Occurrence,Growth and Food of Longheaded Eagle Ray, <Emphasis Type="Italic">Aetobatus flagellum</Emphasis>, in Ariake Sound,Kyushu, Japan

Synopsis The longheaded eagle ray, Aetobatus flagellum, has recently increased significantly in numbers in Ariake Sound. It is assumed that it feeds on bivalves and so, to prevent predation by eagle rays on bivalves, a ‘predator control program’ aimed at reducing the ray population has been in place since 2001. We examined their occurrence, age, growth and food in Ariake Sound to obtain data on the ecology of the eagle ray and provide basic information on their potential impact on bivalve stocks in Ariake Bay. The eagle ray is a seasonal visitor to Ariake Sound, increasing in numbers from April, and peaking during the summer. None were captured during surveys in December and February. Their movement pattern around the bay differed according to sex. Pregnant females were caught in the estuary during August and September. Females grew to a larger size than males and apparently lived longer. The maximum ages were 19 years for females and 9 years for males. Growth until two years was similar in both sexes, but after 2 years females grew larger. The eagle ray fed only on bivalves, especially Ruditapes philippinarum and Atrina pectinata, very important fishery species farmed in Ariake Bay.     

Age and size at sexual maturity for the winter skate, <Emphasis Type="Italic">Leucoraja ocellata</Emphasis>, in the western Gulf of Maine based on morphological,histological and steroid hormone analyses

Synopsis We determined age and size at sexual maturity in male and female winter skates, Leucoraja ocellata, from the western Gulf of Maine. Age estimated from vertebral band counts resulted in an Index of Average Percent Error (IAPE) of 5.6%, suggesting that this method represents an accurate approach to the age assessment of L. ocellata. Size at sexual maturity was assessed by evaluating three endpoints: steroid hormone concentrations, and morphological and histological criteria. Our results suggest that 50% maturity in males occurs at a total length of 730 mm and at 11 years of age. For females, our results suggest that 50% maturity occurs at a total length of 760 mm and between 11 and 12 years of age. Collectively, our study suggests that analyzing a combination of reproductive parameters offers an accurate estimation of sexual maturity in the winter skate. Moreover, our results indicate that L. ocellata is a late-maturing and long-lived species, characteristics which make it highly susceptible to over-exploitation by commercial fisheries.     

Age and growth of the blacknose shark, <Emphasis Type="Italic">Carcharhinus acronotus</Emphasis>, in the western North Atlantic Ocean with comments on regional variation in growth rates

We examined the age and growth of the blacknose shark, Carcharhinus acronotus, in the western North Atlantic Ocean by obtaining direct age estimates using vertebral centra. We verified annual deposition of growth increments with marginal increment analysis and validated it by analyzing vertebrae marked with oxytetracycline from a female blacknose shark held in captivity. Von Bertalanffy growth parameters indicated that female blacknose sharks have a lower growth constant (k), a larger theortical maximum size (L), and are longer lived than males. We compared these growth parameters for blacknose sharks in the western North Atlantic Ocean to growth parameters for blacknose sharks collected in the eastern Gulf of Mexico to test for differences between regions. Females in the western North Atlantic Ocean have a significantly lower L, lower k, and a higher theoretical longevity than females in the Gulf of Mexico. Males in the western North Atlantic Ocean have a higher L<>, lower k, and higher theoretical longevity than males in the Gulf of Mexico. The significant differences between these life history parameters for blacknose sharks suggest that, when possible, future management initiatives concerning blacknose sharks should consider managing the populations in the western North Atlantic and the Gulf of Mexico as separate stocks.     

Comparison of Reproductive Indicators and Analysis of the Reproductive Seasonality of the Tinfoil Barb, Puntius schwanenfeldii, in the Perak River, Malaysia

The reproductive seasonality of Puntius schwanenfeldii from the Perak River, Malaysia was investigated over a 19 month period. Females greater than 160g had mature or rematuring ovaries, and males of all sizes had mature testes throughout the study period. Analysis of female reproductive condition was based upon the presence of post ovulatory follicles (POF), the gonadosomatic index (GSI) and the volume fraction of stage IV oocytes (IV%), and GSI and presence of tubercles for males. Recrudescence followed immediately after ovulation, which allowed the use of objective thresholds to identify recently spawned females during the GSI and IV% recovery period. GSI and IV% were the best indicators of reproductive patterns as a result of their recovery period being longer than for POF. Male tubercles and GSI showed some statistically significant variation, but no clear relation with observed changes in female indicators. Reproduction was apparently aseasonal, and this pattern is likely an effect of flow regulation by dams which have virtually eliminated the dominant flood period and most seasonal flow variation. Hypothesized shifts in the reproductive seasonality due to flow regulation are consistent with predictions based on life history theory under conditions of altered environmental seasonality.     

Biology of Anguina plantaginis Parasitic on Plantago aristata

Among 17 species and cultivars of plants exposed to Anguina plantaginis, only Plantago aristata (bracted plantain) was a host. Larvae penetrated the emerging apical meristem; reproduces and migrated progressively; caused twisting and galling of leaves, looping andspiraling of peduncles, and transformation of floral structures into galls. Extreme infections caused stunting and death of entire plants. Hypertrophy and hyperplasia of leaf mesophyll, cell separation and disintegration, and xylem wall thickening in older galls occurred. Only third-stage larvae were infective, and they exhibited cryptobiosis under adverse conditions.     

Life history and male intertroop mobility among Japanese macaques (Macaca fuscata)

Male intertroop transfer among Japanese macaques (Macaca fuscata) often coincides with the mating season. However, no necessary connection exists between mating by newly arrived males and whether they join a troop—visitors often mate, and males that join troops may show little mating success. On the other hand, intertroop transfer often coincides with major events in the developmental and social life history of males, such as the attainment of sexual maturity and full adult body size or rise in dominance rank. Thus, intertroop transfer may reflect age-specific behavioral patterns in which males maintain a position in the age-rank structure of troops, where the rank acquired in a new troop is partially determined by age.