Latitudinal variation in parr growth and maturation in anadromous masu salmon Resident Anadromous Kentaro Morita & Toru Nagasawa (Hokkaido Nat. Fish. Res. Inst., Kushiro, Japan) International Symposium on Formosa Landlocked Salmon and Masu Salmon，口頭発表，2009年10月，台北．
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Latitudinal variation in parr growth and maturation in anadromous
masu salmon
ResidentAnadromous
Kentaro Morita & Toru Nagasawa(Hokkaido Nat. Fish. Res. Inst., Kushiro, Japan)
International Symposium on Formosa Landlocked Salmon and Masu Salmon，口頭発表，2009年10月，台北．
Alternative life historiesEgg
Parr
Smolt
Anadromous
Resident
Sea
Maturing
Good riverine growth conditions promote residency !
Age 0+ May
Age 0+ Sep
Age 0+ May
Age 0+ Sep
Smolt: Age 1+ May
Age 2+ May
Age 0+ May
Age 0+ Sep
Smolt: Age 1+ May
Age 2+ May
ResidentResident
AnadromousAnadromous
Female mature Female mature parrparr
Latitudinal variation in alternative life histories
Anadromy
Residency
N
S
Background
Prediction
Good growth conditions at warmer southerly latitudes
promote residency.
Object• In this study, we examined the latitudinal
variation in riverine growth and parrmaturation in masu salmon.
• Main objective was to relate the causes of latitudinal variation in growth and maturation to latitudinally changing environmental gradients.
Study sites• Twelve rivers located
between 36ºN and 45ºN that drain into the Japan Sea
• Sampling periods: 2007-2008
• No records of artificial releases
Methods• Water temperature
– Measured by fixing data loggers• Sampling
– Electrofishing– Sampling reaches: average 610m2, with a
range of 240–820m2
– Sampling periods: mid-Sep to early Oct 2007–2008, during the breeding season of masu salmon
– Density: two-pass removal method• Fish measurement
– All fish were sampled for subsequent laboratory measurements (n = 1,932)
– Fork length, weight, sexual maturity, age
StowAway Tidbit
Otolith
Length-frequency histograms • High growth at
southerly latitudes.• High maturity rate at
southerly latitudes.
02040
02040
02040
02040
0
20
0
20
0
20
0
20
0
20
0
20
0
10
0
10
0
10
0
10
0
10
0
10
0
5
0
5
0
20
0
20
02040
02040
0
10
0
10
0
5
0 5 10 15 20 25 300
5
0 5 10 15 20 25 300
50
5
Males FemalesN
S
45N
44N
41N
40N
38N
37N
36N
42N
43N
LatitudeFL at age 0+ -0.772**
Maturity rate -0.813***
Maturity rate -0.382ns
Temperature -0.719**
Density 0.532*
MatureImmature
Fork length (cm)
Num
ber o
f fis
h
0.01 0.1 1
10
15
20
25
10 12 14 16 18
10
15
20
25
Factors affecting growth
TemperatureDensity (n/m2)
0+
1+
2+
Fork
leng
th (c
m)
Fork
leng
th (c
m)
R2=0.79(May to Sep)
0.01 0.1 1
10
15
20
25
10 12 14 16 18
10
15
20
25
Factors affecting growth
TemperatureDensity (n/m2)
0+
1+
2+Temperature and density are more closely linked to growth compared with latitudes.
Fork
leng
th (c
m)
Fork
leng
th (c
m)
R2=0.79(May to Sep)
6 8 10
0
20
40
60
80
10 15 20
0
20
40
60
80
100
Factors affecting maturation
Fork length (cm)Fork length (cm)
r = 0.91r = 0.80
Males age 0+ Females age 1+
Temp. Density
Mat
urity
rate
(%)
Mat
urity
rate
(%)
6 8 10
0
20
40
60
80
10 15 20
0
20
40
60
80
100
Factors affecting maturation
Fork length (cm)Fork length (cm)
r = 0.91r = 0.80
Males age 0+ Females age 1+Growth are more closely linked to maturation compared with latitudes.
Temp. Density
Mat
urity
rate
(%)
Mat
urity
rate
(%)
Temperature and maturity rate
Temp. Maturity rate
May r = 0.89
Jun r = 0.81
Jul r = 0.62
Aug r = 0.65
Sep r = 0.658 10 12 14
0
20
40
60
80
Temperature in May
r = 0.89Male age 0+
Mat
urity
rate
(%)
1412
108
6
0
20
40
60
80
100
5
10
15Pro
babi
lity
of m
atur
ing
(%)
Fork length (cm
)Temperature in May
Temperature, fork length, and maturity rate
Autumn
Spring
Onset of maturation
Mature
1412
108
6
0
20
40
60
80
100
5
10
15Pro
babi
lity
of m
atur
ing
(%)
Fork length (cm
)Temperature in May
Temperature, fork length, and maturity rate
Autumn
Spring
Onset of maturation
Mature
Temp CF in Sep
May r = 0.42Jun r = 0.63Jul r = 0.64Aug r = 0.68Sep r = 0.71
Temperature in May affect maturity rate independent of body size.
Plasticity or genetic variation?
Body size
Pro
babi
lity
of m
atur
ing In white-spotted charr,
the relationship between body size and the probability of maturing was PLASTICALLY modified by temperatures.Morita et al. (2009) Biol. Lett. 5: 628-631.
The relative contribution of genetic and plastic effects remains unclear.
High
tem
pera
ture
Low
tem
pera
ture
5 6 7 8 9 10 11 12 13 140
5
10
5 6 7 8 9 10 11 12 13 140
2
4
Differences between above-dam and below-dam
Fork length (cm)
Above-dam
Below-dam
Num
ber o
f fis
h
Males at age 0+ yr
Mature males
Age 1+
Age 0+
Age 0+Sneaker !
Low sneaking success ?
Tomari R.
Conclusions
• Most of the variation in parr growth and maturation was explained by latitudinally changing conditions in temperature and population density.
• Our study supports the hypothesis that freshwater residency was promoted by favourable growth conditions at southerly latitudes.
MaturationGrowth
Temp
Density
Latitude
Anadromous
Resident
+
- +
-
+
Resident
Temperature in May!
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