Back to the IMR: Putting Otoliths into Words
From the vessels, the otoliths travel as they are, as hard bony parts representing fish and they all end up at the IMR. Huse, as well as some of the other scientists at the FDG, has piles of the boxes filled with little brown envelopes and glass boxes in her office. All the otoliths collected by the RF and other arenas for data collection are stored at the IMR. Actually, a large amount has been collected by scientists since the early twentieth century, and they still store them, in case new methods can make it possible to get even more information from the otoliths (IMR 2010d).
We already know that the fish sampled by the RF are a part of the NEA cod stock assessment, represented by the otoliths. More specifically, the otoliths are a part of the VPA.
Now, I focus on how the otoliths are transformed from an object to a number, which is the fish’s age. In order to make this transformation from bony structure to number, the IMR has a lot of tools which make it possible to ‘read’ the otolith. So, in addition to checking the forms from the Offshore RF and punching the handwritten forms from the Coastal RF, the otoliths they send in must be ‘read’.
How the ‘reading’ is done is where we go next. I then turn to the forms filled in by the RF fishers, which I have mentioned several times – below I introduce them properly. The otoliths cannot travel alone; they have to come with ‘identification papers’ which include the S and T forms and the marked envelopes. This is important since the scientists must be able to trace each otolith back to the fish head it came from, and in order to make this possible, the RF fills in the forms provided by the IMR.
Reading Otoliths at the IMR
The ‘reading’ of the otoliths is an important and time consuming task at the IMR. The RF fishers contribute a constant flow of these to the FDG, especially the Offshore RF which
sends them in glass boxes and gets quotas in return31. From the FDG, they are redistributed to the IMR’s otolith readers. Here, all the otoliths are read and the fish’s age is determined and the coastal cod is distinguished from the NEA cod. It is obvious that this is considered an important task at the IMR. The large amount of otoliths is one clue and the extra payment the fishers get is another indication. In addition, reading each otolith is time consuming, and the otoliths are always an issue at the annual meetings. As described earlier, I can find the otoliths at the ICES as numbers.
Obviously then, somewhere during its voyage from the fish head to the ICES, it must have been transformed from a thing to something very different than an object: language. As numbers in a spreadsheet, the fish – represented by otoliths – can become combinable with all the other information that goes into the VPA. These are the numbers we can later find as age keys within the strict ICES framework.
From Bony Structures to Numbers: from Hardware to Software
At the IMR, the age readers are located in different departments, and at the FDG I see the piles of otoliths and I talk with the ‘readers’. Some have their offices at the FDG and others work elsewhere. Each fish species has different people reading them, since it is a very specialized task. For instance, ‘Ida’ ‘reads’ haddock, while ‘Kim’ ‘reads’ cod. Both of them
‘read’ otoliths from the the Coastal RF and the Offshore RF, which are stored in Huse and Borge’s offices. Maybe you have noticed that I refer to the otolith reading with quotation marks. This is because I find referring to the aging of fish as reading a bit misleading. In order to ‘read’ them, one needs a lot of training, a microscope and other tools. During my
fieldwork, I never learnt how to do the reading myself, but I have interviewed some of the FDG scientists about the process, and this is described below.
According to scientific theories on otolith reading, aging the fish is possible because the fish’s age and growth history are encoded in the microstructure of the organs (Bermejo 2007; Jones 2000). The growth pattern continues throughout the fish’s lifetime, creating growth pattern in the otoliths. Hence, according to theory it is possible to make a correlation between the number of opaque or translucent rings and fish age (Campana 2001). However, it is not possible just to ‘read’ the otoliths as they are when they are taken out from the fish’s head. Otoliths must be manipulated in order to make the rings visible. Even when the rings are made visible, an untrained eye cannot read them. The reader must undergo training in
31 This is further described in the following chapter.
order to interpret what he/she sees when looking at the otolith. This is difficult and only a handful of people are qualified to do it.
Just after Christmas in 2008, a course was arranged at the IMR for new age-readers.
Some of the scientists that participated at the course work at the FDG, and I was allowed to observe, take pictures and ask questions as the trainees practised. The course is important, because one needs to learn how to interpret what they see when they look at an otolith.
According to one of the age readers, those that have years of experience of ‘reading’ teach the new ones. Each species has one person who is responsible for the ‘reading’. The idea behind this is that if a mistake is made, or new science is developed, there is a systematic error, since it is the same person making the mistakes (personal communication, Stian). The otolith reader remains a trainee for a couple of years, and must check the reading with the ‘otolith
responsible’. Uncertainties are quite common, but as the ‘reader’ becomes more experienced, he/she seems to become more confident. The comments from the new trainees exemplify this.
For instance, soon after the 2008 course, Ida stated that
As time went by, their statements changed. When I visited Ida in her office in 2009, she showed me again how she ‘reads’ the otolith. With experience, the nature of her comments has changed, expressing certainty. For instance, she showed me an otolith under her microscope and stated:
Some of the species can be ‘read’ from photographs, like the red fish. The cod otolith, however, needs shadow from a special angle in order for someone to ‘read’ the lines. I have observed how Ida read the otoliths and this is described below, mixed together with the IMR’s guidelines for how to read otoliths.
First of all, Ida has to break or cut the otolith in two to see its lines: ‘Break the otolith It is difficult. It is difficult to be sure. You know, you have false lines sometimes … And it is so hard on your eyes!
This is a typical line, look!
in two at the centre with your fingers (half of the nucleus in each part)’ (IMR 2006: 34) Then, Ida places one half into something that resembles chewing gum so it remains still and in a good position for the light: ‘One half is stuck by its sharp end into plasticine or another material that is suitable for mounting. Observe the broken plane under the microscope with light coming in from the side horizontally.’ (IMR 2006: 34). Then, Ida uses a pencil to manipulate the shadow: ‘Use a stick (e.g. pencil) to shadow the surface (the broken plane).
The light will be refracted in the otolith towards the objective.’(IMR 2006: 34).
Ida invited me to try it myself, and it is quite difficult, just as Ida experienced when she first started. According to Ida, it becomes quite easy after a while. As I watched the otolith through the microscope, I could see the lines, which resemble the age-rings in trees (see Picture 19). However, it can be quite difficult to distinguish the lines from one another, and there are also false lines: if the line is not complete all the way around the otolith, it is false. The handbook states that ‘The hyaline zones (winter zones, narrow) will be light and the opaque zones (summer zones, wide) will be dark’ (IMR 2006: 34). Again, this becomes easier with experience, according to Kim and Ida. Concentration is vital in order to do the counting, and the age readers follow a set of rules for how they should be interpreted:
Count the number of summer zones to determine the age of the specimen (AGE). In the first year of spawning and the subsequent spawning years, the summer zones will be narrower. The number of these zones should be recorded (SPAWNING ZONES) and the age of fish at first spawning (SPAWNING AGE) (IMR 2006: 34).
When reading the cod otoliths, it is also necessary to give each a code according to what type it is according to how the reader interprets the otoliths, from one to three:
For cod one must decide the type of otolith (TYPE). (…) Legibility 1: Age determined with ordinary degree of certainty 2: Uncertain age determination 3: Illegible or missing otoliths (IMR 2006: 35).
When Ida ‘reads’ the otolith from one of the Coastal RF vessels, she notes all this information on the brown envelope, and later she punches it into the otolith files, the V forms (see figure 14 below). Some of the otolith readers also work with the RF and they both read and plot the otoliths, like Ida. Other IMR scientists get the information from an otolith reader and then
punch it into a V form. One of the FDG scientists explained the process: