A meta‐analysis of native and non‐native Amur three‐lips ( Opsariichthys uncirostris uncirostris ) population growth rates in western Japan

The growth rates of freshwater fish are known to change among populations under different habitat conditions. The Amur three‐lips ( Opsariichthys uncirostris uncirostris ), a cyprinid predator, is an endemic subspecies in the Lake Biwa–Yodogawa River system and Lake Mikata in western Japan but has also been unintentionally introduced into nonindigenous regions. Non‐native populations are known to have downsized owing to their adaptation to small habitats; however, only two habitats with substantially different sizes have been assessed previously. Therefore, in this study, native and non‐native Amur three‐lips populations were assessed, and their growth rates associated with population type (i.e., native/non‐native), habitat size, and sample period (i.e., in the 1960s or after the 2000s) were analyzed statistically. According to a literature search, seven previous studies reported the growth of this species and included mean length‐at‐age data (measured as body length with estimated age using otolith reading). They included three cases from the largest native habitat, Lake Biwa from different sample periods. The result of the multivariate analysis indicated that the growth rate of Amur three‐lips was higher in native populations than in non‐native populations and increased as habitat size increased. In addition, a model selection approach indicated that population type was a more influential covariate than habitat size. These findings suggest that Amur three‐lips exhibit “home‐field advantage” in terms of growth rate, that is, native populations grow larger than non‐native populations. Future studies conducted on a larger geographic scale will provide further insights into the adaptation of Amur three‐lips under various habitat conditions.