Early life ecology of nigorobuna Carassius auratus grandoculis in reed zone of Lake Biwa and physiological adaptation to the environment

Abstract

Nippon Suisan Gakkaishi 77(3), 387 401 (2011) 琵琶湖沿岸のヨシ帯におけるニゴロブナCarassius auratus grandoculis の初期生態とその環境への適応 The early life ecology of nigorobuna Carassius auratus grandoculis was investigated in order to determine the requirements for developing breeding grounds and eŠective release sites for its stock enhancement in Lake Biwa.Larval nigorobuna within the well-developed reed zone swarmed actively near the shoreline immediately after release and began to leave the reed zone when they grew to the juvenile stage of approximately 16 mm in standard length. Zooplankton used as food for the larvae were abundant near the shoreline in the reed zone, but there was

Hypoxic conditions enhance refuge effect of macrophyte zone for small prey fish from piscivorous predators

“…extremely low DO that increased gradually towards the offshore side, was continuously observed from early spring to late summer; this corresponds to the period when nigorobuna carp larvae and juveniles use the macrophyte beds (Miura 1966). Fujiwara et al (2011) also confirmed a similar DO gradient in another macrophyte zone of the same lake, although their observations were performed only during spring, which suggests that the presence of DO gradients in macrophyte beds is a general phenomenon. However, the slope of the DO gradient changed seasonally; it was steep in spring but gentle in summer (H. Yamanaka, unpublished data), suggesting that the breadth of the physiological refuge for nigorobuna carp fluctuates seasonally, similar to that observed diurnally (Fig.…”

Body size and temperature dependence of routine metabolic rate and critical oxygen concentration in larvae and juveniles of the round crucian carp Carassius auratus grandoculis Temminck & Schlegel 1846

“…Conversely, hypoxic areas can also serve as refugia for these prey fishes (Chapman et al, 2002;Yamanaka et al, 2007). For example, the Phragmites australis reed zone in Lake Biwa provides a hypoxic area in its inner region (Fujiwara et al, 2011). Such areas function as a physiological refuge for round crucian carp against predation by piscivorous fishes (e.g.…”

“…They often inhabit the littoral zone of the lake and use the macrophyte zone for reproduction (Yuma et al, 1998), although such zones are likely to be hypoxic (Petr, 2000;Fujiwara et al, 2011). Cyprinid fish are the dominant taxonomic group of the local fish fauna.…”

“…Cyprinid fish are the dominant taxonomic group of the local fish fauna. They often inhabit the littoral zone of the lake and use the macrophyte zone for reproduction (Yuma et al, 1998), although such zones are likely to be hypoxic (Petr, 2000;Fujiwara et al, 2011). Local government and fisheries unions have engaged in efforts to increase some local fish species by releasing artificially reared juveniles.…”

Juvenile migration of the exclusively pelagic cyprinid, Gnathopogon caerulescens (Honmoroko) in Lake Biwa, Central Japan

“…Any such relationship, however, between migration timing and environmental factors such as precipitation, can only be clarified over a longer time frame (Heermann & Borcherding, 2006). (Fujiwara et al, 2011), many juveniles and some dead individuals occurred on the water surface around the weir near the Daido River mouth during the closure of the former in mid-June 2013. At that time, the lack of water movement near the weir resulted, in lower dissolved oxygen concentrations near the bottom (daytime dissolved oxygen concentration 2·8 mg l −1 ) than the other stations (> 7·0 mg l −1 ), such being a probable cause of the surfacing (and death) of migrating juveniles.…”