Black sea bass (Stereolepis gigas)
|Also known as:||Giant sea bass|
|Size||Length: up to 250 cm (2)|
|Weight||up to 255.6 kg (2)|
Classified as Critically Endangered (CR A1bd) on the IUCN Red List 2004 (1).
As implied by its alternative name of giant sea bass, the most dramatic feature of this fish is its conspicuous size, with the largest individual recorded reaching a phenomenal 255.6 kg – a true giant of the ocean (2) (3)! The bulky, robust fish has a large mouth, small teeth and a distinctive single, strongly-notched dorsal fin (4). Almost as impressive as its size is the variation in colour displayed by this species. Juveniles start out life as a bright orange colour with black spots, with the orange turning a more bronzy purple as the individual grows and the spots fading as the fish gets darker. Large adults often appear solid black to grey, with a white underside, but retain the ability to display large black spots. Indeed, black sea bass are in fact capable of rapid and dramatic colour changes, from dark above and light below to displaying white mottling or simply changing from jet black to pale grey. These colour changes are thought to act as a form of communication between individuals or to be an indication of stress (3).
Found in the Eastern Pacific, from Humboldt Bay in California, U.S.A., to the tip of Baja in Mexico, as well as being found in the northern half of the Gulf of California. Recorded also in the coastal waters of northern Japan, although this occurrence is suspected to represent a misidentification (1).
Adults typically inhabit rocky bottoms near kelp beds in waters deeper than 30 m, while juveniles usually occur in and around kelp beds as well as sandy bottom areas at depths of 12 to 21 m (1).
Black sea bass can swim very fast for short distances (4) but are not built for sustained speed and the vast majority of their prey is caught on the sea bed (3). As the black sea bass rapidly opens its huge mouth a vacuum is produced, which draws in organisms crawling across the bottom or buried just below the surface, although some mid-water fish are also ambushed and sucked in. The diet largely consists of a range of fish such as sting rays, skates, flatfish, small sharks, as well as various crustaceans and octopus and squid (3).
Black sea bass mature at seven to ten years. Large spawning aggregations form over the period of June to September, and remain together for a period of one to two months (1). Large females are capable of producing enormous numbers of eggs, up to 60 million or more, which hatch in around 24 to 36 hours. The larvae then drift around feeding on plankton for about a month before becoming bottom-dwelling juveniles (3). Remarkably, individuals have been known to live to an age of at least 70 years (2).
The black sea bass has been massively over-fished in both California and Mexican waters, leaving this water giant Critically Endangered. Indeed, so dramatic were these declines that between 1932 and 1980 commercial landings diminished from 115 tonnes biomass to 5 tonnes in Californian waters, and from 363 tonnes to 12 tonnes in Mexican waters. The species’ limited distribution, large size and aggregation in spawning areas made it an easy target for fisheries (1). Unfortunately, its slow growth and late onset of sexual maturity make the fish extremely vulnerable to population collapses from over-fishing, and slow to recover (5). Additionally, it appears that the black sea bass may also be suffering from toxin poisoning. Sediments along the coast of California have been found to carry very high levels of toxins such as DDE and PCB, with an area off the Palos Verdes peninsula thought to contain possibly the highest loads of DDE (a breakdown product of DDT) in the world’s oceans. The toxins cannot be broken down so, as a mid-level predator, black sea bass ingest the cumulative toxins in increased concentrations from the food chain below it, and have been found to be carrying extremely high body burdens of DDE and PCB in southern California. The chemicals have been recorded to interfere with normal reproductive biology in other species of fish, as well as amphibians, reptiles and birds, but more research is needed into the effects they are having on this giant fish and its process of recovery in California (3).
The black sea bass has been protected in California since 1981 and in Mexico since 1992. Both commercial and recreational fishing of this species were prohibited in California in 1981, although two fish per angler per trip are allowed to be caught south of the U.S.-Mexican border and one fish per trip to be taken incidentally by commercial fishermen. The law also limited the amount of black sea bass that could be caught in Mexican waters and landed in California (1). Although these laws have prevented commercial fishermen from targeting and profiting from these fish, they have failed to protect the habitats occupied by the species from fishing and have probably done little to reduce incidental mortality, since black sea bass entangled in nets have simply been discarded back into the sea (5). Indeed, many fish in spawning aggregations in the summer have been caught and released, frequently receiving injuries in the process (6). However, the banning of gill nets in California in 1990 has probably helped significantly reduce the incidental mortality of this species, and anecdotal data suggest that numbers may be beginning to rebound (1) (5). Nevertheless, either voluntary or imposed seasonal and/or area closures would undoubtedly help further minimise incidental mortalities and greatly aid the recovery of this magnificent and dramatic giant of the sea (3) (6).
For more information on the black sea bass see:
IUCN Red List:
California Department of Fish and Game, Marine Region – Giant Sea Bass:
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IUCN Red List (December, 2009)