Liver Oil Shark

fieldmarks: A slender, long-nosed houndshark with vestigial anterior nasal flaps, large horizontally oval eyes with internal nictitating lower eyelids, subocular ridges obsolete, an arched mouth, moderately long upper labial furrows that fall short of lower symphysis, bladelike compressed teeth with oblique cusps and distal cusplets in both jaws, second dorsal fin much smaller than first and about as large as anal fin, and an extremely long terminal caudal lobe about half the dorsal caudal margin. Snout moderately long and parabolic in dorsoventral view, preoral length about equal to mouth width. Eyes horizontally oval and lateral, subocular ridges obsolete. Anterior nasal flaps vestigial, formed as small, low, angular points, well separated from each other and mouth; no nasoral grooves. Internarial width over 2.5 times nostril width. Mouth broadly arched and long. Labial furrows moderately long, uppers ending well behind level of upper symphysis. Teeth bladelike, compressed, and cuspidate, similar in upper and lower jaws, anteroposteriors with oblique cusps and cusplets; medial teeth well differentiated from anteroposteriors. First dorsal fin moderately large, base half length of dorsal caudal margin or less; origin over or slightly behind pectoral free rear tips, midbase slightly closer to pectoral bases than pelvics. Second dorsal much smaller than first, less than half height of first. Anal fin about as large as second dorsal. Ventral caudal lobe strong in young and adults; terminal lobe of caudal fin long and about 2 times in dorsal caudal margin.

Maximum 195 cm (large females of the eastern North Pacific form); males maturing between about 120 and 170 cm and reaching a maximum of 155 to 175 cm, females maturing between about 130 and 185 cm and reaching a maximum of 174 to 195 cm (combined figures for Californian, South African and Australian G. galeus); young born at about 30 to 40 cm long. Data from California soupfin sharks (Ripley, 1946) indicates that there is an allometric change in length/weight relationships in adult females but possibly not for males. Logarithmic length/weight curves given by Ripley (1946) indicate log Wt (lbs) = -5.573 + 3.270 log total length (cm) for female soupfin 40 to 149 cm but jumping to log Wt (lbs) = -7.490 + 4.156 log total length (cm) for females 150 cm and larger (N = 869); for males (N = 42) this is log Wt (lbs) = -5.411 + 3.186 log total length (cm). For males and immature females, weight increases at slightly more than the cube of the length, indicating a retention of the slim build of young sharks, but as females mature they become relatively stockier and grow at over the 4th power of their length. Olsen (1954), with a smaller sample (254) for females and larger one for males (278) suggested that for the Australian school shark there was no such change in females, but his plot of female length/weight relations (Olsen, 1954, fig. 3), suggests that females above 135 cm may be departing the curve calculated for all females (which is almost the same for that of males, Wt [lbs] = 4.86 x 10-6 total length exp 3.18; males, Wt [lbs] = 4.80 x 10-6 total length exp 3.17).

An active, strong-swimming, abundant, coastal-pelagic species of temperate continental and insular waters, often found well offshore (but not oceanic) as well as at the surfline, in shallow bays, and in submarine canyons; often occurs near the bottom, at depths of 2 to 471 m.It is best known and is very abundant in cold to warm temperate continental seas and tropical records of the species (particularly off West Africa but also Laysan island) need to be confirmed and may be based on some other species (off East Africa, possibly based on Hypogaleus hyugaensis). It apparently occurs in small schools that are highly migratory in higher latitudes in their range, in some places moving poleward during the summer and equatorially in the winter (European waters and the Eastern North Pacific, and southern Australia in part), or into deeper offshore waters in winter longitudinally in other areas (southern Australia in part). [more...] Ovoviviparous, without a yolk-sac placenta; number of young 6 to 52 per litter, increasing with the size of the mother and averaging greater in the Eastern North Pacific soupfin (in which the size at maturity and maximum size is greater, mean about 35) than in Australian school sharks (28) or European topes (possibly less than 20). Australian school sharks are recorded as producing litters with more males than females (54:46), but in two year old juveniles the ratio of males to females is reversed, apparently from increased mortality of males for unknown reasons. In school sharks the growth rate is regular and apparently does not show much seasonal variation. Male Australian school sharks mature at over 8 years old and mate at about 9 years, while females mature at at least 11 years old and give birth at at least 12 years old; the life expectancy of a large female school shark is at least 22 years.Preys heavily on bony fishes, taking a wide variety of bottom and schooling midwater fishes [more...] Although primarily an opportunistic predator on moderate-sized bony fishes (taken alive), this shark readily feeds on some invertebrates; young sharks may take more invertebrate prey than adults, and in some areas crabs and squid may be important prey items. This shark is little inclined to scavage, however, judging from the virtual absence of garbage and meat from terrestrial and large marine mammals in its reported diet (unlike the largely sympatric spotted sevengill shark, Notorynchus cepedianus, which readily eats such fare), as well as its strong preference for very fresh fish or squid bait over slightly stale or even fresh-frozen bait presented on hooks.Natural predators of this shark includes larger and more macropredatory sharks found in temperate waters, such as the great white shark (Carcharodon carcharias ), possibly the spotted sevengill shark (Notorynchus cepedianus ), and probably marine mammals.

This species is an important shark for fisheries, especially off Uruguay and Argentina, California, and southern Australia, but it is also fished elsewhere where it occurs. Its meat is excellent for human consumption and is eaten fresh, fresh frozen, or dried salted; its liver contains oil that is extremely high in vitamin A; and its fins are used for sharkfin soup.It is caught with bottom and pelagic gillnets, bottom and pelagic longlines, bottom and pelagic trawls, and with hooks and lines . A large fishery for this species existed off California in the thirties and forties, which peaked at 4186 tons landed in 1939 but declined with overfishing and the substitution of synthetic vitamin A for that extracted from shark liver oil. A very similar fishery existed off South Africa at about the same time as the Californian fishery, and went through a similar cycle of growth and collapse. Currently these sharks are the object of an expanding commercial and sports fishery for human food off California, but stocks are already showing some signs of depletion there. It is doubtful whether stocks off California have in recent years attained the size of those exploited before the second world war. Fisheries in Australia and New Zealand have been restricted or have collapsed due to findings of high mercury levels in school sharks caught there. Topes figure prominently in a South African fishery centred in Gans Bay, and are processed for vitamin oil, fins, and "biltong" or dried meat. FAO records of Galeorhinus galeus catches started in 1989 with 74 t reported by UK in area 27 (Northeast Atlantic) and have stabilized since. The catches reported in the "Impact of fisheries" section (see on top of this page) for New Zealand and France have probably been reported to FAO at a more generic level than species and are mixed with those of other species under the categories "Squalidae" and "Squalidae, Scyliorhinidae". Topes are also a common and popular catch of sports anglers, being commonly taken by rod and reel particularly in the British Isles, off South Africa and in California. The total catch reported for this species to FAO for 1999 was 4 256 t. The countries with the largest catches were New Zealand (3 633 t) and France (383 t). This shark will fight actively when hooked, but is currently not considered a game fish by the International Game Fish Association. Tope is among the most extensively fished sharks in the world. There have been important directed fisheries for this species in California, Australia, and Argentina. The outcomes of these enterprises vary from collapses to long-term commercial exploitation. The fishery for tope (locally known as soupfin shark) in the west coast of North America boomed in the late 1930s due to the discovery of the extremely high contents of Vitamin A in the liver oil of this species. Uncontrolled fishing led to a gold-rush phenomenon. Although available data from the fishery suffers from inconsistencies and does not accurately reflect what happened in the fishery (Roedel and Ripley 1950) catches and CPUE appear to have declined sharply in the period 1940-44 signalling a decrease in the size of the stock (Ripley 1946). The fishery ended with the industrial production of synthetic Vitamin A. Today, almost 50 years later, there are no indications that the stock of tope along the west coast of North America has returned to its original size (Holts 1988). Off Southern Australia, the tope (locally known as school shark) has partially sustained the world's oldest surviving commercial shark fishery dating at least from the 1920s. Overfishing in the 1950s (Olsen 1959, Walker 1996) led to the depletion of tope from the Port Phillip Bay nursery area. The lack or a recovery in this nursery area almost 40 years later might be due to changes in the habitat that make it unsuitable for tope recolonisation (Walker 1996). Catches of tope in the last 30 years have varied substantially but average about 1,500 t/y with management-induced decreases down to 800 t in 1996 (Walker et al. 1989, Anon. 1998b). According to a recent assessment the breeding stock of tope in southern Australia is currently 13-43% of its virgin size (Anon. 1998b). The assessment concluded that the exploitation rate of tope has been unsustainable despite many management measures for the fishery. This assessment recommended an immediate reduction in fishing for tope of at least 20-30% to allow the stock a 50/50 chance of stabilising at its current level in 15 years (Anon. 1998b). The tope fishery has been under different management regimes since at least 1952. There is limited entry since 1991 and there are currently plans of introducing an ITQ regime in 1998 (Anon. 1998b). In New Zealand, tope catches were about 100-500 t/y since the 1940s (Anon. 1997) but have varied around 100-5,000 t/y in the last 20 years (Bonfil 1994). An ITQ management system cut the catch by some 2,000 t in 1986. Tope has been fished in Argentina since at least 1935 (Chiaramonte and Corcuera 1995). The fishery underwent the typical boom and boost of the 1940s shark liver fisheries of the world, which declined sharply after the industrial production of synthetic vitamin A. Catches have rebounded since the late 1970s to supply shark meat export markets, but landings have not surpassed 5,000 t/y. The CPUE of tope in Argentina has varied widely during 1990-96 with no apparent trend, but the CPUE data is full of qualitative problems that render it unsuitable to assess the status of the stock (Chiaramonte 1998). Small catches of tope have increased recently in the Azores up to about 100 t/y (ICES 1998). Conservation Status : The tope has one of the lowest intrinsic rebound potentials found among 26 shark species analysed by Smith et al. (1998). The tope has been proposed as a Vulnerable species at the global level for IUCN Red List purposes, whilst the Australian and New Zealand stocks are proposed as Lower Risk/Conservation Dependent (Stevens in press). However, this classification is awaiting IUCN Shark Specialist Group consensus. Given the depletion of the California stock and its apparent lack of recovery after several decades, exploited stocks should be protected through special and extremely careful management. The worldwide distribution of tope and its still relatively high abundance likely provide a buffer against a possible overall depletion of the species, but conservation measures are strongly needed for individual stocks. In Australia, several coastal nursery areas for tope have been protected by no-fishing or strictly limited fishing policies (Anon. 1998b). Additional information from IUCN database Additional information from CITESdatabase