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MAR-ECO B.Sci. STUDENTS AT THE AALESUND UNIVERSITY COLLEGE, NORWAY

Supervised by MAR-ECO scientists Anne Stene and Inge Fossen, a group of bachelor students in the mid-Norway port Aalesund are analysing samples from the 2004 expedition aboard the longliner MS Loran.  The longliner worked alongside the RV G.O.Sars for three weeks and sampled a wide range of deepwater bottom-living fishes.

MAR-ECO Students
Susana de la Frontera an exchange student from Cadiz, Spain, Ingrid S. Stadsnes,  Kaja D. Andersen, Margrethe Emblemsvåg and May Siri Stene
B.Sci. students at Ålesund University College

Topic
analysis of biological material to learn more about the life history adaptations of the abyssal grenadier

The Abyssal Grenadier and its realitives

The exchange-student Susana de la Frontera from Cadiz, Spain, is one of a group of students who works on samples of the Abyssal Grenadier Coryphaenoides armatus. Other members of the group are Ingrid S. Stadsnes,  Kaja D. Andersen, Margrethe Emblemsvåg and May Siri Stene.

The aim of this study is to analyse material that can contribute to a better understanding of life history adaptations of the abyssal grenadier; a species with circumglobal distribution in the deepest troughs and ocean basins.

Susana’s task is to integrate results from the entire group. Ingrid and Kaja’s aim is to estimate the age of individual grenadiers using otoliths, or earstones. All bony fishes have a hard part in their inner ear formed from aragonite (calcium carbonate). The otolith grows with the fish, and has so-called growth zones that can be counted.

Counting, counting and recounting…

In many fishes, a full double growth zone is formed annually. Each zone consists of a more or less transparent ring reflecting slow growth, and an opaque wide ring usually formed in the summer growing season. Ingrid and Kaja counted the opaque zones to determine the age of individual fish, assuming the growth zones were actually formed annually.

While working with 200 photos of otoliths, the young researchers realised that counting otoliths is not always straightforward.

The structures are sometimes unclear, and difficult to count consistently. They counted separately, compared results and counted again the mismatching results. But it seems likely that the age range is 10-15 years.

Following the age determination, Ingrid and Kaja plotted individual fish length at different ages to study growth. They found that the females grew faster than the males after about 6 opaque zones, and that the females also grow larger.

Russian caviar does not seem so tempting now!

Margrethe (shown in photo, left) and May Siri have been examining female gonads (ovaries) from three closely related grenadiers;

Coryphaenoides armatus (Abyssal grenadier), Coryphaenoides rupestris (Roundnose grenadier) and Macrourus berglax (Onion-eyed or roughhead grenadier).

They have estimated the total number of eggs by counting the number of eggs in a small sub-sample of the gonad. 

To measure the homogeneity, they checked whether the eggs were the same size on the top, bottom and middle of each gonad.

To estimate how many eggs a female is likely to spawn in a given year, they counted the number of mature eggs before the spawning season.

Links to previous articles about the sampling by the MS Loran.

The Loran is chartered

Cruise report

Some Loran results

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