temperatures, the larger fish in water ranging from 18°C to 22°C and the smaller fish in warmer waters ranging from 23°C to 25°C (Sella, 1931).

Baglin (1982) found no mature fish among 12 six-year-old females and 15 seven-year-old females sampled during June in the Mid-Atlantic Bight, whereas generally it is accepted that eastern Atlantic/Mediterranean bluefin tuna mature sexually in the third year (Tiews, 1963; Rodriguez-Roda, 1971; Cort and Liorzou, 1990b). The study by Rodriguez-Roda (1967) of 50 eastern Atlantic/Mediterranean bluefin tuna en route to spawning locations appears to be the primary data for the postulated size at maturity in this stock: 50% of three-to four-year-old fish were mature, whereas 100% of four-to five-year-old fish were mature (Cort and Loirzou, 1990b). The works of Baglin (1982) and Rodriguez-Roda (1967) appear to form the primary basis for the hypothesis that size at, and age of, sexual maturity in western Atlantic bluefin tuna (200 cm and 10 years) are larger and greater, respectively, than for eastern Atlantic/Mediterranean bluefin tuna (130 cm and five years).

Clay (1990) criticized Baglin (1982), noting that (1) sample sizes of each year class in Baglin's study were small; (2) sampling was carried out in June, near the end of the spawning season; and (3) vitellogenic oocytes in the six-and seven-year-old fish were being resorbed. This note concerning resorption is important because rapid resorption in fish makes it impossible to report whether or not a particular fish has spawned if it has been sampled only a few weeks after the spawning period (VanDerKraak, pers. comm.).³ On this basis, Clay (1990) suggested that western Atlantic bluefin tuna also might become sexually mature before the age of 10 years. Clay (1990) also criticized the study of Rodriguez-Roda (1967) by noting that only one immature female in the length interval of 75 to 80 cm was included in his analysis (the next size interval was 115 to 120 cm, where all fish were mature) and that the fish were from the south Atlantic coast of Spain and may not have adequately represented the eastern Atlantic/Mediterranean population. Clay (1990) noted that the sample sizes and seasonal representation of individuals in both studies were inadequate and that conclusions based on the hypothesis of differences in spawning locations between western Atlantic and eastern Atlantic/Mediterranean bluefin tuna were compromised. The geographic extent of sampling in these studies was inadequate. The basis for a difference in spawning age and size between western Atlantic and eastern Atlantic/Mediterranean bluefin tuna depends primarily on two studies, neither with adequate sampling of seasons and locations. Because differences in life history characteristics could signal significant biological or genetic differences among