The reproductive system of the red stingray Hemitrygon akajei was described from 1,418 specimens, 682 males and 736 females, sampled year-round (2003-2014) from Ariake Bay to provide reproductive life history information for conservation and management of the species. Females reach sexual maturity at a larger size than males with the size at 50% sexual maturity 522.2 mm disc width (DW) and 321.5 mm DW, respectively. Male stingrays had semen in the seminal vesicles year-round. Dental sexual dimorphism was aseasonal. The mating period is protracted, spanning 7 consecutive months October-April but ovulation occurred during May. This suggests female sperm storage, which has not been described for dasyatid stingrays. Females have a single functional ovary and uterus (left) and reproduce via aplacental viviparity with lipid histotrophy. Gestation required 3 months with parturition during late July and early August. Uterine eggs without macroscopic embryos were observed during the first half of gestation suggesting a short period of arrested development or diapause. Developmental cohorts based on morphological features were described for embryos and can be used to characterize embryo growth and development for other stingray species. Observations of foetal mortality (1.25%) and morphologically abnormal embryos (0.72%) were uncommon. Pregnancy rate was 90% and reproduction was annual and synchronous. Hemitrygon akajei fecundity ranged from 7 to 25 and increased with female size. Although H. akajei is a medium-sized dasyatid ray, it has the highest fecundity reported for any batoid species. Elasmobranchs life histories usually are associated with a low degree of productivity that results in rapid population decline with increased fishing pressure. Producing high numbers of small young is a successful reproductive strategy for H. akajei that may be partly responsible for their resilience to fishing pressure and continued abundance in Ariake Bay. This study is the first to describe reproduction of H. akajei, an economically important top predator inhabiting coastal ecosystems throughout Asia.

Size at sexual maturity, reproductive cycle,

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Recent taxonomic and molecular work on the eagle rays (Family Myliobatidae) revealed a cryptic species in the northwest Pacific. This species is formally described as Aetobatus narutobiei sp. nov. and compared to its congeners. Aetobatus narutobiei is found in eastern Vietnam, Hong Kong, China, Korea and southern Japan. It was previously considered to be conspecific with Aetobatus flagellum, but these species differ in size, structure of the NADH2 and CO1 genes, some morphological and meristic characters and colouration. Aetobatus narutobiei is particularly abundant in Ariake Bay in southern Japan where it is considered a pest species that predates heavily on farmed bivalve stocks and is culled annually as part of a ‘predator control’ program. The discovery of A. narutobiei highlights the paucity of detailed taxonomic research on this group of rays. This discovery impacts on current conservation assessments of A. flagellum and these need to be revised based on the findings of this study.

Age, growth and sexual maturity of the fan ray Platyrhina sinensis in Ariake Bay, Japan were determined from specimens collected from May 2002 to September 2006. Age determination was conducted by vertebral centrum analysis using soft X-radiography. Annual band pair deposition was determined by marginal increment and edge analyses. The von Bertalanffy growth model best described the overall pattern of growth for both males and females (males Lϰ = 455.2, k = 0.56, t0 = -1.09; females Lϰ = 555.8, k = 0.28, t0 = -1.77; Lϰ is the theoretical asymptotic total length in mm, k is the growth rate coefficient and t0 is the theoretical time at zero length). Parameter estimates suggest that females attain a larger asymptotic total length and grow more slowly than males. The observed maximum ages were 5 years for males and 12 years for females. Age at 50% sexual maturity was 2.1 years for males and 2.9 years for females. The results indicate that this species is relatively fast-growing, short-lived and early maturing compared with many batoid species.

Determining the population parameters of herbivorous fishes facilitates our understanding of their overall effects on ecosystems. However, this has not been successful with species such as Kyphosus bigibbus that are difficult to age using otoliths. In this study, we estimated the age, growth and age at sexual maturity of K. bigibbus off the west coast of Kyushu, Japan, using fish scales and otoliths. Scales were found unreliable because they caused underestimation of the age of fish older than 5 years, whereas otoliths were reliable when used with our improved otolith-sectioning methodology. The maximum age and fork length were 46 years and 574mm for females and 32 years and 506mm for males. According to the von Bertalanffy growth curves, females became slightly larger than males, and both sexes showed nearly asymptotic fork lengths after 10 years. The age at 50% sexual maturity for females and males was 3.2 and 1.9 years respectively, which is extremely early considering their maximum age. The year-class composition of K. bigibbus suggests that its recruitment may have increased rapidly since 1999, following noticeable losses of kelp forests in this region. Our findings will contribute to the understanding of algal forest ecosystems and advancement of fish ageing studies.

Nomozaki, where a relatively high-density seaweed patch remained, and were tracked for more than 4 months using a biotelemetry system. During the survey, signals from the S. fuscescens were recorded with high frequency in the daytime and with low frequency at night. These was a similar trend of signals from K. bigibbus, but nove was recorded at night. The total signals per day decreased when the water temperature fell to 20°C for S. fuscescens and to 16 17°C for K. bigibbus. The movement patterns of S. fuscescens and K. bigibbus may change with water temperature, however, they still stayed around the seaweed patch oŠ Nomozaki during the winter and never migrated.There is a possibility of causing serious damage to seaweed during autumn and winter, because the activity ofˆsh extended over a long period of time as a consequence of the recent rise of water temperature.

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