DOI: 10.25338/b8hs83
title: Effects of acclimation temperature and feed restriction on the metabolic performance of Green Sturgeon

description: Green Sturgeon (Acipenser medirostris) is an anadromous threatened species
 of sturgeon found along the Pacific coast of North America. The southern
 Distinct Population Segment (sDPS) only spawns in the Sacramento River and
 is exposed to water temperatures kept artificially cold for the
 conservation and management of winter-run Chinook Salmon (Oncorhynchus
 tshawytscha). Past research has demonstrated the costs of cold-water
 rearing including reduced growth rates, condition, and survivorship of
 juvenile Green Sturgeon. Our research investigates how the multiple
 stressors of water temperature and food limitation influence the metabolic
 performance and capacity of Green Sturgeon. We reared Green Sturgeon at
 two temperatures (13 and 19°C) and two ration amounts (100% and 40% of
 optimal feed). We then measured the routine (RMR) and maximum (MMR)
 metabolic rates of sturgeon acclimated to these rearing conditions across
 a range of acute temperature exposures (11 to 31°C). Among both
 temperature acclimation treatments, we found that feed restriction reduced
 RMR across a range of acute temperatures. The influence of feed
 restriction on RMR and MMR interacted with acclimation temperature. Fish
 reared at 13°C preserved their MMR and aerobic scope (AS: the difference
 between the MMR and RMR) despite feed restriction while fish fed reduced
 rations and acclimated to 19°C showed reduced MMR and AS capacity
 primarily at temperatures below 16°C. Our results indicate that the
 sympatry of threatened Green Sturgeon with endangered salmonids produces a
 conservation conflict. While cold-acclimated sturgeon preserved their
 metabolic scope despite feed restriction, warm-acclimated (19°C) fish
 exhibited reduced metabolic capacity at cold temperatures (&lt; 16°C),
 indicating that cold water releases and poor food availability would
 constrain the metabolic performance of juvenile Green Sturgeon.
 Understanding the impacts of environmental conditions (e.g., temperature,
 dissolved oxygen) on the ecological interactions of Green Sturgeon will be
 necessary to determine how salmonid-focused management actions will
 influence this species.
description: The juvenile Green Sturgeon used in this experiment were spawned
 from wild nDPS adults caught on the Klamath River by fishermen of the
 Yurok Tribe in April 2016. Adult fish were transported to the Center for
 Aquatic Biology and Aquaculture (CABA) at UC Davis where they were spawned
 in accordance with methodology from Van Eenennaam et al. (2001). Eggs were
 held at 15°C until hatch, afterwards, larvae were reared at 18°C in 815 L
 circular tanks. Larval fish were provided continuous flow of aerated,
 non-chlorinated fresh water from a dedicated well. After the development
 of exogenous feeding (ca. 15 days post-hatch [dph], 0.1g, 3cm total length
 [L<sub>T</sub>]; Van Eenennaam et al. 2001) fish were fed
 continuously ad libitum with semi-moist pellets (Ragen, Inc.;
 www.rangen.com) until the experiment began. This
 experiment utilized a 2x2 design with fish experiencing one of two
 acclimation temperatures (13 or 19°C) and one of two feed rates (100%
 optimal feed rate [OFR] or 40% of optimal feed rate [LFR]). 32 dph fish
 were randomly placed into one of eight, 470 L round tanks initially set to
 18°C (n= 25 per tank). Two replicate tanks were used for each temperature
 and feed ration combination. Water temperature was adjusted at a rate of
 1°C day<sup>-1</sup> until acclimation temperatures were
 reached. Once target temperatures were achieved, ration treatments were
 initiated. Ration treatments were maintained until the end of the
 experiment (Table 1: Treatment Duration). Feed rates
 for each treatment group were determined using the optimal feed rate model
 for <em>A. transmontanus</em> (Deng <em>et
 al.</em>, 2003; Lee <em>et al.</em>, 2014) as well as
 data on growth rates of <em>A. medirostris</em> under multiple
 feed rations (Zheng <em>et al.</em>, 2015). These feed rations
 were the same as those used in Poletto et al. (2018) and further
 information regarding their derivation can be found there. To maintain
 100% or 40% optimal feed the feed rates were recalculated every three
 weeks to reflect the increasing size of the fish and updated daily to
 account for fish mortality or experimental use. Feed restriction for both
 the 13 and 19°C groups began on the same day. Due to the effects of the
 ration on growth (see Poletto <em>et al.</em>, 2018),
 treatment groups entered metabolic experiments at similar sizes, but
 different ages, and therefore different durations of exposure (Table 1).
 All groups were held under their treatment conditions for at least 33
 days. All protocols and handling procedures were reviewed and approved by
 the UC Davis Institutional Animal Care and Use Committee (Protocol
 #18767). <em>Respirometry</em>
 Fish underwent metabolic trials in one of three, 5L automated
 swim tunnel respirometers (Loligo, DNK). Two tunnels were controlled using
 a single computer system and the third was controlled with a separate
 system. Water for each swim tunnel system was pumped (1260, Eheim, DEU)
 from a designated sump into an aerated water bath surrounding each swim
 tunnel which overflowed to the sump. Sump water was continually supplied
 with non-chlorinated fresh water from a designated well and aerated with
 porous air stones. The temperature of the sump (and therefore the swim
 tunnels) was maintained by circulating water through a heat pump (model
 DSHP-7; Aqua Logic Delta Star, USA) and pumping it back to the sump using
 a high-volume water pump (PM700, Pondmaster, USA). In addition, each sump
 contained an 800 W titanium heater (TH-800, Finnex, USA) connected to a
 thermostatic controller. Water temperature within the swim tunnels was
 maintained to a precision of ±0.5°C. Swim tunnels and associated sump
 systems were disinfected with bleach weekly to reduce the potential for
 bacterial growth within the system. Dissolved oxygen
 saturation within the swim tunnels was measured using fiber-optic dipping
 probes (Loligo, DNK) which were continuously recorded via AutoResp™
 software (version 2.3.0). Oxygen probes communicated to the AutoResp™ via
 a Witrox-4 oxygen meter (Loligo) for the two-tunnel system and a Witrox-1
 oxygen meter for the single-tunnel system. Oxygen probes were calibrated
 weekly using a two-point, temperature-paired calibration technique. The
 water velocity of the swim tunnels was quantified and calibrated using a
 flowmeter (Hontzcsh, DE) and regulated using a variable frequency drive
 controller (models 4x and 12K; SEW Eurodrive, USA). The velocity
 (precision &lt;1 cm s<sup>-1</sup>) for each tunnel was
 controlled remotely using the AutoResp™ program and a DAQ-M data
 acquisition device (Loligo). Swim tunnels were surrounded by shade cloth
 to reduce experimenter disturbance on the fish. Fish were remotely and
 individually monitored using infrared cameras (QSC1352W; Q-see, CHN)
 connected to a computer monitor and DVR recorder.
 Oxygen consumption rates for both routine and maximum metabolic
 rates were measured via intermittent respirometry (Brett, 1964). A flush
 pump (DC30A-1230, Shenzhen Zhongke, China) for each tunnel was pumped in
 aerated fresh water through the swim chamber and was automatically
 controlled via the AutoResp™ software and DAQ-M system. The DAQ-M would
 seal the tunnel and enable the measurement of oxygen consumption
 attributable to the fish. Oxygen saturation levels were kept above 80% and
 restored within 3 min with the influx of fresh, oxygenated water. Due to
 routine weekly sanitization, controls for background bacterial respiration
 were not conducted. <em>Routine Metabolic Rate
 (RMR)</em> Test fish were fasted for 23.8 ± 2.10
 hours in 0.5m x 1.0m rectangular holding tanks with aerated flow-through
 water at their acclimation temperature. Fish were then transferred into a
 swim tunnel respirometer between 9:30 and 16:00 to account for differences
 in time needed to acclimate fish to test temperatures.  Fish were provided
 a 30-minute acclimation period at their acclimation temperature before a
 brief training swim wherein fish were exposed to a 25 cm/s current for 30
 min followed by 10 min at 45 cm/s. After the training swim, the fish were
 allowed to recover for 1 hr before adjusting the temperature of the swim
 tunnels. The temperature was adjusted at 2°C h<sup>-1</sup> to
 one of the swimming test temperatures (7 to 9 temperatures ranging from 11
 to 31°C, Table 2). Once the temperature was achieved, the fish were given
 another 1-hour acclimation period, after which RMR data was collected
 (Verhille <em>et al.</em>, 2016; Zillig <em>et
 al.</em>, 2023). Using intermittent flow respirometry oxygen data
 was sampled overnight (13.5 ± 2.63 hours). Fish activity was monitored by
 overhead infra-red cameras and data from fish which were not quiescent
 were discarded. RMR was calculated by averaging the three lowest RMR
 values (Poletto <em>et al.</em>, 2017). RMR measurements were
 concluded by 08:14 ± 22 min. Works Cited
 Deng D-F, Koshio S, Yokoyama S, Bai SC, Shao Q, Cui Y, Hung SSO
 (2003) Effects of feeding rate on growth performance of white sturgeon
 (<em>Acipenser transmontanus</em>) larvae.
 <em>Aquaculture</em> 217: 589–598. Lee S,
 Wang Y, Hung SSO, Strathe AB, Fangue NA, Fadel JG (2014) Development of
 optimum feeding rate model for white sturgeon (<em>Acipenser
 transmontanus</em>). <em>Aquaculture</em> 433:
 411–420. Poletto JB, Cocherell DE, Baird SE, Nguyen TX,
 Cabrera-Stagno V, Farrell AP, Fangue NA (2017) Unusual aerobic performance
 at high temperatures in juvenile Chinook salmon, <em>Oncorhynchus
 tshawytscha</em>. <em>Conservation Physiology</em> 5:
 1–13. Poletto JB, Martin B, Danner E, Baird SE,
 Cocherell DE, Hamda N, Cech Jr JJ, Fangue NA (2018) Assessment of multiple
 stressors on the growth of larval green sturgeon <em>Acipenser
 medirostris</em>: implications for recruitment of early life-history
 stages. <em>Journal of Fish Biology</em> 93:
 952–960. Van Eenennaam JP, Webb MAH, Deng X, Doroshov
 SI, Mayfield RB, Cech JJ, Hillemeier DC, Willson TE (2001) Artiﬁcial
 Spawning and Larval Rearing of Klamath River Green Sturgeon.
 <em>Transactions of the American Fisheries Society</em> 130:
 159–165. Verhille CE, English KK, Cocherell DE, Farrell
 AP, Fangue NA (2016) High thermal tolerance of a rainbow trout population
 near its southern range limit suggests local thermal adjustment.
 <em>Conservation Physiology</em> 4: 1–12.
 Zillig KW, Lusardi RA, Cocherell DE, Fangue NA (2023)
 Interpopulation variation in thermal physiology among seasonal runs of
 Chinook salmon. <em>Can J Fish Aquat Sci</em> 00:
 1–13.
description: # Effects of acclimation temperature and feed restriction on the metabolic
 performance of Green Sturgeon
 [https://doi.org/10.25338/B8HS83](https://doi.org/10.25338/B8HS83) Data
 provided were gathered from metabolic trials on juvenile Green Sturgeon as
 described in the Manuscript "Effects of Acclimation Temperature and
 Feed Restriction on the Metabolic Performance of Green Sturgeon" by
 Zillig et al. (in review). Metabolic trails were conducted on fish
 acclimated to one of two temperatures (13 or 19C) and provided one of two
 rations (an Optimal Feed Rate [OFR] or Low Feed Rate [LFR]). Each fish was
 trialed in a Loligo Swim tunnel and we measured both a Resting Metabolic
 Rate (RMR) and a Maximum Metabolic Rate (MMR), from which we could then
 calculate the Aerobic Scope (AS = MMR - RMR) and Factorial Aerobic Scope
 (FAS = MMR/RMR). We additionally took metrics on fish mass, length, and
 condition factor. ## Description
 "Dryad\_Green\_Sturgeon\_Metabolism\_2023.csv" The dataset
 contains all necessary values to recreate the analyses in the manuscript
 entitled "Effects of acclimation temperature and feed restriction on
 the metabolic performance of Green Sturgeon". ###### Column
 descriptions: SEQ : num 1 2 3 ... | Unique row number FISH_NUM : chr
 "Fish3" "Fish4" "Fish5" "Fish6"
 ... | Unique fish ID TRIAL_DATE: Date, format: "2016-07-06"
 "2016-07-06" ... | Date of the trial (yyyy-mm-dd) AS_NUM : num 2
 2 3 3 4 ... | Identifier for which aerobic scope trial the fish belonged
 to. Each fish only belongs to one aerobic scope trial. ACC_TEMP : num 19
 19 19 ... | Acclimation Temperature (C), two values 19 or 13 FEED_RATE :
 chr "OFR" "OFR" "OFR" "OFR" ... |
 Feed rate, two values OFR = optimal feed rate, LFR = low feed rate
 TEST_TEMP : num 22 22 11 11 19 | ... Metabolic trial temperature, values
 range from 31-11C MASS : num 10.21 11.46 12.72 9.88 12.32 ... | Fish mass
 (grams) FL : num 12.7 12.5 13.3 12 12.9 12.8 10.8 12.7 11.3 11.5 ... |
 Fork Length (cm) TL : num 13.7 13.7 14.4 13.1 14.1 15.1 11.8 13.9 11.4
 12.9 ... | Total Length (cm) DPH : 'difftime' num 65 65 66 66
 ... | Age of fish (days) since hatch. TANK_ID : chr "NF-4"
 "NF-7" "NF-4" "NF-7" ... | Specific tank
 identifier for the rearing tank of fish TUNNEL_ID : chr "B"
 "A" "B" "A" ... | Specific Tunnel the fish
 was trialed in., three possible values (A, B, C) RMR : num 4.24 4.01 1.59
 1.87 3.14 ... | Resting Metabolic Rate (RMR: mgO2 kg-1 min-1) MMR : num
 8.02 10.49 7.55 6.85 13.69 ... | Maxmimum Metabolic Rate (MMR: mgO2 kg-1
 min-1) AS : num 3.78 6.48 5.96 4.99 10.54 ... |Aerobic Scope (AS: mgO2
 kg-1 min-1) FAS : num 1.89 2.62 4.76 3.67 4.35 ... | Factorial Aerobic
 Scope which is derived by dividing the MMR by the RMR, it is a unitless
 value. FAST_DUR : chr "27H28M" "27H28M"
 "25H27M" "25H27M" ...| The amount of time between when
 a fish was removed from its rearing tank and when it entered a swim
 tunnel. The fish would not have had access to food for this amount of time
 prior to the metabolic trial. RMR_DUR : chr "13H6M"
 "13H6M" "11H34M" "11H34M" ... | Duration of
 the RMR trial in hours (H) and minutes (M) COND_FAC : num 0.397 0.446
 0.426 0.439 0.439 ... | Fulton's condition factor of the fish
 calcualted as COND_FAC = MASS / (FL ^3) * 100 KN : num 0.751 0.877 0.835
 0.836 0.872 ... | The relative condition factor calcualted using the
 equation Kn = Mo / Mp, where Mo is the observed mass (MASS) of a fish and
 Mp is the predicted mass of the fish. Calculation for the predicted mass
 is log10(Mpr) = -1.60117 + 2.774xlog10(FL), where FL is the fork length of
 the fish. Constants are taken from Poletto et al. 2018, which studied the
 same cohort of green sturgeon. KA : num 1.1 1.24 1.21 1.2 1.23 ... | The
 allometric condition factor calculated using the equation Ka = 100 x
 MASS/TL^b. The Scaling exponent *b* is derived using the mass/length
 relationships from fish used in Poletto et al. 2018 which studied the same
 cohort of green sturgeon. Values for each treatment are as follows:
 19OFR|2.61, 13OFR|2.74, 19LFR|2.51, 13LFR|2.66. There are no missing
 values. ###### Cited References: Poletto JB, Martin B, Danner E, Baird SE,
 Cocherell DE, Hamda N, Cech Jr JJ, Fangue NA (2018) Assessment of multiple
 stressors on the growth of larval green sturgeon *Acipenser medirostris*:
 implications for recruitment of early life-history stages. *Journal of
 Fish Biology* 93: 952–960. ## Sharing/Access information Additional
 information can be requested from Dr. Ken Zillig
 [(kwzillig@ucdavis.edu)](mailto:kwzillig@ucdavis.e)