During a SCUBA survey on herring spawning beds on and near Fisherman's Bank (NAFO Div.4T) conducted in September 1985, divers observed a spawning bed with heavy egg depositions, whichfrequently reached thicknesses between 20 to 30 layers. Continuous egg carpets of this thicknessextended over an area of approximately 200 × 500 m. Most of the egg mass on this spawning bed wasin a state of deterioration, showing mass mortality and extended fungi coverage.

Egg samples taken from various layers showed that almost all eggs were fertilized. Live egg batches were incubated for further observation. Embryos were found to be in various developmental stages. The rate of development was obviously related to the position within the egg mass. Many embryos from the surface appeared to be normal. All eggs located below the second layer exhibited embryoswith various malformations.

Egg samples did not show any evidence of the presence of Ichtyophonus, a known fungal disease in herring. None of the isolates obtained are known to be pathogenic to fish eggs. The observed mass mortality of herring eggs on the spawning bed was mainly caused by spontaneous intensive mass spawning leading to an unusually dense packing of the deposited eggs and therefore not permitting sufficient separation for water exchange and oxygen supply.

Environmental factors accompanying such spontaneous mass spawning are not well understood.Vertical temperature profiles from nearby locations showed sudden sub-surface temperature changescoinciding with the time of spawning. Meteorological conditions indicated wind-related water displacement near the spawning bed. While no drastic change in temperature was observed near the surface, changes of about 8 °C occurred in one day, at 20 m depth. These events may have triggered the mass spawning in a restricted area, later resulting in heavy mortalities when embryos reached advanced developmental stages requiring substantial oxygen supplies.

Sixteen silver eels (Anguilla anguilla L.) were tagged with pressure-sensing ultrasonic transmitters and tracked for 1 to 152 hours, 12 in the western Mediterranean and 4, treated with pituitary extracts, in the Sargasso Sea. When released on the shelf of the Mediterranean near Gibraltar the eels preferred a course which led them continuously to deeper water. Four specimens released on the Morrocan shelf, reached depths of 350 m, continued to swim north or changed their earlier easterly course towards the north. Three eels in the Sargasso Sea showed progress in a southwesterly direction. No influence of tidal stream on the swimming course and speed is obvious except for one eel, released in the Straits of Gibraltar. In the Mediterranean, the eels exhibited conspicuous daily vertical migration downward during dusk and upward during dawn with a mean swimming depth of 196 m during darkness, 344 m during daylight. Depth preference during night probably varied with the phase of the moon. Maximum swimming depth near Gibraltar as well as in the Sargasso Sea was nearly 700 m. The eels in the Mediterranean swam at a mean speed of 0.3 m.s−1 and were slower than most eels tracked in northern waters. Differences in the speed and in the directed swimming in the course of the lunar or the solar day are visible.

Les stocks de clupéidés situés le long des côtes ouest-africaines vivent et se reproduisent dans des zones d'upwelling saisonnier ou permanent. Ce sont des milieux fluctuants où la productivité est très variable d'une zone et d'une saison à l'autre. Les principales nurseries sont distribuées de façon discontinue le long des côtes ouest-africaines et ne sont pas toujours situées dans les zones les plus productives. Les reproductions les plus intenses sont localisées là où le plateau continental s'élargit et où la côte s'incurve par rapport à la direction prépondérante des vents. Ces particularités topographiques, communes aux zones de reproduction, minimisent localement la dérive vers le large de la couche d'eau superficielle. En Côte-d'Ivoire et au Congo, l'activité reproductrice est maximale durant la saison d'upwelling. Le long de la façade atlantique, la reproduction est parfois décalée par rapport à l'upwelling, elle est maximale avant et/ou après la saison d'upwelling. Les périodes d'abondance duzooplancton n'étant pas toujours en phase avec l'upwelling, les saisons de reproduction semblent être décalées par rapport à l'upwelling afin d'offrir des conditions optimales pour le développement des larves. Un schéma théorique est proposé pour illustrer les stratégies spatio-temporelles de la reproduction suivant l'intensité de l'upwelling, en considérant deux facteurs limitants: la production planctonique et la stabilité du milieu. L'intensité des upwellings est variable d'une année à l'autre. Au Sénégalles stratégies de reproduction répondent à cette variabilité en modifiant le calendrier de la reproduction suivant l'intensité de l'upwelling. De nombreux faits ne valident pas le schéma théorique proposé. Ces écarts au modèle peuvent être perçus comme des facteurs de régulation potentiels face au caractère non prévisible de l'environnement. Dans une perspective évolutioniste, ces exemples illustrent l'adaptabilité des stratégies de reproduction.

Cette étude a pour objet le développement de la pêche artisanale dans un petit pays insulaire de Polynésie occidentale. La modernisation de la petite pêche et l'accès à la pêche au large contraignent les pêcheurs à une nouvelle gestion des moyens de production, de l'espace, du temps et de l'argent fondée sur des valeurs occidentales qui sont en contradiction avec l'environnement socio-culturel traditionnel. Des contraintes dues à un héritage ethno-historique ancestral constituent un frein au développement et à l'assimilation de nouveaux moyens de production. L'enquête a été menée au coursd'un séjour de deux mois aux îles Tonga en 1987, précédé de deux missions de chacune six mois en 1974 et 1983 consacrées à l'étude des techniques rituelles de pêche en les insérant dans une analyse globale de la société.

Specimens belonging to 20 species (7 families) of catfishes have been collected in French Guyana. The anatomy and histology of the male reproductive tracts have been studied. In the most primitivespecies (Helogeneidae, Ariidae) no seminal vesicle is present in the males. In the Pimelodidae,Loricariidae and Callichthyidae (and also in an african Bagridae), there is a progressive transition, going from anterior to posterior in the male tract, from testicular tissue towards round germ cell-free tubules and finally to seminal vesicular tissue. All these families produce round-headed spermatozoa and have external fertilization. The Auchenipteridae and Ageneiosidae are characterized by elongated sperm nuclei, internal fertilization with the aid of a gonopodium and sperm storage in the ovaries. In the Auchenipteridae there is a clear-cut distinction between testes and seminal vesicles. In the Ageneiosidae there is no seminal vesicle, but the dilated deferent duct displays a high secretory activity. Depending on the family and species, the seminal vesicles may carry out either one or both of the two main functions: secretion and sperm storage. In addition, in some species, sperm is also stored in one or two accessory pouches until fertilization. The trends that we have observed in the changes in the organization of the reproductive tracts are in agreement with the hypotheses proposed for catfish evolution from comparative anatomical data.

Males of Myleus ternetzi, at various maturation stages were netted in a French Guyana river. Testes were histologically and ultrastructurally analysed. Leydig cells were always present in large numbers. In mature or almost mature testes, they were characterized by a large spherical nucleus and an extensively developed smooth endoplasmic reticulum (SER) composed of very narrow tightly packed tubules. In regressed testes, most of the Leydig cells had a smaller nucleus with an irregular shape, a disorganized SER and the fine structure of the mitochondria was greatly affected. These changes would reflect different phases throughout a metabolic cycle in relation to spermatogenesis.

The skeletochronological analysis of pectoral spiny rays in the silurid Arius proops, collected during the "little summer of March", confirms the presence of a slow growth period during March and April in the rivers of French Guyana. Moreover, this study shows that the longevity of the species is short, 3 and a half years for the females and 3 years for the males, while their growth rate is relatively high, especially during the first half of their life.