566 
National Marine 
Fisheries Service Fishery Bulletin 
NOAA <%* established in 1881 
Spencer F. Baird 
Firs! U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Recovery of visual function in Pacific halibut 
{Hippoglossus stenolepis ]) after exposure to 
bright light 
Email address for contact author: chris.magel@noaa.gov 
Abstract —Commercial fishing ex¬ 
poses Pacific halibut (.Hippoglossus 
stenolepis) to a myriad of stressors 
during capture, processing, and dis¬ 
carding, including exposure to di¬ 
rect sunlight that causes diminished 
retinal sensitivity. It is unknown, 
however, whether recovery occurs. 
We therefore employed both electro- 
retinography and a behavioral assay 
to measure recovery of retinal sensi¬ 
tivity and visual function in halibut 
exposed to 15 min of simulated sun¬ 
light. We used electroretinography 
to measure changes in retinal light 
sensitivity after recovery periods 
of 2, 4, 6 and 10 weeks and a be¬ 
havioral assay to measure respon¬ 
siveness to simulated prey (i.e., in 
behavioral trials) to measure visual 
function after recovery periods of 2 
to 6 d. Exposure to simulated sun¬ 
light significantly reduced retinal 
sensitivity to light with no apparent 
recovery after 10 weeks. Although 
retinal sensitivity was reduced, fish 
exposed to direct sunlight displayed 
no demonstrable deficits in visual 
function during behavioral trials. 
Manuscript submitted 24 January 2017. 
Manuscript accepted 7 September 2017. 
Fish. Bull. 115:566-575 (2017). 
Online publication date: 20 September 2017. 
doi: 10.7755/FB.115.4.12 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Christopher Ma§el {contact author} 1 
Clifford Rytu 1 
Richard Brill 2 
1 Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
2030 S. Marine Science Drive, Building RSF951 
Newport, Oregon 97365-5296 
2 Northeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
P.O. Box 1346 
Gloucester Point, Virginia 23062-1346 
One-quarter of the catch of world¬ 
wide fisheries comprises nontarget 
species (i.e., as bycatch or inciden¬ 
tal catch) that are often discarded 
(Alverson et ah, 1994). Fish may be 
dead when discarded, or may subse¬ 
quently expire as a consequence of 
physical injury and stress incurred 
during capture and release. Mortal¬ 
ity rates for discarded fish are, how¬ 
ever, rarely known and represent a 
large source of uncertainty in fish¬ 
eries models (Davis, 2002). In some 
instances, compromised fish succumb 
to predation hours or days after being 
discarded (Davis, 2002). For exam¬ 
ple, juvenile walleye pollock ( Gadus 
chalcogrammus ) and sablefish (Ano- 
plopoma fimbria) subjected to stress¬ 
ors simulating escape through trawl 
codend meshes have been shown to 
be more vulnerable than control fish 
to predation in staged predator en¬ 
counters (Ryer, 2002, 2004). In other 
instances, fish may recover but expe¬ 
rience lower fitness as a consequence 
of injuries or stress. Atlantic cod ( Ga¬ 
dus rnorhua) stressed through simu¬ 
lated trawl avoidance produced poor 
quality eggs and larvae (Morgan et 
ah, 1999); and sockeye salmon (On- 
corhynchus nerka ) that escaped gill 
nets incurred physical injuries and 
physiological impairments that re¬ 
duced spawning success by 50% 
(Raker and Schindler, 2009). Re¬ 
duced growth and body size may also 
impact reproduction. Using a bioen¬ 
ergetics model, Meka and Margraf 
(2007) estimated that catch-and-re- 
lease can reduce growth of rainbow 
trout ( Oncorhynchus mykiss) up to 
15% when there is no physical injury, 
and up to 164% where debilitating 
hook injuries are incurred. Although 
these studies have documented out¬ 
comes of bycatch stress, they rarely 
address the mechanisms that cause 
the stress. In particular, scant infor¬ 
mation exists on how capture and 
release may impair sensory systems 
such as vision, which fish rely on to 
locate food and avoid predation. 
Pacific halibut ( Hippoglossus 
stenolepis) are captured in trawl and 
longline fisheries targeting ground- 
fishes along the contiguous United 
States and Canada (Davis and Olla, 
