588 
Age, growth, and mortality of California halibut, 
Paralichthys californicus, along southern and 
central California 
Leslie S. MacNair 
Michael L. Domeier 
Calvin S. Y. Chun 
California Department of Fish and Game 
4665 Lampson Avenue, Suite C 
Los Alamitos, California 90720 
E-mail address (for C. S Y Chun, contact author): cchun@dfg.ca gov 
Abstract— California halibut, Paralich- 
thys californicus, collected by a 400- 
mesh eastern trawl in southern (Mex- 
ican border to Point Conception) and 
central (Point Conception to Tomales 
Bay) California were aged by using 
whole and sectioned otoliths (sagittae) 
to determine age, growth, and mor- 
tality. Males represented 69% of the 
sample from southern California and 
53% of the sample from central Califor- 
nia. A higher proportion of California 
halibut were older in southern Califor- 
nia than in central California. Although 
California halibut can live as long as 30 
years, the oldest fish found in our study 
was 13 years old. For southern Califor- 
nia, the von Bertalanffy growth func- 
tion (VBGF) was L,=925.3(l-e-° 08u+2 - 2 >) 
for males and L ( =1367.7(l-e _008u+1 ' 2) ) 
for females. For central California, the 
VBGF was L,=956.7(l-e-° 10 “ +21 >) for 
males and L ( =1477.1( l-e _010( ' +0 - 2) ) for 
females. The VBGF showed that at the 
same age, females on average were 
larger than males in both southern 
and central California. The VGBF also 
showed that both male and female hal- 
ibut in central areas on average were 
larger than halibut from southern Cal- 
ifornia. Instantaneous mortality rates 
of halibut in southern California were 
estimated at 0.91 for males and 0.68 for 
females. Mortality estimates for cen- 
tral California could not be calculated 
because of small sample sizes. 
Manuscript accepted 9 March 2001. 
Fish. Bull. 99:588-600 (2001). 
California halibut, Paralichthys califor- 
nicus, is an important flatfish species 
for sport and commercial fisheries in 
nearshore waters off central and south- 
ern California (Frey, 1971). The gear 
most commonly used commercially to 
harvest California halibut are otter 
trawls, gill nets, and trammel nets, 
whereas hook-and-line or spear are 
used mostly in the recreational fishery 
(Kramer and Sunada, 1992). 
Information on age, growth, and mor- 
tality of California halibut are impor- 
tant to the management of both the 
sport and commercial halibut fisheries. 
Previous studies have addressed these 
issues to a limited extent. Pattison and 
McAllister (1990) studied techniques to 
age halibut and determined length-at- 
age of halibut along the California coast, 
but most of the fish were taken south 
of Point Conception and they did not do 
separate analyses for southern and cen- 
tral California. Sunada et al. (1990) an- 
alyzed age, size, and sex composition of 
commercial landings in southern Cal- 
ifornia. Haaker (1975) studied the bi- 
ology of California halibut in Anaheim 
Bay, including age and growth, but the 
fish he used were generally less than 
three years of age, immature, and in- 
cluded fish only to 510 mm total length. 
In contrast to other studies, our study 
provides information on age and growth 
for central and southern California sep- 
arately. Mortality for southern Califor- 
nia was also calculated. 
Methods 
Southern California was defined as the 
area between the U.S. -Mexico border 
and Point Conception, and central Cali- 
fornia as the area between Point Con- 
ception and Tomales Bay. Bottom trawl 
surveys were conducted off central Cal- 
ifornia from 8 July through 3 August 
1993 and off southern California from 
14 February through 18 March 1994. 
California halibut were caught with a 
400-mesh eastern trawl (15 m wide x 
1.5 m high; 9.8 cm mesh body, 8.5 cm 
mesh codend). For both areas, sampling 
effort was stratified by depth: 0-20 
fathoms (fm), 21-40 fm, and 41-60 fm. 
Fifty stations within each depth stra- 
tum were randomly selected for sam- 
pling by trawling parallel to isobaths 
at each station. The sample sizes were 
not proportional to the estimated area 
of the strata (Table 1). 
An additional ten California halibut 
were collected with the same 400-mesh 
eastern trawl gear in southern Cali- 
fornia from July 1994 to June 1995. 
These were included in the age and 
growth determinations. However, they 
were not used for mortality estimates 
because they were collected at a differ- 
ent time period from the other halibut 
collected off southern California. 
Each halibut was measured to the 
nearest millimeter for total length (TL) 
and standard length (SL). Gonads were 
examined visually to determine the sex 
of the fish. Sagittal otoliths were re- 
moved and stored dry in vials for age 
determination. Pattison and McAllis- 
ter (1990) determined that when com- 
pared with other fish structures, oto- 
liths provided the most reliable ages for 
California halibut. They found that in 
an otolith, an opaque band was formed 
during spring and summer (from April 
to October) and a translucent band was 
