One of the elements in common among eel scientists throughout Europe is the supposed spawning stock. During this meeting results have been presented shedding some light on this commonality. In order to enhance and facilitate further studies, we have to coordinate our work and cooperate in research that no single member country can achieve on its own. What follows is a proposal for a cooperative research programme on recruitment of glasseels.
We are advocating a cooperative programme within the limits of national research programmes and therefore initially we are not looking for international funding. International fund-raising will be much easier when national workers have made a start of their own, and when preliminary results show the usefulness of the programme. International funding would then be sought to extend the ongoing research.
The study will cover both the spatial and temporal aspect of glasseels which will require to be based on samples. Therefore the first priority of the current proposal is to organize a well planned sampling programme. A well planned sampling programme will serve to achieve the following objectives:
- reading of ages of the immigrating glasseels
- identifying spatial and temporal distribution patterns, including possible spatial diversity
- possible genetic identification by DNA sequencing
- compilation of a bank of well-preserved glasseels from the whole distribution area as reference material for future investigations
Other goals may be identified during these activities.
It is proposed to use standardized sampling procedure. What follows may not be an ideal sampling scheme but a compromise between what is desirable and what is achievable in Europe.
Spatial: Glasseels to be collected at the following localities:
| 1. | Norway | 1 locality |
| 2. | Denmark/Sweden | 1 locality representative for the Baltic |
| 3. | Denmark/Germany | 1 locality |
| 4. | Netherlands | 1 locality (Den Oever) |
| 5. | Belgium | 1 locality (Yser) |
| 6. | England | 2 localities (Severn, Thames) |
| 7. | Scotland | 2 localities (East, West) |
| 8. | Ireland | 2 localities (North, South) |
| 9. | France | 3 localities (Manche, Loire/Vilaine, Adour) |
| 10. | Spain | 1 locality (North) |
| 11. | Portugal | 2 localities (North, South) |
| 12. | Morocco | 1 locality |
| 13. | Italy | 1 locality |
| 14. | Greece | 1 locality |
| 15. | Egypt | 1 locality |
The Mediterranean localities are aleady covered by a programme within the CIESM framework.
The number of localities per country should be considered as the minimum necessary for a detailed picture of the spatial component of the inshore migration of glasseels. Participants should be encouraged to sample more localities.
Temporal: Fishing for glasseels has to be done each month, if possible on the first day, or as close to it as possible.
Measurements: Measurements have to be taken of abiotic, biotic and anthropogenic factors on each locality, one each sampling date.
Abiotic: These include temperature (seawater, freshwater), tidal phase.
Biotic: Several measurements have to be made of 200 (or as many as possible) glasseels per sampling month on each location.
- total length in mm, including fins, jaws
- body weight (in units of 10 mg) using a sieve to remove excess water
- stage of pigmentation following Elie et al., 1982.
Measurements should be taken as soon as possible after catch, but not later than two days afterwards. After measurements, the glasseels have to be preserved in 70% alcohol (pigmentation stages apart!) and stored in darkness.
All participants should record all measurements, if possible. However, if, for instance, staging the pigmentations is considered to be a stumbling block, one should not quit the sampling programme altogether. However, alteration of measurement procedures should be avoided since this would make data incomparable. Absence of data may be regrettable, but wrong data would spoil the final results.
Anthropogenic: Catch techniques are to be described and both catch (by numbers and/or weight) and effort, recorded. It is considered to be not essential that all participants use the same catching technique as long as the technique does not change in time. The programme relies on the experience of the researcher on the spot concerning the most efficient or convenient way to catch glasseels in a given locality.
It is suggested that this research programme has a coordinator who will be in charge of a steering group consisting of representatives from the eel distribution area. During the intersessional period, the steering group will be in charge of the organization of the programme and of the uniformity of the data bank of glasseels. At a later stage, the steering group may also formulate an application for international funding. The steering group could start its work almost immediately, i.e. in autumn 1991. Data should be made available to the steering group representatives before the next working party meeting tentatively planned for May 1993 and during that meeting the results should be discussed and continuation of the programme considered.
This proposal needs to be discussed also with colleagues working on the other side of the Atlantic. Although it is not the intention of the Working Group to cover both Atlantic species in one programme, pairing of programmes on both sides of the Atlantic is advisable.
Elie et al., 1982. Vie et Milieu 32 (3): 149–157.
