
Damselfish are those fish within the
subfamilies Abudefdufinae,
Chrominae,
Lepidozyginae,
Pomacentrinae, and
Stegastinae within the
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Pomacentridae
Pomacentridae is a family of ray-finned fish, comprising the damselfishes and clownfishes. This family were formerly placed in the order Perciformes or as indeterminate percomorphs, but are now considered basal blenniiforms.
They are primaril ...
.
Most
species
A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
within this group are relatively small, although the four largest species (''
Hypsypops rubicundus'', ''
Microspathodon bairdii'', ''
M. dorsalis'' and ''
Nexilosus latifrons'') can reach 30cm (12 in) in length.
Most damselfish species exist only in
marine environments, but a few inhabit
brackish
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
or
fresh water
Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salt (chemistry), salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include ...
.
These fish are found globally in
tropical
The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
,
subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...
, and
temperate
In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ran ...
waters.
Habitat
in
tropical
The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...
rocky or
coral reef
A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in group ...
s, and many of those are kept as
marine aquarium pets. Their diets include small
crustacean
Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...
s,
plankton
Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
, and
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
. However, a few live in fresh and
brackish
Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...
waters, such as the
freshwater damselfish, or in warm
subtropical
The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...
climates, such as the large orange
Garibaldi, which inhabits the coast of southern California and the Pacific Mexican coast.
Foraging

The domino damselfish ''
D. albisella'' spends the majority (greater than 85%) of its daytime hours
foraging
Foraging is searching for wild food resources. It affects an animal's fitness because it plays an important role in an animal's ability to survive and reproduce. Foraging theory is a branch of behavioral ecology that studies the foraging behavi ...
. Larger individuals typically forage higher in a
water column than do smaller ones. Damselfish of all sizes feed primarily on
caridea
The Caridea, commonly known as caridean shrimp or true shrimp, from the Greek word καρίς, καρίδος (karís, karídos, “shrimp”), are an infraorder of shrimp within the order Decapoda. This infraorder contains all species of true sh ...
and
copepods. Males have relatively smaller stomach sizes during
spawning
Spawn is the Egg cell, eggs and Spermatozoa, sperm released or deposited into water by aquatic animals. As a verb, ''to spawn'' refers to the process of freely releasing eggs and sperm into a body of water (fresh or marine); the physical act is ...
season compared to females due to the allocation of resources for
courtship
Courtship is the period wherein some couples get to know each other prior to a possible marriage or committed romantic, ''de facto'' relationship. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marri ...
and the guarding of
nest
A nest is a structure built for certain animals to hold Egg (biology), eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of ...
s. When current speeds are low, the damselfish forages higher in a water column where the flux of
plankton
Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...
is greater and they have a larger food source. As current speeds increase, it forages closer to the bottom of the column. Feeding rates tend to be higher when currents are faster. Smaller fishes forage closer to their
substrates than do larger ones, possibly in response to
predation
Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
pressures.
Territoriality
There are many examples of resource partitioning and habitat selection that are driven by aggressive and territorial behaviors in this group. For example, the threespot damselfish ''
S. planifrons'' is very defensive of its territory and is a classic example of extreme territoriality within the group. One species, the dusky damselfish ''
S. adustus'' spends the majority of its life within its territory.
Domestication of mysid shrimps
Longfin damselfish (''
Stegastes diencaeus'') around Carrie Bow Cay,
Belize
Belize is a country on the north-eastern coast of Central America. It is bordered by Mexico to the north, the Caribbean Sea to the east, and Guatemala to the west and south. It also shares a maritime boundary with Honduras to the southeast. P ...
(16°48.15′N, 88°04.95′W), have been shown to actively protect planktonic
mysids (''Mysidium integrum'') in their reef farms. The mysids fertilize the
algae
Algae ( , ; : alga ) is an informal term for any organisms of a large and diverse group of photosynthesis, photosynthetic organisms that are not plants, and includes species from multiple distinct clades. Such organisms range from unicellular ...
grown in the reef farms with their excretes which in turn helps the damselfish who feed on algae to be healthier.
In the reef farms that house mysids, damselfish aggressively defends the farm area against other fish that would prey on the mysids, significantly more so than they do when their farms do not house mysid shrimps. These damselfish would eat similar small
invertebrates
Invertebrates are animals that neither develop nor retain a vertebral column (commonly known as a ''spine'' or ''backbone''), which evolved from the notochord. It is a paraphyletic grouping including all animals excluding the chordate subphylum ...
. Despite that, they are docile towards mysid shrimp. In the area, mysid shrimps are not found in swarms except in the farms maintained by damselfish. All these observations point to a pet-like relationship between the mysid shrimps and longfin damselfish in the area, with damselfish being the domesticator and mysids being the domesticate.
Courtship
In the species ''
S. partitus'', females do not choose to mate with males based on size. Even though large male size can be advantageous in defending nests and eggs against
conspecific
Biological specificity is the tendency of a characteristic such as a behavior or a biochemical variation to occur in a particular species.
Biochemist Linus Pauling stated that "Biological specificity is the set of characteristics of living organism ...
s among many animals, nest intrusions are not observed in this damselfish species. Females also do not choose their mates based upon the brood sizes of the males. In spite of the increased male parental care, brood size does not affect egg survival, as eggs are typically taken during the night when the males are not defending their nests. Rather, female choice of mates is dependent on male courtship rate. Males signal their parental quality by the vigor of their courtship displays, and females mate preferentially with vigorously courting males.
Male damselfish perform a courtship behavior called the signal jump, in which they rise in a water column and then rapidly swim back downward. The signal jump involves large amounts of rapid swimming, and females choose mates based on the vigor with which males do so. Females determine the male courtship rates using sounds that are produced during signal jumps. As the male damselfish swims down the water column, it creates a pulsed sound. Male courtship varies in the number and rates of those pulses.
In the beaugregory damselfish ''
S. leucostictus'' males spend more time courting females that are larger in size. Female size is significantly correlated with
ovary
The ovary () is a gonad in the female reproductive system that produces ova; when released, an ovum travels through the fallopian tube/ oviduct into the uterus. There is an ovary on the left and the right side of the body. The ovaries are end ...
weight, and males intensify their courtship rituals for the more
fecund females. Research has shown that males that mate with larger females do indeed receive and hatch greater numbers of eggs.
Mating
Male bicolor damselfish, ''
E. partitus'', exhibit
polygamy
Polygamy (from Late Greek , "state of marriage to many spouses") is the practice of marriage, marrying multiple spouses. When a man is married to more than one wife at the same time, it is called polygyny. When a woman is married to more tha ...
, often courting multiple females simultaneously. Among this species,
evolutionary selection favors those males that begin mating as soon as possible during spawning seasons even if the most favorable egg clutches are spawned at later times. Females often choose which males to mate with depending on the males’ territory quality. Shelter sites are essential for the bicolor damselfish in avoiding predation, and females may evaluate the suitability of these sites at a male territory before depositing their eggs.
Effect of distance on spawning
In the species ''
S. nigricans'', females usually mate with a single male each morning during spawning seasons. At dawn, they visit males’ territories to spawn. The distance to the territory of a mate influences the number of visits that a female engages in with a male. At short distances, females make many repeated visits. At longer ones, they may spawn their entire clutch in one visit. This plasticity in mating behavior can be attributed to two factors: (1) intrusions by other fish to feed in the females’ territories while they are away, which could make the females return frequently to their habitats in order to defend their resources, and (2) predatory attacks on the females, which increase in frequency as the distances that the females travel become longer. Intrusion by other fish into a female’s territory can diminish the habitat of its food and render it unstable. Thus, a spawning female should return to its home as often as possible. However, a greater number of spawning visits increases the chance of being attacked, especially when mating with males that are far away. To minimize overall costs, females change their number of spawning visits depending on male territory distance.
Filial cannibalism
The male cortez damselfish, ''
S. rectifraenum'', is known to engage in
filial cannibalism. Studies have shown it typically consumes over twenty-five percent of its clutches. The males generally consume clutches that are smaller than average in size, as well as those that are still in the early stages of development. Female cortez damselfish tend to deposit their eggs with males who are already caring for early-stage eggs, rather than males with late-stage eggs. This preference is seen particularly in females that deposit smaller-sized clutches, which are more vulnerable to being consumed. For the males, filial cannibalism is an adaptive response to clutches that do not provide enough benefits to warrant the costs of parental care.
References
{{reflist
External links
Tiny Damselfish May Destroy A Caribbean Reef''National Public Radio'', 11 August 2009.
Pomacentridae
Fish common names