How fish behave in the wild

Fish Behaviour in the wild

Fish’s behaviour is affected by the rythms of nature. Fish recognise dawn and dusk and behave appropriately. Fish also recognise the seasons and will mate at the correct time of year that is best suited for the hatching and growth of their young. Fish will go into hibernation at the onset of winter.

Most fish are active during the day and rest during the night. At the break of dawn the fish will be most hungry and active in search of food in the shallows for the first couple of hours of the morning. After they have had their fill of breakfast then they retire to safer, deeper and more reclusive spots in the lake or river.

Young fish tend to congregate in the shallows for 3 reasons

      1. Food is more abundant in the shallows

      2. The sun heats the shallows and fish grow faster in warmer water

      3. Large fish avoid the shallows

Young fish have dull colours such as grey,brown or green that makes them invisible on the muddy banks between the plants and amongst the algae. This helps them avoid being eaten by adult fish.

How do Fish sleep?

Fish will slow down their metabolism, sink to the bottom in a safe spot while remaining relatively motionless. They do not close their eyes because they have no eyelid. It is though that they turn off most of their senses while mainting their lateral line sense active. Any disturbance and with a flick of their tail fin they will dart off to safety.

Some parental fish don’t sleep when guarding their nest of eggs or fry. They remain alert all night and fan the eggs and guard the young from predators.

Fish feeding behaviour

When a fish finds a good source of food it gets excited and starts to gulp the food down. Other fish will notice the excitement and will also get excited and swim towards the food. A feeding frenzy follows where more and more nearby fish notice the commotion and head towards it. All the fish will try and gulp down as much food as possible as quick as possible before the other fish finish it off.

Fish generally swallow their food whole and don’t chew much of it at all. But they will sometimes a bite at a piece of food that is too big and wriggle about until a piece snaps off.

They swallow food by expanding their throat pouch, which has the effect of creating a suction, where food just in front of them will be sucked up into their mouth along with some water. When the food is inside the mouth, the fish will close its mouth trapping the food inside. The fish will expel the excess water through its gills while keeping the food trapped in its mouth. The fish will then taste the food. If the food is stale or inedible the fish will expel the food from its mouth.

Teeth of fish

Most fish are omnivores which means they eat both vegetable matter and living food such as insects and other fish. Omnivores have peg shaped teeth that enable the fish to bite and hold onto its food. Some fish specialise in eating algae. These fish have specically adapted teeth that are flattened into a shape making them ideal fro rasping out algae attached to rocks.

Predator fish have sharp backward pointing teeth that can pierce the flesh of other fish and sometimes scissor together to slice through the flesh allowing the fish to bite off chunks.

Fish sometimes have specialise pharyngal teeth based in the roof of a fish’s mouth. These teeth workin in combination with a fish’s tongue to provide an additional mechanism to allow the fish to grip its food.

Some fish feed on hard shelled creatures such as snails, shrimps or molluscs. They have specialised teeth that enable them to crush or crack open snails shells by use of their pharyngal teeth while biting hard using powerful jaw muscles.

Many bottom feeding fish sift through the sediment at the bottom of the pond or river bed. The sediment contains decaying organic matter where worms and insects grow. Bottom feeders feed off these creatures as well as broken off bits of flesh and plants.

Some fish are mostly vegetarian so feed off the leaves of plants and maybe snatches of algae. These types of fish are hungry fish and generally will eat throughout the day because weight for weight plant matter holds less protein and calories than animal matter.

Coordination of swimming in fish

About half the know species of fish swim about in groups. There are two methods that this achieved

  1. How fish school

Schooling is where the fish of the group swim together in a tightly knitted coordinated way keeping a set distance apart from each other while trying to swim at the same speed and direcdtion as its neighbour. When a lead fish turns its neighbour will turn which in turn leads to its neighbour turning. This is done so fast that it looks like all the fish turn at the same time. This coordinated effect of many fish is called the Trafalgar effect. Schooling is said to provide protection from predators because of a predators inability to focus on a single fish and having multiple confusing targets.

  1. How fish shoal

However, shoaling is when fish swim together in loose groups but without coordinated swimming behaviour. This behaviour is exhibited by social fish. Each fish will try and keep within social distance of other fish in its group. When a threat comes close to the group the group will scatter away from each other and will only re-group when the threat has gone.

Each fish in a shoal has a personal space that it tries to maintain most of the time. In fast currents the shoal will tighten and the fish will swim closer together than in slow or still water where the fish will be in a shoal but further from each other.

Most fish are social animals as can be witnessed by their shoaling behavior. Fish keep tabs on each other by use of sight, smell and use of the lateral line sense.

Members of a shoal tend to be the same size and nearly always of the same species. Any sick or small fish are shunned and excluded from the shoal.

Fish aggression

Fish will fight over food, territory and mates.

Male fish will fight more aggressively to win a mate than they would fight over food. Males usually fight to defend a territory so when the time comes the fish can attract a female to its patch to mate with. Some species will defend a territory around its nest after breeding. They will defend the nest of eggs or young fish from predators. This is when the parents are at their most aggressive. They can kill other fish that are curious and come close to the nest. In some species it is just the male that will guard while in other species both parents will guard.

The largest, strongest or even the most aggressive fish will be the most dominant and will get the best and biggest territory. There is a pecking order of fish from the largest most dominant down to the weakest, smallest fish. Once the pecking order is established fish then tend to not fight each other. Sub dominant fish will give way to more dominant fish. When a new fish turns up in an area fighting will break out between the new fish and the settled fish. The new fish will start out quite low in the pecking order and will over the following days or weeks fight its way up the pecking order until it finds its natural place in the pecking order.

The best breeding territories are defended by the most dominant males. These areas are surrounded by smaller and not so good territories occupied and defended by less dominant males. Further out in smaller and least good territories the weakest males will try to defend their small patch too. These territories border each other with no buffer zone. Border disputes occasionally occur but quickly resolve themselves. The fish do not chase after neighbouring fish by following a neighbour because they would leave their own territory unguarded.

When a female who comes along and is in mating mood she will usualy go the the male with the best territory. All the fish will try to entice the female to their territory by displaying frantically. Only occasionally will she mate with a subordinate male.

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