARVAL DEVELOPMENT OF BLUE GRENADIER, MACRURONUS 

 NOVAEZELANDIAE (HECTOR), IN TASMANIAN WATERS 



B D BruceI 



ABSTRACT 



The development of Macruronus novaezelandiae is described and illustrated from both reared speci- 

 mens and larvae from Tasmanian waters. Eggs of M. novaezelandiae are pelagic, spherical (1.08-1.18 

 mm diameter), and have a single oil droplet (0.36-0.42 mm diameter). Eggs hatch after 55-60 hours 

 at 14°-19°C. Larvae are 2.2-2.3 mm at hatching. Characteristic pigmentation, a myomere count of 

 78-80, and the sequence of fin development separate M. novaezelandiae from other known gadiform 

 larvae. Development is direct, with no marked change in body morphology. Fin development proceeds 

 in the sequence: second dorsal, anal, first dorsal, pelvic, caudal, pectoral. However, adult fin comple- 

 ments are reached in the sequence: first dorsal, pelvic, anal, second dorsal, caudal, pectoral. 



Caudal development is late in Macruronus. Flexion begins at 20 mm and is not complete until 28 

 mm. The caudal fin is based on two ural centra, four hypurals, two epurals, and a parhypural. X and 

 Y bones are present although they are not readily distinguishable from dorsal and anal pterygio- 

 phores. 



The genus Macruronus comprises four nominal 

 species, which occur in southern temperate conti- 

 nental shelf and slope regions. Two species, 

 Macruronus novaezelandiae and M. magellanicus 

 support commercial fisheries. The blue grenadier, 

 M. novaezelandiae , forms the basis of fisheries in 

 New Zealand and Australia where total annual 

 catches range up to 97,750 and 1,100 t respec- 

 tively (Patchell 1982; Wilson 1981, 1982). 

 Macruronus magellanicus is fished commercially 

 off South America. The remaining species, M. 

 maderensis and M. capensis , are known only from 

 a limited number of specimens (Svetovidov 1948; 

 Cohen 1986). Despite their economic importance 

 and widespread distribution, very little is known 

 of the early life history of any member of the 

 genus. Patchell (1982) identified winter spawn- 

 ing grounds on the west coast of the South Island 

 for New Zealand populations of M. novaeze- 

 landiae and similarly Wilson (1981, 1982) has 

 suggested a winter spawning, on the west coast of 

 Tasmania, for Australian M. novaezelandiae. 

 This paper presents the first published informa- 

 tion on the larvae of Macruronus . 



In 1984, the Division of Fisheries Research of 

 the Commonwealth Scientific and Industrial Re- 

 search Organization established a multidisci- 



ICSIRO Division of Fisheries Research, GPO Box 1538, Ho- 

 bart, Tasmania 7001, Australia; present address: South Aus- 

 tralia Department of Fisheries, GPO Box 1625, Adelaide, South 

 Australia 5001, Australia. 



Manu.scnpt accepted September 1987. 

 FISHERY BULLETIN: VOL. 86. NO. 1, 1988. 



plinary program to investigate the biology and 

 ecology of blue grenadier in Tasmanian waters. 

 An integral part of this program was a study of 

 larval ecology. As such, it was first necessary to 

 establish criteria for the identification of blue 

 grenadier larvae. This paper describes the larval 

 development of M. novaezealandiae from Tasma- 

 nian waters. 



MATERIALS AND METHODS 



Specimens were obtained from samples col- 

 lected aboard the CSIRO Fisheries Research Ves- 

 sel Soela between April 1984 and September 

 1985. Details of sampling strategies, locations, 

 and procedures will be described in a subsequent 

 manuscript. Larvae were obtained by sampling 

 with a rectangular midwater trawl (RMT 1+8; 

 Baker et al. 1973), aim diameter ring net (500 

 [im mesh), and free-fall, vertical drop nets of 64 

 |jLm and 200 fxm mesh (Heron 1982). Juvenile 

 specimens were obtained with an Engels 352 

 pelagic trawl fitted with a 10 mm liner. 



Newly hatched larvae were reared from eggs 

 stripped and fertilized at sea. Eggs and milt 

 stripped from ripe adults trawled from 500 m 

 were mixed in 1 L plastic jars filled with sea- 

 water. Despite the jars being located in a sea- 

 water bath, incubation temperatures varied con- 

 siderably (14°-19°C). On return to the 

 laboratories at Hobart, the eggs were transferred 

 to 2 L glass jars and placed in a constant temper- 



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