430 
NOAA 
National Marine 
Fisheries Service 
Fishery Bulletin 
& established 1881 
Spencer F. Baird 
First U S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Behavior-dependent selectivity of yellowtail 
flounder iLimanda ferruginea ) in the mouth 
of a commercial bottom trawl 
Melanie J. Underwood (contact author ) 1 - 2 ' 3 
Paul D. Winger 3 
Anders Ferno 2 
Arill Engas 1 - 2 
Email address of contact author: melanie.underwood@imr.no 
Abstract— To improve the efficiency 
of a commercial bottom trawl for 
catching yellowtail flounder ( Liman- 
da ferruginea), we studied the be- 
havior of individuals in the middle 
of the trawl mouth. Observations 
were conducted with a high-defini- 
tion camera attached at the center 
of the headline of a trawl, during the 
brightest time of day in June 2010 
off eastern Newfoundland. Behavior- 
al responses were quantified and an- 
alyzed to evaluate predictions relat- 
ed to fish behavior, orientation, and 
capture. Individuals showed 3 differ- 
ent initial responses independent of 
fish size, gait, and fish density: they 
swam close to (75%), were herded 
away from (19%), or moved vertically 
away from (6%) the seabed. Individ- 
uals primarily swam in the direction 
of initial orientation. No fish were 
oriented against the trawling direc- 
tion. Fish in the center of the trawl 
mouth tended to swim along the bot- 
tom in the trawling direction. Only 
individuals that were stimulated to 
leave the bottom were caught. Indi- 
viduals in peripheral locations with- 
in the trawl mouth more often swam 
inward and upward. Fish that swam 
inward were twice as likely to be 
caught. Fish size, gait, and fish den- 
sity did not influence the probability 
of capture. A trawl that stimulates 
yellowtail flounder to orient inward 
and leave the bottom would increase 
the efficiency of a trawl. 
Manuscript submitted 9 September 2014. 
Manuscript accepted 5 August 2015. 
Fish. Bull. 113:430-441 (2015). 
Online publication date: 2 September 2015. 
doi: 10.7755/FB. 113.6. 
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. 
1 Institute of Marine Research 
P.O. Box 1870 
Nordnes, 5817 Bergen, Norway 
2 Department of Biology 
University of Bergen, 
P.O. Box 7800 
NO-5020 Bergen, Norway 
3 Fisheries and Marine Institute 
Memorial University of Newfoundland 
P.O. Box 4920 
St. John's, Newfoundland, Canada A1C 5R3 
The bottom trawl fishery in New- 
foundland for yellowtail flounder (Li- 
manda ferruginea), hereafter called 
“yellowtail,” re-opened in 1998 after 
a moratorium from 1994 to 1997. As 
a result of efforts to maintain a sus- 
tainable fishery after the re-opening, 
the industry faced restrictions that 
included yearly quotas, minimum 
legal sizes, discard bans, and short- 
term area closures due to summer 
spawning, as well as closures re- 
sulting from bycatches of American 
plaice ( Hippoglossoides platessoides) 
and Atlantic cod (Gadus morhua). In 
addition, declines in the quality of 
fish that occur before the spawning 
season create an incentive to harvest 
the entire quota while the market 
value for yellowtail is highest. There- 
fore, ensuring that the harvesting of 
this species is not only sustainable 
but also efficient is a key concern for 
the fishing industry for yellowtail in 
Newfoundland. 
Understanding fish behavior can 
help to improve the harvesting pro- 
cess (Winger, 2008). How fishes re- 
spond to demersal trawls is indica- 
tive of their catchability and has 
been studied for the different catch 
zones of a trawl where individuals 
may occur either 1) in the path of 
a trawl (i.e., the area between the 
wings of a trawl net), which results 
in a high probability of capture; 2) 
in the path of the sweeps (i.e., the 
area swept by the doors and ground 
wires), where they have a lower but 
still significant probability of cap- 
ture; or 3) outside the paths of the 
trawl and sweeps, where there is a 
minimal probability of capture. Only 
fishes that stay in or are herded into 
the path of the trawl mouth (i.e., the 
area where the footgear connects to 
the net) are ultimately caught in 
the net (see Winger et al. [2010] for 
review). 
Flatfishes, because of their gener- 
ally poor swimming ability that can 
be attributed to their unique body 
