McDOWALL: SALMONIFORMS 



153 



tation is sparse, limited to spaced melanophores along the ab- 

 domen. The larva remams very elongate, the vent at about 85% 

 of total length. Eigenmann ( 1 928) reported that A. manmis (=A. 

 taenialus) spawns in the sea but this has never been corroborated 

 (see Campos. 1969). 



Galaxiidae. — Diadromous species: Spawning is usually in fresh- 

 water. Eggs of Galaxiasfasciatus are deposited in autumn-win- 

 ter on stream-side forest debris during floods and develop out 

 of water, hatching when re-immersed during a subsequent flood. 

 The larvae go to sea on hatching, returning in spring as elongate, 

 transparent juveniles about 45 mm long. A minor metamor- 

 phosis involves shrinkage at freshwater entry. The eggs are of 

 moderate size (~2 mm) and number many thousands; devel- 

 opment takes about 30 days. Most other diadromous species 

 have unobserved habits. G. maciilatus spawns in tidal estuaries 

 where streamside vegetation is inundated at high spring tides 

 and development takes place between successive series of spring 

 tides. Most adults die after spawning and larval life is marine. 

 The eggs are simple, spherical, demersal and adhesive, varying 

 from 1-2 mm diameter and more or less colourless. Benzie 

 (1968a) described eggs of G. maculatus as "finely etched." Lar- 

 vae at hatching have a well developed yolk sac. with a single 

 oil globule, the sac below and behind the pectoral fins. The larvae 

 are slender and elongate at hatching, 7-8 mm long, and have 

 the finfold continuous from about mid dorsal around tail to yolk 

 sac. The vent is posterior, at about 75% of total length. 



Non-diadromous species: Most species in the family are non- 

 diadromous (31 of 37 species). Those known spawn on sub- 

 strates near adult habitats and the pelagic "whitebait" juvenile 

 stage is omitted. Eggs are laid in aggregations (G. vulgaris). Lar- 

 vae on hatching, where described, resemble those of G. mac- 

 ulatus. 



Galaxiella pusilla is distinctive in being sexually dimorphic, 

 spawning in pairs, the females laying eggs individually on stream 

 vegetation. Individual placement of eggs is also reported for 



Brachygalaxias bullocki. The ability to aestivate is recorded for 

 some species (Neochanna. New Zealand) and spawning follows 

 restoration of water. It is suspected in others (Galaxiella. Aus- 

 tralia; Brachygalaxias. Chile) and may involve drought survival 

 of eggs (see Benzie, 1968a, b; Backhouse and Vanner, 1978; 

 Cadwallader, 1976; Campos, 1972; McDowall 1968b, 1978; 

 McDowall et al., 1975; Mitchell and Penlington, 1982). 



Little IS known about the marine larval/juvenile life of any 

 of these southern salmoniforms. Small numbers of Galaxias 

 larvae (Fig. 80) have been collected at sea (McDowall et al., 

 1975), as have a few, usually pre-migratory Retropinna. The 

 presence of a pelagic-living, transparent, elongate, migratory 

 juvenile seems to be common to most species that are marine 

 or lacustrine at some slage— Galaxias. Retropinna. Prototroctes. 

 Aplochiton. This is likely to have little phylogenetic significance 

 but to relate more to their pelagic, oceanic habits. These small 

 fish resemble many other unrelated fish with pelagic juveniles. 

 The marine, pelagic phase is followed in all instances by a minor 

 metamorphosis on entry to fresh water. Principally this involves 

 rapid assumption of pigmentation and in some species a distinct 

 change in body form. Shrinkage is recorded in a few species. 



Identification of oceanic larvae and juveniles to family is 

 assisted by dorsal fin position and the early development of an 

 adipose fin in all but galaxiids. The elongate form with the vent 

 at about 75% of total length is helpful. Differences have been 

 recorded in pigment patterns between some of the diadromous 

 galaxiid juveniles although insufficiently to use as diagnostic 

 differences (McDowall and Eldon. 1980). Meristic differences 

 between species are of little value for specific identification ow- 

 ing to their wide ranges and latitudinal variability. Identification 

 remains a difficulty and improvement will depend on the capture 

 and examination of additional material. 



Fisheries Research Division, Ministry of Agriculture and 

 Fisheries, Christchurch, New Zealand. 



Osmeridae: Development and Relationships 

 M. E. Hearne 



OSMERIDAE, the true smelts, are a small family of northern 

 hemisphere salmoniform fishes. The family includes 2 

 subfamilies, 6 genera, 10 species, and 13 forms (monotypic and 

 subspecies). They have marine, anadromous or landlocked and 

 freshwater life histories in the Pacific, Arctic and Atlantic oceans 

 and their drainages (McAllister, 1963). These silvery tasty little 

 fishes are captured by both recreational and commercial pur- 

 suits along the open coast beaches and rivers during their spawn- 

 ing runs. 



Development 

 The smelts are highly selective spawners, choosing to spawn 

 on very specific sub-tidal areas, beaches and rivers. Some species 



spawn in the daytime, and some spawn at night. The eggs of 

 osmerids possess an adhesive membrane that attaches to sand 

 grains and plant material. This anchor membrane results from 

 the ruptunng of an outer "chorion" during spawning, which 

 turns out and onto the substrate. This adaptation for demersal 

 spawning is observed in all 10 species of osmerids (Hamanda, 

 1961; Thompson et al., 1936; Morris, 1951; McAllister, 1963; 

 Simonsen, 1978; DeLacy and Batts, 1963; Hearne, 1983). 



The first description of smelt development was made by Eh- 

 renbaum (1894) for the Elbe River smelt, Osmerus eperlans 

 illustrating embryological stages, yolk-sac larva, transforming 

 larva, and the juvenile. Up to now, the yolk-sac stage of many 

 of these species has been at least illustrated or photographed. 



