Sutherland and Richards: Aging Lophius americanus based on length-mode progression of a strong cohort 23 
than previously thought. This finding has impli- 
cations for our understanding of productivity 
in this species. Previous measurements of the 
length at which 50% of fish reach sexual matu- 
rity are 38 cm TL in males and 44 cm TL in 
females (Richards et al., 2008). Age estimates 
associated with these lengths are 4.3 years for 
males and 4.9 years for females (Richards et al., 
2008). Results of our study indicate that goosefish 
instead reach the median length at maturity in 
their first 2 years. Similarly, the minimum legal 
size in the fishery (43 cm TL), previously thought 
to correspond to ages 4—5 (Richards et al., 2008), 
would instead correspond to age 2 under our 
current understanding. More research, and an 
effective method for estimating ages, will be 
needed to develop a full growth curve. 
i= 
< 
= 
D 
f= 
2 
is) 
ie 
fo) 
ke 
Age (years) 
Figure 9 
Mean lengths at age of goosefish (Lophius americanus) captured in 
the spring along the Atlantic coast from Virginia to Georges Bank, 
as estimated from 4 sources: modal analysis of length frequencies of 
fish from the 2015 year class caught in surveys during 2015-2018 
(squares), readings of illicia from fish captured for this study (circles), 
readings of vertebrae from fish captured for this study (diamonds), 
and readings of vertebrae from historical data in Richards et al. (2008) 
Conclusions 
Results of our validation study indicate that ages 
cannot be estimated from either illicia or verte- 
brae of goosefish at present. Although results of 
(triangles). 
young-of-the-year fish attaining lengths of 10 cm TL 
shortly after settlement conflict with the conclusion by 
Able et al. (2007) that the first annulus is laid down at an 
average length of 9.6 cm TL. A settlement check or false 
annulus may have been misinterpreted as an annulus in 
the Able et al. (2007) study. 
In a number of Lophius species, growth curves derived 
from age estimates from vertebrae, illicia, or otoliths 
have been approximately linear with little evidence of 
slowing with age (Farifia et al., 2008; Maguire et al., 
2008). However, past results for white anglerfish indi- 
cate that too many rings may be counted and that growth 
may be underestimated, particularly among young fish 
(<3 years) (Velasco et al., 2008). Our results indicate 
a similar pattern of underestimation of size at age up 
through age 3 in goosefish. Faster growth at earlier ages 
would be expected to result in a curvilinear growth curve, 
as is typical of most fish species, even if size at age for 
older fish was essentially linear. 
Our revised understanding of the growth of goosefish in 
the first few years of life brings it more in line with knowI- 
edge of the growth of a congener in Europe, the white ang- 
lerfish, which reaches about 40 cm TL by age 2 (J6nsson’). 
This size closely matches the 42 cm TL modal length we 
observed in our study for goosefish at age 2 (in June 2017). 
Maximum observed size is comparable between the 2 spe- 
cies, given that the maximum observed size is 138 cm TL for 
goosefish (Richards et al., 2008) and 125-142 cm for white 
anglerfish (Jonsson’; Landa et al., 2013; Ofstad et al., 2013). 
The observed growth rate, based on the progression 
of the length mode for goosefish at ages 0-3, is faster 
the marginal increment analysis indicate that a 
ring is laid down on the illicium in spring—sum- 
mer, age estimates from both illicia and vertebrae 
had insufficient levels of accuracy and precision 
to be used for age estimation. 
Despite this outcome, important observations were 
made about growth rates in goosefish. Size at age 3 was 
nearly double previous estimates from vertebral aging, 
indicating that the species has higher productivity than 
has previously been thought. 
It remains important to find a valid aging method for 
this species so that growth rates can be modeled and the 
population can be managed more effectively. Other struc- 
tures, such as the operculum or other bones (Elzey et al., 
2015), may be worth investigating. Other future efforts 
could include microchemical analysis (Siskey et al., 2016) 
or staining (Natanson et al., 2007), which could help in 
identifying annuli in illicia or vertebrae. In-person train- 
ing to learn methods for reading illicia from experienced 
personnel in Europe may also help with reading illicia of 
goosefish. 
Acknowledgments 
We would like to extend our appreciation to A. Linares, A. 
Jones, and M. Durst-Scarlett for help with dissections and 
preparation of samples. Thank you to P. Hasslund for pre- 
paring and imaging the lapillar otoliths and to D. Secor for 
training the first author in these methods. A. Miller and 
C. Tholke assisted with generating the figures. We also are 
grateful to the staff of the NEFSC Ecosystems Surveys 
Branch, the crews and staff of the Study Fleet program, 
and the fishery monitors for collecting samples and to the 
anonymous reviewers for their insightful comments. 
