LETTERSUndercover. Many Alpheidae shrimps live deep in the reef and are impossible to collect nonlethally. Published by AAAS

Tropical transpacific fishes occur on both sides of the world's largest deep-water barrier to the migration of marine shore organisms, the 4,000-to 7,000-km-wide Eastern Pacific Barrier (EPB). They include 64 epipelagic oceanic species and 126 species of shore fishes known from both the tropical eastern Pacific (TEP) and the central and West Pacific. The broad distributions of 19 of 39 circumglobal transpacific species of shore fishes offer no clues to the origin of their TEP populations; TEP populations of another 19 with disjunct Pacific distributions may represent isthmian relicts that originated from New World populations separated by the closure of the Central American isthmus. Eighty species of transpacific shore fishes likely migrated eastward to the TEP, and 22 species of shore fishes (12 of them isthmian relicts) and one oceanic species likely migrated westward from the TEP. Transpacific species constitute~12% of the TEP's tropical shore fishes and 15-20% of shore fishes at islands on the western edge of the EPB. Eastward migrants constitute~7% of the TEP's shore-fish fauna, and a similar proportion of TEP endemics may be derived from recent eastward immigration. Representation of transpacific species in different elements of the TEP fauna relates strongly to adult pelagic dispersal ability-they constitute almost all the epipelagic oceanic species,~25% of the inshore pelagic species, but only 10% of the demersal shore fishes. Taxa that have multiple pelagic life-history stages are best represented among the transpacific species. Among demersal teleosts that have pelagic larvae, pelagic spawners are better represented than demersal spawners among transpacific species, perhaps because offshore larval development and longer pelagic larval durations provide the former with greater dispersal capabilities. There are strong phylogenetic effects on representation in the transpacific fauna: (1) elasmobranchs are proportionally better represented than teleosts, even teleosts with more pelagic life-history stages; (2) a pelagic juvenile stage with great dispersal potential allows tetraodontiforms that produce demersal or pelagic eggs to be well represented; and (3) various speciose central Pacific families with "adequate" larval dispersal characteristics lack transpacific species. El Niiios potentially enhance eastward migration by increasing eastward flow and halving transit times across the EPB. However, that effect may be offset by low productivity and high temperatures in those eastbound flows. There is little clear evidence of strongly increased migration across the EPB during El Niiios, including recent extreme events (1982-1983 and 1997-1998). During such events shore fishes in the TEP experience range expansions and become locally abun-

Ecology, sedimentology, and diagenesis of reefs 2. Application of uniformitarian thinking has lead to intensive studies of Recent reefs which provide the opportunity to observe progressive reef formation from initial growth to completely lithified and even partly altered reef rock. Field observations are being supplemented by laboratory experiments. Results, criteria, and concepts obtained in this way need to be tested with respect to their general application by regional comparison, and with respect to their validity in geologic history by comparing reefs of various ages. Work on fossil reefs, in addition, provides further questions to be answered.It is hoped that this symposium contributes to the understanding of reef formation and stimulates further studies.References DUNHAM, R.J.. Classification of carbonate rocks according to depositional texture. --Amer. ZusammenfassungDie rezenten Korallenriffstrukturen an der 5stliehen Pazifikkiiste yon Panam~t zeigen starkes Waebstum. Von den 20 vorhandenen Arten hermatypiseher Coelenteraten ge-h6ren 8 zu der Gattung Millepora, die erslanals im ostpazifischen Rattm beobaehtet

ABSTRACT1. Recent approaches to the planning of marine protected area (MPA) networks for biodiversity conservation often stress the need for a representative coverage of habitat types while aiming to minimize impacts on resource users. As typified by planning for the Australian South-east Marine Region, this strategy can be manipulated by political processes, with consequent biased siting of MPAs. Networks thus created frequently possess relatively low value for biodiversity conservation, despite significant costs in establishment and maintenance.2. Such biases can be minimized through application of the data-driven and species-based concept of key biodiversity areas (KBAs).3. By mapping locations of threatened species and populations that are highly aggregated in time or space, the KBA process allows marine sites of global biodiversity significance to be systematically identified as priority

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