No abstract

The feeding ecology and seasonal pattern of occurrence of the 0 + year classes of the fish Aldrichetta forsteri, Cnidoglanis macrocephalus, Sillago bassensis, and Arripis georgianus were investigated to determine relationships between these economically important species and surf-zone accumulations of detached macrophytes along the coast of Western Australia. The main prey of A. forsteri, C. macrocephalus and A. georgjanus and the second most important prey of S. bassensis was the arnphipod Allorchestes cornpressa; the distribution of A. compressa was restricted to detached plants in the surf-zone. The arrival in winter, of 3 of the fish species on the open coast corresponded with the period of greatest deposition of detached plants in the nearshore zone, and there appeared to b e sufficient plant material, and associated amphipods, to support fish during summer. The large patches of vegatation in the surf-zone of sandy beaches support densities of A. compressa up to a mean of 110 g-' dry wt vegetation and provide an alternative feeding habitat for these benthic feeders, one of which is restricted to estuaries in other regions of Australia. It is also likely that this vegetation provides shelter from potential predators such a s diving birds and larger fish.

The distribution and relative abundance of the 0 + year classes of 16 commercially and recreationally important fish species from the inshore marine and estuarine waters of south-western Australia were investigated. The results of this study, together with data obtained from an investigation of the way in which juvenile fish used the Blackwood River estuary (Lenanton 1977), revealed that only three of these species in this region could be exclusively regarded as estuarine-dependent: two of the species entered the estuary for the entire year and the third was a seasonal migrant. The remaining 13 species all made use of at least 30% of the inshore marine environment sampled during the study, which was equivalent to the total area of nursery habitat available in the Blackwood River estuary. The main conclusion of this study is that for these species, the inshore marine environments of south-western Australia provide otherwise unavailable alternative nursery areas to those traditionally found in estuaries.

Scales and ovarian material were examined from Australian herring taken from the amateur line fishery in waters off Rottnest Island, W.A., over the period 28 March to 23 June 1973. The age-length distributions of a number of samples of both males and females are presented. Those fish sampled were predominantly 3+ years old. Resting or undeveloped ova were translucent and less than 0.1 mm in diameter. Developing ova were opaque and greater than 0.1 mm in diameter. Mature or ripe ova were translucent, slightly elliptical, unpigmented with a central oil globule, and were between 0.6 and 1.1 mm in diameter. Spawning was deduced to have occurred during early June. Most fish taken during the 1973 amateur fishery were in an immediate prespawning condition. Only one of the 516 females examined had ovaries containing ripe ova. The equation F = 298 L1.924 describes the relationship between estimated fecundity (F) and fish length (L).