McBride et al.: Expansion of spawning and nursery grounds of Centropristis striata into a warming Gulf of Maine 
329 
Occurrence of mature female black sea bass (Centropristis striata) in trawl 
surveys conducted during spring by the Massachusetts Division of Marine Fish¬ 
eries (MA-DMF) and the Northeast Fisheries Science Center (NEFSC) at the 
northern distributional limit of this species off southeastern Massachusetts, 
from 1983 to 2016. Most fish are from the MA-DMF survey (Suppl. Material), 
but we examined fish from both surveys because the NEFSC survey shows 
broader spawning across the continental shelf. Mature fish are depicted in 3 
spawning conditions: developing (orange circles), spawning (red triangles), and 
postspawning (brown squares). Numbers of fish in each spawning condition (n) 
are provided. Black lines indicate the 50- and 100-m isobaths. 
and longer summer durations appear to favor growth, 
which increases their biomass (Henderson et al., 2017). 
Our new analyses support a hypothesis that increasing 
reproductive productivity by the northernmost spawn¬ 
ing contingents is driving the broader increasing abun¬ 
dance of this northern stock. As evidence, we define 
black sea bass spawning seasonality at the northern 
extent of its range, comment on juvenile growth rates, 
and examine geographic shifts in spawning females 
and settled juveniles. Trends in the northward expan¬ 
sion of settled age-0 fish are also correlated with a 
warming trend in the southern Gulf of Maine. 
Spawning seasonality 
Using an otolith microincrement method, we found that 
black sea bass spawning seasonality does not conform 
to Kendall’s (1972) preliminary proposal that spawning 
for this species occurs progressively later with latitude. 
True, peak spawning is much earlier in the year south 
versus north of Cape Hatteras, North Carolina, but 
black sea bass also have the potential for a very pro¬ 
longed spawning period in some regions but not oth¬ 
ers. In the south, in offshore waters of South Carolina 
and Georgia, Wenner et al. (1986) documented an early 
and prolonged spawning peak, from January to April, 
and a smaller peak in September. Farther north, in 
offshore waters of the middle Atlantic seaboard, from 
North Carolina to New York, spawning appears pro¬ 
tracted from as early as April to as late as November 
(Table 1). At the northernmost extent of black sea bass 
distribution, as shown herein, spawning begins later 
but appears less prolonged: from May to July, peak¬ 
ing in June. Earlier spawning is not likely, because 
adults return to Massachusetts waters in spring, from 
an overwintering migration. We postulate that later 
