of ETP vs CO ichthyoplankton (Table I) can be juvenile and adult stages relative to large scale related to overall higher primary productivity hydrographic and ...
Unesco technical papers in marine science 49
Pelagic biogeography Proceedings of an international conference The Netherlands 29 May-5 June 1985 Edited by: AC. Pierrot-Bults S. van der Spoel B.J. Zahuranec R.K. Johnson
ICoPB
Sponsored by: United Nations Educational, Scientific and Cultural Organization International Association for Biological Oceanography Netherlands Ministry of Education and Science Royal Netherlands Academy of Sciences National Science Foundation, U.S.A Office of Naval Research, U.S.A Netherlands Council for Sea Research Amsterdam University Society
408 ANNIVERSAIRE
40th ANNIVERSARY
Unesco 1986
ISSN 0503-4299 Published in 1986 by the United Nations Educational, Scientific and Cultural Organization, Place de Fontenoy, 75700 Paris. Printed in Unesco's workshops.
Reproduction authorized, providing that appropriate mention is made of Unesco Technical Papers in Marine Science and voucher copies are sent to the Division of Marine Sciences.
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IMPORTANCE OF VERTICAL DISTRIBUTION STUDIES IN BIOGEOGRAPHIC UNDERSTANDING: EASTERN TROPICAL PACIFIC VS. NORTH PACIFIC CENTRAL GYRE ICHTHYOPLANKTONASSEMBLAGES VALERIE J. LOEB Moss Landing Marine Laboratories. U.S.A.
RESULTS
INTRODUCTION Biogel)Jraphic studies of mesopelagic fishes traditionally have been based on distributions of juvenile and adult stages relative to large scale hydrographic and biological features (e.g., water masses and productivity levels). Enhanced understanding of factors possibly affecting the composition and structure of fish assemblages within different zoogeographic regions might result from an examination of both larval and adult stages relative to finer scale distributions of physical and biological conditions. As an example are the results of a comparative study of 0-1 OOm ichthyoplankton assemblages sampled by replicated 25m depth stratified bon~ tows at 28 N 155 W in the North Pacific central gyre (C6) and near 13 N and 130 W in the Eastern Tropical Pacific (ETP) during late summer (Loeb & Nichols, 1984). 6
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Doubled estimated abundance and lower diversity of ETP vs CO ichthyoplankton (Table I) can be
related to overall higher primary productivity and hydrographic complexity and variability of the ETP ecosystem relative to the CO. Despite similar mixed layer temperatures and depths (ca. 26'C, 40m) the assemblages had significantly different (KolmOlJ)rov-Smirnov test, P90~ of total larvae in the two areas, however, both families had significantly deeper distributions in the ETP than
Table I. Comparisons of ichthyoplankton collected in nighttime stratified bongo samples in the North Pacific central gyre and eastern tropical Pacific during late summer. Mixed layer temperature (ca. 26'C) and depth (ca. 40m) was similar in both cases. EASTERN TROPICAL PACIFIC
