Dicentrarchus labraxEuropean bass(Also: Sea bass; White salmon)

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Geographic Range

European sea bass are found from northern England to northern Africa and throughout the Mediterranean and Black Sea. (Wheeler 1975)

Habitat

The European sea bass is typically an inshore species found in the surf zone, around outcrops of rocks, and in shallow coastal waters. Because they are found to be capable of surviving in estuaries in almost fresh water, it is thought that they could adapt to life in fresh water. In British waters they are migratory, approaching inshore in spring and summer, and moving into deeper water in late autumn. They spawn in inshore areas. (Wheeler 1975)

Physical Description

European sea bass are approximately 1 meter long. The body of a sea bass is covered by large, regular scales. Its color varies considerably, depending on the fish's origin, ranging from dark grey, blue or green on the back to a white or pale yellow belly. The flanks are silver-blue, sometimes pale gold or bronze. The head in young bass appears quite pointed, but it becomes blunter in older fish. Sea bass in their first year tend to be paler in appearance than older fish, and usually have dark spots on the back and upper sides. Normally these spots have disappeared by the time the fish is 1 year old, although some fish retain them well into adulthood. (Wheeler 1975, Pickett and Pawson 1994)

  • Range mass
    9 to 10 kg
    19.82 to 22.03 lb

Reproduction

Adult sea bass reproduce sexually by using external fertilization. The adults spawn from February to July. Temperature provides an important cue for the initiation and location of spawning because sea bass eggs are rarely found where the water is colder than 8.5-9.0 degrees Celsius or in water warmer than 15 degrees Celsius. During the spawning season, each mature female may produce between a quarter and half a million eggs per kilogram of her own body weight. Sea bass egg are planktonic and hatch between 4 and 9 days after fertilization, depending on sea temperature. During the following 2-3 months, the growing larvae drift from the open sea inshore towards the coast, and eventually into creeks, backwaters, and estuaries. These sheltered habitats are used by juvenile sea bass for the next 4-5 years, before they mature and adopt the migratory movements of adults. (Pickett and Pawson 1994)

  • Average age at sexual or reproductive maturity (female)
    Sex: female
    1460 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    730 days
    AnAge

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    15 years
    AnAge

Behavior

At an early age European sea bass form shoals. The shoals may vary from a few dozen individuals to many thousands, according to the strength of the year class and local conditions. Research suggests that bass may remain in distinct groups for several years at a time, and they may retain a shoaling habit throughout most of their lives. Aggression and territorial behavior:

When a sea bass appears to be threatened by a larger animal, it either retreats rapidly or adopts a typical defense posture. It makes itself appear larger and presents as many sharp spines to the aggressor as possible. There is little evidence of aggressive behavior between European sea bass of similar size, although they may be territorial when occupying summer feeding areas.

Swimming:

European sea bass are strong swimmers and their swimming power and speed increases with size. They are not inconvenienced by strong tides and turbulence and are particularly adept at using back-eddies and other slack water to avoid the strongest currents. Swimming power is gained from the large caudal fin, and the bass propels itself forward by bursts of three to four flicks of its tail, with all other fins flattened to the body to reduce drag. They can sustain a high average swimming speed while migrating.

Flashing:

This behavior occurs when fish are resting in a shoal near the bottom and then suddenly move forward, turn on one side and appear to rub one flank on the substrate. As a result of this action, an observer above sees the sudden silvery flash of a fish's flank. There are two explanations for flashing: either it is intended to disturb small crustacean food items buried in a sandy bottom, or it is an attempt to get rid of ectoparasites.

Burying and escape mechanisms:

European sea bass sometimes bury themselves in a soft substrate. This behavior is thought to be linked to flashing. The movement begins with a couple of flashes, followed by a pronounced sideways dig of the snout into the sediment. The fish partly bury themselves on their sides, and they stay buried for 30 to 60 seconds. This behavior is thought to result from perceived threat from predators and fishermen. (Pickett and Pawson 1994)

Communication and Perception

Food Habits

The European sea bass is a predatory species feeding on mainly small pelagic fish such as sardines, sprats, and sand smelts. They also feed on sand-eels and other bottom-living species, crustaceans, and squids. Young fish tend to eat more invertebrates than do older fish. European sea bass are opportunistic predators and are known to attack prey species quite violently. Throughout their life, they develop a wide range of tactics to find and capture their prey. One specific tactic they use is to drive upwards toward the surface and attack from below at a steep angle. They tend to feed on whatever prey species are seasonally abundant in a particular location. (Wheeler 1975, Pickett and Pawson 1994)

Economic Importance for Humans: Positive

The European sea bass is a renowned sporting fish, which is rated by British sea anglers as their best fighting fish. It is a species equally important to sport anglers and commercial fishermen. There is a strong international market for European sea bass and high prices are paid for them. (Pickett and Pawson 1994, Wheeler 1975)

Conservation Status

The European sea bass is not an endangered species, but there is a threat of over-exploitation of bass stocks. This is due to the fact that it is a very slow-growing species that can be over-exploited with only a little fishing effort. (Wheeler 1975)

Contributors

Julie Brosowski (author), University of Michigan-Ann Arbor.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

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.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

tactile

uses touch to communicate

References

Pickett, Graham D., Pawson, Michael G. 1994. Sea Bass-Biology, Exploitation, and Conservation. Chapman & Hall, London.

Wheeler, Alwyne. 1975. Fishes of the World. Macmillan Publishing Co., Inc., New York.