The biology of a landlocked form of the normally catadromous salmoniform fish Galaxias maculatus (Jenyns). I. Life cycle and origin

Abstract

In contrast to most other members of the family Galaxiidae which live and reproduce in fresh water, Galaxias maculatus, the common jollytail of Australia and "whitebait" of New Zealand, is normaIly catadromous throughout its range (south-eastern Australia, New Zealand, and southern South America). In some athalassic inland lakes on the volcanic plains of south-western Victoria, however, a number of populations apparently descended from this species have becomelandlocked. The life cycle of the forminhabiting one of these lakes (the "landlocked jollytail" of Lake Modewarre) may be briefly summarized as follows: Gonadal maturation in the adult fish, which live in the slightly saline landlocked lake, begins around March and is almost completed by about June. The final stage of maturation is not reached, however, until these fish migrate short distances up intermittent inflowing creeks when the latter begin to flow in late winter and spring (July-October). Spawning takes place when the creeks are swollen after heavy rain, the eggs being deposited amongst flooded vegetation in shallow areas of slow-flowing water along the creek banks. Many of the spent fish die after spawning. The eggs, which are stranded when the flood-waters subside, develop amongst the vegetation on the banks above the normal water level. After development is complete reimmersion by the first flood to cover them stimulates hatching. The normal developmental period is probably about 2 weeks, but in the absence of flooding hatching can be delayed up to at least a month after fertilization. The newly hatched larvae are washed downstream into the lake where they feed and grow to maturity. They migrate upstream to spawn in the following late winter-early spring season at an age of approximately 1 year. The fish grow to about 9 cm in their first year, 14 cm in their second, and 17 cm in their third year. The average size of the females is greater than that of the males. The general features of the life history of this landlocked form are compared and contrasted with those of the stream-dwelling species G. maculatus and a number of other salmoniform fishes. The geological origin of the complex of lakes in south-western Victoria inhabited by landlocked galaxiid populations is discussed, and an hypothesis concerning the origin of the Lake Modewarre form from an ancestral population of G. maculatus in the Barwon-Leigh River system is advanced.

Spatial and temporal distribution of landlockedGalaxias maculatusandGalaxias platei(Pisces: Galaxiidae) in a lake in the South American Andes

“…McDowall et al (1994) found similar durations for the first life stages when they found that G. maculatus lived at sea (free embryo and larval periods) for 103-202 days. The different adult, egg, and free embryo size of landlocked (Pollard 1971;Cussac et al 1992;Cervellini et al 1993) and diadromous populations (Benzie 1968) and probably slower larval growth rate in fresh water could be partly attributed to the scarce food resources available in oligotrophic lakes. Particularly, low food availability in the limnetic zone may be the cause of the smaller maximum metamorphic size in landlocked populations (28 mm SL), as compared with diadromous populations (>35 mm SL, McDowall et al 1994).…”

“…Then, as they develop into juveniles, pigmentation develops rapidly, head length increases, and a pouch-like stomach develops (McDowall 1968). Larvae of landlocked G. maculatus forms are smaller than their marine counterparts (Ringuelet et al 1967;Benzie 1968;McDowall 1968McDowall , 1971Pollard 1971;Campos 1974;Cussac et al 1992;Cervellini et al 1993). In the Andes, their ontogenetic habitat shifts have only been studied in a very small, shallow lake (6 ha surface area, 3 m max.…”

Early development of the endangered Oxleyan pygmy perchNannoperca oxleyanaWhitley (Percichthyidae)

“…and the two freshwater Macquaria species (2.5-4.2 mm) (Shipway 1949;Lake 1967;Llewellyn 1974;Cadwallader and Rogan 1977;Pen and Potter 1990;Harris and Rowland 1996;Neira et al 1998;Morgan and Beatty 2000;Pusey et al 2004;Trnski et al 2005 Throughout its distributional range, N. oxleyana is known to co-occur with 16 species of fishes belonging to the families Eleotridae, Melanotaeniidae, Pseudomugilidae, Galaxiidae, Ambassidae, Plotosidae, Percichthyidae, Anguillidae, and Poeciliidae (Arthington and Marshall 1993;Arthington 1996;Knight 2000, in press). Of these, the two anguillids spawn in the deep ocean (Allen et al 2002), the poeciliid Gambusia holbrooki is viviparous (live bearers) (Milton and Arthington 1983), Galaxias maculatus spawns eggs that develop out of water on moist, riparian vegetation (Pollard 1971;Allen et al 2002), and the percichthyid Macquaria novemaculeata is catadromous, breeding in estuarine areas in winter (Harris 1986;Trnski et al 2005). Eggs of N. oxleyana can be distinguished from those of the remaining sympatric species through a combination of egg shape, size and the absence of filaments (Table 4).…”

Producción de larvas de peces: Innovación y avances en la nutrición para contribuir al mejoramiento y escalamiento de los cultivos

“…Se caracteriza por poseer poblaciones lacustres y diadrómicas, las primeras viven en los lagos interiores con o sin conexión con el mar y realizan su reproducción en los mismos lagos, como lo han demostrado Pollard (1971) y Campos (1979. De la población que más conocimiento biológico existe es de las estuarinas, en las que su ciclo de vida es ampliamente conocido (Figura 3), principalmente en Nueva Zelanda y Chile.…”

“…El tamaño del pez es pequeño, la longitud promedio de un adulto es de 7-8cm, carece de escamas y habita aguas límnicas y estuarinas. Las poblaciones lacustres sin conexión con el mar completan su ciclo de vida en el propio lago (Pollard, 1971). Las poblaciones estuarinas, cuyo ciclo de vida es ampliamente conocido en Chile y Nueva Zelanda, los reproductores que habitan aguas limnéticas como ríos y arroyos, migran hacia el estuario donde desovan luego, la larva va al mar y regresa al río como post-larva cristalina.…”