National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
@ established in 1881 << 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Abstract—Understanding patterns 
of foraging and competition in nurs- 
ery habitats can elucidate patterns of 
productivity in multispecies fisheries. 
Yellowfin sole (Limanda aspera) and 
northern rock sole (Lepidopsetta polyx- 
ystra) co-occur throughout the Bering 
Sea where they support major fisher- 
ies. We examined the diets and foraging 
ecology of juvenile yellowfin sole and 
northern rock sole (35-100 mm in stan- 
dard length) captured along the north 
side of the Alaska Peninsula and in the 
Port Moller-Herendeen Bay system, 
the largest marine embayment in the 
southeastern Bering Sea. As observed 
in other parts of their ranges, the diets 
of both species included polychaetes 
and amphipods. The primary difference 
in the diets of these species was that 
the prey of yellowfin sole were almost 
exclusively endobenthic and epiben- 
thic invertebrates (>82.7% by weight 
combined) and the northern rock 
sole consumed substantial amounts 
of hyperbenthic mysids and pelagic 
euphausiids (42% combined). Overall 
dietary overlap was low (Schoener index 
[SI]=0.39), in part due to differences in 
microhabitat use. At sampling stations 
where both species co-occurred, dietary 
overlap was notably higher (SI=0.55). 
Patterns of functional foraging hab- 
its and juvenile niche separation that 
facilitate coexistence of these species 
throughout their range were expressed 
with a novel application of principal 
components analysis of the abiotic 
(habitat characteristics) and biotic (con- 
sumer traits) factors associated with 
commonly occurring prey types. 
Manuscript submitted 11 February 2021. 
Manuscript accepted 9 November 2021. 
Fish. Bull. 120:1—12 (2021). 
Online publication date: 22 December 2021. 
doi: 10.7755/FB.120.1.1 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Functional foraging habits and dietary overlap of 
yellowfin sole (Limanda aspera) and northern rock 
sole (Lepidopsetta polyxystra) ina coastal nursery of 
the Bering Sea 
Nissa C. Ferm! 
Janet Duffy-Anderson? 
Thomas P. Hurst (contact author)? 
Email address for contact author: thomas.hurst@noaa.gov 
" Lynker Technologies LLC 
for Resource Assessment and Conservation 
Engineering Division 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE, Building 4 
Seattle, Washington 98115 
* Resource Assessment and Conservation 
Engineering Division 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
7600 Sand Point Way NE, Building 4 
Seattle, Washington 98115 
Understanding how species respond 
to variation in their environment and 
how they interact with their prey, pred- 
ators, and competitors is critical to 
predicting the consequences of climate 
change on marine ecosystems and fish- 
eries. Many ecosystems include pairs 
or groups of ecologically and morpho- 
logically similar species that co-occur 
in space and time. Niche separation or 
partitioning is generally assumed to 
be a critical component of community 
ecology allowing such species to coex- 
ist. Conversely, niche overlap is gen- 
erally assumed to support ecosystem 
stability through efficient utilization 
of available resources and buffering of 
predator—prey linkages (Neutel et al., 
2002). In the marine environment, 
niche partitioning and overlap are 
most commonly described by using 
physical habitat associations and diet 
composition (Ross, 1986). 
3 Fisheries Behavioral Ecology Program 
Resource Assessment and Conservation 
Engineering Division 
Alaska Fisheries Science Center 
National Marine Fisheries Service, NOAA 
2030 South Marine Science Drive 
Newport, Oregon 97165 
There is a diverse assemblage of 24 
flatfish species in the Gulf of Alaska 
(GOA) and Bering Sea (Mecklenburg 
et al., 2002), of which 13 species are 
commercially harvested (Fissel et al., 
2021). In the southeastern Bering Sea 
(SEBS), harvest is focused on yellowfin 
sole (Limanda aspera) and northern 
rock sole (Lepidopsetta polyxystra), 
with several other species harvested 
at lower rates (Fissel et al., 2021). The 
yellowfin sole supports the largest fish- 
ery (by landings) of any flatfish species, 
worldwide. Although abundances of 
both species recovered from overhar- 
vesting in the 1960s and 1970s, spawn- 
ing biomass of yellowfin sole has been 
in general decline since a peak was 
reached in the mid-1990s (Wilderbuer 
et al., 2018). Throughout their ranges, 
these species have overlapping distri- 
butions on the continental shelf, indi- 
cating the potential for competition. 
