Identification and biogeography of early life stages of cephalopods of the Atlantic Ocean

• Main Author: Roelofs, Dimitry A.
• Format: Thesis
• Language: English
• Published: 2007
• Subjects: north atlantic current; North Atlantic; Subarctic
• Online Access: https://oceanrep.geomar.de/id/eprint/50685/; https://oceanrep.geomar.de/id/eprint/50685/1/Roelofs,DA,IDuBio.pdf

In the years 1980 to 1983 and 1992 to 1993 plankton and micronekton samples were collected by Rectangular Midwater Trawl (RMT 1 + 8) and open nets from the Atlantic Ocean (as part of the Amsterdam Mid North Atlantic Plankton Expedition). After preservation and sorting into animal groups, the members of the Cephalopoda were identified and a specimen list was made for each ocean with the objective to gain insight in the biogeography of larval squid with a special interest in seasonal differences, horizontal distribution, vertical dispersion, diumal vertical migration and the existence of faunal boundaries. The result is a total of 2788 specimens belonging to 31 families of the Class: Cephalopoda. The number of specimens and taxa was highest in the spring of 1980 and the most abundant families are the Cranchiidae and Pyrotethidae. Based on the three mayor currents (The northem and southem branch of the N orth Atlantic Current and the Canary Current), three areas can be distinguished. Of these areas the Subarctic Zone stands out most. Due to a strong current and the seasonal formation of a Sub Polar Front, the Subarctic waters are inhabited by few species, of which the Gonatidae are the most characteristic. The Subtropical Zone shows the highest diversity of cephalopods and almost no seasonal variation, while the Transitional zone is an intermediate between the Subartic Zone and the Subtropical Zone and shows strong seasonal fluctuations directly related to the width and strength ofthe southem branch of the North Atlantic Current. Most ofthe samples were taken from depths up to 500 meters and trawls were made at both day and night. The cephalopods have been caught mainly in the epipelagic and shallow mesopelagic layers. This might indicate a preference for shallow waters, especially during the night. Support for several Diumally Vertically Migrating species has been found. These animals are found deeper in the water column during the day to avoid predators and rise to the surface waters at night to feed. The ...