FISHERY BULLETIN: VOL. 76. NO 2 



test organism for evaluating the toxic effect of 

 copper upon the early life history stages of marine 

 fish. The Pacific herring is a commercially impor- 

 tant fish that spawns along both eastern and w^est- 

 ern Pacific coasts (Eldridge and Kail 1973; Hart 

 1973). Herring spawn great numbers of demersal, 

 adhesive eggs on shallow intertidal substrates. 

 The egg is relatively large, 1.3 to 1.6 mm in diame- 

 ter, and is covered by a thick, three-layered, 

 opaque chorion (Blaxter and Holliday 1963). De- 

 velopment of the embryo is comparatively slow, 

 taking 7 to 9 days at 14 °C (Alderdice and Velsen 

 1971). The tough chorion permits easy collection 

 and handling, and the slow development of the 

 embryo allows observation time not available in 

 more rapidly developing species. 



Three bioassays were conducted to evaluate the 

 sensitivity of herring embryos and larvae to cop- 

 per. The first two assays were designed to evaluate 

 the sensitivity of embryos and larvae to continu- 

 ous copper exposure, while the third examined the 

 sensitivity of embryos to brief copper exposures. 

 Since the form of copper to which the herring em- 

 bryos and larvae were exposed may play a sig- 

 nificant role in the toxic response ( Pagenkopf et al. 

 1974), the partitioning of copper among the com- 

 ponents of the water in the bioassay system was 

 also determined. 



MATERIALS AND METHODS 



Collection and Handling of Test Organisms 



Intertidal collections of Pacific herring eggs 

 were made along the shore of Belvedere Island and 

 the Tiburon Peninsula, San Francisco Bay, Calif. 

 The eggs were collected directly into a 15-gal, in- 

 sulated ice chest containing aerated seawater 

 from the egg collection site and were transported 

 to the laboratory within 2 h after collection. The 

 water temperature at the collection site was 

 11.0°-11.5°C and upon arrival at the laboratory 

 the temperature of the water increased to no more 

 than 13.5°C. Only eggs deposited in single layers 

 onFucus si).,Laminaria sp., or Gracilaria sp. were 

 chosen for testing. Before placing the eggs into 

 exposure chambers, they were removed from the 

 seaweed by bending the frond and then gently 

 brushing them with a finger into a sorting dish 

 containing seawater kept at 12°C. The eggs were 

 examined with a microscope at 20 x; only viable 

 embryos at the same stage of development were 

 chosen. No more than 51 embryos were placed in 



any exposure chamber. All transfers of embryos or 

 larvae were carried out with a large-bore, polished 

 glass pipette. 



Embryos at two different stages of development 

 were used for the tests. The age of the earlier stage 

 embryos, collected 7 February 1975, was esti- 

 mated to be 12 h after fertilization since they were 

 undergoing epiboly (Ahlstrom's stage IV 

 ( Ahlstrom 1943)). These embryos were exposed to 

 copper continuously, each of seven groups being 

 exposed to a different copper concentration. The 

 age of the later stage embryos, collected 26 Feb- 

 ruary 1975, was estimated to be 48 to 50 h after 

 fertilization (Ahlstrom's stage IX). These embryos 

 were divided into four groups. Three groups were 

 exposed for 36 h to the same copper concentration 

 but during different developmental stages. The 

 fourth group was maintained in flowing seawater 

 from the time of collection to within 1 h after 

 hatching, and then continuously exposed to differ- 

 ent copper concentrations as larvae. 



Bioassay System 



The organisms were exposed to copper in 5-1 

 clear plastic bowls (Figure 1). The exposure solu- 

 tion was introduced into each chamber by gravity 

 flow from a mixing chamber into which seawater, 

 at a rate of 11 ml/min, and copper chloride solu- 

 tion, pH 3, at a rate of 1 ml/h, were pumped con- 

 tinuously. Approximately 17 h was required for 

 replacement of 90'7f of the water in the chamber. 

 The height of water in the exposure chambers was 

 maintained by a constant-level out-flow siphon. 

 The diameter of the mouth of the out-flow siphon 



Seawate 



Copper 



Plastic 



mixing 



chamber 



Outflow siphon 



Clear plastic cover 



Clear plastic o o 

 ^exposure chamber °^ 



Figure 1 . — Diagram of the exposure chamber and flow- through 

 dehvery system used to expose Pacific herring embryos and 

 larvae to copper. 



348 



