Tope, Galeorhinus galeus
The Tope, Galeorhinus galeus, whose Spanish common name is tiburón aceitoso, is a species in the family Triakidae, the Hound Sharks known as cazónes in Mexico. This fish is also known as the Soupfin Shark. Globally, there is only one species in the genus Galeorhinus, this fish, which if found in Mexican waters of the Pacific.
The Tope has an elongated slender body with a long snout. They have a gray or brown back and sides that transition to white ventrally. The underside of the snout tip is translucent. The fins do not have distinguishing marks with the exception that the pectoral fins have pale edges. Some fish have scattered pals spots on the flank. The head has a rounded mouth, very small front nasal flaps, horizontal oval eyes and small teeth of equal size on both jaws and broadly triangular with serrations on one side. The anal fin is the same size as the second dorsal fin and its origin is a behind the origin of the second dorsal. The caudal fin is strongly asymmetrical with a long upper lobe and a well-developed lower lobe (a key to a correct identification). The first dorsal fin is much larger than the second and is inserted well behind the pectoral fins. They have five gill slits with the last two being over the pectoral fins.
The Topes are a coastal schooling pelagic species that occur over the continental shelf and are demersal. They are found at depths up to 470 meters (1,545 feet) and reach a maximum of 200 cm (6.5 feet), with females being slightly bigger than males, making them the largest member of the family. The Tope feed on crabs, isopods, polychaetes worms, shrimp, squid and a wide variety of small fishes. In turn they are preyed upon by larger predatory bony fish including the Great White Shark, Carcharadon carcharias, the Sevengill Shark, Notorynchus cepedianus, and the larger marine mammals. They are a highly migratory species with both wintering and summer grounds and travel up to 2,500 km between. Reproduction is aplacental viviparous with embryos being nourished by a yolk-sac placenta with litters of twenty to thirty five 26 cm (10 inch) to 40 cm (16 inch) live pups being born. They have life spans of up to 60 years. In general they are poorly studied and very little is known about their behavioral patterns. The Topes are found in all Mexican waters of the Pacific north of Mazatlán.
Due to the shape of the tail his species cannot be easily confused with any other species.
The Tope has a wide global distribution in temperate waters and from a conservation perspective and is considered to be of Least Concern in Mexican waters but Vulnerable globally with decreasing populations. Major factors affecting their long term survival include targeting fishing with gillnets and longlines, without regulations, habitat destruction in nursery areas, and a very low reproduction rate due do to females requiring 10 years to reach sexual maturity. They have known pupping areas in shallow, protected bays and estuaries which makes them easy targets for commercial fishermen and they are an important recreational species in some parts of the world. In the Eastern Pacific they were a focused species between 1936 and 1944 as a source of Vitamin A but with the invention of synthetic Vitamin A the demand has been eliminated and they have had a chance to recover. Globally a modest demand exists for liver oil, meat and their fins. In general the meat is considered to be of marginal quality and not of economic significance. In Mexico over the last year all sharks have become protected species. This species is considered to be harmless to humans.