Begg et al.: Use of otolith morphometries for identification of stocks of Melanogrcimmus oeglefinus 
7 
-1.5i 
- 1 -3.0- 
-3.5 J — i 1 1 1 1 1 — 
1(94) 2(95) 3(93) 3(94) 4(93) 5(92) 
-2.4-1 
-4.0 — i 1 1 1 1 1 — 
1(94) 2(95) 3(93) 3(94) 4(93) 5(92) 
2.5- 
2.4- 
2.3- 
2 . 2 -^ 
2.1 — i 1 1 r 1 1 — 
1(94) 2(95) 3(93) 3(94) 4(93) 5(92) 
2.9 1 . 1 1 r- 
1(94) 2(95) 3(93) 3(94) 4(93) 5(92) 
Age group (year class) 
Figure 3 
Mean ± standard deviation of age-specific internal otolith growth morphometries (Al, HI, A2, H 2, and otolith length, area, perim- 
eter, circularity, and rectangularity) for eastern Georges Bank (squares) and western Georges Bank (circles) haddock. 
Discussion 
We found significant differences in the internal otolith 
structure between eastern and western Georges Bank 
haddock in three out of six comparisons; providing a phe- 
notypic basis for stock separation across the Bank. Of the 
three nonsignificant comparisons, two were influenced by 
low sample sizes (n = 18), whereas the third was margin- 
ally nonsignificant (P>0.07) (Table 6). Eastern Georges 
Bank haddock tended to have smaller internal otolith mor- 
phometries than western Georges Bank haddock, particu- 
larly during the first year of life when growth differences 
between progeny from the two spawning components may 
be most apparent. 
Differences in the internal otolith structure of eastern 
and western Georges Bank haddock corresponded with ap- 
parent differences in their growth rates. Commercial land- 
ings data indicated smaller mean lengths and weights at 
age for eastern than for western Georges Bank haddock, 
indicative of slower growth rates (and resultant smaller 
otoliths) for eastern Georges Bank haddock (Brown 2 ). 
Likewise, other studies have found significant relation- 
ships between linear and shape otolith morphometries 
and fish growth (e.g., Mosegaard et al., 1988; Reznick et 
al., 1989; Secor and Dean, 1989; Smith and Kostlan, 1991; 
Fowler and Short, 1996). Consequently, regional differ- 
ences in growth rate may be a principal determinant in 
2 Brown, R. W. 2000. Annual assessment data (unpubl. data). 
Food Web Dynamics Program, Population Dynamics Branch, 
Northeast Fisheries Science Center. 166 Water St., Woods Hole, 
MA 02543. 
