Kolmos et al.: Temporal changes in the life history of Hyporthodus niveotus off North and South Carolina 
319 
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April May 
June July 
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Aug. Sep. 
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Figure 7 
Proportion of adult female (active and inactive) snowy grouper (Hyporthodus 
niveatus) that were spawning daily, (A) by 100-mm bin for total lengths and 
(B) by age group (2-year groups for fish 3-10 years old and a terminal group 
for fish with ages >11 years). Note that 2 data points for the month of June in 
panel A were omitted because of low sample sizes (number of adult females in 
each group [n]<10). Specimens were collected off North and South Carolina 
during spawning season (April-September) in 1979-2012. 
These larger, older females may have been saving ener¬ 
getic resources for sex transition and forgone some spawn¬ 
ing events. Recent studies of a closely related serranid and 
2 grouper species revealed a similar pattern of reduced 
spawning frequency in larger, older females. Klibansky 
and Scharf (2018) proposed that decreased egg production 
prior to sex transition in black sea bass (Centropristis stri¬ 
ata) allows females to allocate energy to somatic growth, a 
switch that would be beneficial during the subsequent 
male phase. Gamboa-Salazar et al. (2019) observed 
moderate to strong declines in female 
spawning frequency relative to age and 
size in gag and scamp (M. phenax), 
declines that they also have proposed 
are linked to increasing future reproduc¬ 
tive success as males. 
In addition to the effects of size and 
age, spawning in snowy grouper is 
influenced by lunar phase. This find¬ 
ing is noteworthy for this grouper spe¬ 
cies because it inhabits deep waters, 
where less light reaches during spawn¬ 
ing. Spawning of snowy grouper occurs 
more frequently around the new moon 
(waning crescent to waxing crescent), 
when there is less moonlight and pos¬ 
sibly less predation on eggs (Fig. 8). It 
makes intuitive sense that this timing 
would increase survivorship possibly by 
affecting larval transport and predation. 
Farmer et al. (2017) conducted an anal¬ 
ysis of monthly relationships between 
lunar phase and spawning and concluded 
that spawning in snowy grouper most 
commonly occurred from June through 
August during waning crescent to full 
moon periods by using a data set limited 
to fishery-independent sources for the 
period 1990-2013. Results of our study 
based on aggregated data from a longer 
period, 1982-2012, and on both fishery- 
independent and fishery-dependent 
sources indicate a different relationship 
between spawning and lunar phase. We 
found that the major peak of spawning 
in snowy grouper occurs within 5 d, 
before and after, of a new moon. Farmer 
et al. (2017) also found that snowy grou¬ 
per exhibit multiyear use of spawning 
areas, but the resolution of their data 
was insufficient to confirm the pres¬ 
ence of spawning aggregations. This life 
history characteristic is important and 
should be investigated further because 
the presence of spawning aggregations 
would increase the vulnerability of 
snowy grouper to fishing and, therefore, 
would have implications for the manage¬ 
ment of this species. 
The updated information we provide here on life history 
parameters of snowy grouper supports the notion that 
the stock off North and South Carolina is in a slow recov¬ 
ery from overfishing. Given that significant plasticity in 
life history parameters has been observed over time in 
this population of snowy grouper, continued monitoring 
of this stock is necessary to assess its status and to allow 
managers to accurately adjust future regulations, includ¬ 
ing commercial quotas and trip limits, with the ultimate 
goal of maintaining the recovery of this stock. 
