Atractoscion nobilis inhabits brackish waters and usually prefers demersal areas. Rocky reefs and soft bottomed habitats are ideal. Juveniles are often found in shallow water along the coast, just beyond the surf zone where they preys upon mysids and drifting macrophytes. Juveniles can also be found in estuaries and coastal bays, which serve as nursery stations until individuals are large enough to survive further offshore. Maximum depth for A. nobilis is about 122 m.
Range depth: 122 (high) m.
Habitat Regions: saltwater or marine
Aquatic Biomes: reef ; coastal ; brackish water
Other Habitat Features: estuarine
Although predation on juveniles likely has a major impact on the distribution and abundance of white seabass, juvenile specific predators are currently unknown. However, it’s likely that any carnivorous fish will prey on them if they have the opportunity. Although adults have few predators within their ecosystem, great white sharks and California sea lions have been known to attack white seabass trapped in gill nets. Because it is a prized food fish, it has long been the target of commercial and sport fishers. Thus, humans are the most significant predators of white seabass. The coloration of white seabass may help help reduce risk of predation.
Known Predators:
Anti-predator Adaptations: cryptic
White seabass are moderately elongate and silver. They have two dorsal fins; the anterior dorsal fin contains 9 to 11 spines, and the posterior dorsal fin contains one spine with several soft rays extending behind it. They also have pelvic fins on the thorax, which are slightly posterior to the pectoral fins, a general characteristic of the family Sciaenidae. The lower jaw is marginally longer than the upper jaw, and the teeth are relatively small. The lateral line is slightly curved and extends from the operculum past the caudal peduncle to the edge of the indented tail fin. They also have a ridge that runs along their underbelly, a characteristic unique to this species. White seabass under 61 cm in length are considered reproductively immature. Young A. nobilis have dark yellow fins, and are predominantly silver, with 3 to 6 dark vertical bars on their sides. Adults are countershaded, with a ventral silvery color and a bluish-gray or copper dorsal color. Adults can grow to be 152 cm long and can weigh up to 41 kg. Sexual dimorphism has not been reported in this species.
Range mass: 41 (high) kg.
Range length: 61 to 152 cm.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
As small fry (between 0.6 and 5.7 cm long), white seabass inhabit coastal waters ranging from 3.6 to 9 m in depth. At 1 to 3 years of age, they seek out the calm waters of various bays, where they find refuge in eel grass beds. Lifespan in the wild is unknown, however, data recovered from tagged and recaptured individuals suggests they can live to be greater than 12 years old.
Range lifespan
Status: wild: 12 (low) years.
White sea bass can be found along the Pacific coastline, from Alaska to Baja California and in the Gulf of California. Larval and juvenile white seabass are often found in Sebastian Vizcaino Bay and San Juanico Bay, Baja California.
Biogeographic Regions: nearctic (Native ); pacific ocean (Native )
Atractoscion nobilis feeds on northern anchovy, market squid, Pacific sardines, blacksmith, silversides, and pelagic red crab. Larger A. nobilis also feed on Pacific mackerel, and juveniles feed almost exclusively on mysid shrimp.
Animal Foods: fish; mollusks; aquatic or marine worms; aquatic crustaceans; other marine invertebrates; zooplankton
Primary Diet: carnivore (Piscivore )
White seabass are secondary and tertiary consumers of smaller fish within rocky bottom areas and giant kelp forests. It is not known whether they directly compete with other predatory fishes within these ecosystems. White seabass are host to a number of different endo- and ectoparasite. Studies have found at least three species of copepod (Neobrachiella gracilis, Lepeophtheirus thompsoni, and Lepeophtheirus abdominis) throughout the exterior body and inside the mouth. Endoparasites known to use white seabass as a host include three different species of cestodes (Lacistorhyncus tenuis, Callitetrarhynchus gracilis, and Grillotia smarisgora), which were found within the internal organs and the mesentery, and two types of protozoans (Kudoa clupeidae and Ceratomyxa venusta), found within muscle tissue and gall bladder. Other parasites known to occupy the tissues of white seabass at some point throughout their life cycle include flatworms and roundworms, most of which can be found in the intestines. White seabass rarely experience significant negative effects due to parasitic infestations.
Commensal/Parasitic Species:
White seabass are an important commercial fish species, and are taken by commercial trawlers and sport fishermen. However, overfishing has led to a serious decline in the population, which is why white seabass hatcheries have been developed. The development of these hatcheries has helped to increase the population of white seabass and to create jobs.
Positive Impacts: food ; research and education
There are no known negative economic impacts to humans.
White seabass have the largest eggs of the six of Sciaenidae species found throughout the coastal waters of southern California. Fertilized eggs (1.24 to 1.32 mm in diameter) are most commonly found off the coast of Baja California, near Sebastian Viscaino Bay and San Juanico Bay. After hatching, larvae are about 2.8 mm in length. Juvenile fry have black bands which disappear at sexual maturity around 4 years of age. Maximum length of an adult white seabass is 1.5 m, with a maximum weight of 45 kg.
White seabass are currently listed as a species of least concern on the IUCN's Red List of Threatened Species. Although their numbers are low when compared to historical abundance, population size has increased over the past 30 years due to conservation and management efforts, including stricter regulations on fishing limits and the development of hatcheries. However, a small subpopulation in the Gulf of California is suspected to be in serious decline due to overfishing.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Aside from adaptations common to most bony fish species, little is known about how Atractoscion nobilis communicates with conspecifics and perceives its local environment. However, all members of Sciaenidae produce drumming sounds, a characteristic unique to this family. These low-frequency sounds are created by muscles that vibrate the swim bladder, making a sound like a drum roll. Males often make drumming calls just prior to spawning.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
In the mid 1970's, Hubbs-Sea World Research Institute in Carlsbad, California was founded under contract of the California Department of Fish and Game and became operational in 1995. It serves as an important resource, working in tandem with the White seabass Management Plan, to raise White seabass from eggs spawned in captivity through the juvenile stage before fry are released into the ocean. Once the fertilized eggs hatch, larvae are held in a cone tank without food for 4 days. For the next 25 days, fish larvae are fed newly-hatched nauplius larvae of brine shrimp (Artemia salina) and are moved to a round tank after 18-20 days spent in the cone tank. When the fish are 40-50 days old, their diet is slowly changed to dry pellets, and the fish are moved into a series of 6 tanks to allow them to grow but also to keep the larger individuals separate from smaller ones, since white seabass are cannibalistic. When average size and weight reaches about 10cm and 10g, small tags are inserted into the fish's cheek. While being handled and tagged, fish are placed into an anesthetic bath. Each tagged fish is put into a tube with a metal detector to make sure the tag has been successfully inserted. After being tagged, the fish are moved from their indoor tanks to outdoor pens in bays and coastal lagoons, where they will be held and fed for a minimum of 90 days or until they reach 20cm in length. Animals are released shortly there after.
Money collected from the sale of fishing license stamps bought in California between Santa Barbara and the San Diego funds the Sea World-Hubbs Research Institute. The hatchery is capable of producing 350,000 juvenile white seabass annually. A person who returns the head of a legal-sized tagged White seabass to the California Department of Fish and Game is entered in a raffle to win $500.00. Since hatcheries became operational, over 1800 fish have been recaptured, of which 156 were legal size (over 71 cm). The oldest tagged fish was released in 1994 and recaptured in 2007.
White seabass are promiscuous. Males and females spawn multiple times with different partners.
Mating System: polygynandrous (promiscuous)
White seabass can spawn up to 5 or 6 times a year. Spawning generally occurs between April and August, when water temperatures are 18 degrees Celsius. Generally, white seabass reach sexual maturity between 3.5 and 4.5 years of age. Females are mature by 4 years of age and nearly 61 centimeters long, and males become sexually mature by 3 years and 51 centimeters long. Females can produce over 1.5 million eggs per spawning event. As a female becomes ready to spawn, she develops distinct black lateral bars and decreases her swim rate. When identified as a reproductive female, she is pursued by multiple males, which compete for prime spawning positions. After the eggs are fertilized, adults do not remain to protect them. Eggs develop while suspended in the water column until several months later, when they develop into free-swimming fry.
Breeding interval: White Sea Bass spawn several times a year.
Breeding season: Spawning occurs from spring to early summer.
Range age at sexual or reproductive maturity (female): 3.5 to 4.5 years.
Range age at sexual or reproductive maturity (male): 3.5 to 4.5 years.
Average age at sexual or reproductive maturity (male): 3 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); broadcast (group) spawning; oviparous
As White seabass are broadcast spawners, parental care is nonexistent. Fertilized eggs develop while suspended in the water column.
Parental Investment: no parental involvement
White seabass or white weakfish, Atractoscion nobilis, is a species of croaker occurring from Magdalena Bay, Baja California, to Juneau, Alaska. They usually travel in schools over deep rocky bottoms (0–122 m) and in and out of kelp beds.
The body of the white seabass is elongate, and somewhat compressed. The head is pointed and slightly compressed. The mouth is large, with a row of small teeth in the roof; the lower jaw slightly projects. The color is bluish to gray above, with dark speckling, becoming silver below. The young have several dark vertical bars. The white seabass is closely related to the California corbina, but is the only California member of the croaker family to exceed 20 pounds in weight. The largest recorded specimen was over 5 feet, 93.1 pounds. They are most easily separated from other croakers by the presence of a ridge running the length of the belly. C The diet of white seabass includes fishes, especially anchovies and sardines, and squid. At times, large fish are found which have eaten only Pacific mackerel. At the minimum legal length of 28 inches, the average white seabass is about 5 years of age, weighs about 7.5 pounds and has been sexually mature for at least one spawning season.
White seabass are fished primarily with live bait in relatively shallow water, but they will also take a fast-trolled spoon, artificial squid or bone jig. Live squid appear to be the best bait for a white seabass, but large anchovies and medium-size sardines are also good. At times, large white seabass will bite only on fairly large, live Pacific mackerel. The young of this species are exceptionally vulnerable to sport anglers for two reasons: The first is that as juveniles they inhabit shallow nearshore areas, bays, and estuaries, and the second is that they are not easily recognized as white seabass by the average angler. Commonly, these young fish are mistakenly called "sea trout" because of their sleek profile and vertical bars or "parr marks". To add to the confusion, these bars fade as the fish grows.
In California, there is a minimum 28 inch size limit and current fishing regulations should be checked concerning bag limits.
White seabass or white weakfish, Atractoscion nobilis, is a species of croaker occurring from Magdalena Bay, Baja California, to Juneau, Alaska. They usually travel in schools over deep rocky bottoms (0–122 m) and in and out of kelp beds.
