本州中部の温帯河川に定着したフクドジョウBarbatulaoreasの繁殖特性

誌名誌名 水産増殖 = The aquiculture

ISSNISSN 03714217

著者著者畠山, 類北野, 忠

巻/号巻/号 66巻2号

掲載ページ掲載ページ p. 123-131

発行年月発行年月 2018年6月

農林水産省 農林水産技術会議事務局筑波産学連携支援センターTsukuba Business-Academia Cooperation Support Center, Agriculture, Forestry and Fisheries Research CouncilSecretariat

Aquacult. Sci. 66 (2), 123 -131 (2018)

Reproductive biology of a boreal N emacheilid loach

Bαrbαtula oreαs introduced into a temperate river

in central Honshu, Japan

Rui HATAKEYAMA1'* and Tadashi KlTAN02

Abs仕act:The reproductive traits of Bαrbαtula oreas were examined in a population established in the Kaname River, Kanagawa prefecture. Males exhibited unclear seasonal pa仕ernsin their

monthly mean gonadosomatic index (GSI), and discharged semina from their genital ducts throughout the ye町.Females exhibited obvious seasonal patterns in the monthly mean GSI, which

was higher in spring (March-April) and lower in summer (July-August). Ovarian maturity was

divided into three developmental phases (resting, vitellogenic and maturation), and the ovaries in the maturation phase, which had the characteristics of ovaries in the spawning season, were

observed from March to July. Post-ovulatory follicles were found even in the ovaries of small fish （く 100mm SL), indicating spawning at age-1. Total fecundity was 1,049-10,671 per ovary,

increasing exponentially with the increasing SL. It was considered that vitellogenesis occurred at a wide range of water temperatures and day lengths (7.5-20.8°C, 9 h 47 min-14 h 33 min), and spawn-ing season began when there was a transition to a suitable spawning temperature (10.2-18.5℃）．

This population, which matured at age-1, seemed to have a higher intrinsic rate of natural increase compared to a native population.

Key words: Barbαtula oreas; Acclimatization; Alien species; Gonadal maturity

Fukudojo, Barbatulαoreas is a boreal loach

belonging to the family Nemacheilidae, and

is naturally distributed in Hokkaido, Japan

(Kottelat 2012）.官官 distributionalareas of B.

oreas have expanded rapidly to lower latitudinal

rivers, such as the Abukuma River, Agano River,

Mogami River, and Kuji River in northeastern

Honshu, Japan, probably due to the release

of salmonid seed (Toujo and Hosoya 1998;

Ministry of Land, Infrastructure, Transport and

Tourism 2007). In recent years, B. oreas have

also established in the upstream Kaname River

in central Honshu (Yashima et al. 2011), which

is the lowest latitude river invaded by this

species.

There are many unclear aspects regarding

the ecological impact of B. oreas establishment.

Bαrbatula oreas may compete for food or habitat

Received 16 November 2017; Accepted 30 May 2018.

with native fish, including commercial species,

because it feeds on benthos such as aquatic

insects (Miyadi et al. 1963), hides under stones

during the daytime (National Institute for

Environmental Studies 2005), and tends to be

the dominant species in its natural and invasive

ranges (Nogami et al. 2001; Nagasawa et al.

2009; Hatakeyama et al. 2017）.胞1owledgeof

reproduction in this species, in addition to feed-

ing and behavior, is essential for an appropriate

assessment of ecological impact.

百1eobjective of the present study was to clar-

ify first肱theenvironmental conditions in which the gonadal maturity of B. oreas progresses, and

therefore in which river environments there

is the potential to reproduce, and secondly, to

identi命thereproductive traits of B. oreas estab-

lished in a temperate river.

1 Civil Engineering and Eco-Technology Consultants Co., Ltd., 2-23-2 Higashiikebukuro, Tashima, Tokyo 170-0013, Japan. 2 School of Humanities and Culture, Takai University, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 259-1292, Japan. *Corresponding author: Tel, (+81)3-3988-2634; Fax, (+81)3-3988-3885; E-mail: hatake@kensetsukankyo.co.jp (R. Hatakeyama).

124 R. Hatakeyama and T. Kitano

In the present study, the scientific name, B.

areas, was used according to Ko仕elat(2012), who reviewed the confused taxonomy and nomen-

clature of loaches, a suborder of Cobitoidei,

although names such as B. toni toni (Miyadi et al. 1963), B. toni (Nakamura 1984), Noemacheilus toni (Saito 1988), N barbatulus toni (Masuda and Kobayashi 1994) and Nemacheil倒 的rbatulustoni

(Hosoya 2013) were used hitherto.

Materials and methods

Fish collectioれandenvi：γon制側taldαtα

Specimens were collected from a 1 km section

ups仕earnof血eKaname River in cen仕alHonshu,

Japan (35°23'24"N, 139°13'36官）. Sampling was

conducted once a month, from April 2012 to

August 2015. Collection was by scooping with hand

nets from April 2012加 May2013, and in conjunc-

tion wi血 anelectric shocker (LR-20B: Smi出－Root,

USA）企omJune 2013 to August 2015. Du出1g出e

sampling period, a data logger (UA-002・64:Onset

Computer Co., USA) was placed in the water,

and temperature data recorded every hour to

be calculated as daily mean water temperature.

Day length data was obtained from Yokohama,

Kanagawa Prefecture, Japan, which was出enear-

est mo凶to巾 gsite初出eKaname River (National

Astronomical Observatory of Japan 1994).

Fish meαsurementsαnd dαtαα%α：lysis

The collected fish were anesthetized with

MS-222 in a laboratory and the standard length

(SL) and body weight (B＂ワ measured.Sex was basically identified from the pectoral fin-shape

according to Ikeda (1936). In fish in which the

secondary sex characteristics of the fin were

undeveloped, sex was identified by checking the

gonads under a stereomicroscope. Fish having

translucent and string-like gonads and no visi-

ble oocytes were treated as sexually unidenti-

fied. Fish having slightly clouded and enlarged

gonads with no visible oocytes, and fish having

visible oocytes, were treated as male and female,

respectively. In all fish，出egonads were removed

and the gonadal weight (G＂乃 measured.As an index of gonadal development, the gonadoso-

matic index (GSI) was calculated as follows:

GSI = 100×GW/BW.

Sexing fish, including the yearling, were

used for analyzing gonadal maturity and annual

reproductive cycle, because the gonads of year-

ling fish developed rapidly但atakeyamaet al.

2017), suggesting spawning at age-1. Males, col-

lected after April 2014, were examined with the

naked eye whether semen was discharged from

the genital duct upon pressing the abdomen.

Female fish gonads were monitored by record-

ing external features such as color, and oocyte

diameters; the gonads were photographed

using a digital camera, and then preserved in

70% ethanol after :fixation in 10% neutral forma-

lin or Bouin’s solution for 24 h. Some ovaries

fixed in Bouin’s solution were embedded in paraffin, sagittally sectioned at 4 μm thickness,

and stained with Mayer’s hematoxylin-eosin.

The developmental stages of germ cells were

observed under an optical microscope.

Some ovaries fixed in 10% neutral formalin

were used to estimate the number of oocytes

and their diameters. Oocytes weighing approx-

imately 1 / 5th of the ovary weight were laid

out on a 1× 1 mm mesh on a petri dish and

photographed by a digital camera, and the

numbers and diameters were measured using

image analysis software (JCAM software:

]-SCOPE, Japan). Total fecundity (TF）但unter

et al. 1992), which was the standing stock of

advanced yolked oocytes in the ovary, was cal-

culated by gravimetric method as follows:

TF=GW×C,

where C is oocyte density (number of advanced

oocytes per gram of ovarian tissue). For compar・・

ison with the native population, TF of fish in the

Komaoi River, Hokkaido, was also calculated for

some ovaries, which were removed from sped-

mens collected by Hatakeyama et al. (2017).

Results

Conαdαl制 αtuγ＃ヲα汎dα汎nualγepγoducti匂ecycle

A total of 462 fish had SLs ranging from 53.6-

149.4mm (Fig. l). The GSI was 0.1-1.2 in sex-

ually unidentified (53.6-91.1 mm SL, n = 25),

125 Reproductive biology of Barbatula oreαs

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Fig. 1. Standard length of Barbatula areas collected monthly in the present study. o, male (n = 201); ×，female (n = 236）；・，unidentified(n = 25).

60

developmental phase, histological characteris-

tics and frequency distribution of oocyte diame-

ters were investigated.

(1) Vitellogenic phase: GSI was 3.9-27.1 (n

= 108) (Fig. 3). The ovaries were enlarged and

light yellow in color, and large oocytes (290-

850 μm, n = 200) were visible and densely

distributed (Fig. 4a). Ovaries observed histolog-

ically had oocytes at the tertiary yolk stage or

lower (120.0-134.5 mm SL, GSI = 4.8-15.9, n =

4）σig. 4b). The ovaries in this phase had one

or two modes in oocyte diameter (Fig. 5a, b); an

ovary in November had one oocyte group con閉

sisting of oocytes at the tertiary yolk stage and

lower, but an ovary in February had another

advanced group (> 600 μm in oocyte diameter)

consisting of oocytes at the tertiary yolk stage,

even though two oocyte groups having each

mode were not completely separated in terms

of oocyte diameter (Fig. 5b). The ovaries in

the vitellogenic phase were defined as being in

a s句tein which oocyte development was pro同

gressing toward the next spawning season.

(2) Maturation phase: GSI was 4.3-24.0 (n =

61) (Fig. 3). The ovaries in the final maturation

or ovulation were enlarged, transparent and

light orange in color, and the oocytes were not

clearly visible (Fig. 4c). The ovaries that had

spawned at least once were more deflated than

those in the most enlarged state of the vitello-

genic phase, with large, clearly visible oocytes

σ50-970 μm, n = 172) (Fig. 4e) that were

light yellow in color and sporadically distrib-

uted. The ovaries in this phase had two modes

in oocyte diameter, even though two oocyte

groups having each mode were not completely

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Fig. 2. Monthly changes in relative frequency (%) of male Barbatula areas discharging clouded semen企omthe gen-ital duct. ., with semen；圏， withoutsemen.百1eArabic numerals indicate the number of individuals.

0.2-2.8 in males σ6.5-148.8 mm SL, n = 201) and

0.4-27.1 in females (67.5-149.4 mm SL, n = 236).

The monthly mean GSI in males varied

between 0.8 and 2.1, with unclear seasonal paι

terns. Semina from genital ducts (84.4-139.3 mm

SL, n = 71) were observed throughout the yeaじ

but relative frequency was greater出an60% in

all months from autumn to spring (April-May

2014, November 2014-May 2015) (Fig. 2).

The monthly mean GSI in females varied

seasonally between 1.9 and 19.4. The mean GSI

was the highest in March (2013 and 2014) and

April (2015), and the lowest in July (2012) and

August (2013 and 2015) (Fig. 3). The mean GSI

in December 2012 and January 2015 reached

84.7% and 91.0% of the peak values in 2013 and

2015, respectively. The mean GSI decreased

rapidly to less than half the peak value in May

(2013 and 2015) and June (2014).

Ovarian maturity was divided into three

developmental phases as follows on the basis of

the exterior features. In some ovaries in each

126

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AMJ J ASONDJ FMAMJ J ASONDJ FMAMJ J ASONDJ FMAMJ J A 2012 2013 2014 2015

Fig. 3. Monthly changes in the gonadosomatic index in Barbatula oreas. o, vitellogenic phase (n = 108）；×，

maturation phase ( n = 61）；・， restingphase ( n = 67). The symbols with vertical bars indicate means ±

standard deviations.

Fig. 4. The ovaries in the three developmental phases of Barbatula oreas. (a) exterior of the ovary in the vitellogenic

phase (120.0 mm SL, GSI 15.9, January 2013); (b) histological features of the ovary of (a); (c) exterior of the ovary in the

maturation phase, during宣nalmaturation (111.3 mm SL, GSI 4.3, April 2014); (d) histological features of the ovary in the

maturation phase, during final maturation, with oocytes in the migratory nucleus stage (95.0 mm SL, GSI 5.9, June 2014);

(e) exterior of the ovary in the maturation phase (134.6 mm SL, GSI 6.5, June 2013); (f) histological features of (e) with

post-ovulatory follicles; (g) exterior of the ovary in the resting phase (128.3 mm SL, GSI 1.0, July 2014); (h) histological

features of (g). Abbreviations: ar, atresia; runs, migratory nucleus stage; pns, perinucleolus stage; pys, primary yolk stage;

sys, secondary yolk stage; tys, tertiary yolk stage; yvs, yolk-vesicle stage. Arrowheads indicate post-ovulatory follicles.

(Fig. 3). The ovaries had the most shrink-

age among the three developmental phases

(Fig. 4g), and were transparent and orange.

The oocytes were not clearly visible but a few

atresias (230-650いm,n = 30) from the previ-ous spawning season were scattered in some

ovaries. The oocytes in the perinucleolus stage

occupied a large portion of the ovary with a few

oocytes at the yolk-vesicle stage intermixed

(87.0-148.3 mm SL, GSI = 1.0-6.6, n = 10)

σig. 4h）.官1eovaries in the resting phase were

defined as being in a state immediately following

the termination of the previous spawning season.

The developmental phases were observed

during summer-spring (August 2012-May 2013,

September 2013-May 2014, and September

2014-March 2015) for the vitellogenic phase,

spring-summer (April-June 2013, and March-

July 2014 or 2015) for the maturation phase,

and summer-winter (July-October 2012, June

2013-January 2014, and June-November 2014)

for the resting phase (Fig. 6).

127 Reproductive biology of Barbatula areas

separated (Fig. Sc); in ovaries observed histo-

logically (89.9-134.5 mm SL, GSI = 5.9-9.6, n

= 9), the advanced oocyte group consisted of

oocytes at the tertiary yolk stage and higher,

and the other group consisted of oocytes at the

secondary yolk stage and lower (Fig. 4d, f).

Post-ovulatory follicles (Fig. 4f) were found

in six ovaries, which included four ovaries in

fish ofく100mm SL (87.0-95.3 mm SL, GSI =

2.6-6.7), and were also found with advanced

oocytes, which was the migratory nucleus stage

in the most advanced oocytes. The ovaries in

the maturation phase were defined as being in a

state in which it was possible to spawn or very

close to spawning, or just after spawning.

(3) Resting phase: GSI was 0.4-6.6 (n = 67)

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Water temperature changed seasonally

between 5.0 and 22.8。C (Fig. 7). Day length

varied from 9 h 46 min to 14 h 34 min. The envi-

ronmental conditions were 7.5-20.8。Cand 9h 47 min-14 h 33 min for the vitellogenic phase,

and 10.2-18.5℃and 11 h 55 min-14 h 33 min for

the maturation phase (Fig. 8).

Totαlfecunditヲ

TF was calculated using ovaries in出evitello・

genic phase, close to spawning, collected from

January to March (73.2-149.4 mm SL, n = 34).

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Fig. 5. Relative frequency(%) distribution of oocyte diame-ters in Barbatula areas. (a) vitellogenic phase (121.0 mm SL, GSI 15.0, November 2012, n = 424); (b) vitellogenic phase (114.8 mm SL, GSI 15.7, February 2015, n = 321); (c) matu-ration phase (125.8 mm SL, GSI 7.4, June 2013, n = 405).

400 500 600 700 800 Oocyte diameter (μm)

300

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Fig. 6. Monthly changes in relative frequencies(%) of ovarian-developmental phases in Barbatula areas.瞳，vitellogenicphase; •. maturation phase；囚，restingphase. The Arabic numerals indicate the number of individuals.

128 R. Hatakeyarna and τ：Kitano

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Fig. 7. Seasonal changes in daily mean water temperature (solid line) and day length (dashed line) in出eKaname River.

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Fig. 8. Relationship between water temperature and day length at appearance of ovarian-developmental phases in Barbαtula areas.×，maturation phase (n = 16）；・，restingphase (n = 21); 0, vitellogenic phase (n = 27). The dark and light-shaded areas indicate the range of combinations of water temperature and day length, when ovaries are in the maturation and vitellogenic phases, respectively.

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Kaname River: TF = 0.0007SL3・3263 r = 0.94

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60 80 100 120 140 160 Standard length (mm)

Fig. 9. Relationship between standard length and total fecundity in Barbatula areas. e, Kaname River (n = 34); 0, Komaoi River (n = 6).

Based on the frequency distribution of oocyte

diameter, oocytes of > 600 μm in diameter were

defined as advanced yolked oocytes.

TF numbered 1,049-10,671 per ovary (Fig. 9).

The relationship between the TF and SL was

regressed by power functions as follows:

TF = 0.0007SL3・3263 (n = 34, r = 0.94).

Meanwhile, the TF of fish in出eKomaoi

River numbered 1,564-2,685 per ovary (86.3-

105.3 mm SL, n = 6) (Fig. 9).

Discussion

It was estimated that B. oreas ofく 100mmSL in April were born in the previous year in

the Kaname River (Hatakeyama et al. 2017). As

post-ovulatory follicles were detected in fish of

く100mm SL, it is apparent出atfemales spawn

at age-1. Semina, which likely include sperma-

tozoa, from genital ducts in fish ofく 100mmSL

suggest that males may also spawn at age-1.

Males produced semen throughout the year,

while females exhibited an obvious annual cycle in

GSI and ovarian maturity. The ovaries in由ematu-

ration phase, at a state of spawr血g,appe訂 ed企om

March to July.百1erefore,B. oreas is believed to spawn from March to July, with the timing

regulated by female maturation. Spawning may

occur mainly in earlier months, as small fish of

く20mm SL were found only in the自rsthalf of

the spawning period (Hatakeyama et al. 2017).

In spring『earlys山田nerspaWIIing species, yolk

globules begin to accumulate from autumn;

October, e.g. in Misgurnus anguillicaudatus (Kinlura and Koya 2011), Pseudorasboraρugnax (Ohnaka et al. 2009), and age-1 Gnαthopogon

caerulescens (Okuzawa et al. 1986), and September, e.g.加Micropterusdolomieu 01.ambe et al. 2004), and age-2 M. salmoides 01.odo and Kinlura 2002). The earlier initiation in accumulation of yolk glob-

ules in B. oreas, which was from August, suggests

that vitellogenesis progresses under a wider

Reproductive biology of Barbatula oreas 129

range of water temperatures (7.5-20.8℃） and/

or day lengths (9 h 47 min-14 h 33 min), com-

pared with other species.

Iρnger days and/ or increasing tempera加res

were mentioned as important environmental

factors determining the initiation of spawning

periods in spring-early summer spawning spe-

cies (Shimizu and Hanyu 1983; Asahina et al.

1985; Ota et al. 2015）.百1emonthly mean GSI of

female B. oreαs was already high during winter,

but the ovaries in the maturation phase did not

appe訂 untilMarch (10.2℃， 11 h 55 min）.官官

closely-related B. bαrbatulus in Siberia spawns not only from April to May, but also from August

to October, iム undershort-day length, in a ye訂

in which water temperature is higher (Skryabin

1993). Although the influence of day length is

unclear, B. oreas spawning in the Kaname River seems to occur when there is a transition to a suit-

able temperature, approximately l0°C in spring.

As at least two oocyte groups existed simul-

taneously in an ovary, the process of oocyte

development in B. oreas is categorized as being group-synchronous oocyte development

(Wallace and Selman 1981; Takano 1989). In

most species with group-synchronous oocyte

development, total fecundity provides an indi-

cation of annual fecundity, the total number of

eggs spawned by a female per ye肌 becauseno

yolked oocytes are not regarded as developed

and are not added to the larger oocyte group after

initiation of vitellogenesis in the ov訂 y但unteret

al. 1992; Kurita 2010). To阻lfecundity in B. oreas may also be an indication of annual fecundity.

The simultaneous appe訂 anceof post-ovulatory

follicles and advanced oocytes in an ovary implies

that this species spawns advanced oocytes

dividing into several clutches. However, the two

oocyte groups were not completely separated

and intermediate diameter oocytes were present

during the pre叩 awningto spawning season,

although they were few in number. More detailed

consideration is needed as to whether small

oocytes develop and are spawned.

According to the growth equation of B. oreas in 出eKaname River但atakeyamaet al. 201η，body size is calculated to be approximately 80 mm SL

in April at age-1, approximately 110 mm SL at

age-2, and approximately 125 mm SL at age-3.

Therefore, total fecundity of B. oreas in the Kaname River is estimated to be approximately

1,497 eggs per spawning at age-1, approximately

4,319 eggs at age-2 and approximately 6,608 eggs

at age-3, and出etotal number of eggs produced

during the lifetime is estimated to be 12,424.

Mαtur，α：tio汎 αηdfeγtili;句切 αte慨zperiα：teγi悦 γ

The spawning period of B. oreas in the Kaname River was regulated by the female maturation.

Vitellogenesis began from August (19.9℃， 13 h

24 min) and continued until the next spawning

season, occurring under a wide range of water

temperatures and day leng吐lSσ.5-20.8℃， 9h

47 min-14 h 33 min). The spawning season

appeared to begin from March (10.2℃， 11 h

55 min) and continue until July (18.5℃， 14 h

14 min). These environmental conditions, which

enable ovarian maturity, may exist widely in

lower latitudinal rivers in Japan than the Kaname

River.羽市enB. oreas is introduced into such rivers, gonadal maturity is expected to progress.

For B. oreas naturally distributed in the subarctic regions, high temperature seems to

influence establishment when introduced in

lower latitudinal regions. However, the upper

temperature limit for B. oreas survival is not clear, though it is doubtless able to withstand up

to approximately 23°C, which was the maximum

temperature in the Kaname River habitat. It is

known that the lower limit of its distributional

range corresponds with that of Oncorhynchus mαsou, extending to some lower reaches in the rivers of Hokkaido (Miyadi et al. 1963). The

upper temperature limit at which feeding ceases

or dying-off begins is 26℃ in 0. masou (Takami and Sato 1998）.百1erefore,the high-temperature

tolerance limit in B. oreas may be around 26°C. Bαrbαtu！αoreαs, distributed naturally in the

Komaoi River, grow to approximately 55 mm SL

at age-1, approximately 95 mm SL at age-2 and

approximately 135 mm SL at age-3但atakeyama

et al. 2017), and is presumed to spawn for the

宣rsttime at age-2但atakeyamaet al. 2017）.百1e

TF-SL relationship is unknown in B. oreas in the Komaoi River, but TF was not greatly different

from出atin the宣shin the Kaname River. When

130 R. Hatakeyama and T. Kitano

the relationship was applied to B. oreas in the

KomaoiRive乙吐1etotal number of eggs produced

in a lifetime was estimated to be 11,187, in con-

trast to 12,424 in the fish in the Kaname River.

Taki and Kanou (2008) expressed the sim-

plest concept of alien fish invasiveness as

follows: Invasiveness = Invasive biological char-

acteristics (e.g., habitat characteristics, feeding

habit, fertili町）× Highintroductive opportuni-

ties. Fertility is an important parameter deter-

mining invasiveness. The potential fecundity

in a lifetime of B. oreas may not differ much

between the Kaname River and Komaoi River,

however, B. oreas in the Kaname River mature

in the short term; that is, they have a high

intrinsic rate of natural increase.

The life history仕aitsof B. oreas may differ

depending on the environmental characteristics

in each river (Villeneuve et al. 2005; Trippel and

Harvey 2011), but the spawning season may

also be initiated earlier in the lower latitudinal

rivers, because a thermal rise in spring occurs

earlier (Lam 1983; Conover 1992; Hatakeyama

et al. 201η．百ms, it is predicted 出at出e

grow吐1period after hatching will be prolonged.

Additionally, growth is possible during winter

due to higher temperatures但atakeyamaet al.

201η．τberefore, when this species is in仕oduced

in rivers further south than出eE匂nameRive乙

where the water tempera加redoes not rise above

a certain level during s山田ne乙itis expected出at

也eSL at first maturation will be larger and the

fertility of the population will increase fur仕1er.

Acknowledgemen臼

We血ankShinichi Murata, Ryosuke Tanamoto,

Sho Terachi, and Kazutaka Togashi, of the

School of Human Environmental Studies, Tokai

University, for their help with the field survey.

References

Asahina, K, T. Matsuoka, H. Fujimoto, H. Hirose and T. Hibiya (1985) Effect of temperature and photo-period on gonadal activity in a Japanese minnow Pseudorasbora ραrva. Bulletin of the College of Agricultural and 防terinaryMedicine, Nihon Universi砂，42, 203-210 (in Japanese with English abstract).

Conover, D. 0. (1992) Seasonality and the scheduling of life history at different latitudes. ]ournαl of Fish Biology, 41 suppl. B, 161-178.

Hatakeyama, R., T. Kitano and Y. Machida (2017) Growth and early gonadal development in boreal Barbatula oreas (Jordan & Fowler, 1903) introduced into a tern-perate river in central Honshu, Japan. Biogeography, 19, 163-171.

Hosoya, K. (2013) Family Cobitidae. In “Fishes of Japan with Pictorial Keys to the Species.防l.1. 3rd edition" (ed. byT. Nakabo), Tokai University Press, Tokyo, pp. 328-334 (inJapanese).

Hunter, J. R., B. J. Macewicz, N. Chyan-huei Iρand C. A. Kimbrell (1992) Fecundity, spawning, and maturity of female Dover sole Microstomusρacificus, with an eval-uation of assumptions and precision. Fishery Bulletin, US., 90,101目 128.

Ikeda, H. (1936) On the sexual dimorphism and the taxonomi-cal s匂加sof some Japanese loaches. Zoological Magazine, 48, 983-994 (in Japanese with English abstract).

Kimura, A. and Y. Koya (2011) Annual reproductive cycle of a wild population of oriental weather loach Misgurnus anguillicaudatus in Gifu Prefecture, central Japan. Japanese Journal of Ichthyology, 58, 1-12 (in Japanese with English abstract).

Kottelat, M. (2012) Conspectus cobitidum: an inventory of the loaches of the world (Teleostei: Cypriniformes: Cobitoidei). The Raffles Bulletin of Zoology, Suppl. 26, 1-199.

Kurita, Y. (2010) Influence of spatio-temporal changes in stock reproductive potential on the recruitment levels of fish. Bulletin of the Japanese Socie砂ofFisheries Oceanography, Suppl. 74, 4-18 (in Japanese with English abstract) .

Lam, T. J. (1983) Environmental influences on gonadal activity in fish. In “Fish Physiology，防l.IX'’（ed. by W. S. Hoar, D. J. Randall and E. M. Donaldson), Academic Press, New York, pp. 65-116.

Masuda, H. and Y. Kobayashi (1994) Cobitidae. In “Grand Atlas of Fish L俳 Modes”， TokaiUniversity Press, To防o,pp.4（ト41(inJapanese).

Ministry of Land, Infrastructure, Transport and Tourism (2007) River Environmental Database. http://mizukoku.nilim.go.jp/ksnkankyo/index.html, accessed on 11 Oct. 2016 (in Japanese).

Miyadi, D., H. Kawanabe and N. Mizuno (1963) Barbatula toni toni (DYBOWS阻）.In “Coloured Illustrations of the Freshwαter Fishes of Japan”， Hoikusha, Osaka, pp.139-140 (in Japanese).

Nagasawa, T., K. Morita and J. Tsuboi (2009) Iρngitudinal distribution and changes in the fish fauna of a mid-scale river, Shorn River system, eastern Hokkaido, wi仕1notes on signal crayfish.Japanese Journal of Ichthyology, 56, 31-45 (in Japanese with English abstract).

Nakamura, M. (1984) Cobitidae. In “Keys to the Freshwater Fishes of Japan, Fully Illustrated in Colors”（ed. by M. Nakamura), Hokuryukan, Tokyo, pp. 56-57 (in Japanese).

National Astronomical Observatory of Japan (1994) Local Calendar. http://eco.mtk.nao.ac.jp/koyomi/ dni/index. html.en, accessed on 11 Oct. 2016.

Reproductive biology of Barbatula oreas 131

National Institute for Environmental Studies (2005)

Invasive Species of Japan. https://www.nies.go必／biodiversity /invasive/DB/ detail/50780.html, accessed on 11 Oct. 2016 (in Japanese).

Nogami, T, Y. Watanabe and M. Nakatsugawa (2001)

Research on fish habitats in the Makomanai River. Proceedings of Hydraulic Engineering, 45, 1123-1128 (in Japanese with English abstract).

Ohnaka, T, T Maeda, T Kitano and Y. Koya (2009) Annual

reproductive cycle of the threatened cyprinid species, Pseudorasbora pumila subsp. sensu Nakamura (1963). Japanese ]ournαl of Ichthyology, 56, 47-58 (in Japanese with English abstract).

Okuzawa, K., K. Furukawa, K. Aida and I. Hanyu (1986) Annual reproductive cycle of the honmoroko Gnαthopogon elongatus caerulescens. Bulletin of the Japanese SocieかofScient♂c Fisheries, 52, 1957-1960 (in Japanese with English abstract).

Ota, Y., Y. Ishihara, H. Saitho, T Onuki and N. Akiyama (2015) The environmental factors influencing the ini-tiation of spawning period of bitteling Acheilognathus melanogaster. Aquαculture Science, 63, 437-445 (in Japanese with English abstract).

Saito, Y. (1988) Homalopteridae. In“The Fゐhesof the Japanese Arch争elago.防l.1. 2nd edition" (ed. by H. Masuda, K. Amaoka, C. Araga, T Uyeno and T Yoshino), Tokai University Press, Tokyo, p. 59 (in Japanese).

Shimizu, A and I. Hanyu (1983) Environmental regulation of annual reproductive cycle in a spring-spawning bit-terling Acheilognathus tabira. Nippon Suisan Gakkαishi, 48, 1563-1568 (in Japanese with English abstract).

Skryabin, A G. (1993) The biology of stone loach Barbatula barbatulus in the River Goloustnaya and Olkha, East Siberia.Journal of Fish Biology, 42, 361-374.

Takar凶， Tand H. Sato (1998) Influence of high water tem-perature on feeding responses and thermal death of juvenile masu salmon under aquarium settings. Scientific Reporおofthe Hokkαido Salmon Hatchery, 52, 79-82.

Takano, K. (1989) Ranso no kozo to haigushikeisei (Ovarian structure and gametogenesis). In “Reproductive Biology

of Fish and Shellfish＇’（ed. by F. Takashima and I. Hanyu), Midori-Shobo, To防o,pp. 3-34 (in Japanese).

Taki, Y. and M.Kanou (2008) Gairaigyo to do tsuki-auka但owshould we associate with alien fish?). In “Gairai seibutsu no risuku kanri to yuko riyo (Risk Management and Effective Utilization of Alien Species）”（ed. by Association of Japanese Agricultural Scientific Societies), Yokendo, Tokyo, pp. 147-170 (in

Japanese). To吋o,K. and K. Hosoya (1998) Fukushima-shi surikami-

gawa de saishu sareta fukudojo Noemαcheilus barba-tulus toni (Dybowsky) (Noemacheilus barbatulus toni (Dybowsky) from the Surikami River in Fukushima City). Fukushima Seibutsu, 41, 33-36 (in Japanese).

Trippel, E. A. and H. H. Harvey (2011) Reproductive responses of five white sucker (Catostomus commer-sonz) populations in relation to lake acidity. Cαnαdian Journαl of Fisheries and Aquαtic Sciences, 44, 1018-1023.

Villeneuve, F., G. H. Copp, M. G. Fox and S. Stak，とnas(2005)

Interpopulation variation in growth and life-history traits of the introduced sunfish, pumpkinseed Lepomis gibbosus, in southern England. Journal of Applied Ichthyology, 21, 275-281.

Wallace, R. and K. Selman (1981) Cellular and dynamic aspecお ofoocyte growth in teleosts. American Zoologist, 21, 325-343.

Yambe, H., A. Munakata, K. Aida, N. Fusetani and S. Kitamura (2004) Reproductive cycle of smallmouth bass in Lake Akimoto. Nippon Suisan Gakkaishi, 70, 896-906 (in Japanese with English abstract).

Yashima, N., T Tamino and T Kitano (2011) Notes of Pungtungia herzi and Noemancheilus barbatulus toni as domestic alien species collected from Kaname River. Nαtural History Report of Kanagawa, 32, 109-113 (in Japanese).

Yodo, T and S. Kimura (2002) Gonadal maturation of large-mouth Bass Micropterus salmoides in Lakes Shorenji and Nishinoko, Central Japan. Nip戸onSuisan Gakkaishi, 68, 151-156 (in Japanese with English abstract).

本州中部の温帯河川に定着したフクドジョウ Barbatulaareasの繁殖特性

畠山類・北野忠

神奈川県・金目川に定着した北海道原産のフクドジョウ Barbatulaoreasについて繁殖特性を調べ

た。雄では GSIの季節変化が不明瞭で，精液の出る個体が周年認められた。雌では GSIが季節的に

変化し， 3～ 4月に高く， 7～ 8月に低かった。卵巣の成熟段階は 3相に分けられ（卵黄蓄積相，成

熟相，休止相），産卵期の特徴を示す成熟相の卵巣は 3～ 7月に認められた。排卵後j慮、胞は満 1歳と

推定される体長100mm以下の個体でも認められ，解化の翌年には成熟すると判断された。第一卵群

の卵母細胞数は1,049～ 10,671で，体長増加に伴い累乗関数的に増加した。卵巣への卵黄蓄積は幅広

い水温と日長の条件下（7.5～ 20.8°C, 9 h 47 min～ 14 h 33 min）で進み，産卵期の開始は産卵適水

温（10.2～ 18.5℃）への移行により起こると考えられた。満 1歳で成熟する本個体群は，自然分布域

の個体群に比較して高い内的自然増加率を持つと考えられた。