Les conditions écologiques de la mer de Chine Méridionale

This paper deals with a job of synthesis of previous notes written by the most passionate researchers at the Nhatrang Institute of Oceanography. Its purpose is to provide biologists with an idea on the physical and physico-chemical aspect of the South China Sea.

Biologie de Penaeus duorarum notialis en Côte d'Ivoire. 4 - Rélations entre la répartition et les conditions du milieu. Étude des variations du sex-ratio

The analysis of the geographic and bathymetric distribution of Penaeus duorarum and, particularly P. d. notialis off Côte d'Ivoire and in its whole distribution area leads to the definition of the adult ecological requirements (temperature, salinity, grain size and sediment composition, organic matter) and the importance of the thermocline in the bathmetric distribution. The population structure study shows: (1) variations of size with depth, (2) variations of sex ratio, with size, depth and seasons.

Geographic patterns in the lag of temperature response to insolation for El Niño vs. La Niña conditions [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): The most important control on the annual cycle of temperature is insolation, with secondary influences from terms related to moisture, yet direct statistical analysis of the moisture-driven modulations (such as El Niño) of the response of temperature to insolation are not available. We have examined one aspect of the relationship between insolation and the instrumental record of maximum daily temperature - the lag between the two - at 252 stations in the western United States.

The chaetognatha of the Eastropic Expedition, with notes as to their possible value as indicators of hydrographic conditions

ENGLISH: The purpose of this study was to investigate the possibility that certain species of Chaetognatha found in Eastern Tropical Pacific waters can serve as biological indicators of oceanographic features. "Indicator" organisms have been found useful in identifying water types, in tracing the pattern of current systems, and in tracing the origin of moving water masses. To be of use in this type of study, the organisms must be sufficiently abundant to be readily sampled, and easily identified to species; they must also, at least partially, fulfill the additional requisites listed and discussed by Sverdrup, Johnson, and Fleming (1942, pp. 866-867). Among several groups of organisms fulfilling these requirements are the Chaetognatha. Specimens of this group of animals occurred in large numbers in the plankton samples used for this study. The works of Thomson (1947), Fraser (1942), Ritter-Zahony (1911), and Sund (1959) were used for identification. SPANISH: El objetivo de este estudio ha sido el de investigar la posibilidad de utilizar ciertas especies de quetognatos encontrados en el Pacífico Oriental Tropical como indicadoras biológicas de características oceanográficas. Organismos "indicadores" fueron encontrados útiles para la identificación de tipos de agua, el trazado del régimen de los sistemas de corrientes y la determinación del origen de masas de agua en movimiento. Para servir a este tipo de estudios, los organismos deben ser lo suficientemente abundantes como para ser fácilmente muestreados e identificados hasta la especie; también deben satisfacer, por lo menos parcialmente, los requerimientos indicados y discutidos par Sverdrup, Johnson y Fleming (1942, pags. 866-867).

Relación entre la abundancia y estructura de la comunidad de peces y el régimen hidrológico, en lagunas de la alta cuenca del río Salado

This thesis explored the relationship between hydrological variability and associated changes in fish communities in the upper Salado river lakes (Pampa plain, Argentina). The sampling design included five sites along the river connected lakes being explored for fish, hydrological and environmental data during different hydrological conditions. The temporal dynamic of main environmental characteristics of these lakes show that hydrology largely regulates some of the most important factors influencing fish ecology. Changes in fish communities associated with this hydrological and environmental dynamic allow to speculate a first approach towards the functioning of the system as a whole. Following oscillation between droughts and floods, study lakes have shown significant changes on abundance of major fish species, as well as on their recruitment success, which finally leaded to marked changes in fish community structure. Interestingly, trophic structure of communities did not change as much. iOdontesthes bonariensis/i was more abundant during droughts and in saltier sites but also displayed an improvement in recruitment success during these harsh abiotic conditions. Conversely, the abundance of iParapimelodus valenciennis, Cyphocharax voga/i and iCyprinus carpio/i as well as its recruitment success, were largely favoured by lower water residence times and total salinity. This dichotomy is mainly based on different life history strategies of these species against flor and environmental variability and it support the existence of different functional groups among the fish species of upper Salado river lakes. iOligosarcus jenynsii/i did not showed as evident functional response. In conclusion, hydrological and environmental variability can be considered as one of the main factors regulating the functioning and structure of fish communities in these very shallow lowland river lakes of the Pampa plain. Following these results some implications for an eventual regulation of the river regime are discussed.

La pêche au chalut en Côte d'Ivoire. Maximum de rendement économique

This paper analyses the relations between effort and catch per unit effort of trawlers which worked in Côte d'Ivoire from Jan 1966 to Dec 1970. A fishing effort permitting to exploit fishery in the best rentability conditions is proposed.

Note sur les biomasses pélagiques évaluées par écho-intégration dans la zone équatoriale du Golfe de Guinée: premiers résultats

An Echo-Integration survey on the equator made during he GARP Atlantic Tropical Experiment indicated an important biomass in the layer 0/100m. The changes of that biomass have been connected to hydrological conditions. Measurements of target strength have been made, and the biggest schools have been measured.

Variabilité, circulation et chlorophylle dans la région du Dôme d'Angola en février-mars 1971

In February-March 1971 the hydrological conditions off Angola did not display the thermal dome mapped by Mazeika's averages (1967). Cold water cells observed are connected at the surface to a sinuous boundary between low-salinity coastal waters and high-salinity tropical oceanic waters. That boundary coincides rather regularly with an area where trades and SW winds alternate; photosynthesis growths rapidly in a thermoclinal layer that rises until 10 m of the surface but never outcrops. Below a poor and permanent homogeneous surface layer, chlorophyll concentrations show a distribution which is typical of divergence areas. Geostrophical and measured currents show off a transient process in horizontal and vertical movements, however the general curvature of the circulation is propitious to upwelling. Oxygen oversaturations of about 110%, suggest a moderate potential primary production which confirms slowness and alternation of movements. Also, the regular range of the various chemical and biological levels and moderate chlorophyll concentrations suggest an ecosystem where nutrients supply rapidly equilibrate phytoplankton consumption and not at all a 'phytoplankton bloom' area as that which exists in coastal upwelling. Values of Richardson's number show that instability becomes visible at the bottom of the euphotic layer. An evaluation of the vertical motion is inferred by the peculiar distribution and diurnal alternance of the winds shows that 'doming' structures may be sustained by local meteorological events.

Biologie de la phase lagunaire de Penaeus duorarum en Côte d'Ivoire: biométrie et croissance.

Principal biometric relations have been calculated for juvenile pink shrimp Penaeus duorarum, of Côte d'Ivoire lagoons. Growth has been studied from weekly sampling using Petersen's method and Von Bertalanffy's equation. Results are very similar to those obtained by the authors working in the same environmental conditions, especially concerning temperature.

Biomasses du phytoplancton et du zooplancton dans l'Atlantique tropical le long du méridien 1O' W (Résultats de la campagne Capricorne 7314)

The standing stock of chlorophyll, the quantities of copepods collected with a 30 liter Niskin bottle and the standing stock of zooplankton collected with a 'Bongo' net were measured from 0 to 200 m depth during a cruise along 10' W from 1' N to 12' S. These parameters are correlated to hydrological conditions measured simultaneously. 6 zonal areas have been delimited and described; the north equatorial convergence, the northern flow of the south equatorial counter-current, the trade winds drift, the south equatorial counter-current and the Benguela's drift.

Étude de la pollution bacterienne en lagune Ebrié

Details are presented of a bacteriological study in Ebrié Lagoon (Abidjan-Côte d'Ivoire) conducted during Oct-Dec 1974. Sampling sites are shown, and estimated and confirmed values for coliforms are given. The significance of the values obtained is briefly discussed, but further important factors, such as meteorological conditions and state of the sea, need clarification before definite conclusions can be made.