Cephalopods from the mid-Atlantic Ridge

Meso- and bathypelagic cephalopods sampled by large midwater trawls along the Biscay-Azores Ridge and the mid-Atlantic Ridge north of the Azores

By: Cornelia Warneke-Cremer

Biozentrum Grindel und Zoologisches Museum, Martin-Luther-King-Platz 3, 20146 Hamburg
email:  cornelia.warneke-cremer@uni-hamburg.de

 

Fig. 1: Abraliopsis morisii*

Fig. 2: Histioteuthis sp.*

In June 1982 FRV Walther Herwig II, leg WH 52/2,  focussed  on the exploration of the species composition and distribution patterns of the bathy- and  benthopelagic fish fauna along the Biscay-Azores Ridge and the mid-Atlantic Ridge (MAR) north of the Azores. For the first time, sampling in this area was conducted with large commercial fishing nets (Engel Midwater Trawl MT 1600, net opening 600 m²⁾ ) at  depths between 250 m and 3200 m. Most of the pelagic hauls went deeper than 800 m attaining the scattered echo layer or going below this layer. Bottom trawls (BT 140’) were also used but each trawling resulted in damaged or lost nets because of the rocky bottom. 

In total, 675 cephalopods were sampled from the by-catches with the EMT 1600. These specimens belong to 13 families and more than 25 species were identified. Size analyses based on morphometric measurements and the interpretation of meristic characters are additional  results of the research work. The dominant cephalopod families in the region are the Cranchiidae and Histioteuthidae. Besides the studies on abundance, distribution patterns are related to different biotic and abiotic parameters, including hydrographic aspects.  A main topic will be the comparison of the results with a similar cephalopod collection sampled in the summer of  2004 on RV G.O. Sars along the MAR.

The analysed cephalopods were fixed and stored in the Zoological Museum of the University of Hamburg. They have been added to the collection of around 8000 other cephalopod individuals collected from all world oceans by the German research vessels Anton Dohrn, Walther Herwig I – III,  Meteor, Polarstern, Sonne and Weser. The oldest cephalopods in the museum collection were collected by  Goddefroy in the 19^th century. Most of the cephalopods were sampled with the FRVs Walther Herwig I – III in the Atlantic in the years 1960 – 1980.  The Zoological Museum in Hamburg accommodates an unique and significant collection of neretic and oceanic cephalopods of the South Atlantic.

		Fig. 5: FRV Walther Herwig II  (Johann Heinrich) von Thünen-Institut, Hamburg
Fig. 3: Bathyteuthis abyssicola*	Fig. 4: Mastigoteuthis flammea*