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This page contains 2 species of Stickleback:

3-spined Stickleback

15-spined Stickleback

15-spined stickleback
A male 3-spined Stickleback showing the red belly used to attract the female and warn off other males.

3-Spined Stickleback ( Gasterosteus aculeatus ) - This small fish is 5-8 cm long and is quite distinctive with the three spines coming off in a line along the dorsal surface. The colour is an olive-green. They do not have scales but bone plates. The number of these plates can vary between different races and specially between those in freshwater and estuaries. The freshwater varieties have only 4 - 5 plates whilst those found in saline conditions have 20 -30 bony plates on the body flanks. There is also a smaller, 10-spined stickleback Pungitius pungitius .

This a freshwater fish which has adapted to live in brackish conditions. It can be found in ponds, slow-moving rivers and estuarine. Very wide distribution in Europe.

ECOLOGY: This stickleback is well able to cope with osmoregulation (regulating its water content). The estuarine variety has developed the 20 -30 bony plates on the body flanks as an adaptation to the salt. This allows them freedom to swim up saltmarsh creeks at high tide, out into seawater and back to freshwater without the problem of water concentrations. It feeds on small crustaceans (copepods, daphnia and ostracods). The male makes a nest on the bottom of the pond and attracts the female down to it with a zigzag dance. At this time he has a bright red belly, as much to mark out the territory against other males, as much as attracting the female. If receptive she lays here eggs in the nest. The male follows and deposits sperm on top of them. After the external fertilisation they eventually hatch into small fry which the male then looks after until they become too large to manage. It has tough spines on the back to protect it from be eaten by larger fish; As the predator tries to swallow them the stickleback raises the spines which get jammed in the throat. All the predator can do is spit them out. However, it does not always work as a predator like pike will be lightning fast!

15-spined stickleback

15-Spined Stickleback (Spinachia spinachia) - This little fish is quite impressive: long and narrow but very toughened with fifteen distinctive spines emerging from the dorsal surface. It grows to around 15 cm. and has a long snout.

Although found on the lower rocky seashore and in rock pools it is most abundant in river estuaries and brackish water. Throughout the UK.

ECOLOGY: The toughened body sides help to protect it from the problems of osmosis in the estuary, where water is likely to enter the body tissues. It feeds on small crustaceans. Like the 3-spined Stickleback the male makes a nest although this is amongst seaweed. It has tough spines on the back to protect it from being eaten by larger fish; they jam in the throat and a predator spits them out.










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