Brill et al.: Effects of rapid decompression and exposure to bright light on visual function in Sebastes melanops and Hippog/ossus stenolepis 429 
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Figure 1 
A schematic graph of the time course of pressure changes to which black 
rockfish ( Sebastes melanops) were subjected in flow-through hyperbaric 
aquaria. Control and experimental fish received the same treatments, with 
the exception that control fish were not subjected to the rapid decompres- 
sion and recompression shown at approximately 160 h (simulating capture 
and subsequent return to depth). Time zero indicates the point at which 
the fish were initially placed in the chamber. 
dip net and placed in circular polyethyl- 
ene tanks (2.0 m diameter, 0.8 m depth) 
for up to three days before evaluation 
of visual function. These holding tanks 
were supplied with seawater (flow rate: 
8 L/min, temperature 10-12°C, salin- 
ity: 30-32%e) and maintained under 
dim fluorescent light (0.01 pmol pho- 
tons/m 2 /s) for a 12-hour photoperiod. 
Fish were not fed during this period. 
Bright light exposure experiments 
with Pacific halibut 
Individual Pacific halibut were removed 
with a dip net from their holding tank 
and held in a seawater bath (12°C). A 
high intensity xenon lamp (CVI Laser 
Spectral Products, Albuquerque, NM) 
was used to produce simulated sun- 
light. The spectral range of the lamp 
(=320-700 nm) approximated the vis- 
ible (400-700 nm) plus UV range of 
sunlight at sea level when the sun is 
directly overhead (Lalli and Parsons, 
1997). Light, conducted by fiber optic 
guide, was aimed at one eye of the fish for 15 minutes. 
Light intensity at the exit of the fiber optic light guide 
was 2000 pmol photons/m 2 /s (measured over the visible 
spectral range of 400-700 nm) and matched the inten- 
sity of sunlight (2010 pmol photons/m 2 /s) measured at 
Newport, OR, under a clear sky at 12:00 noon PST on 5 
October 2007. The 15-minute period of exposure to simu- 
lated sunlight was chosen to mimic the minimum time 
that fish would be left on deck during sorting operations 
on commercial trawl vessels (Davis and Olla, 2001; Davis 
and Schreck, 2005). Control fish were treated in the same 
manner except that the light source was not turned on. 
Evaluation of visual function 
Fish were maintained under dim light conditions during 
transport, weighing, and drug injection procedures. 
They were anesthetized with ketamine hydrochloride 
(Ketaset, Butler Animal Health, Middletown, PA, dose= 
30 mg/kg) injected intramuscularly and paralyzed with 
the neuro-muscular blocking drug gallamine triethiodide 
(Flaxedil, Sigma Chemical Co., St. Louis, MO, dose=20 
mg/kg) injected directly into the caudal vein. Additional 
doses of the drugs were administered during the course 
of an experiment. Fish were euthanized at the conclu- 
sion of the experiment with a massive overdose (>300 
mg/kg) of sodium pentobarbital ( Beuthanasia-D, Scher- 
ing-Plough Animal Health Corp., Union, NJ) injected 
intramuscularly. 
After drug injections, individual fish were moved into 
a light-tight enclosure and placed on a perforated rub- 
ber sling stretched across an acrylic box. The majority 
of the body was submerged; only a small portion of the 
head and the eye receiving the light stimulus remained 
above the water. The box was supplied with running 
seawater (12°C) and a small submersible pump continu- 
ously circulated water over the gills of the fish. Fish 
were allowed to acclimate to the dark for at least one 
hour before any measurements were taken. 
Silver-silver chloride electrodes, constructed from 
teflon-coated silver wire, were used for recording the 
ERGs. The active electrode was lightly placed on the 
corneal surface and the reference electrode either in one 
of the nares or on the skin over the head. (Electrodes 
were positioned under dim red light [peak wavelength 
660 nm] produced by light-emitting diodes [LEDs].) 
The recording system was grounded to the seawater 
through a stainless steel plate. ERG signals were am- 
plified by using a 10,000x gain with 1 Hz high pass and 
1 kHz low pass filter settings (amplifier model DAM 50, 
World Precision Instruments, Sarasota, FL). The resul- 
tant signal was further filtered with a Humbug® active 
electronic filter to remove 60 Hz noise (Quest Scientific, 
North Vancouver, BC, Canada), and digitized at 1 kHz 
sampling frequency with a multifunction data-acquisi- 
tion card (model 6024E, National Instruments, Austin, 
TX). Data recording and stimulus presentations were 
controlled by a custom-designed software developed by 
Eric Warrant (University of Lund, Lund, Sweden) us- 
ing the LabVIEW graphical programming system for 
measurement and automation (National Instruments, 
Austin, TX). In order to account for any influence of 
circadian rhythms on visual responses (Mangel, 2001), 
experiments were conducted during the hours the fish 
holding tanks were lit (herein referred to as “day”), 
and then repeated on the same individual during the 
hours the fish holding tanks were in darkness (herein 
referred to as “night”). As a result, the night experi- 
