Wilborn et al.: First observation of the use of coral habitat by larval Sebastes polyspinis 77 
was captured was predominantly soft sediment but had 
some cobble and boulder-sized rocks intermixed through- 
out. Corals (especially Callogorgia sp.) were abundant at 
the deployment location where the larva was captured and 
on the surrounding seafloor (Fig. 1). The specimen was 
5.53 mm in length and weighed 0.2 g. The size of extrusion 
for northern rockfish is not known but is expected to be less 
than 6.1 mm (Matarese et al., 1989), and in general the size 
of extrusion for most rockfish species is 5-7 mm (Love et al., 
2002). The specimen was visually identified as a rockfish 
(Sebastes sp.) and was considered to have recently extruded 
because of its small size. 
The larval specimen in question differed by 1 bp at posi- 
tion 246 from the vouchered northern rockfish specimen 
(UW155787) but was an exact match to the our newly 
sequenced northern rockfish specimen (UW189442) and 
to 2 specimens of northern rockfish in GenBank: catalog 
no. EF446443.1 (voucher no. UW113251) and catalog no. 
DQ678512.1 (voucher no. SQFSC121-69 (Hyde and Vetter, 
2007). Therefore, we concluded that this larval fish was a 
northern rockfish. 
For the additional 11 larvae associated with corals, all 
sequences associated with Plumarella superba and 4 of the 
5 larvae associated with Callogorgia compressa matched 
the sequence for our recent specimen (UW189442) (Table 1) 
and were identified as northern rockfish. One individ- 
ual associated with Callogorgia compressa matched the 
sequence for DQ678476.1 (SWFSC173-8) and was identi- 
fied as a harlequin rockfish (S. variegatus) (Hyde and Vet- 
ter, 2007). These 11 larvae were all found in corals, settled 
among polyps as shown in Figure 1. This observation is 
similar to that of Baillon et al. (2012), who also observed 
larvae of Atlantic redfish (Sebastes sp.) situated among 
polyps of pennatulaceans in trawl hauls. Baillon et al. 
(2012) observed the Atlantic redfish larvae in bottom- 
trawl hauls that also captured adult Atlantic redfish; 
therefore, the larvae may have been extruded in the net 
and swept into the pennatulacean polyps by the action of 
the trawl gear. During the bottom-traw] survey conducted 
in 2017 in the Gulf of Alaska, adult northern rockfish did 
occur in 1 of the 2 trawl hauls in which its larvae were also 
captured, but adult harlequin rockfish did not occur in the 
bottom-trawl haul in which the larval harlequin rockfish 
was found, indicating that the occurrence of these larvae 
on corals was not necessarily a consequence of the capture 
process inducing extrusion of rockfish larvae within the 
trawl] net. 
The capture of free-swimming northern rockfish lar- 
vae by using a plankton pump is the first in situ record 
of a rockfish larva confirmed to have been captured from 
within deepwater coral habitat. Little is known of the early 
life history of Alaska rockfishes or of northern rockfish in 
particular, but species of Sebastes generally have an exten- 
sive pelagic larval phase of up to 1 year in duration and 
a limited lifetime dispersal indicated by genetic studies 
(Miller and Shanks, 2004; Hyde and Vetter, 2007; Gharrett 
et al., 2012; Kamin et al., 2014). These 2 characteristics 
of their life history appear to be somewhat in conflict, in 
that species with the potential for long-distance dispersal 
would not be expected to have restricted geographic dis- 
semination. However, results of a study of 11 microsat- 
ellite loci of northern rockfish captured along the range 
of this species in the Bering Sea and Aleutian Islands 
of Alaska reveal a significant isolation-by-distance rela- 
tionship, indicating limited lifetime dispersal of between 
approximately 12 and 120 km for this species (Gharrett 
et al., 2012). Reduced currents downstream of coral habi- 
tat (and potentially other highly structured habitats) may 
provide a process for larval rockfish to be retained near 
where they were spawned, creating an important mecha- 
nistic link between the known genetic structure of north- 
ern rockfish and restricted dispersal. 
This unique observation of a larval northern rockfish 
in deep-sea coral habitat improves our knowledge of the 
early life history of this commercially important species 
and may provide insight into a potential mechanism for 
larval retention for a taxonomic group that has a high 
degree of population structure and limited lifetime dis- 
persal. The result also highlights the further impor- 
tance of deepwater coral habitat as essential habitat for 
rockfishes. 
Acknowledgments 
The University of Washington Fish Collection archived 
most of the material examined for this study, and we 
appreciate the support of its curator (L. Tornabene) and 
collections manager (K. Maslenikov). 
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