Life history and reproductive ecology of the endangered Itasenpara bitterling Acheilognathus longipinnis (Cyprinidae) in the Himi region, central Japan

Abstract

The life history, reproductive ecology and habitat utilization of the Itasenpara (deepbody) bitterling Acheilognathus longipinnis were investigated in a lowland segment of the Moo River in Toyama Prefecture, central Honshu, Japan. Analysis of 1285 individuals revealed that the study population comprised a single size class, an age at maturation of 3 months and a life span of 1 year. On the basis of the growth pattern, the life cycle was divided into two stages: the juvenile stage, characterized by rapid growth, and the adult stage at which growth ceased. Spawning by A. longipinnis was recorded between early September and late October. Female A. longipinnis in the 0+ year age class began to mature when they reached a standard length (LS ) of 56·4 mm. Mature females had a large clutch size (maximum 273 eggs) and deposited highly adhesive and relatively large eggs (2·55 mm(3) ; major axis, 3·12 mm; minor axis, 1·22 mm) via a short ovipositor (mean length, 21·5 mm) into freshwater mussels. The embryos remained in the gill cavities of the freshwater mussels (used as a spawning substratum) and emerged as juveniles (LS , 9 mm). Habitat utilization during spawning was analysed using a generalized linear model. The best-fit model showed that three environmental factors (freshwater mussel availability, water depth and vegetation cover) were important variables for habitat utilization by A. longipinnis. Shallow areas (water depth, 250-330 mm) created for rice paddy management and areas with an abundance of cover were particularly effective for predator avoidance. These results suggest that maintenance of water level fluctuations corresponding with rice cultivation and the abundance of vegetation on the river bank (particularly avoidance of concrete revetments) is essential for conservation of this species under current practices for rice cultivation in Japan.

Morphological changes and habitat shifts with growth of endangered floodplain fish: Possible adaptations to fluctuating environments

“…It may be difficult to reproduce flood pulses, but environmental fluctuations should be maintained to maintain Itasenpara bitterling populations. The Moo River has been functioning as a floodplain habitat for Itasenpara bitterling via water‐level fluctuations and the presence of freshwater mussels as a spawning substratum (Nishio et al, , , ). To maintain Itasenpara bitterling and freshwater mussels as a spawning substratum in the Moo River, the fluctuating environments (i.e.…”

“…Emergent plants, including the common reed Phragmites australis and Manchurian wild rice, are abundant. Several bitterling species, including Itasenpara bitterling, the southern red tabira bitterling ( Acheilognathus tabira jordani ), the slender bitterling ( Tanakia lanceolata ) and the Chinese rose bitterling ( Rhodeus ocellatus ), inhabit the study site (Nishio et al, ).…”

“…The lifespan of Itasenpara bitterling is reported to be c . one year (Nishio et al, ). Additionally, the Itasenpara bitterling is a threatened cyprinid fish that is found in only three regions of central Japan: the Osaka, Nobi and Toyama plains (Kitanishi et al, ).…”

“…This bitterling is a freshwater fish that engages in an unusual spawning symbiosis with freshwater mussels during the autumn . The hatched larvae live in the mussels for about seven months, after which the swim-up larvae emerge from the mussels in June and mature during the following autumn, and spawning is recorded between early September and late October (Nishio, Edo, & Yamazaki, 2017;Nishio, Kawamoto, Kawakami, Edo, & Yamazaki, 2015;Nishio et al, 2016). The lifespan of Itasenpara bitterling is reported to be c. one year (Nishio et al, 2015).…”

Mitochondrial genotyping of an endangered bitterling Acheilognathus typus (Cyprinidae)

“…Acheilognathus typus is the sister species (Kawamura et al 2014) and ecologically similar to Acheilognathus longipinnis Regan 1905 which is adapted to pulsed habitats (Odum et al 1995) with annual flood-drought cycle (Ogawa 2011, Nishio et al 2015). …”