Time of day was determined for spawning of several species of sciaenid fishes by examin~ng development stages of eggs collected in estuarine and near-shore plankton samples. Estuarine samples were taken at different times of day and night but newly spawned Cynoscion nebulosus and Bairdiella chrysoura eggs were taken only during a period from just before to 3 or 4 hours after sunset. Sclaenops ocellatus and Mentichirrhus sp. eggs from near-shore Gulf of Mexico samples, taken during the morning, all contained tail-bud stage embryos, indicating evening spawning in these species. It is proposed that evening spawning reduces predation on sciaenid eggs by allowing dispersal of eggs during the night when planktivores may be less active. Overnight dispersal reduced C, nebulosus egg density from 100 m-3 during evening spawning to 1 m-3 the next afternoon. Lower egg densities during the day would reduce egg mortality due to predation. Egg predation experiments showed that predation rates increased with increasing egg density but no difference was found in predation rates between trials run in light and total darkness.

Appendages and eggs of benthic marine crustacea are often populated with the characteristic filaments of the bacterium Leucothrix mucor. Planktonic crustacea and fish eggs free of L. mucor become infested when held in aquaria in the absence of antibiotics. Isolates from these organisms are grossly indistinguishable from isolates from algae. Although L. mucor is not a pathogen, it may be involved in high mortalities by causing pelagic eggs to sink below the surface and by interfering with the filtering apparatus of larval forms. Antibiotics that prevent development of L. mucor (and other microorganisms) reduce the mortality in developing eggs and larvae. Direct microscopic examination of 48 seaweeds from the lagoon at Majuro Atoll in the Marshall Islands for L. mucor indicated its presence on 81% of the samples. When 18 randomly chosen samples were put in enrichment culture, detection increased to 100%. These observations are at variance with a previous report that L. mucor is either absent or rare in warm waters.

The functional relation between the harpacticoid copepod Tisbe carolinensis and 4 algal strains was examined in the laboratory. T. carolinensis reared either in suspensions of the green alga Chlorella autotrophica (Strain 580) or the 2 blue-green algae Agmenellum quadruplicatum (Strain PR-6 ) and Anabaena sp. (Strain CA) showed marked differential mortalities between sexes, and had fecal production rates of < 0.2 ind-' h-'. T. carolinensisin these algal cultures produced smaller numbers of brood and fewer viable nauplii than those exposed to the pennate diatom Cylindrotheca sp. (Strain N-1) or a mixed diet of all 4 algae. T carolinensis fed actively on S t r a~n N -l and on the mixture, and fecal pellet production rates averaged > 1.2 ind-' h -' Under laboratory conditions (30 %, 24 "C) with Strain N -l , interclutch interval was estimated to be 4 to 4.5 d , of w h~c h 24 to 33 h was required for oviposition and 3 d for embryonic development. Successful f e e d~n g and reproduction on Strain N -l and on algal mixture may be associated with larger particle size and somewhat higher nutritional value (i.e. protein and l~p i d content) of the diatom. This study emphasizes the importance to the copepods of algal type, cell size, and algal protein, carbohydrate, and lipid content, and suggests how these factors may combine to affect T. carolinensispopulation in the field via their effects init~ally on feeding activity and survival rate, and subsequently on e g g production and development

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