Microhabitat use by the larvae of cryptic lamprey species in Lethenteron reissneri in a sympatric area

Abstract

Microhabitat use by the larvae of two cryptic lamprey species in Lethenteron reissneri, Lethenteron sp. N (northern form) and Lethenteron sp. S (southern form) larvae, as well as intraspecifi c variations on a size-related basis, were examined in a study area (500 × 5 m) located on a stream where they showed sympatric distribution. The total number of individuals collected from each of 31 quadrats (60 × 60 cm) ranged from 0 (0 n/m 2 ) to 13 (36.1 n/m 2 ). The distinct difference in habitat use was not observed between the two species in the present study area. Lamprey density was not signifi cantly independent among the size groups (small and large) for each of Lethenteron sp. N and Lethenteron sp. S. The density of each size group of the two species was signifi cantly correlated with some habitat variables, and stepwise multiple regression analysis revealed a positive association for a substrate with a smaller particle size and deeper depth for large individuals of Lethenteron sp. N and Lethenteron sp. S, respectively, suggesting that these conditions would be suitable for burrowing. On the other hand, small individuals of both species tended to occur in areas where there was a high content of medium sand and a faster current velocity, probably refl ecting a preference for respiratory effi ciency. Various condition of habitat should be maintained to conserve the cryptic lampreys.

Recent microscale disturbance of gene flow in threatened fluvial lamprey, Lethenteron sp. N, living in a paddy water system

“…In other words, the temporal heterogeneity of gene flow indicates that recent events, such as the installation of sluice gates, have changed patterns of gene flow among populations, such that migration is no longer continuous and unbiased. Because lamprey larvae have limited swimming ability and have strong and specific habitat preference, they generally exhibit restricted dispersal and are therefore expected to represent a subpopulation structure within the river system (Sugiyama and Goto 2002;Yamazaki 2007). However, strong currents, such as those that occur during flooding, are expected to disperse larval individuals downstream (Holčík 1986;Derosier et al 2007).…”

“…N (sensu Yamazaki et al 2003) inhabits streams, tributary, and canals throughout its life (Japan Ministry of the Environment 2003; Yamazaki 2007). This lamprey has a larval period of some 3 or 4 years, burrowing in sandy-mud substrate; following metamorphosis, the adults do not feed and undergo a short upstream migration in the fall, spawn, and die the following spring (Takayama 2002; Japan Ministry of the Environment 2003).…”

“…Lethenteron sp. N has been classified as ''vulnerable'' in Japan (Japan Ministry of the Environment 2003), because their habitat has been reduced by artificial stream reconstruction, leading to straighter current ducts and water pollution (Yamazaki 2007). Furthermore, since fluvial lamprey have generally lower ability to swim compared with fluvial fishes such as salmonids (Malmqvist 1983;Holčík 1986) and size at maturation of Lethenteron sp.…”

Effects of configuration of instream wood on autumn and winter habitat use by fish in a large remeandering reach

“…abundance was positively related to the proportion of fine bed material. Lethenteron larvae usually burrow into the riverbed, and hence, the sedimentation of the fine bed materials, such as silt or sand, is essential for their habitat (Beamish & Jebbink, 1994;Beamish & Lowartz, 1996;Sugiyama & Goto, 2002;Torgersen & Close, 2004;Yamazaki, 2007). The fine bed materials were more abundant at the sites with wood structures (particularly at the log-jam sites) than at the sites without wood structures.…”

Lampreys: Biology, Conservation and Control

“…S, are morphologically indistinguishable from each other (Yamazaki and Goto 1997) but, on the basis of molecular studies, are clearly distinct (Yamazaki andGoto 1996, 1998;Yamazaki et al 2003Yamazaki et al , 2006. For example, two non-parasitic species in Japan, which have been referred to as Lethenteron sp.…”