Age, growth, and reproduction of blackspot snapper Lutjanus fulviflammus (Forsskål 1775) around Yaeyama Islands, southern Japan, between 2010 and 2014

Abstract

Age, growth, and reproductive characteristics of blackspot snapper Lutjanus fulviflammus around the Yaeyama Islands (24°N, 124°E) in southern Japan were investigated between 2010 and 2014. Samples were caught by angling or purchased monthly at fish markets to cover all size ranges and seasons. Specimens consisted of 280 females (176–347 mm fork length), 177 males (193–325 mm), and 17 juveniles (42–128 mm). Spawning was confirmed from April to August by the presence of postovulatory follicles, which, based on the occurrence of yolked oocytes possibly also occurred in March and September. Maximum fork length and age in the specimens around Yaeyama Islands were 347 mm and 23 years for females and 325 mm and 21 years for males. These results were compared to those reported previously for the species in other regions by standardized criteria. Possible spawning duration of 7 months in the population around Yaeyama Islands is similar to that in New Caledonia (22°S, 5 months) and Okinawa Island (26°N, 6 months), but shorter than that in Tanzania (8°S) and the southern Arabian Gulf (25°N) (~12 months). The maximum body sizes and ages around Yaeyama Islands are also similar to the populations in New Caledonia and Okinawa Island (>300 mm FL, >20 years old), but larger/older than those in Tanzania and the southern Arabian Gulf (<300 mm FL, <20 years old). These differences are thought to reflect water temperature, i.e. spawning duration is shorter in lower temperature regions (annual mean <26°C, New Caledonia, Okinawa Island, Yaeyama Islands) than in higher temperature regions (annual mean >27°C, Tanzania, southern Arabian Gulf). Subsequently, a shorter spawning duration extends the life-span as well as the maximum body size. Longevity of blackspot snapper is thought to be negatively correlated with the duration of the spawning season.