NOTE Stark: Age- and length-at-maturity of female Atheresthes stomias in the Gulf of Alaska 
329 
I60WW I55°0'0"W 
Figure t 
Locations where arrowtooth flounder ( Atheresthes stomias ) were collected by bottom 
trawl during National Oceanic and Atmospheric Administration Alaska Fisheries Science 
Center cruises during February 2002 (x) and July 2003 (+) in the Gulf of Alaska. 
To determine if ovary growth occurred between Feb- 
ruary and July, the gonadosomatic index (somatic body 
weight/ovary weight, 7G) of females > A 50 was deter- 
mined by methods described by Stark (2007). The com- 
parison did not include females with hydrated oocytes 
or postovulatory follicles. 
Results 
In the February 2002 collection, approximately 50% of 
the females were classified as spawning and 10% were 
nearing spawning condition (advanced yolk). By July, 
spawning activity was <5% but continuing, and 20% of 
the females were at the advanced yolk stage of maturity 
based on the 2003 collection. 
Mature female arrowtooth flounder were found in 
every location where sample collections were made, 
namely on the outer continental shelf at 101-200 m 
depths and upper slope at 301-700 m depths, during 
February 2002. During July 2003, the locations and 
depths sampled ranged from the intertidal zone at 1- 
100 m down to the continental banks, gullies, and outer 
shelf at 101-200 m. Mature female specimens were as 
young as 3 years of age and 260 mm L. 
This study was the first to determine that age was 
a significant predictor (PcO.001) of maturity for female 
arrowtooth flounder. The estimated age at 50% matu- 
rity (A 50 ) was 7.0 years, based on the February 2002 
collection (Fig. 2, Table 1). The February 2002 result 
did not differ significantly (P= 0.38) from the July 2003 
result (6.6 years). Of the two results, the February 
2002 A 50 estimate had a much lower variance (Table 2) 
and consequently was the most reliable. The estimated 
length at which 50% of the females were mature 
was 460 mm for the February 2002 collection (Fig. 3, 
Table 2) and did not differ ( P= 0.68) for the July 2003 
collection (464 mm). However, the variance of the L 50 
estimate was much lower for the February 2002 collec- 
tion, and thus February represented the more optimal 
month for assessing arrowtooth flounder maturity. Oo- 
cyte development was consistent within the ovaries and 
between each ovary pair for every compared specimen. 
No significant growth occurred between February and 
July, based on the 7G results, which declined from a 
mean of 3.6 IG in February 2002 (n = 167) to 1.8 IG in 
July 2003 (n = 115). 
Discussion 
This study was the first to establish arrowtooth flounder 
age-at-maturity. The estimated age at 50% maturity 
(A 50 = 7 years) in the GOA was based on the February 
