The ecology of galaxias vulgaris (pisces : salmoniformes : galaxiidae) in the river Glentui, Canterbury, New Zealand
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
The family Galaxiidae is considered to belong to the order Salmoniformes (Greenwood et al, 1965) and together with the families Aplochitonidae and Retropinnidae forms the suborder Galaxiodei. The family Salangidae was considered by Greenwood et al (loc. cit.) to belong to the Galaxioidei, though Weitzman (1967) and McDowall (1969b) have since indicated that it should be a group distinct from the other three families. The Galaxioidei form a compact southern temperate radiation related to and comparable with the northern temperate diadromous salmoniforms. The family Galaxiidae is widespread, with species occurring in Australia, New Zealand, South America and South Africa and also on many islands near these land masses (Stokell, 1953: Darlington, 1957: McDowall, 1970). The taxonomy of the Galaxiidae has been the subject of much confusion. However, the work of Stokell (1938, 1945, 1949, 1959) and McDowall (1967, 1969b, 1970, 1972) has greatly clarified the systematics of the New Zealand fauna. Thirteen species are now recognized in New Zealand (McDowall, 1970, 1972) and are divided into two genera, namely Galaxias with ten species and Neochanna with three species. Apart from Galaxias maculatus, which forms the basis of a commercial and sport fishery (see Hopkins and McDowall, 1970), little attention has been given to the ecology of galaxiids. Most freshwater fish studies in New Zealand have been concerned with the ecology of the introduced salmonids, particularly Salmo trutta, Salmo gairdneri and Oncorhynchus tshawytscha (see, for example, Phillipps, 1924: Philips, 1929; Parrot, 1932: Percival, 1932: Hobbs, 1937, 1940, 1948, 1953: Allen, 1951; Percival and Burnet, 1963; Lane, 1964; Burnet, 1968, 1969a, b; Hopkins, 1970; Hardy, 1972) which form the basis of a thriving sport fishery (Watkinson and Smith, 1972). As pointed out by McDowall (1968b), a number of galaxiids, particularly G. divergens, G .. vulgaris, G. paucispondylus, G. fasciatus and G. argenteus, do not seem to be compatible with the introduced salmonids and appear to be adversely affected by their presence, although the interactive mechanisms are not understood. To understand the interrelations between the native and introduced fish faunas, it is first necessary to have an understanding of the ecology of the native fish. This study was undertaken in order to provide such an understanding of one of the species considered by McDowall (1968b) to be incompatible with the introduced Salmonids, viz. Galaxias vulgaris. Galaxias vulgaris is restricted to the South Island of New Zealand and is found in most of the major river basins to the east of the Southern Alps and also in the Upper Buller River System on the west of the Alps. It is not usually found in streams entering lakes (Stokell, 1949; McDowall, 1970). It was first described by Stokell (1949) who also (Stokell, 1959) described Galaxias anomalus which has since been synonymized with G. vulgaris by McDowall (1970). It is a rather variable species, the variability being caused by its wide range and the fact that it is confined to freshwater and is therefore unable to disperse from one river system to another by marine routes. Gene flow is therefore restricted to population exchanges by means of stream capture and perhaps by unusual flood conditions, when waters of two or more river systems are temporarily confluent (McDowall, 1970). Galaxias vulgaris is found in the fast or broken water of rivers and streams, where it occurs beneath and between boulders. Benzie (1961 unpublished, 1968d) compared the life histories of G. vulgaris and G. maculatus, with special emphasis on embryology, growth rates and breeding cycles. The aims of the present study were: 1. To establish the basic population parameters of G. vulgaris in one locality. 2. To examine the stability and range of movement of the population. 3. To investigate the interrelations of G. vulgaris and cohabiting fish species, with a view to understanding the relationships between the native fish, particularly the Galaxiidae, and the introduced Salmonids, particularly S. trutta. The first part of this thesis is concerned with the age, growth and condition of G. vulgaris. Subsequent sections, in order, deal with breeding biology, home range and movement, food habits, feeding mechanisms, the relationship between dorsal brain pattern and ecology, and interspecific relationships.