Fish aggression

Last updated

Aggression refers to negative behavior or attitudes toward another, mainly by applying physical force. Evolution on the other hand, is any process of formation or development of something like habit, trait or character in a population from generation to generation. Evolution can explain why fish exhibit aggression because it is a simple emotion. This emotion increases an individual's survival or reproduction. Aggressive behavior can derive in fish species due to territory, sex specific selection and genetic variation. There is no specific fish species who display invasive behavior. Almost all fish are aggressive sometimes in their lives depending on their surroundings.

Contents

Territorial aggression

Fish territories are defended areas generally ruled by a single individual or by breeding pairs. The guarded resource may include food, shelter, sexual partner or offspring. While protecting their regions, fish often display aggressive behavior against their intruders. The territory owner strikes at competing fish directly ending in a bite, or a bump. Such aggressive behavior is seen in large juveniles, females and other fish of the same kind from the same area. To better understand this topic, consider the male three-spine stickleback, Gasterosteus aculeatus, as an example. Theo Bakker's paper claims the three-spine stickleback male fish is polygynous—meaning they prefer two or more female mates in a territory. Thus, males are highly aggressive so they have access to females in a particular territory, which also leads to intrasexual selection among males. Intrasexual selection is selection within the same sex. For instance, some male animals compete against one another, physically, for access to females for their kind. So, characteristics like a long tail, sharp teeth or similar weaponry that can be used against other males of the same species as means of mating with females is a selective advantage.

There is a deep relationship between the aggression in fish and the size of the regions owned by them. In a smaller territory, female fish often disappear before mating. Female fish are not bound to mate with a particular fish. If by chance a female is attracted to another male, she can dump the previous partner without any hesitation. In this situation, the ditched male fish becomes more aggressive to find mates in order to reproduce. Their levels of aggression increase more when the rates of sneaking by rival males go up too. The sneaking males enter the nest and release their own sperm over the eggs of the breeding fish. The rival fish here are using alternative reproduction methods like parental, sneaker or satellite to avoid being hurt by breeding males. On the other hand, the breeding males have higher mating success and endure less looting of eggs in large territories. Once the eggs have been gathered, the breeding males decrease their territories to protect their offspring from the predators during their parental phase. After the eggs have hatched, the males continue to show similar or more invasive behavior due to increased reproductive value of offspring and the awareness of newly hatched young fish against enemies.

Territorial aggression can take place not only due to the pressure of mating, producing offspring, or intruders, but also from light intensity. The term intensity is used to describe the rate at which light spreads over a surface of a given area some distance from a source. At lower light levels, the risk of losing resources like food and mates gives rise to aggressive behavior among the fish belonging to a territory. Additionally, for further understanding on how the rate of aggression and distance among neighboring fish varies with nighttime light intensities in the same area, Sveinn Valdimarsson and Neil Metcalfe conducted an experiment with the juveniles of Atlantic salmon, Salmo salar. At the beginning, S. salar were exposed to four different nighttime light intensities (0.00, 0.01, 0.50 and 1.00 lx) for 24 hours. From the result, it was concluded that fish showed less aggression when the intensity of the light was lower. This is because when the level of light was intense, due to darkness of night the territorial fish failed to detect their food or other members in the same area. So they decreased their territory size and remained closer to each other rather than attacking. This was a good example of evolution of cooperation among the fish. Additionally, as the light intensities of the light increased, those fish could see each other to defend their space. The territory size increases during bright lights. In short, the aggressive behavior of the salmon toward their rivals is highly manipulated by light intensities. Thus, the size of the space that the fish is defending increases or decreases between day and night. [1]

Sex-specific aggression

Male and female fish both get involved in aggressive confrontation. Yet varying selection pressures affecting each sex result in gender differences in aggressive syndrome during competition. Aggressive syndrome is a social condition describing an individual's need to show his distaste or dislike against certain individuals. Adult female fish usually gather in groups, including adult females and non-reproductive males. Aggressive behavior is displayed in females especially when the female fish attack each other directly. Dominance relationships can take place among female association. For instance, females of higher status (size) have better opportunities to mate than minors residing in the same group. Then females become aggressive when there are two dominant females trying to select the same male fish for mating. This selection can be based on intersexual selection, which is selection between two sexes. Females use such selection while choosing mates with good genes. For example, female peacocks tend to prefer male peacocks with bright plumage. The females think that if they mate with males with bright plumage, the offspring will have similar characteristics.

S. Josefin Dahlbom and colleagues, experimented on zebra fish, Danio rerio, to study the difference in aggression level between males and females if they are put together under similar environment. For this test, fish were paired with one of the same sex. As the experiment continued, it was observed that both dominant males and females increase their aggression level until day four. On the fifth day, the dominant female members in the group stopped being aggressive. The authors suggested that this could be because the subordinate females stopped challenging the dominant female early in the study, and thereby the dominant female did not need to prove her superiority. In contrast, male subordinates continued fighting against the dominant males. As a result, the dominant males showed more aggression to suppress the subordinate males and to maintain their position among others.

In the paper ‘Gender differences in aggressive behavior in convict cichlids’ Gareth Arnott and Robert W. Elwood investigated if gender related variations in aggression are seen in convict cichlids, Amatitlania nigrofasciata. To see gender-related changes in aggression, they tested if intersexual agonistic events take place between isolated males and females, who were not previously paired to each other as breeding partners. At the end, it was detected that in terms of encroachment, Texas cichlids males used lateral display along with tail biting; whereas, the females used frontal display with biting. These two different displays have an explanation. Convict cichlids generally use either their left or right eye while swimming. Therefore, these fish use either their left or right hemisphere of the brain. Aggressive males are believed to use only their left hemisphere; whereas, aggressive females navigate based on their right eyes. Although a clear conclusion cannot be drawn from this study between the hemispheres and the aggression levels, it is fairly clear that males and females show variation in aggression syndrome. In short, various forces affecting each sex can result in different aggressive behaviors among male and female fish. [2]

Aggression for genetic makeup

Evolution of aggression can occur in fish due to their genetic makeup. To examine the relationship between aggression and genetic makeup, a team from CNRS/Laboratoire Neurobiologie et Développement conducted an experiment on zebra fish, spiegeldanio. At the beginning, the team of CNRS organized behavioral tests to quantitatively measure the three characters of aggressive behavior. In the experiment, it turned out that this particular fish has a mutation in its fgfr-1 gene summarizing for a membrane receptor sensitive to FGF (Fibroblast Growth Factor), which is a key for growth factor in those fish. As a reaction to the mutation, this group of fish displays low brain levels of histamine. Histamine is a neurotransmitter that controls appetite, sleep and attention in a species. Due to low histamine levels, zebra fish exhibit aggressive behavior. Therefore, the link between the fgfr-1 genes to histamine regulates the behavioral status of aggression in zebra fish.

In another experiment Katrina Tiira performed a different test on land-locked salmon, Salmo salar to see if juveniles with low estimated genetic diversity showed less aggression. To continue the theory, researchers selected one group of fish with low genetic diversity and another group with high genetic diversity, and compared aggression levels. They observed that salmon fry with low genetic variation showed less aggression than the other group. In the group of less variation, the researcher used closely related parents. The juveniles were genetically related sharing high number of alleles with each other. Thus, they display low aggression to their competitors as they used kin recognition method on others. In conclusion, it can be explained that genetic variation in salmon can manipulate the agnostic syndrome if the individuals in a group are closely related.

Aggression in fish can be increased by the effect of growth hormone, or GH, which has an essential growth factor in this species. They control the use of nutrients in tissue synthesis. Thus, it increases the metabolic demands in species resulting in aggression to fight for daily needs. An experiment was designed on juvenile rainbow trout, Oncorhynchus mykiss. They selected two control fish (C/C pairs), two growth hormone treated fish (GH/GH pairs) or one growth hormone-treated and one control (C/GH pairs). From the testing, it was analyzed that the GH increases aggression levels in all groups of O. mykiss. It indirectly improved the swimming activity along with the attacking rate between competitors. In summary, growth hormone plays a vital role in controlling aggression in rainbow trout and other fish.

Related Research Articles

<span class="mw-page-title-main">Behavioral ecology</span> Study of the evolutionary basis for animal behavior due to ecological pressures

Behavioral ecology, also spelled behavioural ecology, is the study of the evolutionary basis for animal behavior due to ecological pressures. Behavioral ecology emerged from ethology after Niko Tinbergen outlined four questions to address when studying animal behaviors: What are the proximate causes, ontogeny, survival value, and phylogeny of a behavior?

<span class="mw-page-title-main">Jack Dempsey (fish)</span> Species of fish

The Jack Dempsey is a species of cichlid fish that is native to freshwater habitats from southern Mexico to Honduras, but also introduced elsewhere. Its common name refers to its aggressive nature and strong facial features, likened to that of the famous 1920s boxer Jack Dempsey.

<span class="mw-page-title-main">Blue-footed booby</span> Species of bird

The blue-footed booby is a marine bird native to subtropical and tropical regions of the eastern Pacific Ocean. It is one of six species of the genus Sula – known as boobies. It is easily recognizable by its distinctive bright blue feet, which is a sexually selected trait and a product of their diet. Males display their feet in an elaborate mating ritual by lifting them up and down while strutting before the female. The female is slightly larger than the male and can measure up to 90 cm (35 in) long with a wingspan up to 1.5 m (5 ft).

<span class="mw-page-title-main">Dominance hierarchy</span> Type of social hierarchy

In the zoological field of ethology, a dominance hierarchy is a type of social hierarchy that arises when members of animal social groups interact, creating a ranking system. A dominant higher-ranking individual is sometimes called an alpha, and a submissive lower-ranking individual is called a beta. Different types of interactions can result in dominance depending on the species, including ritualized displays of aggression or direct physical violence. In social living groups, members are likely to compete for access to limited resources and mating opportunities. Rather than fighting each time they meet, individuals of the same sex establish a relative rank, with higher-ranking individuals often gaining more access to resources and mates. Based on repetitive interactions, a social order is created that is subject to change each time a dominant animal is challenged by a subordinate one.

<span class="mw-page-title-main">Harem (zoology)</span> Animal group consisting of one or two males, a number of females and their offspring

A harem is an animal group consisting of one or two males, a number of females, and their offspring. The dominant male drives off other males and maintains the unity of the group. If present, the second male is subservient to the dominant male. As juvenile males grow, they leave the group and roam as solitary individuals or join bachelor herds. Females in the group may be inter-related. The dominant male mates with the females as they become sexually active and drives off competitors, until he is displaced by another male. In some species, incoming males that achieve dominant status may commit infanticide.

<span class="mw-page-title-main">Alloparenting</span> Parenting not done by the birth parents

Alloparenting is a term used to classify any form of parental care provided by an individual towards young that are not its own direct offspring. These are often referred to as "non-descendant" young, even though grandchildren can be among them. Among humans, alloparenting is often performed by a child's grandparents and older siblings. Individuals providing this care are referred to using the neutral term of alloparent.

<span class="mw-page-title-main">Convict cichlid</span> Species of fish

The convict cichlid is a fish species from the family Cichlidae, native to Central America, also known as the zebra cichlid. Convict cichlids are popular aquarium fish and have also been the subject of numerous studies on fish behaviour.

<span class="mw-page-title-main">Intraspecific competition</span> Species members compete for resources

Intraspecific competition is an interaction in population ecology, whereby members of the same species compete for limited resources. This leads to a reduction in fitness for both individuals, but the more fit individual survives and is able to reproduce. By contrast, interspecific competition occurs when members of different species compete for a shared resource. Members of the same species have rather similar requirements for resources, whereas different species have a smaller contested resource overlap, resulting in intraspecific competition generally being a stronger force than interspecific competition.

<i>Tropheus moorii</i> Species of fish

Tropheus moorii is a species of cichlid endemic to Lake Tanganyika in Africa. Over 40 different color morphs of this species are dispersed throughout the lake, ranging from dark green to flame red and yellow. They mostly feed on filamentous algae on the rocky shallows they inhabit. T. moorii is a maternal mouthbrooder, so eggs are fertilized and young are carried in the mouth of the female while they hatch and develop.

<span class="mw-page-title-main">Nile tilapia</span> Species of fish

The Nile tilapia is a species of tilapia, a cichlid fish native to parts of Africa and the Levant, particularly Israel and Lebanon. Numerous introduced populations exist outside its natural range. It is also commercially known as mango fish, nilotica, or boulti.

Monogamous pairing in animals refers to the natural history of mating systems in which species pair bond to raise offspring. This is associated, usually implicitly, with sexual monogamy.

<span class="mw-page-title-main">Mozambique tilapia</span> Species of fish

The Mozambique tilapia is an oreochromine cichlid fish native to southeastern Africa. Dull colored, the Mozambique tilapia often lives up to a decade in its native habitats. It is a popular fish for aquaculture. Due to human introductions, it is now found in many tropical and subtropical habitats around the globe, where it can become an invasive species because of its robust nature. These same features make it a good species for aquaculture because it readily adapts to new situations. It is known as black tilapia in Colombia and as blue kurper in South Africa.

<i>Neolamprologus pulcher</i> Species of fish

Neolamprologus pulcher is a species of cichlid endemic to Lake Tanganyika where it prefers locations with plenty of sedimentation. The common names for N. pulcher include daffodil cichlid, fairy cichlid, princess of Zambia and lyretail cichlid. This species can reach a length of 10 centimetres (3.9 in) TL. It can also be found in the aquarium trade.

The dear enemy effect or dear enemy recognition is an ethological phenomenon in which two neighbouring territorial animals become less aggressive toward one another once territorial borders are well established. As territory owners become accustomed to their neighbours, they expend less time and energy on defensive behaviors directed toward one another. However, aggression toward unfamiliar neighbours remains the same. Some authors have suggested the dear enemy effect is territory residents displaying lower levels of aggression toward familiar neighbours compared to unfamiliar individuals who are non-territorial "floaters".

A biological ornament is a characteristic of an animal that appears to serve a decorative function rather than a utilitarian function. Many are secondary sexual characteristics, and others appear on young birds during the period when they are dependent on being fed by their parents. Ornaments are used in displays to attract mates, which may lead to the evolutionary process known as sexual selection. An animal may shake, lengthen, or spread out its ornament in order to get the attention of the opposite sex, which will in turn choose the most attractive one with which to mate. Ornaments are most often observed in males, and choosing an extravagantly ornamented male benefits females as the genes that produce the ornament will be passed on to her offspring, increasing their own reproductive fitness. As Ronald Fisher noted, the male offspring will inherit the ornament while the female offspring will inherit the preference for said ornament, which can lead to a positive feedback loop known as a Fisherian runaway. These structures serve as cues to animal sexual behaviour, that is, they are sensory signals that affect mating responses. Therefore, ornamental traits are often selected by mate choice.

The challenge hypothesis outlines the dynamic relationship between testosterone and aggression in mating contexts. It proposes that testosterone promotes aggression when it would be beneficial for reproduction, such as mate guarding, or strategies designed to prevent the encroachment of intrasexual rivals. The positive correlation between reproductive aggression and testosterone levels is seen to be strongest during times of social instability. The challenge hypothesis predicts that seasonal patterns in testosterone levels are a function of mating system, paternal care, and male-male aggression in seasonal breeders.

Polygyny is a mating system in which one male lives and mates with multiple females but each female only mates with a single male. Systems where several females mate with several males are defined either as promiscuity or polygynandry. Lek mating is frequently regarded as a form of polygyny, because one male mates with many females, but lek-based mating systems differ in that the male has no attachment to the females with whom he mates, and that mating females lack attachment to one another.

Polyandry in fishes is a mating system where females mate with multiple males within one mating season. This type of mating exists in a variety of animal species. Polyandry has been found in both oviparous and viviparous bony fishes and sharks. General examples of polyandry occur in fish species, such as green swordtails and Trinidadian guppies. Specific types of polyandry have also been classified, such as classical polyandry in pipefish cooperative polyandry in cichlids and convenience polyandry in sharks.

<span class="mw-page-title-main">Polyandry in animals</span> Class of mating system in non-human species

In behavioral ecology, polyandry is a class of mating system where one female mates with several males in a breeding season. Polyandry is often compared to the polygyny system based on the cost and benefits incurred by members of each sex. Polygyny is where one male mates with several females in a breeding season . A common example of polyandrous mating can be found in the field cricket of the invertebrate order Orthoptera. Polyandrous behavior is also prominent in many other insect species, including the red flour beetle and the species of spider Stegodyphus lineatus. Polyandry also occurs in some primates such as marmosets, mammal groups, the marsupial genus' Antechinus and bandicoots, around 1% of all bird species, such as jacanas and dunnocks, insects such as honeybees, and fish such as pipefish.

References

  1. Valdimarsson, Sveinn K.; Metcalfe, Neil B. (June 2001). "Is the level of aggression and dispersion in territorial fish dependent on light intensity?". Animal Behaviour. 61 (6): 1143–1149. doi:10.1006/anbe.2001.1710. ISSN   0003-3472.
  2. Arnott, Gareth; Elwood, Robert W. (1 November 2009). "Gender differences in aggressive behaviour in convict cichlids". Animal Behaviour. 78 (5): 1221–1227. doi:10.1016/j.anbehav.2009.08.005. ISSN   0003-3472 . Retrieved 25 January 2024.