Observations on the abundance of anchovy eggs in the Gippsland Lakes were made. From these observations, the duration and extent of spawning were inferred. Ten stations along the main salinity gradient were sampled from November 1978 to March 1980. Egg densities ranged from 1 to 38 170 eggs per 100 m3, densities of over 1000 eggs per 100 m3 being recorded on 16 occasions. Larval densities were much lower, only five records being greater than 100 larvae per 100 m3. Spawning extended from October to March. Peak egg and larval densities occurred in January for the two spawning periods examined. Eggs were found from McLennans Strait to the Entrance, with a few also collected from Bass Strait. Limited spawning did occur in the La Trobe River and in Lake Wellington during the 1967-1968 drought, when salinities were considerably higher than normal. The mean 'bottom' to 'top' density ratio for eggs was 3.8 to 1, probably as a result of vertical differences in salinity. Eggs were collected over a temperature range of 14.8-24.2�C, although the main spawning occurred above 18�C. The observed range in salinity was 2.3-35.5, but egg numbers in water below 15.8 were very low.
Acute toxicity tests were carried out on the larvae of P. quadridentatus and 96-h LC50 values of 0.17, 0.49, and 1.23 mg/l were determined for copper, cadmium, and zinc respectively. Potency ratios of the three metals were as follows: Cu/Cd 3.1, Cu/Zn 7.2, and Cd/Zn 2.4. Larvae were found to be nine times more sensitive to zinc and at least 29 times more sensitive to cadmium than were adults. The larval 96-h LC50 values multiplied by an application factor of 0.01 (as recommended in Victorian water quality criteria) results in derived 'safe' concentrations, which in the case of copper and zinc are below the stated 'minimal risk concentrations' of 10 and 20 �g/I respectively. In view of the known greater sensitivity of larvae of many taxa to heavy metal toxicity, the validity of using the same application factor for both adult and larval stages is questioned.
Effects of food quality and quantity on certain fitness traits of G. pectrnatus were examined to develop methods of culture. Five generations were successfully reared on excess Isochrysis galbana, despite intense inbreeding. The effect of food quantity was tested using outcrossed offspring fed I. Galbana at four concentrations. Generation time (from hatching to egg) decreased from 43.2 days at 1 × 104 cells ml-1 (lowest concentration) to 19.6 days at 5 × 105 cells ml-1 (highest concentration). An increase occurred in female body length (0.88 to 1.01 mm) and egg number (21.2 to 51.3) with increasing food concentration, and the total number of adults produced per brood was significantly lower at 1 × 104 cells ml-1. Results on a Dunaliella tertiolecta diet were similar to those for I. Galbana at the one food concentration tested (1 × 105-2 × 105 cells ml-1); however, unlike I. galbana, D. tertiolecta did not sustain viable egg production and was therefore nutritionally inadequate for multiple generation culture. Larval mortality was high on diets of Tetraselmis chuii and Phaeodactylum tricornutum. Body lengths and egg numbers of cultured females fed I. Galbana were greater than those of the 'wild' parental females, thus indicating the suitability of the culture conditions.
Acute toxicity tests were carried out with three metals on the marine copepods Scutellidium sp., Paracalanus parvus and Acartia simplex. The resulting 24-h LC50 values showed that copper was the most toxic metal, with cadmium more toxic than zinc for two of the three species. Scutellidium sp. was more sensitive than P. parvus and A. simplex to all metals, LC50 values being 0.18, 0.66 and 1.09 mg/l for copper, cadmium and zinc respectively. No consistent trend in relative sensitivity was apparent for the other two species. The results were in general agreement with those for other marine copepods given by other workers. Some experimental problems in conducting toxicity tests with copepods are indicated. Application of the present LC50 data to existing water quality criteria produced unrealistic 'safe' concentrations in the case of copper. Such a finding illustrates the arbitrary nature of application factors and questions the usefulness of acute toxicity tests as the major tool for environmental protection.
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