Complete mitochondrial genomes of two rockfish: Sebastes maliger and Sebastes norvegicus (Scorpaenidae, Scorpaeniformes)

Abstract We report the complete mitochondrial genomes of two rockfish: Sebastes maliger and Sebastes norvegicus. The mitogenomes consist of 13 protein-coding regions, 22 tRNAs, two rRNAs, and one control region. Sebastes mitogenome control regions are highly variable due to the presence of repeat sequences. The mitogenomes for S. maliger and S. norvegicus are 16,403 and 16,401 bp, respectively. Using these two mitogenomes and 25 additional Sebastes mitogenomes from GenBank, we examine the phylogenetic relationships in Sebastes. Sebastes maliger is sister to a clade including S. rubrivinctus, S. nigrocinctus, S. umbrosus, and S. oculatus, while S. norvegicus is sister to S. fasciatus.

Sebastes (Cuvier, 1829) is a diverse genus of marine fish, comprising at least 110 species found mostly in the North Pacific, with a small number of species in the Atlantic, Arctic, and Indian Oceans (Kim and Lee 2004;Hyde and Vetter 2007). The Quillback rockfish, Sebastes maliger (Jordan and Gilbert, 1880), is found in the North-East Pacific Ocean (Munk 2001;Love et al. 2002;West et al. 2014); whereas the Golden redfish, Sebastes norvegicus (Ascanius, 1772), is found in the North Atlantic Ocean (Rolskii et al. 2020). Although previous studies have focused on the mitogenomes of Western Pacific rockfish, few studies have evaluated the mitogenomes of East Pacific and Atlantic species. We provide further resolution of the phylogenetic relationships in Sebastes by assembling the complete mitogenomes of S. maliger and S. norvegicus.
We collected S. maliger near Excursion Inlet, Alaska in the Gulf of Alaska (58.4854, À135.4521) using hook-and-line sampling (IACUC-approved protocol #15-0602). A liver sample was placed in RNAlater (MilliporeSigma, St. Louis, MO, USA), frozen at À20 C, transported to Brigham Young University, and stored at À80 C until processed. A morphological voucher was not retained. We extracted DNA and sequenced it using an Illumina HiSeq 2500 system (Illumina, San Diego California, USA) at Brigham Young University's DNA Sequencing Center (Provo, Utah, USA). The tissue sample (267106) was deposited at the Monte L. Bean Life Science Museum, Brigham Young University (Jerald B. Johnson, jerry. johnson@byu.edu) and raw sequences were deposited in the SRA database (SRR15573079). We retrieved DNA sequences of S. norvegicus (ERR1473911) from the SRA database on NCBI (Malmstrøm et al. 2017). This specimen was collected near Ballstad in Lofoten, Norway (68.0713, 13.5361) by commercial fishermen (M. Malmstrøm, personal communication, November 29, 2021).
The mitogenomes were annotated using MitoAnnotator (Iwasaki et al. 2013). For our phylogenetic analysis, we acquired a total of 25 rockfish mitogenomes from GenBank. We generated multiple sequence alignments separately for each of the 13 protein-coding genes using MAFFT v. 7.475 (Katoh and Standley 2013) before concatenating them into a final file that was 11,412 bp in length after all positions with missing data were removed.
The complete mitogenomes of S. maliger and S. norvegicus, assembled against S. fasciatus (KX897946), were 16,403 and 16,401 bp in length, respectively (MW846222, MW846223). Depending on which reference mitogenome was used during assembly (KX897946, MN218776, KJ775792), the complete mitogenomes of S. maliger and S. norvegicus were between 16,401 and 17,609 bp, consistent with studies showing that the mtDNA control region of Sebastes is highly variable due to repetitive DNA sequences (Zhang et al. 2013;Sandel et al. 2018;Kim et al. 2019). Twelve of the 13 protein coding genes had an ATG start codon; COX1 had a GTG start codon. Six genes (ND1, COX1, ATP8, ND4L, ND5, and ND6) had a TAA stop codon, three genes (ND2, ATP6, and COX3) had an incomplete TA stop codon, and four genes (COX2, ND3, ND4, and CytB) had an incomplete T stop codon.
Two phylogenetic trees were generated using W-IQ-Tree (Trifinopoulos et al. 2016) and BEAST 2.5 (Bouckaert et al 2019). We used Sebasticus tertius (MT117231) as an outgroup. Both phylogenetic analyses indicated that S. maliger is sister to a clade including S. rubrivinctus, S. nigrocinctus, S. umbrosus, and S. oculatus, and that S. norvegicus is sister to S. fasciatus (Figure 1). For the maximum likelihood phylogeny, all relationships are consistent with those previously published, except for S. steindachneri, which is sister to S. minor instead of S. melanostictus (Sandel et al. 2018;Kim et al. 2019), and S. owstoni, which is sister to S. taczanowskii instead of S. minor (Hyde and Vetter 2007). The Bayesian phylogeny (not shown) is identical to the maximum likelihood phylogeny except that S. steindachneri is sister to S. melanostictus instead of S. minor, and S. nigrocinctus is sister to S. rubrivinctus instead of S. umbrosus and S. oculatus. Several nodes in our maximum likelihood phylogeny had low bootstrap support ( 95) while all nodes in the Bayesian phylogeny had posterior probabilities >.99. Although additional species and analyses are needed to explore the differences seen in our phylogenies, the mitogenomes of S. maliger and S. norvegicus provide new insight into the phylogenetic relationships in Sebastes.

Ethical approval
Sebastes maliger was collected under Brigham Young Universities' IACUC-approved protocol #15-0602 for DKS. Sebastes norvegicus was caught by commercial fisherman (Malmstrøm et al. 2017). Mark C. Belk: Conception and Design, Analysis and Interpretation, Writing -Review and Editing. R. Paul Evans: Conception and Design, Analysis and Interpretation, Writing -Review and Editing. All authors approve the publication of this manuscript and agree to be accountable for all aspects of the work.