Paralabrax clathratusKelp bass(Also: Sea bass)

Geographic Range

Kelp bass are endemic to the eastern Pacific Ocean, along the western coast of North America. They are found from southern Baja, Mexico, north to the Columbia River in Washington state (48°N-23°N). This species is most commonly found along the Californian coast and is considered to be rare north of Point Conception, California. (Froese and Luna, 2013; Iwamoto, et al., 2010)


Kelp Bass typically inhabit kelp forests and are found almost exclusively in this habitat type. Individuals occupy several different micro-habitats within the complex three dimensional structures of these communities. For example, individuals will feed and take shelter in different and separate areas within the forest. Immature kelp bass nestle among kelp blades and seaweed in intertidal rocky areas, while adults may move further away from the kelp forest and venture deeper into rocky habitats, as they are less susceptible to predation. Adults typically prefer rock/boulder and artificial habitats because these environments offer high vertical relief, shade, and large holes in which to shelter. Mature kelp Bass can be found at depths of up to 61 m, but are most common in shallower waters (2.4-21 m). (Froese and Luna, 2013; Goodson, 1998; Iwamoto, et al., 2010; Love, et al., 1996; Young, 1963)

  • Range depth
    2.4 to 61 m
    7.87 to 200.13 ft

Physical Description

Immature kelp bass are light brown, while older fish are olive green. The upper portion of the head is mottled with pale yellow spots and the body also has black, white, and/or olive green blotches dorsally. There hare rows of rectangular white spots on the back, and the ventral areas are cream or white in color. Kelp bass are distinguished from other marine bass by their calico-like spotting under the belly. A large spine is present on the margin of the operculum. The third, fourth, and fifth dorsal fin spines are all the same length. These fish may reach lengths of 72 cm and the maximum published weight is 7 kg. Kelp bass are sexually dimorphic: males have an orange tint to their chin and lower jaw areas. ("Species infomation: Paralabrax clathratus", 2013; Cordes and Allen, 1997; Froese and Luna, 2013; Goodson, 1998; Gotshall, 1989)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    7.0 (high) kg
    15.42 (high) lb
  • Range length
    72 (high) cm
    28.35 (high) in


After being released from a female and fertilized in the water column by a male’s sperm, eggs hatch into larvae (within 36 hours, in a laboratory setting). Larvae are pelagic for 28-30 days and are carried to shallow water by the currents. Larvae settle on algae, particularly within kelp forests. As juveniles develop, they remain in the kelp forest for protection, going deeper into the ocean as they age. Kelp bass grow the most during their first year of life; annual growth is estimated at 17.78-8.1 cm SL. As a fish’s length increases, its annual growth decreases. The theoretical average maximum size of a kelp bass is 52.07 cm and there is a positive correlation between warmer temperatures and increased growth. (Cordes and Allen, 1997; Erisman and Allen, 2006; Iwamoto, et al., 2010)


Adult kelp bass form breeding aggregations, typically under and around structure such as kelp canopies and fronds near reef slopes, and sometimes around man-made structures such as piers, usually from 8-18 m in depth. These aggregations vary widely in size, from 3 fish to over 200; most commonly, aggregations consist of at least 50 individuals. During courtship, smaller groups (3-22 individuals) will break away toward open water from the larger aggregation. A gravid female will hover over the substrate, while a male performs any of a number of courtship behaviors, including: positioning himself perpendicularly to her; rolling from side to side in front of her (females may also tilt and or roll); hovering nearby; approaching, head on, with his dorsal fin extended; swimming by and rubbing his body against hers; nipping; chasing and swimming behind her; gaping his mouth. During mating, females turn dark gray or black dorsally, and bright white ventrally, while males become a charcoal color, with black bars and white spots. Males and females release gametes synchronously, typically in the evening. (Erisman and Allen, 2006)

Kelp bass spawning season is from May through October, peaking from June through August. Spawning does not appear to be linked to the lunar cycle, and has been observed for 18-38 consecutive days. Males and females may both spawn multiple times during a given period, even multiple times during one evening. Most kelp bass reach sexual maturity at 235 mm SL, which corresponds to an age of 2-4 years for males and 2-5 years for females, on average. (Cordes and Allen, 1997; Erisman and Allen, 2006; Iwamoto, et al., 2010; Love, et al., 1996)

  • Breeding interval
    Gametes may be released multiple times a night, for up to 38 consecutive days.
  • Breeding season
    Kelp bass breed from early May to late October, with a peak from June to August.
  • Average time to hatching
    36 hours
  • Range age at sexual or reproductive maturity (female)
    2 to 5 years
  • Range age at sexual or reproductive maturity (male)
    2 to 4 years

Kelp bass do not exhibit any form of parental investment beyond production of gametes. (Young, 1963)

  • Parental Investment
  • no parental involvement


The oldest wild kelp bass on record was 34 years of age. In captivity (Scripps Institution of Oceanography Aquarium), the oldest known individual was 12 years of age. Average lifespan in the wild is estimated at approximately 10 years, after which kelp bass typically fall within legal size limits for fishing. (Fitch and Lavenberg, 1971; Fitch and Lavenberg, 1975; Iwamoto, et al., 2010)

  • Range lifespan
    Status: wild
    34 (high) years
  • Average lifespan
    Status: wild
    10 years
  • Range lifespan
    Status: captivity
    12 (high) years


Kelp bass are diurnal, and are found near the substrate and throughout the water column during both day and night, though they are usually associated with some sort of cover; shade improves their ability to see and hunt effectively. They are quite curious and display strong site fidelity. A mark, release, and recapture study found that young kelp bass display a broader scale of movement patterns and dispersal, while older kelp bass display less movement. This shift in activity may be associated with an ontogenetic change in diet. Juveniles are active throughout the daylight hours, when zooplankton are more abundant. Small body size makes juveniles more susceptible to attack, which causes them to seek refuge in kelp beds at night. Sub-adults may feed more at night, due to their more varied diet and the availability of food. Adults become piscivorous, their diet consisting mainly of other fish, and can be found feeding during twilight. Congregations typically occur in pelagic waters during spawning and sometimes during group attacks on prey. (Goodson, 1998; Lowe, et al., 2003; Miller and Lea, 1972; Snyderman and Bailey, 1998)

  • Range territory size
    33 to 11224 m^2
  • Average territory size
    3250 m^2

Home Range

Tagging studies have shown home ranges of widely varying sizes, from 33-11,224 m^2, with an average of 3,328-3,349 m^2. Kelp bass move throughout their entire range during both day and night. Range size does not appear to be associated with fish size, as in many other species. (Lowe, et al., 2003; Miller and Lea, 1972)

Communication and Perception

Kelp bass perceive their environment through visual channels. Individuals display certain color patterns at specific times, particularly during mating encounters. During late spring and summer, these fish become dichromatic, signaling their reproductive status. Physical displays are also part of mating behaviors. Like other fishes, kelp bass have nares, used to sense dissolved chemicals in the water, and lateral line systems that sense vibrations and changes in water pressure associated with prey items and predators. They also have well-developed inner ears, with which they can detect auditory cues. (Bond, 1996; Erisman and Allen, 2006; Froese and Luna, 2013; Iwamoto, et al., 2010)

  • Communication Channels
  • visual

Food Habits

Kelp bass are carnivorous. Juveniles feed on items including plankton and small benthic invertebrates. Subadults feed on amphipods, brittle stars, shrimp, and other small fishes. Fully grown adults will feed on schooling fishes such as grunion (Leuresthes tenuis), anchovies (Engraulis mordax), saurys (Cololabis adocetus), and perch (Hyperprosopona argenteum), as well as octopus, squid, crab, and shrimp. They also demonstrate cannibalistic tendencies. Congregated feeding times are usually before and after spawning season, late spring and early fall. Kelp bass, though generally solitary, will form assemblies during spawning to feed on small schooling sh, working together in order to attack from all angles. They feed lightly in the winter and most heavily while spawning, from May through September. (Froese and Luna, 2013; Iwamoto, et al., 2010; Snyderman and Bailey, 1998)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans
  • other marine invertebrates
  • zooplankton


Larval kelp bass are a common food source to many creatures in the kelp forest, and adults are prey to many larger carnivorous fish, as well as to humans. Cryptic coloration may prevent them from being consumed by other marine animals. (Iwamoto, et al., 2010; Miller and Lea, 1972)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Kelp bass are carnivorous, consuming many of the organisms living in the high-complexity kelp forest habitat. They help to regulate the community, preventing overpopulation. Increased population density of kelp bass produces a greater output of larvae, which in turn provides more abundance of food for the entire kelp community. Just as the kelp habitat depends on kelp bass, these fish are equally dependent upon the availability of kelp habitat. (Snyderman and Bailey, 1998)

Kelp bass may serve as hosts to a number of ectoparasitic and endoparasitic species. They may seek out "cleaner fish" in order to have ectoparasites removed. ("Manter Collection Search", 2012; "Señorita", 2012; Bailly, 2013)

Mutualist Species
Commensal/Parasitic Species

Economic Importance for Humans: Positive

Kelp bass are one of the most common and important recreational fishing species in the nearshore waters of southern California. In Mexico, kelp bass are fished intensively for food. This species is viewed as a great game fish because of its willingness to strike artificial lures and a plethora of baits. (Fitch and Lavenberg, 1971; Fitch and Lavenberg, 1975; Iwamoto, et al., 2010)

  • Positive Impacts
  • food

Economic Importance for Humans: Negative

There are no known adverse effects of kelp bass on humans.

Conservation Status

In recent years, kelp bass have risen dramatically in popularity as a recreational fishery species in southern California. It is estimated that as many as a million kelp bass may be taken annually by recreational fishermen and commercial passenger fishing vessels. Commercial fishing of this species has been prohibited in California since the 1950s. Currently, populations in California appear to be stable, given the closure of the commercial fishery and implementation of catch size limits in recreational fisheries. Minimum size limits of 12 inches apply for sport fishing, with a bag limit of 10 bass. As of 2013, kelp bass are abundant in southern California and are listed as a species of least concern. However, this species should continue to be carefully monitored, given its long lifespan and slow growth rate. Currently, this species is expected to recover completely with the implementation of a system of effective no-take Marine Protected Areas in Southern California. (Gotshall, 1989; Iwamoto, et al., 2010; Young, 1963)


Tewa Canterbury (author), San Diego Mesa College, Veronica Pyper (author), San Diego Mesa College, Paul Detwiler (editor), San Diego Mesa College, Jeremy Wright (editor), University of Michigan-Ann Arbor.



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.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map


uses sound to communicate


Referring to an animal that lives on or near the bottom of a body of water. Also an aquatic biome consisting of the ocean bottom below the pelagic and coastal zones. Bottom habitats in the very deepest oceans (below 9000 m) are sometimes referred to as the abyssal zone. see also oceanic vent.

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.


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


having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

  1. active during the day, 2. lasting for one day.

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

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.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

intertidal or littoral

the area of shoreline influenced mainly by the tides, between the highest and lowest reaches of the tide. An aquatic habitat.


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).

keystone species

a species whose presence or absence strongly affects populations of other species in that area such that the extirpation of the keystone species in an area will result in the ultimate extirpation of many more species in that area (Example: sea otter).


seaweed. Algae that are large and photosynthetic.


eats mollusks, members of Phylum Mollusca


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.


reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.


An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).


photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)


an animal that mainly eats fish


an animal that mainly eats plankton


the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.


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


remains in the same area


reproduction that includes combining the genetic contribution of two individuals, a male and a female


lives alone


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).


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.)


2012. "Manter Collection Search" (On-line). Laboratory of Parasitology: University of Nebraska State Museum. Accessed June 27, 2013 at

2012. "Señorita" (On-line). Monterey Bay Aquarium. Accessed June 27, 2013 at

2013. "Species infomation: Paralabrax clathratus" (On-line). Smithsonian Tropical Research Institute: Shorefishes of the Tropical Eastern Pacific. Accessed June 24, 2013 at

Allen, L., D. Pondella II, M. Horn. 2006. The Ecology of Marine Fishes: California and Adjacent Waters. Berkley and Los Angeles, California: University of California Press.

Bailly, N. 2013. "Paralabrax clathratus (Girard 1854)" (On-line). World Register of Marine Species. Accessed June 24, 2013 at

Bond, C. 1996. Biology of Fishes, 2nd Edition. Belmont, CA: Thomson/Brooks Cole.

Castro, P., M. Huber. 2003. Marine Biology 4th Edition. New York, NY: McGraw-Hill.

Cordes, J., L. Allen. 1997. Estimates of age, growth, and settlement from otoliths of young-of-the-year Kelp bass (Paralabrax clathratus). Bulletin of the California Academy of Sciences, 96/2: 43-60. Accessed June 24, 2013 at

Erisman, B., L. Allen. 2006. Reproductive behaviour of a temperate serranid fish, Paralabrax clathratus(Girard), from Santa Catalina Island, California, U.S.A. Journal of Fish Biology, 68/1: 157-184. Accessed April 01, 2013 at

Fitch, J., R. Lavenberg. 1971. Marine Food and Game Fishes of California. Berkeley and Los Angeles, California: University of California Press.

Fitch, J., R. Lavenberg. 1975. Tidepool and Nearshore Fishes of California. Berkeley and Los Angeles California: University of California Press.

Froese, R., S. Luna. 2013. "Paralabrax clathratus" (On-line). Fish Base. Accessed March 06, 2013 at

Goodson, G. 1998. Fishes of the Pacific Coast. Stanford, California: Stanford University Press.

Gotshall, D. 1989. Pacific Coast Inshore Fishes. Monterey, California: Daniel W. Gotshall.

Iwamoto, T., B. Smith-Vaniz, R. Robertson. 2010. "Paralabrax clathratus" (On-line). The International Union for the Conservation of Nature and Natural Resources. Accessed June 24, 2013 at

Joseph, D., E. Barrett, H. Clemens, . Carlisle, J. Kutkuhn, K. Cox, P. Young, P. Tomlinson, R. Hallock, . Abramson. 1962. The Kelp Bass (Paralabrax Clathratus): And Its Fishery, 1947-1958, Volumes 114-125. California: Resources Agency of California, Department of Fish and Game,.

Love, M., A. Brooks, D. Bussato, J. Stephens, P. Gregory. 1996. Aspects of the life histories of the Kelp bass, Paralabrax clathratus, and Barred sand bass, P. nebulifer, from the southern California bight. Fishery Bulletin, 94: 472-481. Accessed February 12, 2013 at

Lowe, C., D. Topping, D. Cartamil, Y. Papastamatiou. 2003. Movement patterns, home range, and habitat utilization of adult Kelp bass Paralabrax clathratus in a temperate no-take marine reserve. Marine Ecology Progress Series, 256: 205-216. Accessed June 25, 2013 at

Miller, D., R. Lea. 1972. Guide to the Coastal Marine Fishes of California Volume 157. Oakland, California: University of California Press.

North, W., R. Hollis. 1976. Underwater California. Berkeley and Los Angeles, California: University of California Press.

Snyderman, M., M. Bailey. 1998. California Marine Life, a Guide to Common Marine Species. Niwot, Colorado: Roberts Rinehart Publishers.

Vogel, A., K. Selkoe, D. Anderson, S. Edmands. 2009. Development and inheritance of molecular markers in the kelp bass Paralabrax clathratus. Fisheries Science, 75/2: 525-527.

Young, P. 1963. The Kelp Bass (Paralabrax clathratus) and its Fishery, 1947–1958. Fish Bulletin, 122: 1-67. Accessed February 16, 2013 at