The seventh in a series on the Leptophlebiidae (Ephemeroptera) of New Caledonia, this papers treats three new genera(Paraluma, Oumas, and Amoa) and 12 new species. For Paraluma gen.n., the type species P. cancellata sp.n., P. triangularissp.n., P. gilva sp.n. and P. minuta sp.n. are described from male and female imagos and nymphs, P. pulla sp.n. from male imagosand nymphs, and P. maculata sp.n. from male and female imagos. For Amoa gen.n., the type species A. fronini sp.n., A. subsolanosp.n. and A. orthogonia sp.n. are described from male and female imagos and nymphs, A. cressonensis sp.n. from nymphsonly and A. hebes sp.n. from the male imago only. Oumas orbis gen.n. sp.n. is described from male and female imagos andnymphs.

In the south-west lagoon of New Caledonia, the first sexual maturity size is 45 mm for Annachlamys flabellata (Bernadi), 60 mm for Comptopallium radula (L.) and 50 mm for Mimachlamys gloriosa (Reeve). The global sex-ratio was not significantly different from 1:1 for C. radula unlike A. flabellata andM. gloriosa (1.3:1 for two species). The significantly greater mean size of females suggests a protandric sex reversal. The reproductive cycle was studied monthly for two years for M. gloriosa and one year for C. radula and A. flabellata, then weekly over periods of 12 months for M. gloriosa and 6 months for C. radula. Reproduction of the three species occurs throughout the year with a maximal activity during the warm season. M. gloriosa and C. radula are capable of spawning several times a month. Fluctuations of reproductive intensity are related to temperature and salinity fluctuations.

Factors influencing the spatial distribution of the bivalves Atactodea striata. Gafrarium tumidum and Anadara scapha were analysed on the south-west coast of New Caledonia, using a multivariate approach (correspondence analysis). A. striata is abundant on sandy beaches with a high coarse sand content. G. tumidum is preferentially distributed on substrates located close to the lower limit of neap tide and seems to be independent of sediment granulometry. A. scapha adults occur at lower bathymetric levels, with sediment composed of 40% medium, fine and very fine sand, and 30% very coarse and coarse sand. For this species, juvenile migration is suggested by the differential distribution of young and adults.

Different random samplings were used to assess the biomass of intertidal bivalves on two main biotopes of the south west coast of New Caledonia. Over the 46.5 km line of sandy beach, the total bivalve biomass is 4.3 ± 1.8 t and the mean biomass of Atactodea striata is about 3.2 ± 1.2 t. Over the 9.85 km2 sandy-muddy shore of the study area, bivalve stocks (1.050 ± 392 t) are dominated by Gafrarium tumidum and Anadara scapha; their mean biomasses are respectively 270 ± 132 t and 418 ± 308 t. This resource is expected to meet the demand of the domestic market through an artisanal fishery.