Field guide training: Fish – Part 3

An essential knowledge about the different classes of animals is a must for each field guide. The following blog article provides you with further information about reproduction and growth of fish.

Rangerausbildung: Eine Schnorchlerin mit einem Schwarm Halfterfische

Among freshwater fish there are two very common types of reproduction:

  1. External fertilization is called ovuliparity. This means the female is laying her eggs and afterwards a male fertilizes them, from which the youngsters hatch.

  2. Internal fertilization is called oviparty, when the female sheds zygotes or developing embryos which have been fertilized inside the female fish.

Naturguide: Ein Walhai mit Sicht von oben auf den Ruecken

The nesting behaviour of freshwater fish is very diverse. Many species show a keen territorial behaviour which is often used by male fish to impress the females. The females are often looking for special locations where they can place their eggs and the male can fertilize them (e.g. plants, dead wood, crevice). Other species build a nest and look after it. This is not necessarily done by the female. There are species in which the male is responsible for the brood care, so that the female can mate with other fish after laying the eggs.

The growth of the juvenile fish is dependent on many different factors. The most important one is the water temperature. In general, it can be said, that the warmer the water the faster the fish grow. During the cooler seasons the growth is limited, but most fish grow – not like other mammals or birds – their whole life. Limiting factors can be lack of nutrition, age and predators.

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