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Temperature-dependent growth rates of Alaskan ‘shallow-water’
flatfish speciesTom Hurst, Michele Ottmar, Cliff RyerFisheries Behavioral Ecology Program
Alaska Fisheries Science CenterNOAA-NMFSNewport, OR
Flatfishes in Alaska
• 24 Species recorded in Alaskan waters
• ~ 15 species common in Gulf of Alaska and/or Bering Sea
• 14 species commercially harvested
• 2011 – 2015 average > 250,000 MT/y ~ $225 M/y
• Most important species
Yellowfin sole – largest landings of any flatfish in world
Rock sole (northern + southern) – second largest landings
Pacific halibut – most valuable – over $130 M/y commercial
+ important recreational + subsistence fisheries
Compiled from: Mecklenburg et al. 2002. Fishes of AlaskaNOAA Commercial fishery statistics websiteNMFS 2014. Fisheries economics of the United States
Species distributions – “shallow water complex”
Northern rock sole Yellowfin sole
Pacific halibut Alaska plaice
English sole Longhead dab
Adult distributions from Matarese et al. 2003LHD distribution from Mecklenburg et al. 2002
All six species reside in shallow coastal nurseries as juveniles.
Temperature-dependent growth rates.
Temperature-dependent growth rates of juveniles measured by Ryer, Hurst, & Boersma. 2012
Northern rock sole
Pacific halibut
English sole
Temperature
5 9 13 16
Sp
ecific
gro
wth
ra
te
0.00
0.01
0.02
0.03
NRS
PH ES
Objectives:Measure temperature-dependent growth rates of
Yellowfin soleAlaska plaiceLonghead dab
Compare thermal responses among 6 Alaskan flatfishes
Contrast yellowfin sole and northern rock solethermal sensitivity, habitat, distribution, and climate responses.
Fish collections
Collection locations:YFS: Kodiak, AKAKP: Nome, AKLHD: Nome, AK
NRS: Kodiak, AKPH: Kodiak, AKES: Newport, OR
Fish collected from nearshore waters3-20 m depthOtter trawl & beam trawlHeld for several days at collection site
Overnight shipment to AFSC laboratoryon campus of OSU in Newport, OR
Experimental facilities
Because of logistical constraints associated with fish numbers and quarantine requirements for some species, we had to do experiments in two different sets of tanks.
“large” round tanks, n=15
Used for: NRS, PH, ES, LHD Used for: YFS, AKP, PH
Crossover: LHD measured in tanks used for earlier studiesAdditional PH expt in small tanks at 9°C
“small” rectangle tanks, n=32
Experimental protocols
Tank mean growth rates used in all analyses
Number of independent tanks = 10-16 per species
Fish acclimated to laboratory culture for at least 2 months prior use in experiments.
Extended low temperature range to 2°C for AKP, YFS, LHD.
Fish acclimated to test temperatures at approx. 1.5°C / day
Acclimated for 2 weeks prior to measuring growth rates.
Fish fed ad libitum once per day; “gel food”
Measured 3-5 times at 2 week intervals
Individual fish identified through size-rank differences
except YFS & Supplemental PH experiment; RFID PIT tags in body cavity
Analyses based on tank mean growth rates
Growth and survival
Temperature (°C)
2 5 9 13 16
Specific
gro
wth
rate
0.000
0.005
0.010
0.015
Surv
ival %
0
20
40
60
80
100
Temperature (°C)
2 5 9 13 16
Specific
gro
wth
rate
0.000
0.005
0.010
0.015
Surv
ival %
0
20
40
60
80
100
Temperature (°C)
2 5 9 13 16
Specific
gro
wth
rate
0.000
0.005
0.010
0.015
Surv
ival %
0
20
40
60
80
100
High survival to temperatures where growth drops off.
Survival declined above temperature of maximum growth.
Low survival at temperatures above 10°C, but surviving fish had high growth.*Not size-dependent.
Alaska plaiceYellowfin sole
Longhead dab
Temperature
5 9 13 16
Sp
ecific
gro
wth
ra
te
0.00
0.01
0.02
0.03
NRS
PH ES
Comparison growth rates patterns across studies
Temperature
2 4 6 8 10 12 14 16
Sp
ecific
gro
wth
ra
te
0.000
0.005
0.010
0.015 AKP
YFS
LHD
Ryer et al. 2012.
See generally similar patterns.Extended experiments to lower temperatures.Stronger effects observed at the highest temeratures.
Comparison growth rates patterns across studies???
Are there methodological differences that can explain the lower rates observed in the current study.
Temperature
2 4 6 8 10 12 14 16
Sp
ecific
gro
wth
ra
te
0.00
0.01
0.02
0.03
AKP
YFS LHD NRS PH ES
But overall slower growth observed in AKP, YFS, LHDthan NRS, PH, ES
Sp
ecific
gro
wth
ra
te
0.000
0.005
0.010
0.015
0.020
0.025
Halibut experiment comparison
An experiment on juvenile halibut conducted in 2016, at the same time as the YFS experiment allowed us to evaluate the potential for procedural differences between experiments.
Ryer et al. 2012tested 5, 9, 13, 16°“large” round tanks7 fish per tanknot taggedmean 69.5 mm TL
Hurst and Planas, unpublished*tested 2 and 9°C“small” tanks5 fish per tankinternal RFID tagsmean 66.7 mm TL
< 10% differencein SGR
Growth at 9°C
*Talk by Planas and Hurst, Tuesday 11am.
Fish length (mm TL)
40 50 60 70 80 90 100
Ma
xim
um
gro
wth
ra
te (
SG
R)
0.010
0.015
0.020
0.025
0.030
0.035
0.040
Size effects?
LHD16°
AKP13°
YFS13°
PH16°ES
16°NRS13°
Not enough size variation within each experiment to describe size-dependent variation in growth.
But, likely not enough to be responsible for the observed differences in measured rates.
Fish length (mm TL)
40 50 60 70 80 90 100
Ma
xim
um
gro
wth
ra
te (
SG
R)
0.010
0.015
0.020
0.025
0.030
0.035
0.040
Size effects? Age effects?
Age 0
Age 1
But, because of differences in the timing ofspawning and settlement:
NRS, PH, ES were collected as age-0AKP, YFS, and YFS were collected as age-1
Is there an age effect on growth potential, independent of the general decline in SGR with increasing size.
H0: age-0 (pre-first winter) fish are “different” than age-1 (post-first winter)?
LHD16°
AKP13°
YFS13°
PH16°ES
16°NRS13°
Similar patterns observed among juvenile gadids.
Laurel et al. 2016
Temperature of maximum SGR
12 13 14 15 16 17
Delta T
50
% S
GR
4
6
8
10
12
NRS
AKP
LHD
YFS
ES
PH
Comparing temperature sensitivity among species
Calculate temperature of maximum SGR
Calculate temperature range to 50% SGR
Temperature (°C)
2 4 6 8 10 12 14 16
Specific
gro
wth
rate
0.000
0.005
0.010
0.015
Rela
tive g
row
th r
ate
0.0
0.2
0.4
0.6
0.8
1.0
Delta T
Eurythermic
Stenothermic
LHD Representative?High mortality at these temps.
Implications for climate change
The “Blob” – extensive area of warm waters over the N. Pacific & Bering Sea
Yellowfin sole may be most sensitive to climate change because of their high thermal sensitivity.
Temperature of maximum SGR
12 13 14 15 16 17
Delta T
50
% S
GR
4
6
8
10
12
NRS
AKP
LHD
YFS
ES
PH
Already have field evidence of sensitivity.
Interannual variation in growth reflects thermal sensitivity
Matta et al. 2010. MEPS.
Collected NRS, AKP, and YFS from Bering Sea where the species distrubutions overlap.
Look at synchrony and climate drivers of annual growth rates.
Otolith ring width index based on within individual, across year variation.
Temperature of maximum SGR
12 13 14 15 16 17
De
lta
T 5
0%
SG
R
4
6
8
10
12
NRS
AKP
LHD
YFS
ES
PH
Eurythermic
Stenothermic
What about other parts of the distribution?
Matta et al. 2010. MEPS.
Yellowfin sole
Northern rock soleNorthernmost range
General models would predict that warming would allow northern rock sole to expand farther north, occupying waters currently inhabited by YFS and AKP.
But, coastal temperatures do not follow latitudinal trends.
Warming may reduce habitat suitability for the high latitude species even in the northern part of their range.
X
Temperature (°C)
2 5 9 13 16
Specific
gro
wth
rate
0.000
0.005
0.010
0.015
Surv
ival %
0
20
40
60
80
100
Summary
Differences among species in thermal sensitivity.YFS have high thermal sensitivity and live in the most thermally
variable environments.Growth responses did not match survival patterns in LHD.
YFS will be more sensitive to climate changes.Climate change may alter habitat use throughout their range.
Future:1. Repeat experiments across ages to clarify size and age effects.2. Perform temperature preference experiments
– link performance to preference.3. Spatially explicit model of seasonal growth potential.
Broader:Explore how to integrate field and laboratory studies to improve understanding of climate and habitat interactions on fish distributions and productivity.
