THE FISH THAT GIVES BIRTH THROUGH ITS MOUTH.

Photo by Jim Lavrakas - The Anchorage Daily News

The Esox lucius, also known as the Northen pike, is a type of fish commonly found in Britain (Ireland), Canada and the United States.

This discovery has baffled scientists all over the world as the northern pike is a relatively aggressive species, especially with regard to feeding. For example, when food sources are sparse, cannibalism develops, starting around five weeks in a small percentage of populations.

This cannibalism occurs when the ratio of predator to prey is two to one. One can expect this because when food is scarce, Northern pike fight for survival, such as turning on smaller pike to feed; this is seen in other species such as tiger salamanders. Usually, pike tend to feed on smaller fish, such as the banded killifish. However, when pike exceed 700 mm (28 in) long, they feed on larger fish.

E. lucius caught and released by an angler in lake Finzula, Croatia

Sources:

- National Geographic (Available at: https://nationalgeographic.com/animals/northern-pike);
- Wikipedia (Available at: https://en.wikipedia.org/archive/northern-pike);
- BBC News (Available at: https://www.bbc.co.uk/news/science-environment-873635);

Once fully developed, they can grow to a relatively large size: the average length is about 40–55 cm (16–22 in), with maximum recorded lengths of up to 150 cm (59 in) and published weights of 28.4 kg (63 lb). The IGFA currently recognizes a 25 kg (55 lb) pike caught by Lothar Louis in Lake on Grefeern, Germany, on 16 October 1986, as the all-tackle world-record northern pike.

Unlike most fish the Northen pike's reproductive system allows it to give birth through its mouth, this phenominon allows the creature to feed its young without exposing it to the dangers of the sea.