Copper Shark, Carcharhinus brachyuus

Copper Shark, Carcharhinus brachyus. Fish caught from coastal waters off Perth, Australia, September 2016. Length: 97 cm (3 feet 2 inches). Catch, photograph and identification courtesy of Eli (obsessiveangling.wordpress.com).

Copper Shark, Carcharhinus brachyus. Fish caught off Point Palmilla, Baja California Sur, April 2022. Length: 1.22 cm (4 feet 0 inches).

The Copper Shark, Carcharhinus braychyus, is a member of the Requiem Shark or Carcharhinidae Family, that is also known as the Bronze Whaler and the Narrowtooth Shark and in Mexico as tiburón de cobrizo. Globally, there are thirty-five species in the genus Carcharhinus, of which seventeen are found in Mexican waters, seven in the Atlantic, four in the Pacific, and six in both the Atlantic and Pacific Oceans.

The Copper Shark is large with a slender, streamlined fusiform shark-like body with bilateral symmetry with a slightly arched profile. They are sexually dimorphic but similar in appearance with differences with the males easily recognized by having proportionately longer and more hook shaped teeth than the females and juveniles. They are bronze to olive-gray dorsally with a metallic sheen color that transitions to white ventrally. Their fins have dark margins and white or dusky tips. Their caudal fin has a bulge near the base of the front edge. Their first dorsal fin has a well-developed lower lobe and a deep ventral notch near the tip of the upper lobe; their first dorsal fin originates over the tips of the pectoral fins and is tall with a pointed apex and a concave trailing margin; their second dorsal fin is opposite the anal fin and is small and low; and, their pectoral fins are large, point and sickle-shaped. They do not have a ridge between the dorsal fins. Their head has a long narrow bluntly pointed broad snout with the nostrils preceded by low skin flaps, moderately large circular eyes that have nicitiating membranes and a mouth that has short furrows at the corners with 29 to 35 rows of narrow, hook-shaped teeth on the upper jaw and 29 to 33 rows of teeth on the lower jaw.

The juvenile Copper Sharks are found in brackish rives, estuaries, shallow bays, harbors and the surf zone at depths up to 30 m (98 feet) and with maturity move to offshore waters at depths up to 100 m (330 feet). They spend the majority of their time as solitary individuals but form large schools for feeding and reproduction. Their schools are segregated by size and sex. They are not found in waters that are less than 12 C (54°F). They are one of the largest coastal sharks reaching a maximum of 3.3 m (13 feet 0 inches) in length and 305 kilograms (671 lbs) in weight. They are ectothermic with body temperatures that are the same as their surroundings. The Copper Shark is a top apex predator, equipped with sophisticated hunting tools including strong senses of vibrations and electro-conductivity, that are often found in schools that consume a wide variety of bottom living and pelagic cephalopods (octopus and squid) and fishes with larger fish focusing on other elasmobranchs, and carrion. The juveniles feed on jellyfishes and benthic crustaceans. In turn their juveniles are preyed upon by larger sharks and killer whales. They make seasonal migrations of up to 1,320 km (820 miles) following temperature changes, reproduction events, and the availability of prey that vary with sex and age. The adult females move to southern warmer waters for the winter and then north in the early spring for mating.  Reproduction is aplacental viviparous with internal fertilization and occurs once every two years. They are promiscuous and will mate with more than one mate throughout their lifetime. They reach sexual majority late in life – 15 to 20 years for females and 13 to 19 years for males. The embryos are nourished by a yolk-sac placenta, require one full year to develop inside their mother and are born live in near shore nursery areas in the spring. Liter sizes are seven to twenty-four 55 cm (22 inch) to 67 cm (2 feet 2 inch) pups that are born in shallow nursery areas that appear as self-sustaining miniature adults. The adults spend the majority of their time over the continental shelf and around offshore islands and banks. The juveniles remain in shallow water at depths less than 30 m (100 feet) for a couple of years to mature and to avoid predation. The adults return to the same areas year after year. They have life spans of 30 years for males and 25 years for females.

The range of the Copper Shark is poorly defined due to confusion with other species. They are the only member of the genus that extends into temperate latitudes. In Mexican waters they are found in both the Atlantic and Pacific Oceans. In the Atlantic they are limited to the southwest Gulf of Mexico and the northeast tip of the Yucatán Peninsula. In the Pacific they are found in all water with the exception of the extreme northern portions of the Sea of Cortez and south of Acapulco, Guerrero. They have a known nursery area in coastal waters off Guerrero Negro, Baja California.

The Copper Shark is difficult to distinguish from other large requiem sharks and are most likely confused with the Blacktip Shark, Carcharhinus limbatus, the Dusky Shark, Carcharhinus obscurus, the Sandbar Shark, Carcharhinus plumbeus, and the Spinner Shark, Charcharhinus brevipinna, all of which have differing upper tooth shape, lack an interdorsal ridge and have different fin markings.

From a conservation perspective the Copper Shark is classified differently by location but generally considered to be VULNERABLE. Although widely distributed, their populations are sparsely distributed with small regional isolated populations around the world and in many areas are considered to be Data Deficient. Their global populations are in significant decline which are attributed to very long reproduction rates, low fecundity, heavy fishing pressure and human induced destruction of their inshore nursery areas. They are caught as a bycatch by commercial fishermen in longline, purse seine and gill net fisheries across many parts of their range. Due their lifestyle and their close proximity to shore disproportionate levels of juveniles and females are caught from inshore waters. Catch and landing rates have significantly declined over the last 15-years. Their meat is considered to be excellent and their fins are sold in Asian markets at elevated prices. The United States has banned all commercial landings. They remain, however, unregulated throughout the majority of their range. They are heavily pursued by recreational anglers in regions where they are abundant. They are considered to be potential dangerous to humans but accurate data is unavailable as the requiem sharks are easily confused. They have been dated to Miocene Period, 5.3 to 23 million years ago.