to 650m. Predation The predators that feed on T. rhombus include various species of ommastrephid squids, dolphin fish, lancet fish, tuna, swordfish, Gempylus serpens, and sharks. Other predators include mammals such as dolphins, rough-toothed dolphin, false killer whale and sperm whale. Reproduction The pairing of males and females occurs at an immature stage where mantle length is less than 100mm and pairs remain monogamous. Mating occurs in a head-to-head position, in which the male uses its hectocotylus to attach to the female's buccal membrane to transfer its spermatophores. Spawning is year round in tropical waters and lasts for 2–3 months, but in temperate regions spawning is more restricted to summer or early autumn periods and warmer currents. T. rhombus is known to be an intermittent spawner and is known to have multiple spawning in succession. Females will produce secretions of gel-like substance from nidamental glands, similar to the Japanese flying squid, during spawning that will enter the water and swell. This swollen secretion will then be molded by the female into a cylinder. Female's oviductal glands will then begin to form two mucous threads, each with one row of eggs, which will fuse into a single cord containing a double row of eggs in the mantle cavity. The fused cord exits through into the water through the funnel where the eggs are met and fertilized with spermatozoa from seminal receptacles that were attached to the female's buccal membrane. The fertilized egg cord is then wound onto the cylinder. A female can produce 8 to 12 masses if properly utilizing its vitelline oocytes. Commercial value T. rhombus is targeted by growing fisheries in near southern and central Japan due to its firm and flavorful flesh. The main fishing grounds are in the Sea of Japan, Okinawa Prefecture, and Kagoshima Prefecture. Majority, about 90%, of captures are located in the Sea of Japan and Okinawa. The Sea of Japan fishery runs from July to February, while the fishery in Okinawa runs primarily between November to April. To capture the diamond squid in the Sea of Japan, inshore trap nets and free-floating angling gear called "taru-nagashi" are used. In Okinawa, free-floating angling gear called "Hata-nagashi" is used for capture. "Taru-nagashi" is gear that consists of a vertical weighted long line with two or three artificial lures and with two or three rows of stainless steel hooks. At the other end of the line,