686 
Fishery Bulletin 99(4) 
Figure 1 
Map of the Oslofjord. The gray shaded area represents the capture location of 
dogfish in the outer Osloljord. 
ased and in future work a correction curve will have to be 
made for the stock in the Oslofjord. 
Embryo development 
Both ovaries of mature females were rinsed to expose eggs. 
The rinsing process consisted of removing and then carefully 
opening the ovaries with a scalpel. The eggs were counted 
and registered as belonging to the right or left ovary. In 
pregnant females the embryos were counted and sexed. The 
embryos were then measured to the nearest 0.1 cm on mil- 
limeter paper. Three stages of embryo development were 
identified according to Gauld 1 : stage 1 (candled embryos) — 
eggs, apparently fertilized, are present in a protective cap- 
sule in the uteri; stage 2 (free-living embryos) — the candle 
has ruptured and embryos bearing an external yolk sac are 
free in the uteri; and stage 3 (full term embryos) — fully 
developed embryos are present in the uteri. The yolk sac is 
fully absorbed and the umbilical slit is more or less closed. 
Results 
Biological parameters 
The fish ranged in length from 54 to 1 10 cm in 1987 (mean 
87 cm) and from 68 to 108 cm (mean 88 cm) in 1997. 
1 Gauld, J. 1979. Reproduction and fecundity of the Scottish- 
Norwegian stock of spurdogs, Squalus acanthias (L. ). ICES, 
Council Meeting (CM) 1979/H:54. 13 p. Directory of fisheries, 
biblioteket, Pb. 185, 5001 Bergen. 
Weights ranged from 0.4 to 5.7 kg (mean 2.6 kg) in 1987 
and from 1.1 to 5.5 kg (mean 2.9 kg) in 1997. Ages ranged 
from 9 to 35 years (mean 25 years) in 1987 and from 10 to 
38 years (mean 23 years) in 1997. 
On average, the fish in 1987 were 1.8 cm longer than 
fish in 1997 at the same age (P=0.02). However, there was 
a large variation in the length, and age could only account 
for 38% of this variability. Length accounted for 76% of the 
variability of the weight in 1987 and 93% in 1997. Fish 
between 80 and 110 cm were about 500 g heavier in 1997 
(P<0.01 ). This difference was reflected in the condition fac- 
tor, which was 3.8 in 1987 compared with 4.2 in 1997. This 
indicates that female dogfish caught in 1987 were longer 
and lighter than in 1997. 
Growth 
Growth appeared to be best represented by a linear growth 
equation for dogfish between the ages of 11 and 38 years, 
with an average annual increment of 0.7 cm per year 
(Fig. 2). There was no sign of reduction in growth with 
increasing age; that is, no asymptote was detected in these 
data. 
Age and length at maturity 
Maturity was defined as females bearing large ovarian 
eggs with a diameter of over 2 cm, candled young or free- 
living embryos. In both 1987 and 1997, most of the females 
matured between 12 and 26 years of age. PROBIT analy- 
sis indicated that dogfish reached 50% maturity at an age 
of 17.6 years in 1987 and 17.0 years in 1997 (Fig. 3). The 
