Common snook are amphidromous fish, moving between fresh and salt water during their life, but not for the purpose of breeding. They can be found in freshwater, brackish, or marine environments at depths up to 22 m. They commonly associate with underwater structures such as pilings, reefs, or sea grass beds, but they most often prefer mangrove-fringed estuarine habitats. As adults, common snook are generally non-migratory, but often assemble in high salinity regions in order to spawn. Most live in waters of temperatures between 25 and 31°C. ("Encyclopedia of Life", 2001; "Texas Parks and Wildlife Department", 2009; Froese and Pauly, 2010; Hill, 2005; Press, 2010)
- Other Habitat Features
- Range depth
- 22 (high) m
- 72.18 (high) ft
Common snook are easily recognized by their elongate body, distinct sloping forehead, concave snout, and protruding lower jaw. They are further characterized by their prominent black lateral line, which is formed by 67 to 72 pored scales, that extends into the caudal fin. Common snook range from 0.14 to 140 cm in length (average 50 cm) and can weigh as much as 23.3 kg. Females are generally larger than males.
Coloration ranges from dark brown to dull gray with a yellow to green tint on the dorsal surface. The lateral surface tends to be silvery, and the ventral surface is generally white. The pectoral fins, pelvic fins, second dorsal fin, and the dorsal lobe of the caudal fin are all bright yellow in color, however, some specimens are considerably darker.
Unlike in other species within the genus Centropomus, the tips of their pelvic fins do not overlap or reach the anus. Common snook have 2 dorsal fins that are well-separated, each with 8 to 9 dorsal spines and 10 dorsal soft rays. The anal fin has 3 spines and 6 soft rays, and the second anal spine does not reach vertical from the caudal base. The pectoral fins have 15 to 16 rays and do not reach vertical from the tip of the pelvic fins. ("Encyclopedia of Life", 2001; "Texas Parks and Wildlife Department", 2009; Froese and Pauly, 2010; Hill, 2005; Press, 2010)
- Sexual Dimorphism
- female larger
- Range mass
- 23.3 (high) kg
- 51.32 (high) lb
- Range length
- 0.14 to 140 cm
- 0.06 to 55.12 in
- Average length
- 50.0 cm
- 19.69 in
The oocytes in follicles of common snook mature in a manner typical of most teleost fishes. The yolk averages 91% of egg mass. Eggs average 0.6 – 0.8 mm in diameter (0.27 mm^3 volume).
Hatchlings measure 1.4 to 1.5 mm in length. Common snook grow slowly in the first month following hatching, but growth rates nearly triple thereafter until the end of the first year. Juveniles can grow as much as 1 mm per day, but this rate slows to about 0.15 mm per day once they reach 2.4 mm in length. Juvenile common snook typically have absorbed their yolk sac by the time they reach 2.2 mm in length (in about 4 days). At 4.0 mm in length, melanophores become visible, and, by 7.0 mm in length, adult pigmentation becomes apparent. Bone ossification begins when juveniles reach roughly 5.0 mm in length, and by 8.6 mm the jaws are completely ossified and lined with teeth. (Hill, 2005)
Although common snook can occupy both freshwater and marine environments, they must spawn in saltwater, as sperm can only become active in saline conditions. Common snook are often observed congregating at the mouths of rivers, inlets, and canals during times of spawning. Several males often follow a single female during these mass spawning congregations. Common snook spawn in the evening over a period of several days. In Florida, two reproductive peaks are often observed, the first from June to July and the second from August to October. Reproductive peaks often occur during times of increased rainfall, which may be the result of increased phytoplanktonic primary production during rainy periods. If so, spawning activity may related to food availability. (Hill, 2005; Press, 2010)
Common snook are protandric hermaphrodites, meaning they change from male to female after maturation. The gonads of common snook contain both male and female sex cells. Female gonads mature directly from mature male gonads shortly after a male has concluded spawning. This transition takes place between the ages of 1 and 7 years. As a result of this process, the majority of small common snook are male and the majority of large individuals are female. In Florida, the ratio of males to females between the ages of 0 and 2 years differs significantly between the east and west coasts of the state. This variation is attributed to protrandry and differences in growth and mortality rates.
Common snook breed seasonally and are often observed congregating at the mouths of rivers, inlets, and canals during times of spawning. In Florida, two reproductive peaks are often observed, the first from June to July and the second from August to October. Spawning often peaks during times of increased rainfall. Common snook practice broadcast spawning. (Hill, 2005; Press, 2010)
- Key Reproductive Features
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sequential hermaphrodite
- broadcast (group) spawning
- Breeding interval
- Common snook generally breed twice each year.
- Breeding season
- In Florida, reproduction of common snook peaks in June and July and again from August to October.
Little information is known regarding the parental investment of common snook in their offspring. As broadcast spawners, however, members of this species are unlikely to provide parental care to hatchlings or juveniles.
- Parental Investment
- no parental involvement
It is estimated that common snook can live about 20 years. The oldest captured common snook on the Atlantic coast was an 18-year-old female, while on the Gulf coast the oldest was a 15-year-old female. (Froese and Pauly, 2010; Press, 2010)
- Range lifespan
- 18 (high) years
- Range lifespan
- Typical lifespan
- 20 (high) years
- Typical lifespan
Common snook, as amphidromous fish, often move between fresh and salt water throughout their life. Common snook congregate seasonally in saltwater near the mouths of rivers, inlets, and canals in order to spawn. Common snook are considered social in that they are often found in groups, especially during times of spawning. (Hill, 2005; Press, 2010)
Home ranges are not recorded for common snook.
Communication and Perception
Common snook, like most fish, uses their lateral line system to detect movement and vibrations in the surrounding water. This sense organ allows a fish to orient itself in the water column, avoid collisions with other fish or submerged objects, and sense the presence of other organisms such as predators or potential prey. Common snook are sight-feeders, using their sense of vision in concert with their olfaction and gustatory senses to find prey. They attempt to capture any moving particle in their mouth, where the potential food item is then either ingested or rejected depending on taste and texture. Marine fishes, including common snook, can distinguish amino acids solutions at concentrations to the order of 10^-9 M using their sense of olfaction. Common snook, with their acute senses of vision and olfaction in combination with their lateral line system, are some of the top predators in their habitat. (Borquez and Cerqueira, 1998; Hill, 2005)
Common snook are pelagic feeders. Daily feeding peaks occurrs 2 hours before sunrise and 2 to 3 hours after sunset. Their feeding behavior is affected by the tidal cycle, and feeding activity noticeably increases with an increase in water flow following a period of standing flood or ebb tides
Common snook are voracious predators and opportunistic carnivores. They primarily feed on other pelagic fish, though diet varies with habitat type. Juveniles generally inhabit freshwater habitats, and their diet primarily consists of palaemonid shrimp, microcrustaceans, copepods and mosquitofish. In saltwater environments, common snook have a similiar diet, but they may also prey upon other species of fish such as sheepshead minnows, bay anchovies, and pinfish. In saltwater environments, common snook also consume zooplankton and larger crustaceans. (Hill, 2005; Press, 2010)
- Animal Foods
- aquatic crustaceans
Common snook are considered top predators in their habitat, and adults do not have any natural predators other than humans. Juveniles are preyed upon by dolphins (Delphinidae and Phocidae), fish-eating birds such as osprey and herons, and larger species of fish. (Hill, 2005; Press, 2010)
Adult common snook are top predators in their environment, preying on many species of pelagic fish, crustaceans, and copepods. Juveniles are preyed upon by dolphins, birds, and larger fish. In Florida, common snook are often parasitized by myxosporeans: Myxobolus centropomi, Fabespora sp., and Ceratomyxa choleospora. (Hill, 2005; Press, 2010)
- Myxobolus centropomi
- Ceratomyxa choleospora
- Fabespora sp.
Economic Importance for Humans: Positive
While commercial fishing of common snook is illegal throughout Texas and Florida, they are prized game fish throughout their known geographic range. They are known as strong fighters when hooked. In 1986, Florida's fisheries and sport fishing enterprises of all game fish were estimated to be worth 5 to 7 billion USD annually. Common snook is prized for its culinary value. ("Texas Parks and Wildlife Department", 2009; Froese and Pauly, 2010; Hill, 2005; Press, 2010)
Economic Importance for Humans: Negative
There are no known adverse effects of common snook on humans.
Populations of common snook have declined over the last 50 years due to commercial and recreational overfishing as well as habitat degradation and destruction. In 1957, a bill was passed in the Florida legislature which prohibited commercial fishing and the sale of common snook. Passage of this bill helped alleviate commercial fishing pressures on native populations, but habitat loss and water quality degradation may have a continued effect on populations of common snook. In January 1999, the Florida Fish and Wildlife Conservation Commission implemented a slot limit for recreational fisherman in order to protect larger breeding females. Florida fisherman can only harvest common snook between 26 and 34 in (66 to 86 cm) in length. Furthermore, there is a bag limit of 1 or 2 fish per person per day depending on the area. Fishing for common snook is closed between December 15 and January 31 statewide in Florida. (Hill, 2005; Press, 2010)
Brandon Shallop (author), University of Michigan-Ann Arbor, Phil Myers (editor), University of Michigan-Ann Arbor, Gail McCormick (editor), Animal Diversity Web Staff.
- Atlantic Ocean
the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the southern part of the New World. In other words, Central and South America.
uses sound to communicate
- bilateral symmetry
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
- brackish water
areas with salty water, usually in coastal marshes and estuaries.
an animal that mainly eats meat
uses smells or other chemicals to communicate
the nearshore aquatic habitats near a coast, or shoreline.
active at dawn and dusk
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
uses electric signals to communicate
an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.
- external fertilization
fertilization takes place outside the female's body
union of egg and spermatozoan
A substance that provides both nutrients and energy to a living thing.
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
having the capacity to move from one place to another.
specialized for swimming
- native range
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
an animal that mainly eats fish
condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products
structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.
- saltwater or marine
mainly lives in oceans, seas, or other bodies of salt water.
- seasonal breeding
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
associates with others of its species; forms social groups.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)
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