Fish behaviour. Swimming behaviour patterns

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1 Fish behaviour The behaviour of fish varies as much as the physical appearance of the different species. It is important to understand the behaviour of fish for these reasons: Behavioural changes are often the first sign of disease. Knowing the normal behaviour of a species means that you are more likely to pick up any abnormal behaviour. The behaviour of the fish impacts on the way that it is fed in a captive situation. The behaviour of the fish may alter the environment that needs to be provided at different stages of its life, eg during breeding. Species behaviour will dictate whether it can be kept with other fish of its own species, with fish of other species, or only with fish of other species. In short, a species behaviour determines its compatibility with other fish/species. Behavioural changes may determine whether a second tank is required at different life stages for some species, eg species that become overtly territorial and aggressive when they mate. Swimming behaviour patterns All species have typical swimming patterns. They may be fast, moderate or slow swimmers and may prefer different areas of the tank/pond to swim in. Fish are commonly categorised as being top, middle or bottom swimmers. Some species prefer open areas to swim in, whilst others prefer heavily planted areas. It is important to some fish that they have schools or shoals to swim with this is a reflection of both swimming and social behaviour. Here are a few swimming behaviours and examples of fish species: Fast swimmers Zebra danio (Brachydanio rerio) most barbs many tetras Moderate swimmers swordtails (Xiphophorus helleri) guppies (Peocilia reticulata) mollies (Poecilia sphenops) sharks 1

2 Slow swimmers angelfish (Pterophyllum scalare) discus fish (Symphysodon discus) many gouramis stonefish Top swimmers gouramis (eg Pearl Gourami Trichogaster leeri) Arowana (Osteoglossum bicirrhosum) middle swimmers most tetras barbs angelfish discus fish Open area swimmers most tetras (although they also appreciate areas to hide from predators!) many barbs as a general rule larger fish prefer more open areas Bottom swimmers Corydoras spp. (catfish) many other species of catfish loaches Solitary swimmers angelfish discus Oscars many African Cichlids gouramis Schooling fish most tetras most members of the Corydoras genus barbs danios many rasboras The following are examples of fish that prefer densely planted areas: killifish some catfish almost all fry new born fish some loaches. Failure to provide appropriate conditions for the fish to express their normal swimming behaviour may result in stress associated conditions, including those resulting from suppression of the immune system. For example, not providing companions for shoal fish eg tetras may result in stress, which in turn can lead to immunosuppression. Although the effect may not be immediately obvious it will most likely lead to a shortened lifespan or increased susceptibility to pathogens. Changes in swimming behaviour Changes in swimming behaviour can be the first signs of disease. For example, fish that alter their swimming areas from the bottom to the top of 2

3 the water may be reflecting problems with the environment or with themselves. Be aware, however, that individual fish can learn to adopt unusual swimming habits. For example, catfish learn to swim at the top of the water as a competitive strategy. Note: It is worthwhile noting that these nominated swimming behaviours are only indicative of what the species do most of the time. When excited, exploring, mating or feeding, fish will often enter parts of the tank that they would normally leave alone. Tetras are described as being middle layer dwellers but during feeding they will typically dart to the surface of the water, grab food and descend again. Feeding habits There is a great variety of feeding behaviours and they can impact on what is fed, how often it is fed, the physical set up of the environment, the species that are kept and the time of feeding. What is fed Some fish are carnivorous and therefore require food with a high level of fish or animal protein. Attention needs to be paid to the dietary needs of omnivorous and herbivorous fish. Some fish will refuse food unless it is a certain size eg discus have relatively small mouths and cannot accept larger pieces of food. Some fish will only accept live food. How often to feed Some fish species are grazers and may need to be fed often during the day, whilst others are able to take large quantities of food in one feeding and therefore only need to be fed once or twice a day. Physical set up of the tank If fish are shy or nocturnal then provision must be made for them to have access to food. There must be a quiet area where they can feed without being harassed by more active or aggressive fish. If live foods are being used there should be provision for some sort of bottom dwelling species to clean up the leftovers so that the food doesn t rot or infiltrate the media. 3

4 The species being kept Aggressive, messy fish are not good feeding companions for those species that are fussy and easily frightened. For example, keeping Oscars with almost any other free swimming species is probably not a good idea. Oscars are aggressive, they intimidate and eat other fish, they are messy eaters and they display disruptive behaviour at feeding time and at all other times. The time of feeding If nocturnal fish are present in the tank it is important that some feeding is done in the half light with tank lights off to allow them access to the food. Many nocturnal feeders are also shy fish that don t compete very successfully with other fish for food. Aggressive and territorial behaviour Many fish are unsuitable for community tanks because they are naturally aggressive. Many African cichlids fall into this category. In many species the aggressive/territorial behaviour is not apparent until they reach puberty. Puberty is weight related rather than age related in fish. For example, many African cichlids are fairly innocuous until they reach puberty, when they start to exhibit antisocial behaviour towards other species and members of their own species. This photo shows an example of an African cichlid. Many are unsuitable for mixing with smaller fish because of their aggressive and sometimes predatory nature. 4

5 It is also important to realise that many fish are predatory and size should always be considered. For example, Angel fish will almost always eat Neon tetras once the Angels have grown large enough. The two species come from the same area of the Amazon and are probably in a natural prey/predator relationship. Some fish are not particularly territorial until they mate. Once this occurs in some species they will try to claim some, or all, of the tank as their territory. If there are members of their own species present they may actually be more likely to attack them rather than non-related species eg Discus, many African cichlids. It is not unusual to find the mated pair occupying 50-80% of the tank whilst the rest of the fish are crammed into the remaining space! Tank bully Occasionally there is a tank bully. This may be a member of any species but is obviously more of a problem when it is a larger fish that has the capacity to hurt other individuals. When this occurs changing the aqua scaping may effect a solution by redefining the territories of the fish. If this fails, the fish should be removed and either placed in a tank with larger fish. Note: Some species aren t necessarily aggressive but their feeding habits may involve nipping anything that looks edible. If that thing happens to be part of another fish, this can lead to serious health implications. For example, Siamese fighting fish are often victimised by barbs, tetras etc because their long flowing fins look like food! Breeding behaviour The breeding behaviour of the fish may determine how the tank is set up. Fish may require certain species of plant, certain patterns of water flow, particular water conditions and so on. All of these requirements will dictate the way that a tank is set up and maintained. Some fish require heavy plantings, clear areas or even half buried pots for their eggs. Summary points Fish behaviour is also an important determinant of husbandry practices. 5

6 Behaviour varies considerably amongst species. Understanding of normal behaviour is important so that abnormal behaviour can more quickly be identified. Inability to express normal behaviour can lead to health problems. In particular, stress-like syndromes may occur, leading to immunosuppression. Compatibility of fish species is based on their physical and behavioural needs. 6