Life cycle, growth and diet of Balston's pygmy perch in its natural habitat of acidic pools in south‐western Australia

Abstract

Nunnutlierinu hulsroni is found in a few acidic pools (pH 3.9-6.0) in the extreme south-western corner of Australia. Although many of these pools become dry during summer and early autumn, they are recolonized by fish from nearby pools that overflow during winter Hoods. N. hdstoni spawns at the end of its first year of life, when, on average, the males and females have reached 60 and 63 mni .r.L., respectively, and then usually die within the next few months. The largest fish, which was one of only three in its third year of life, measured 90 mm and weighed 7.3 g. The von Bertalanffy growth curve parameters for K and to were 71.2 mm, 1.69 and -0,078 for males and 82.6 mm, I .3 I and ~ 0.095 for females. Fecundity ranged from 550 to 1600. N . hulsro/7i spawns during the middle of winter, after heavy flooding and when water temperatures are at, or close to. their annual minima. This enables the larvae and young juveniles to capitalize on those aquatic organisms, especially Cladocera, which are very abundant amongst the flooded riparian begetation that surrounds the pools in winter and spring. Hence, the fish grow rapidly and attain an appreciable aiLe belhrc stinimei-, when the increases that occur in the densities of the larger carnivorous fish species, as a result of marked declines i n water levels, increases the chances of predation. By spring, when most N. hufsioni exceed 25 rnm T.L., the diet changes markedly to one that consists almost exclusively of terrestrial fauna. In contrast, three of the six co-occurring native species of teleost fecd on aquatic and terrestrial fauna throughout the year, while a further two feed only within the water column and the sixth feeds on benthic invertebrates. The pronounced shift in diet exhibited by N . hakioni as it increases in size, allied to dietary differences amongst the other six co-occurring species, reduces any potential for interspecific competition Tor food resources during the summer and autumn. when such resources are declining. I ' 1995 The Fichcries Society of the British Isles

Conservation implications of distinct genetic structuring in the endangered freshwater fish Nannoperca oxleyana (Percichthyidae)

“…Alternatively, as observed by Knight (2000) in the Richmond River coastal floodplain subcatchments, the distribution and abundance of N. oxleyana can be substantially reduced in dry months or years, through the desiccation of ephemeral habitats. A similar scenario has been documented for the Balston's pygmy perch Nannatherina balstoni Regan inhabiting the peat flats of south-western Australia (Morgan et al 1995).…”

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

“…The rate of ontogenesis of eggs and larvae documented in this study may therefore simply reflect the rearing conditions in the laboratory. However, the potentially confounding effects of artificial conditions were minimised by utilising water with physico-chemical properties similar to that of waters supporting wild populations, by adopting the average photoperiod and water temperatures experienced by wild populations during the breeding season, and by providing a diet of zooplankton species recorded in the diets of wild larvae, juvenile and adult pygmy perch (Pen and Potter 1991;Pen et al 1993;Arthington and Marshall 1993;Humphries 1995;Morgan et al 1995;Arthington 1996;Gill and Morgan 1998). Research into the age and growth of N. oxleyana in the wild may assist in assessing if development and growth rates in captivity differ from those of wild fish.…”

“…Although a number of studies have examined various aspects of the biology of pygmy perch, for example, habitat associations (Bond and Lake 2003;Knight and Arthington 2008), reproduction (Humphries 1995;Knight et al 2007), diet and growth (Pen and Potter 1991;Morgan et al 1995;Arthington 1996),…”

Threatened fishes of the world: Nannatherina balstoni Regan 1906 (Nannopercidae)

“…Dietary shift occurs at about 25 mm TL from aquatic invertebrates to almost exclusively terrestrial input (Morgan et al 1995(Morgan et al , 1998Gill and Morgan 1998). Reproduction: Matures at age one, at 60 mm TL.…”

“…Reproduction: Matures at age one, at 60 mm TL. Breeds during mid-winter when water levels are high and temperatures are near their minima (Morgan et al 1995). Breeds amongst flooded vegetation.…”