Temperature-dependent growth rates of Alaskan ‘shallow-water’ flatfish species Tom Hurst, Michele Ottmar, Cliff Ryer Fisheries Behavioral Ecology Program Alaska Fisheries Science Center NOAA-NMFS Newport, 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 Alaska NOAA Commercial fishery statistics website NMFS 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
All six species reside in shallow coastal nurseries as juveniles.
Adult distributions from Matarese et al. 2003 LHD distribution from Mecklenburg et al. 2002 Temperature-dependent growth rates.
Northern rock sole Temperature-dependent growth rates of juveniles measured by Ryer, Hurst, & Boersma. 2012
Pacific halibut 0.03
0.02
0.01 English sole NRS Specific growth rate Specific growth PH ES
0.00
5 9 13 16 Temperature Objectives: Measure temperature-dependent growth rates of Yellowfin sole Alaska plaice Longhead dab
Compare thermal responses among 6 Alaskan flatfishes
Contrast yellowfin sole and northern rock sole thermal sensitivity, habitat, distribution, and climate responses. Fish collections
Collection locations: YFS: Kodiak, AK AKP: Nome, AK LHD: Nome, AK
NRS: Kodiak, AK PH: Kodiak, AK ES: Newport, OR
Fish collected from nearshore waters 3-20 m depth Otter trawl & beam trawl Held for several days at collection site
Overnight shipment to AFSC laboratory on 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 “small” rectangle tanks, n=32
Used for: NRS, PH, ES, LHD Used for: YFS, AKP, PH
Crossover: LHD measured in tanks used for earlier studies Additional PH expt in small tanks at 9°C 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
Alaska plaice Longhead dab Yellowfin sole
100 0.015 0.015 100 0.015 100
80 80 80 0.010 0.010 0.010 60 60 60
Survival % Survival 40 % Survival 0.005 0.005 40 0.005 40 % Survival
Specific growth rate growth Specific Specific growth rate growth Specific 20 rate growth Specific 20 20 0.000 0.000 0.000 0 0 0 2 5 9 13 16 2 5 9 13 16 2 5 9 13 16
Temperature (°C) Temperature (°C) Temperature (°C)
High survival to temperatures Survival declined above Low survival at temperatures where growth drops off. temperature of maximum above 10°C, but surviving fish growth. had high growth. *Not size-dependent. Comparison growth rates patterns across studies
Ryer et al. 2012. 0.03 0.015 AKP YFS LHD
0.010 0.02
0.005 0.01
Specific growth rate growth Specific NRS Specific growth rate Specific growth PH ES 0.000 0.00
2 4 6 8 10 12 14 16 5 9 13 16 Temperature Temperature
See generally similar patterns. Extended experiments to lower temperatures. Stronger effects observed at the highest temeratures. Comparison growth rates patterns across studies???
AKP But overall slower growth observed 0.03 YFS LHD in AKP, YFS, LHD NRS than NRS, PH, ES PH 0.02 ES
Are there methodological differences that can explain the 0.01 lower rates observed in the rate growth Specific current study. 0.00
2 4 6 8 10 12 14 16 Temperature *Talk by mean 69.5 mm TL 69.5 mean taggednot tank per 7 fish “large” roundtanks tested16 13,9,5, Ryer Halibut experiment comparison An An experimenton juvenile conducted halibut in 2016, atthe asYFStimesame experiment et al. 2012 allowed us to evaluatethe potential for procedural differences between experiments. Planas and Hurst,Tuesday ° mean 66.7 mm TL 66.7 mean internaltagsRFID tank per 5 fish “small” tanks tested9 2 and Hurst and 11am Planas . ° C , unpublished*
Spe cific gr ow th r ate
0.025
0.020
0.015
0.010
0.005
0.000 Growth at 9 < 10% difference< 10% in SGR in ° C Size effects?
0.040
0.035 Not enough size variation within each experiment to describe size-dependent variation in growth. PH 0.030 NRS ES 16° 13° 16° But, likely not enough to be responsible for the observed 0.025 differences in measured rates. 0.020 AKP YFS 13° 13° 0.015 LHD
Maximum growth rate (SGR) rate growth Maximum 16° 0.010 40 50 60 70 80 90 100 Fish length (mm TL) Size effects? Age effects?
0.040 But, because of differences in the timing of spawning and settlement: 0.035 PH Age 0 0.030 NRS ES 16° NRS, PH, ES were collected as age-0 13° 16° AKP, YFS, and YFS were collected as age-1 0.025
0.020 Age 1 AKP YFS 13° 13° 0.015 LHD Similar patterns observed among juvenile gadids.
Maximum growth rate (SGR) rate growth Maximum 16° 0.010 40 50 60 70 80 90 100 Fish length (mm TL)
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)?
Laurel et al. 2016 Comparing temperature sensitivity among species
Calculate temperature of maximum SGR
Calculate temperature range to 50% SGR LHD Representative? High mortality at these temps.
12 Eurythermic 0.015 ES 1.0 LHD 10 0.8 0.010 NRS 0.6 8 PH 0.005 0.4 AKP 6 0.2 SGR 50% T Delta Delta T YFS
Specific growth rate growth Specific
Relative growth rate growth Relative 0.000 0.0 Stenothermic 4 2 4 6 8 10 12 14 16 12 13 14 15 16 17
Temperature (°C) Temperature of maximum SGR Implications for climate change
The “Blob” – extensive area of warm waters Yellowfin sole may be most sensitive to climate change over the N. Pacific & Bering Sea because of their high thermal sensitivity.
12 ES LHD 10
NRS 8 PH AKP 6 Delta T 50% SGR 50% T Delta YFS
4 12 13 14 15 16 17 Temperature of maximum SGR
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. 12 ES Eurythermic LHD 10
NRS 8 PH AKP 6 Delta T 50% SGR 50% T Delta YFS
4 Stenothermic 12 13 14 15 16 17 Temperature of maximum SGR
What about other parts of the distribution?
Matta et al. 2010. MEPS. Northernmost range Northern rock sole 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.
Yellowfin sole 0.015 100
80 0.010 60 X
0.005 40 % Survival
Specific growth rate growth Specific 20 0.000 0 2 5 9 13 16
Temperature (°C) Warming may reduce habitat suitability for the high latitude species even in the northern part of their range. 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.