Laboratory observations on spawning and embryonic development of a blue-ringed octopus

The infratidal zonation of animals in a 35 m deep fjord-like South African estuary is described. The barnacle Balanus amphitrite Darwin and the bivalve Musculus virgiliae Barnard form the uppermost zone and extend to a depth of 9 m. The oyster Crassostrea margaritacea (Lam.) forms a zone between 1 and 3 m depth while the sponge Grantessa ramosa (Haeckel) occurs between 3 and 7 m. The tubiculous polychaete Mercierella enigmatica Fauvel is the only species found below 10 m, and attains a depth of 33 m. In the wet season (summer) the surface salinity dropped to 2 and temperatures rose to 24°C. In the dry season (winter) surface salinity rose to 24 and temperatures dropped to 16°C. Salinity and temperature of deep water (6 to 33 m) were more stable and varied only between 32.5 and 35 and between 19.6° and 20.5°C, respectively. In June, water below 12 m was 50 to 60% saturated with oxygen but this declined to less than 5% saturation in January.     

Factors influencing predation of Hyperoche medusarum (Hyperiida: Amphipoda) on larvae of the Pacific herring Clupea harengus pallasi

Predation of different-sized Hyperoche medusarum (Hyperiida: Amphipoda) on larvae of the Pacific herring Clupea harengus pallasi was studied in the laboratory. The attacking rate of H. medusarum was a function of herring larvae size as well as size of the predator, and varied from 0.15 to 0.95 larvae attacked h^-1 per hyperiid. In the range of 7.55 to 16.05 mm total larval length, vulnerability to predation was highest for 13.3 and 13.7 mm larvae. Large hyperiids swam faster and covered a wider area during searching and were more effective predators than small ones. Predation seemed to be influenced by light, and its intensity was dependent on the duration of previous food deprivation of the hyperiid.This study was sponsored by the International Bureau of the Gesellschaft für Kernenergiever-wertung in Schiffbau und Schiffahrt in connection with the German Canadian agreement on scientific and technical cooperation.