Population characteristics of gammaridean amphipod, Grandidierella japonica Stephenson (1938) as the invasive species collected from southern coastal waters in Korea

Abstract

In spite of the ecological riskiness of the invasive populations, comparison of various ecological parameters of them has advantages in the spatial and temporal studies between population structures and different habitats. Grandidierella japonica is one of the most well-known invasive gammaridean amphipod around the Pacific region. We studied on the population dynamics (i.e. life history, size distribution and secondary production) of G. japonica, inhabiting euryhaline environment in tidal creek at Sinji Is., South Korea. The life history pattern was annual and iteroparous, with two dominant recruitments from November 2010 to January 2011, and from June to August 2011. The population was annually consisted of four main cohorts winter-spring cohorts, short early summer cohorts, summer-autumn cohorts, and over-wintering cohorts. The sex ratio was usually female-biased. The maximum size of males, non-ovigerous, and ovigerous females were 10.2 mm, 11.10 mm, and 9.36 mm, respectively. There was a positive relationship between ln value of brood size and the ln value of body length of ovigerous females, and they were significantly different between two breeding periods of winter-spring and summer-autumn periods (p<0.001). The egg volume of stage I (early embryo) in winter breeding period showed significantly higher than that of summer breeding season (p<0.001) while no significant relationship between egg volume and body lponica is one of the most well-known invasive gammaridean amphipod around the Pacific region. We studied on the population dynamics (i.e. life history, size distribution and secondary production) of G. japonica, inhabiting euryhaline environment in tidal creek at Sinji Is., South Korea. The life history pattern was annual and iteroparous, with two dominant recruitments from November 2010 to January 2011, and from June to August 2011. The population was annually consisted of four main cohorts winter-spring cohorts, short early summer cohorts, summer-autumn cohorts, and over-wintering cohorts. The sex ratio was usually female-biased. The maximum size of males, non-ovigerous, and ovigerous females were 10.2 mm, 11.10 mm, and 9.36 mm, respectively. There was a positive relationship between ln value of brood size and the ln value of body length of ovigerous females, and they were significantly different between two breeding periods of winter-spring and summer-autumn periods (p<0.001). The egg volume of stage I (early embryo) in winter breeding period showed significantly higher than that of summer breeding season (p<0.001) while no significant relationship between egg volume and body l