APPENDIX 11
A NEW EEL TRAP DEVELOPED IN THE NETHERLANDS

by

Dr. C.L. Deelder
Rijksinstituut voor Visserijonderzoek
IJmuiden, Netherlands

In recent years a new device for catching eels has been developed in the Netherlands, which became remarkably popular in a short period of time.

The instrument may be described best as a baited eelpot: a narrow elongated box, 70 cm long and with a height and width of about 11 cm made from 1 cm thick wooden ballens, nailed together in a simple way. It is fitted with a sliding lid which can be removed in order to put the bait in to get the eels out. Both ends are left open and in this way a rectangular tube is formed. Each opening is fitted with a simple nylon funnel shaped inlet, which offers no resistance to the entry of eels, but prevents escape. Both nylon funnel inlets are kept stretched by a piece of string, connecting one to the other.

The eel boxes are fitted in addition with two iron bars, nailed to the bottom, which ensure that the box sinks to the bottom and remains there. With a piece of cord, of about 1 m, the boxes are attached to a rope 750 m in length, at a distance apart of 25 m. The ends of the main rope are marked with a buoy. The total length of gear of this type used depends upon the number of hands on board, but a crew of three may handle about 300 boxes, for which many kilometres of rope must be used.

Before placing the boxes in the water, a handful of bait is put into each and thereafter the lid is placed in position. The boxes stay in the water overnight and are hauled up again next morning. At the IJsselmeer the bait preferred is smelt. (Osmerus eperlanus L.) and, if available, fish-roe. Preliminary investigations about using artificial food, such as fishmeal, showed that this type of bait was rejected. Other baits, however, such as worms and old cheese are said to be suitable also.

The ability of the box to catch eels depends obviously on the smell of the bait attracting eels to it and upon there being little or no resistance to the eels wishing to enter through the nylon funnel. In addition, as the boxes are tube-like and furthermore are completely dark, they are attractive to the eels. To facilitate still further the entry of eels into these boxes, some fishermen nowadays provide the boxes with two additional openings in the sides of the box so that in all there are four openings (see Fig. 1).

A new box cannot be used straight away. First, it has to be kept in the water for several weeks, obviously to attain the specific smell of the water in which it will be fished. Some fishermen keep live eels for a while in new boxes and are convinced that in this way the attractiveness of the box to eels is speeded up.

Boxes made of waterproof playwood exhibit varying efficiency in the catch of eels. Some make good catches all the time, others do not. Presumably the differences experienced are due to the variations in the kinds of wood used in the manufacture of the plywood, and the water-soluble elements contained in each some of which must be repellent to eels. A study of this subject has recently been started.

It will be evident that the use of these eel box units provides important possibilities for the fishermen, e.g. easy handling with low labour costs. For this reason the long line eel fishery, formerly such an important item in the IJsselmeer eel fishery has been nearly abandoned and replaced by this method.

The catch returns from this box-fishing in the IJsselmeer are rapidly increasing and nowadays are impressive, as is demonstrated by the following table:

DISCUSSION:

v. Brandt thought that the distance between the valves was too short, and he considered that an eel might tend to escape backwards when his head met the end of the opposite valve and his tail had not yet cleared the valve through which it had entered.

Deelder assumed that the length of the trap could be adjusted to meet local conditions.

Vickers asked Deelder how the trap was baited, and referred to perforated plastic bags as being suitable means of keeping bait intact in a trap.

Deelder said he saw no objection to the use of such bags, but the standard practice in Holland was the use of loose bait in the trap.

Fig. 1