Monk fish
| Monk fish | ||||||||||||
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Monk fish ( Chromis chromis ) |
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| Chromis chromis | ||||||||||||
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The monk fish ( Chromis chromis ) is one of the most common fish species and was the only species of damselfish (Pomacentridae) in the Mediterranean before the Suez Canal was built ( Lesseps migration ) . It is a small fish (typically <15 cm) that can be found in loose shoals in open water over rock reefs or over seagrass meadows at depths of 3-35 m. Life expectancy is a maximum of 9 years.
Appearance and characteristics
The monk fish reaches a length of 134 mm and a weight of up to 40 g. It has a continuous dorsal fin (dorsalis), which is covered in the front part with 14 hard rays, followed by 9-11 soft rays. The anal fin (analis) has 2 hard rays and 9-11 soft rays. The paired pectoral fins (pectoralia) are short, which means that the maximum length is two thirds from the base of the caudal fin. The pelvic fins (ventralia) are also created in pairs and are on the chest, their attachment is below the attachment of the pectoral fins.
Adult animals are mostly chestnut brown to blue-black in color, while the pigmentation on the edge of the scales is denser and darker, which creates a slight longitudinal stripe. The ventral and pectoral fins are almost transparent. The caudal fin (caudalis) contains an almost pigment-free area in the form of a triangle, which lies in the middle and extends to the base of the fin. Because of this, the caudal fin appears very narrow and elongated, making C. chromis easy to identify from a distance. This coloring is also called day coloring.
The monk fish can take on a night color, which is characterized by a purple-gray color of the body and the fins. The longitudinal stripes and the patterns are lost. Only the caudal fin remains dark. This coloration occurs mainly in open water sleepers. The hideaway sleepers and the territorial owners usually stay in their daytime color - even at night. In contrast to this, in winter most monk fish remain in the bright night color all day. This is primarily due to the poor lighting and visibility.
There is also a so-called cryptic coloring. This is characterized by dark gray-brown transverse bands on the rest of the light body. However, this camouflage color is only found very rarely.
The territorial males can adopt a courtship coloration, but do not have to. This color has an almost black, blue shimmering basic color. While the edges of the unpaired fins (dorsal and anal fin) stand out with a bright blue border, a series of small dots. The pelvic and pectoral fins have a light whitish color.
The growing juvenile fish all have a dark brown, blue-black basic color on which bright blue patterns stand out. In the earliest stage, this pattern still covers the whole body, but becomes smaller with increasing size. In the oldest juvenile fish, the pattern is reduced to a small, luminous V on the forehead. All fry, regardless of size, can make the color patterns disappear as soon as they move away from the substrate.
Distribution area and habitat
The distribution area of the monk fish extends over the Mediterranean, the Black Sea and the Sea of Azov . The limit of distribution is on the Atlantic coasts off the Strait of Gibraltar .
During the day, C. chromis can be found in open water in groups a few meters above rocky reefs or sea grass meadows ( Posidonia sp. ). The fish can be found at a depth of 3-35 m, sometimes even deeper, with the main distribution area between 10-25 m. In summer with good visibility, the feeding units can be found up to 20 m above the substrate, while in winter they remain close to the ground when visibility is poor.
There are three main factors that play an important role in living space. This should offer a good offer of shelter, be as flowing as possible and have a good supply of food. Large, current-rich rock reefs that are overgrown and strongly structured are therefore preferred to be settled. Oversized populations can be encountered there, some of which have to migrate to neighboring seagrass meadows in the evening due to a lack of hiding places and sleeping places. Unattractive areas are, for example, wide seagrass meadows or unstructured sand areas. Seagrass meadows have almost unlimited hiding places, but are very poorly structured and mostly protected from currents. Nevertheless, in less preferred areas, a few boulders are sufficient to attract smaller populations. The populations only contain as many individuals as there are places to hide for the night.
In general, hikes over long distances without hiding places rarely occur because they involve great risks. This makes C. chromis a very substrate-bound species.
nutrition
Monkfish are selective plankton snappers and spend the whole day foraging for food. To do this, they are in a loose formation ("feeding cloud"), which is preferably located in the turbulence zones of rock reefs or blocks. If the substrate is of a different nature, elongated "feeding bars" may arise. These formations can contain different numbers of individuals, from a few to thousands. The animals stay in their respective formations via synchronous swimming movements of the pectoral fins. Feeding aggregates can occur up to 1 m below the water surface, whereby the distance from the substrate depends on the visibility. This is particularly noticeable in winter, as the aggregates then only rise to 2‑3 m above the substrate. As soon as the water temperatures drop too much (to 7-9 ° C), the animals are mostly immobilized and feeding is stopped.
Otherwise, the willingness to eat depends on the plankton available and also on the strength of the current. The different size classes stay in mostly separate associations, which, depending on their size, rise at different distances to eat. The maximum distance from the substrate increases with increasing body size.
The diet consists mainly of zooplankton, the largest portion of which make up 50% copepods . Furthermore, be Salpen , Appendikularien , nauplii eaten and fish eggs, this, however, with a very small proportion. The vegetable diet is limited to algae with 2.5% .
Reproduction
Mating behavior
C. chromis shows a monomorphic (identically shaped) segregated sex. The breeding season runs from June to September. The males try to spawn with as many females as possible. The males then take care of their clutch until the larvae hatch. In one season, several cycles are run through in which the males keep building new territories. A cycle can last between 5 and 8 days. Adult males build between 6 and 8 independent, short-term territories each season, which are created in groups. In large populations, up to several thousand males are involved. These first swim around their area for a few hours and then determine a suitable spawning field. At the beginning, possible territories are settled peacefully, but after a few minutes territorial conflicts start. These quarrels take place mainly with the small males (between 60.5 and 83 mm), while the large males (between 83.5 and 134 mm) are very calm and dominant territorial owners and hardly participate in the arguments. The nest is cleaned by the males by removing posidonia leaves and tufts of algae from the substrate by plucking them and carrying away stones and small snails with their mouths. Free growth and sediment layers are finally removed by body punching and trembling. This establishment of a spawning field is possible at any time of the day, but usually begins in the morning and continues into the evening.
As soon as the males show the first signal and flutter jumps, some of the females come down from the feeding aggregates from the open water and initially remain in a layer of females at a height of 1–2 m above the territories. Then the females begin to offer themselves to the males of their choice with the aim of being admitted into the territory. This is mainly practiced by the smaller females. The larger and more experienced females wait for a quiet moment over a territory for the matching male and then swim straight into the territory. In the territory, eggs are laid, which can take up to 10 minutes undisturbed if the female is not driven away by the male. The male shields the female meanwhile and drives away neighbors and other intrusive females. If another female comes along while the eggs are being laid, both are usually driven away immediately. After oviposition, the male inseminates them as soon as possible. The eggs are then fanned with fresh water and often the next females offer themselves, which means that the males have several clutches of different females in their territories. If there are no females available to spawn, the male advertises with fluttering and signal jumps. The next morning the males start to woo again and the whole day is spent laying eggs. On the second day at the latest, all territorial boundaries are clearly defined.
The further sequence now depends on the females in a population, depending on whether they are still capable of spawning or whether further eggs have to mature. If there are still females willing to spawn on the third day, spawning will continue for another day. As soon as hardly any females or no more females spawn, the courtship behavior is stopped and the care phase of the clutch begins.
Monk fish cannot differentiate the sex of their own conspecifics based on external characteristics. Some of the small, sexually mature males without territory take advantage of this and trick other territory owners into inseminating the eggs themselves. The insemination rates of kleptogams are not infrequently higher than those of the territory owners. There are two different strategies of the kleptogamous males.
The "speedsters" try to get to a spawning female quickly and to inseminate her eggs. Then they flee immediately before the territorial owner can even react. "Pseudo-females" are males who present themselves to territorial owners as females in order to then inseminate the eggs in the clutch again. It remains uncertain how successful the subsequent insemination will be.
In the spawning fields it gets very chaotic in this phase, as every insemination success is fought.
Brood care
The clutches are shivered by the territorial owners on the first day of a spawning cycle (trembling of the whole body with abdominal contact with the clutch) and in the further course mainly fanned (violent beating with the pectoral fins). This is also practiced during the night, which is why males do not sleep during this time. If spawning took several days, the male divides the eggs into old and new clutch areas and therefore trembles or fanning them. Unfertilised or dead eggs are plucked out and spawning predators like Labriden and Spariden be chased away.
The males take in hardly any food during courtship and especially at the beginning of brood care. However, as the period of care progresses, the males move further and more often from their clutch in order to take up food. These feeding phases also become longer with advanced care duration, so that if there is a good plankton supply they remain more than a minute away from the nest. However, they always go back in between to fan the eggs. Depending on the water temperature, the larvae hatch after 3-4 days, but always together between 10 p.m. and midnight when no more planktivorous fish are active. This time is independent of the time of day the eggs were laid. The newly hatched larvae are driven off with the current. The males give up their territories in the morning after the last larvae have hatched.
They then return to the feeding units in the open water. In the main breeding season, the pauses between cycles can be as little as 1-2 days, so the males try to eat as much food as possible in this short time.
Enemies
The predators of the subadult and adult animals are diurnal littoral fish and crepuscular and nocturnal predators. Hostile Litoralfische include the amberjack ( Seriola dumerili ), the Common Sea Bream ( Sparus pagrus ), the bream ( Dentex dentex ), the European sea bass ( Dicentrarchus labrax ) and the dusky grouper ( Epinephelus guaza ). Other potential predators are the Mittelmeermuräne ( Murena helena ), the conger ( Conger conger ), the Dark hake ( Phycis phycis ) Phycis blennoides , the common octopus ( Octopus vulgaris ) and cuttlefish ( Sepia officinalis ).
Taxonomy and systematics
The monk fish was first described in 1758 by Carl von Linné in his Systema Naturae under the name Sparus chromis . The genus Chromis with the monk fish as a type species was introduced in 1814 by the French zoologist Georges Cuvier . Today over 100 species belong to it. Synonyms of Chromis chromis are: Sparus chromis Linnaeus, 1758, Heliastes chromis Linnaeus, 1758, Chromis castanea Cuvier, 1814, Heliastes castanea Cuvier, 1814 and Chromis mediteranea Cloquet, 1817.
Use and hazard
Because of its small size, C. chromis is rarely caught in commercial fishing. Sometimes it is used as bait to catch larger fish such as C. conger and D. dentex .
After the classification in 2010, the species is not endangered (LC: least concern,).
Web links
- Monkfish on Fishbase.org (English)
Individual evidence
- ↑ a b c d J. K. Pinnegar: Why the damselfish Chromis chromis is a key species in the Mediterranean rocky littoral - a quantitative perspective . Ed .: Journal of Fish Biology. No. 92 , 2018, p. 851-872 .
- ↑ Vera S. Dominges, Giuseppe Bucciarelli, Vitor C. Almada, Giacomo Bernardi: Historical colonization and demography of the Mediterranean damselfish, Chromis chromis . Ed .: Molecular Ecology. No. 14 , 2005, pp. 4051-4063 .
- ↑ Jakov Dulčić, Miro Kraljević: Age growth and mortality of damselfish (Chromis chromis L.) in the eastern middle Adriativ . In: Fisheries Research . No. 22 , p. 255-264 .
- ^ A b R. Froese, D. Pauly: Chromis chromis (Linnaeus, 1758) Damselfish. Retrieved December 16, 2019 .
- ↑ PJP Whitehead, ML Bauchot, JC Hureau, J. Nielsen, E. Tortonese: Fishes of the North-eastern Atlantic and the Mediterranean . Ed .: UNESCO. tape II , 1986.
- ↑ a b c d e f g h i j k l m n o p q r s Gerald Guldenschuh: The reproductive behavior of Chromis chromis (L.)., The Mediterranean monkey fish (Pisces: Pomacentridae): an etho-ecological study with supplementary studies on morphology and life history . Basel 1986.
- ↑ Marta Picciulina, Laura Verginellab, Maurizio Spotob, Enrico A. Ferreroa: Colonial nesting and the importance of the brood size in male parasitic reproduction of the Mediterranean damselfish Chromis chromis (Pisces: Pomacentridae) . Ed .: Environmental Biology of Fishes. No. 70 , 2004, pp. 23-30 .
- ↑ Chromis in the Catalog of Fishes (English)
- ↑ Chromis on Fishbase.org (English)
- ^ LA Rocha, R. Myers: Chromis chromis. The IUCN Red List of Threatened Species 2015. Retrieved December 16, 2019 .