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The differences between S. mystinus and S. dia- 
conus in length of the anal-fin spines may imply ad- 
ditional mechanistic differences in internal fertiliza- 
tion. Helvey (1982) noted that at the probable point 
of insemination, male and female S. mystinus embrace 
with bodies in a C-shape position with their anal pores 
and anal fins tightly joined, indicating the use of anal- 
fin elements in copulation. The sexual dimorphism in 
anal-fin spine length in S. melanops (Wyllie Echever- 
ria, 1986) and S. mystinus (Wyllie Echeverria, 1986; 
Lenarz and Wyllie Echeverria, 1991) further suggests 
a role for anal fin elements in internal fertilization 
among Sebastes. We did not observe sexual dimor- 
phism in anal-fin spine lengths in this study, although 
sex was only verified on a subsample of specimens, and 
the use of anal-fin elements in sperm transfer has not 
been proven for these species. Therefore, the conjecture 
of differential reproductive morphological features re- 
mains speculative. 
Differential reproductive timing may also play a role 
in prezygotic isolation of these 2 species. Hannah et al. 5 
observed ovary development for both species off central 
Oregon and identified a potential difference of a month 
in the timing of parturition with S. diaconus beginning 
in January and S. mystinus in February. However, sam- 
pling per month was uneven, and larger samples sizes 
may be necessary to confirm this difference. 
Prezygotic isolation can also stem from habitat 
differences and particularly from differences among 
spawning sites. Although previous studies (Burford, 
2009; Burford et al., 2011a, 2011b) found no clear 
evidence of differential habitat or depth preference 
between the 2 species, anecdotal evidence from fisher- 
men and port samplers in central Oregon (Phillips 7 ) 
indicates that adult S. diaconus are collected more 
frequently in deeper waters farther offshore than are 
adult S. mystinus, which are caught closer to shore in 
shallower waters. This variation in depth preference 
could explain the lack of type-1 (S. diaconus) adults 
found by Burford et al. (2011b) in nearshore surveys. 
Only new data on fisheries catches and intensive field 
observation will discern whether these species inhabit 
different physical environments. 
Although previous research (Burford, 2011a) and 
evidence from this study support the possibility of seg- 
regation by means of prezygotic barriers, the possibil- 
ity of segregation by postzygotic barriers, such as hy- 
brid sterility or zygotic inviability, cannot be ruled out 
completely. Postzygotic barriers could be explored with 
controlled laboratory hybridization studies; however, 
breeding in captivity may not be realistic as rockfish 
mature slowly. 
Implications for fisheries 
The molecular analyses of Cope (2004) and of Burford 
and colleagues (Burford and Larson, 2007; Burford and 
7 Phillips, J. 2013. Personal commun. Hatfield Marine Sci- 
ence Center, Oregon State Univ., Newport, OR 97365. 
Bernardi, 2008; Burford, 2009; Burford et ah, 2011a, 
2011b), combined with our morphological results, indi- 
cate definitively that 2 types of blue rockfish differ suf- 
ficiently to merit recognition as distinct species. We con- 
cur with Burford et al.’s (2011a, 2011b) argument that 
fisheries management must recognize that distinction, 
because the 2 species may react differently to varying 
ocean conditions and may experience drastically dif- 
ferent levels of fishing pressure. In the known area of 
sympatry (from Newport, Oregon, south through north- 
ern California), these 2 species hold substantial recre- 
ational importance and, to a lesser degree, commercial 
value. In northern California, blue rockfish (likely both 
species) are the most commonly caught species of rock- 
fish by recreational fishermen and are the second larg- 
est recreational rockfish fishery after S. melanops in 
Oregon (Love et al., 2002). Central and southern Cali- 
fornia populations of blue rockfish (either S. mystinus 
or both species) have declined drastically and many of 
the fish currently being caught are juvenile, indicat- 
ing stock depletion in these areas (Love et al., 2002). 
In response to the known decline, most of the fishery 
and life history research on blue rockfish has focused 
on southern California populations, likely S. mystinus 
(VenTresca et al., 1995; Laidig et ah, 2003; Key et al. 6 ), 
and very little appears to be known about S. diaconus 
from Oregon and Washington. Moreover, it is unknown 
whether fishing pressure in the zone of overlap affects 
1 of the 2 species more than the other. 
Our study provides fisheries managers the crucial di- 
agnostic tool needed to answer these questions: namely, 
the characters that readily distinguish the adults of 
the 2 species, S. mystinus and S. diaconus , in the form 
of color pattern, size of the symphyseal knob and lower 
jaw, ventrum shape (rounded versus flat), and poten- 
tially ovary color. Although pelagic, young-of-year and 
early settled juveniles are more difficult to distinguish, 
as is the case with many young Sebastes (Love et al., 
2002), genetic analysis or collection locality can help 
assign those individuals to these 2 species. Additional 
sampling and observational studies may also be able 
to elucidate ecological and habitat differences. Even 
with some gaps in our knowledge, formal recognition of 
these lineages as distinct species permits the develop- 
ment of proper management regimes for these impor- 
tant groundfishes along the Pacific coast of the United 
States. 
Acknowledgments 
We would like to thank D. Catania (CAS), M. Crag 
(ZMUC), G. Doria (MSNG), R. Fenney (LACM), K. 
Pearson Maslenikov (UW), T. Pietsch (UW), S. Raredon 
(USNM), P. Rask Mpller (ZMUC), L. Rocha (CAS), R. 
de Ruiter (RMNH), M. Sabaj Perez (ANSP), E. Taylor 
(UBC), and N. Vasset (MNHN) for providing access 
specimens or images, M. Burford for providing genet- 
ic samples, S. S. Heppell, K. Hoekzema, T. Laidig, M. 
Love, D. Markle, J. Orr, and K. Schmidt for providing 
