Pacific Science Volume 32, Number 3, 1978

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Pacific Science is a quarterly publication devoted to the biological and physical sciences of the Pacific Region.

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    The Distribution, Abundance, Community Structure, and Primary Productivity of Macroorganisms from Two Central California Rocky Intertidal Habitats
    (University of Hawaii Press, 1978-07) Seapy, Roger R. ; Littler, Mark M.
    A wave-exposed sea stack and a protected boulder beach at Cayucos Point, California, were compared in terms of their intertidal biota on 17-18 February 1973. The major differences between the two sites appear to be due largely to differences in the shearing forces of waves and habitat structure. The mosaic of crevices, rivulets, and angled substrates in conjunction with a broad gradual slope and reduced wave action at the boulder beach habitat resulted in a predominance of macrophytes and a zonational pattern related to both horizontal location on the shore and vertical tidal level, while sessile macroinvertebrates with zonal patterns closely correlated to tidal height dominated the sea stack. Upward shifts in comparable vertical zones at the sea stack were clearly correlated with increased wetting higher on the shore due to waves and splash, in agreement with similar findings by other workers. The most abundant macrophytes at both sites were blue-green algae and Endocladia muricata,-althoughtheotherabundant.speciesweredifferentat-each site. Eive sessile macroinvertebrates (Mytilus californianus, Chthamalus fissus, C. dalli, Balanus (Balanus) glandula, and Pollicipes polymerus) dominated the sea stack, while only three sessile speci((s (Anthopleura elegantissima, C. fissus, and C. dalll) were prevalent on the boulder beach. Of the mobile macroinvertebrates, Tegulafunebralis was the most numerous species at the boulder beach whereas the limpets Acmaea (Collisella) scabra and A. (Collisella) digitalis occurred most abundantly on the sea stack. Although a greater number of taxa and higher species richness values were recorded at the boulder beach, the evenness index and Shannon's index indicated a higher diversity on the sea stack. At the boulder beach, 12 species assemblages were defined by cluster analysis, while only 6 such groups were identified on the sea stack. The boulder beach macrophytes contributed approximately one-third more to total community primary production than did those of the sea stack (169.7 versus 116.5 net mg C m-2 h-1), due mainly to the greater cover and concomitant production by Cyanophyta and fucalean Phaeophyta.
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    Contributions to the Knowledge of Hyperiid Amphipods of the Family Scinidae from near Hawaii, with a Description of a New Species, Scina hawaiensis
    (University of Hawaii Press, 1978-07) Brusca, Gary J.
    This report includes a key and description of nine species of the family Scinidae collected with midwater trawls from off the coast of Oahu, Hawaii. One new species, Scina hawaiensis, is described. Thirty-five additional species from the same samples are discussed by Brusca (1973). Notes are included on vertical distribution and migrations, and the known geographic distributions of the species are reported.
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    Population Characteristics and Food Resource Utilization of Conus in the Galapagos Islands
    (University of Hawaii Press, 1978-07) Nybakken, James
    Two large collections of Conus from the Galapagos Islands permitted the analysis of size, sex ratio, and food of 4 of the estimated 13 species of Conus present in the islands. The species investigated were C. diadema, C. lucidus, C. tiaratus, and C. nux. Significantly unequal sex ratios were found in the samples of C. diadema, C. lucidus, and C. tiaratus, but there was no indication of sexual dimorphism in shell sizes. Conus diadema was found to have the most catholic diet of the species, consuming mainly polychaetes of the family Terebellidae, but also sipunculids, mollusks, and eight other polychaete families. Very few food items were recovered from the guts of C. lucidus and most were polychaetes of the families Sabellariidae and Capitellidae. Conus tiaratus and C. nux were both found to feed primarily on polychaetes of the families Nereidae and Eunicidae. In both cases, the dominant species was Nereis jacksoni. Comparison of diets between cognate species in the Galapagos and the Indo-West Pacific indicated the Galapagos species consumed somewhat different prey species. Although there are significantly fewer Conus speCies peihabitafiri the Galapagos than in the Indo-West Pacific, fhere were no significant differences with respect to number of prey species consumed or prey species diversity between the areas. Thus, there was no evidence of decreased dietary specialization in the presence of fewer competing congeners.
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    General Ecology of Six Species of Hawaiian Cardinalfishes
    (University of Hawaii Press, 1978-07) Chave, E.H.
    Six species of cardinalfishes (Pisces: Apogonidae) are found together in shallow marine waters of Hawaii day and night. All six species remain in holes and caves during the day and emerge at night when they feed. The centers of abundance, ecological ranges, and other requirements of the six species differ during their life histories. During the day, Foa brachygramma is found in crevices or rubble on shallow, calm reef flats and unlike the other species may enter areas of low salinity and poor circulation. Young Foa are found under ledges in deeper water than are adults. Apogon menesemus is most abundant in clear, relatively deep water, especially where the substrate is almost completely covered by live coral. It lives at the back of holes or caves. Apogon erythrinus frequently inhabits small, dark holes in either dead coral heads or basalt cliff caves. Apogonichthys waikiki is most often found in pairs in large, widely spaced living coral heads. Apogon maculiferus adults are found under ledges and in caves at depths of over 20 meters. Young A. maculiferus aggregations are found in shallow water under ledges or at cave entrances. Apogon snyderi has the widest habitat distribution, although it is restricted to substrates with some sand. It lives in the middle of caves close to the floor, and under rubble, coral heads, or ledges. Each species reacts differently to increasing or decreasing light levels. Generally, a species' response to a given amount of light in the laboratory is similar in the field. In shallow water, adult Apogonichthys waikiki is not seen outside holes unless light intensity is less than 1.75 fc. Apogon erythrinus emerges or enters holes at about ±5 fc, A. menesemus at about 16 fc, and A. snyderi at about 88 fc. Adult Foa brachygramma leaves or enters cover at about 2400 fc, young Foa at about 700 fc. Adult Apogon maculiferus emerge and enter cover at about 100 fc and young A. maculiferus at about 2700 fc. Diurnal predators remove more individuals of species living in brighter light intensities; cavedwelling predators remove those living in lower light intensities. At night all species are opportunistic carnivores on zooplankton and benthic invertebrates, but there are differences in their foraging locations. Apogon snyderi and A. maculiferus forage mostly over light-colored substrates, but A. maculiferus feeds nearer dawn, higher in the water, in aggregations, and closer to large objects than does A. snyderi. Apogon erythrinus is found no more than 3 cm from hard substrates, vertical and horizontal. The other three species are found near large underwater objects. Foa brachygramma remains near the bottom when there is a current, and groups of fish rise in the water column on quiet nights when there is a half to full moon. Apogon menesemus is most often found in midwater and is often located in the shadow of large underwater objects on moonlit nights. Apogonichthys waikiki hovers near holes in the isolated coral heads where it is found diurnally. Nocturnal predators take individuals of all species except A. waikiki.
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