The brook trout
Salvelinus fontinalis Mitchill 1814
This colorful representative of the salmonids was imported to Europe from North America as early as 1884. It is therefore classified as a neozoa, alien animals that have entered a faunal area that was originally inaccessible to them through the involvement of humans. It is a very popular fish among anglers and is also valued as a food fish. However, natural reproduction is rare in Europe, so the species can only be preserved by stocking. Because even if it hardly reproduces naturally, the animals form sex products and the artificial reproduction largely corresponds to the methodology used with our brown trout.
The incentive to produce these fish yourself is due to the fact that it was not possible to obtain animals in the colorful appearance so typical of the brook trout, as it is often portrayed.
Why is that? The brook trout is usually used for edible fish production and not as stocking fish - which is a good thing. It simply has no place in open waters, since it hunts its prey in direct competition with the brown trout and occupies similar water structures, potentially displacing them as well. Further advantages compared to the brook trout are that brook trout hardly need shelter - as is unfortunately often the case with our straightened and therefore fast-flowing streams, as well as the better tolerance of acidic water - due to spruce monocultures.
So these fish don't belong in open water and are intended as food fish or for angling - most of them end up straight from the farm directly onto your plate. It is only to be expected that fish farmers have looked for a way to increase their yield, a way that does not necessarily serve the preservation of the natural species, its appearance and it has been found. The solution to being able to produce larger quantities faster is the "Alsässer-Saibling" or "Salvelinus alpinus x fontinalis", a hybrid that was probably first grown in Alsace. In this crossing, Arctic char (alpinus) is used on the female side and brook trout (fontinalis) on the male side. In the case of hybridization, animals are usually optically closer to the mother species - here the arctic char - hence the weaker markings and marbling. It is also often claimed that "Alsatians" are sterile and incapable of reproduction - that is simply wrong. Hybrids are not necessarily sterile, but natural reproduction is as unlikely as that of the parent animals.
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Finding parents with the desired appearance, from a reputable source, turned out to be as difficult as it was tedious. The breeding stock was built up from young fish so that they could get used to the conditions in the breeding facility. We obtained animals from private breeders and even transported them from Bavaria to the Eifel. It should take 4 years until the first eggs could be stripped. In the spring of 2021, the first brook trout eggs arrived in the hatchery. These were picked up from a breeder friend of ours when they were in the eye point stage and we were able to gain initial experience in rearing the larvae up to the seedling. At this point let's go into a little more detail. Breeding the local brook trout naturally has absolute priority - brook trout spawn earlier, however, so we only lay small numbers of eggs, because there must always be enough space for the farios. Therefore, the eggs were placed in the incubator, which has a high capacity and is just as well suited for the rather small char eggs.
An incubator offers various advantages over incubation in channels. The space requirement is very small with, in this case, 0.8 m² with a minimum water requirement of 2L/s and a capacity of up to 120,000 eggs. Another advantage is the possibility of separating the scrims according to trunks, each slot can be divided into up to 8 compartments. So can eggs in the eye point or too. Larval fish can be returned to their original waters.
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The average quantity of eggs in a brook trout rogner is 2,000 - 3,000 per kg of body weight. The eggs of our 4-year-old animals are approx. 3mm in diameter, they can be up to 5mm, so they are more than half smaller than those of the brown trout.
So here on the right in the picture the fertilized eggs in the ocular stage. At this stage, the eggs are largely insensitive to transport. You have to know that we handle the eggs won as little as possible during incubation. A transport is only unfertilized (roe and milk separated), here the fertilization takes place immediately after arrival in the incubator, shortly after the fertilization in a small time window and just after reaching the eye point. This is quite easy to recognize - the eyes of the larva are now so far developed that they can be seen through the membrane of the egg. For transport, the laid eggs are removed from the water, divided into compartments in an insulating container, which, similar to the incubator, are divided into shelves and then stacked.
It may sound wrong at first that the eggs are transported dry, but that is exactly what prevents the eggs from moving too much, they are "fixed" so to speak, because they are not insensitive to shocks and vibrations, which inevitably take place in the sloshing water. The bottom floor is left free and the top one is filled with ice. This defrosts during transport, and the water then drips through the individual floors, thus ensuring sufficient moisture and cooling before it collects again on the lowest level.
Arriving at the incubator, unfertilized eggs are then selected before they are placed in a slot in the incubator. This would have been possible in advance, but it would have been much more convenient to do it in the incubator. Since Salmonids usually multiply during the cold season, transport in this way does not pose a problem in terms of temperature. Depending on what reading you take, brook trout are given with 450 - 470 daily degrees. So let's assume an average of 460 TG at an average water temperature of 6°C, which results in a hatch around the 76th day. Our clutches had at 35-.40. Day reached the eye point, leaving almost 4 weeks time for a transport or 168 day degrees. You should always take this into account beforehand, because the temperature increases during the procedure and, depending on the duration, hatching can then possibly begin.
Afterwards, everyone carefully returns to the water. Here now first in a larger underflow box of a long-flow trough, everything unfertilized is now read out (no eye point recognizable = rejects). Then it goes over the counting plate to determine the exact amount, already in the incubator. From here the daily care begins, as if you had put them on yourself, until hatching. Since brook trout, at least in Europe, are very likely to come from farms, there are usually no problems to be expected in further rearing, which means above all the conversion to exogenous food. Always a critical point in rearing that cannot be missed, but with wild fish this process can often be fraught with problems.
Here are the hatched brook trout in the larval stage. They can best be described as the size of a pin - really very small and filigree. It is all the more astonishing when you imagine that such a tiny thing will become what you will see below. When the first brown trout were released into the wild in April, the char were able to move into a channel that had become free - still quite small but already moving much further in the direction of the fish.
From here on, however, the little ones develop quite quickly, with increasing feed size the more steadily and faster.
The three pictures above show the development quite well. On the right you can already see the characteristic juvenile stripes that are already forming on the flanks, the development of the fins and their reddening as well as the white fin rays. We would have liked to have followed and recorded the development of the small brook trout for longer, but unfortunately this was not possible. On July 14, 2021, the hatchery in Willwerath was damaged by the flood and the water supply was destroyed. Luckily the water in the facility was "only" knee high and all the remaining broodlings in the facility could still be evacuated as the water did not reach the pools.
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Parallel to incubation, we have been looking for year-old animals in order to enable earlier entry into breeding. By selecting animals from other sources and the bred ones, the aim is to create a gene pool that is as broad as possible. As mentioned at the beginning, we had found a company that breeds high-quality fish in Bavaria and was willing to provide us with a sufficient quantity.
For the transport of more than 600km we left in the middle of the night to arrive at the destination in the early morning. The trip took place at the end of March, so no temperature problems were to be expected. The transport trailer has the necessary oxygen system with EPDM air vents and an insulating container that protects the 600 liters of water from heating up during the journey.
Arriving at the breeding facility, our fish were already waiting in the tanks to be picked up. They were caught from the pond the day before, which significantly reduces the stress of transport, as the fish return to the water quite quickly when transferred to the transport container.
After adjusting the oxygen system the fish could be loaded and we made our way back to the Eifel. However, this took longer than the way there - every 45 minutes we took a break to check the oxygen saturation with the oximeter and make adjustments if necessary. The saturation was kept at an average of 95% over the entire route.
Back home, all the char survived the transport well and we could start adjusting. The water only warmed up by 1.5°C during the trip. A third of the water has now been drained from the tank and gradually filled up with water from the pond. In this way, the animals could get used to the water values in a gentle manner and then be moved.
What was left to do now was - wait. The fish had an average size of 15 cm and should have reached the 30 cm mark by the age of three. For this purpose, the feeding began with feed that has an increased carotene content. From 2mm up to 6mm grain. Char have a smaller mouth gap - therefore smaller grain sizes should always be chosen than with brown trout.
After the long wait, we were able to win the first brook trout eggs from our own fish at the end of 2022 and lay them in the hatchery. The animals have developed excellently in recent years, as can be seen in the following pictures.
