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Bottom Fish Exploration


Andrey Dolgov at Bergen Museum
The biology of many deepwater fishes is still rather poorly known. Most earlier investigations concerned taxonomy and distribution, and were too often based on small samples. During the R/V “G.O.Sars” cruise in 2004 a high number of species was collected, and for many species the samples were substantial. This forms an improved basis for more advanced biological and ecological analyses.

By Andrey Dolgov (PINRO, Murmansk, RUSSIA)

During a two-month stay at the Institute of Marine Research and Bergen Museum recently frozen samples of deepwater demersal fishes from MAR-ECO areas were processed. The main attention was paid to the trophic ecology of these species, but the other biological data (length-weight relationships, sex, maturity etc.) were also recorded. Samples for future age reading (otoliths), and muscle tissue samples for analyses of DNA as well as fatty acids and stable isotopes were also taken.

A number of species from the family Alepocephalidae (Alepocephalus agassizi, A.productus, A.australis, Rouleina attrita,Bajacalifornia megalops, Narcetes stomias, Bathytroctes microlepis, Conocara murrayi) and Bean's sawtoothed eel (Serrivomer beanii) were investigated. Additionally some samples of Bathylagus euryops and Etmopterus princeps were analysed together with the German students Markus Busch and Esra Kellermanns.  In total 512 specimens of 11 fish species were worked up.

Rouleina attrira - mature male


Rouleina attrira - mature male

The stomach content analysis showed that there are rather big problems with prey species determination in Alepocephalids. Most stomachs (up to 90 %) contained only very digested food. The prey that could be identified (beaks of squids and some shrimp) were found in only very few stomachs. This discouraging result is surprising because many of the mesopelagic fishes caught in the same areas had stomach contents in rather good condition that could readily be identified. The observation of high fractions of unidentifiable contents

 in demersal fish stomachs may reflect that the species eat infrequently, or that they eat food which is digested rapidly, including during the rather long tows of the trawls used on the cruise in 2004.

The study and stay in Bergen were supported by the MAR-ECO project and by a grant to the Institute of Marine Research from the Norwegian Ministry of Foreign Affairs

Narcetes stomias - mature female with eggs
Narcetes stomias - mature female with eggs

Otolith of Narcetes stomias
Otolith of Narcetes stomias

Otolith of Alepocephalus productus
Otolith of Alepocephalus productus

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