Fish Spawning
The spawning period is the annual climax in the life of fish and provides a most interesting sight for the casual observer. In this introduction some basic information about fish reproduction must therefore be considered.
None of the European species is viviparous, i.e. the spawn is fertilized in the female body. All fish in European freshwaters spawn directly into the water. According to the spawning habitat and the substrate onto which the spawn is deposited, fish can be divided into several groups. The largest group is formed by the species which spawn in aquatic vegetation or flooded meadows and whose spawn adheres to such aquatic plants. They include the majority of the carp family, such as the carp, the common bream, usually the roach and the rudd and also the weatherfish, the carnivorous pike and a number of other fish. A similar type of spawning is made on the bare roots of water plants and on the lesser roots of undermined trees or on submerged branches, coniferous needles, etc.
A further group is formed by fish which spawn on submerged stones or a gravelly base. They include the asp, nase, orfe, chub, zahrte, barbel, sturgeon and many others. This group also includes those species which attach their spawn to stones, gravel or sand and then bury them so that they are not carried away by a strong current or endangered by predators.
Other fish, for example the ziege, which is the only r,epresentative of this group to be found in European freshwaters, have pelagic spawn, which are freely deposited into the water, where they float and are subsequently carried away by the current. A very unusual and danger-free location is chosen for its new generation by the bitterling, the smallest European fish. With the help of an ovipositor the female lays a relatively small quantity of spawn directly into the mantle cavity of the swan mussel. A more protected cradle is difficult to imagine.
Some fish species which lay a large number of eggs, such as the carp, the pike, the tench or the burbot, do not look after their offspring. The reason for this is that the tiny fish hatch from only a small percentage of the deposited spawn and hence only a few grow and reach maturity, but nevertheless it is still highly probable that from such a large number of eggs there will be some survivors. On the other hand, those species which produce only a small number of eggs, such as the mud minnow, the bitterling, the salmon and the grayling, must ensure the safety of their offspring. Therefore, they reproduce in a variety of hideouts or alternatively bury their spawn in the gravel and others construct a nest over which one or both parents stand guard.
The majority of fish live constantly in the places where they also spawn. However, some species travel a long distance to reach a suitable mating ground. These include the eel, the salmon, the sea trout, some herring and some members of the carp family, such as the nase and zahrte.
The spawning process of fish is a most interesting phenomenon to observe. The majority of European fish spawn when the water is pleasantly warm for man; it is however often unnecessary to be in the water to watch the spawning procedure, as fish can be easily observed in shallow waters from a small boat with a glass bottom. Fish are not shy during the breeding season and consequently are neither frightened by the boat nor by man himself should he mingle with them.
