Larvae and Pelagic Juveniles of Blackgill Rockfish, Sebastes melanostomus, Taken in Midwater Trawls off Southern California and Baja California

Abstract

Examination of 217 midwater trawl samples from the coastal basins off southern California and Baja California revealed a recurring group of rockfish species. The late larvae and pelagic juveniles of the blackgill rockfish, Sebastes melanostomus, constituted 16% of the total number of rockfish specimens. The life-history stages of this species are described, with emphasis on the pelagic juvenile stage. Late stage larvae and pelagic juveniles develop a distinctive pattern of melanophore bands which, by disrupting the body outline, may help conceal the young during their midwater existence. Evidence from midwater trawl collections suggests that 30-mm pelagic juveniles migrate or are carried shoreward at a depth of ~ 200 m to the appropriate habitat for settling. The high relative abundance of blackgill rockfish pelagic juveniles in midwater trawl samples suggests that this species may represent a potential resource. Key words: blackgill rockfish, Sebastes melanostomus, larvae, pelagic juveniles, midwater trawls, developmental stages, melanophore patterns, life-history strategy, head-spine development

Early larvae of the swordspine rockfish (Sebastes ensifer) identified by molecular methods

“…Spines measured include the preopercular (APO1-4 and PPO2-4), parietal, nuchal, pterotic, postorbital, first lower infraorbital, and posttemporal. Spine terms follow those of Moser and Ahlstrom (1978). Larval lengths refer to BL of ethanol-preserved larvae, and descriptions of pigmentation refer to melanistic pigment.…”

“…Larvae older than the early preflexion stage are known for only 3 Sebastomus species in the North Pacific: the starry rockfish (Sebastes constellatus), known to the mid-flexion stage (Moser et al, 1977;Moser and Butler, 1987;Moser, 1996b) and the late postflexion to pelagic juvenile stages (Rocha-Olivares et al, 2000); the rosethorn rockfish (S. helvomaculatus), known from the late flexion to pelagic juvenile stages (Richardson and Laroche, 1979); and S. ensifer, illustrated at extrusion stage by Moser (1967) and described here through the early postflexion stage and by Rocha-Olivares et al (2000) from the late postflexion to pelagic juvenile stages.…”

“…Sebastes are live-bearers, and larvae are readily obtained from pregnant females and occur commonly in plankton samples, particularly during late winter and spring (Moser et al, 1993). Owing to this availability and to the use of larvae in providing fishery-independent estimates of spawning biomass (e.g., Moser and Butler, 1987;Moser et al, 2000;Ralston et al, 2003;Ralston and MacFarlane, 2010), considerable effort has been directed toward improving our ability to identify Sebastes larvae (Kendall, 1991;Moser, 1996b). However, the larvae are difficult to rear (e.g., Kendall, 1991), and there is considerable overlap among species in meristic, morphological, and pigment characters (Moser, 1996b).…”

“…Differences among larvae of Sebastomus species are quite small (e.g., Moser, 1996b;Rocha-Olivares, 1998;RochaOlivares et al, 2000), and currently larvae of none of these species can be reliably identified with traditional morphological and pigment characters. Complete larval development for any Sebastomus species is still unknown; to date, extrusion larvae are known for 7 of the 15 species, and some later stages are known for 4 species, including the cape redfish (S. capensis) of the Southern Hemisphere (e.g., Westrheim et al 1 ;Moser, 1967;Moser et al, 1977;Richardson and Laroche, 1979;Moser and Butler, 1987;Matarese et al, 1989;Sabatés and Olivar, 1990;Moser, 1996b;Rocha-Olivares et al, 2000). Larvae of another species, probably buccaneer rockfish (S. exsul) or spinyeye rockfish (S. spinorbis), have been described through the postflexion stage (Moser et al, 1977).…”

A Process for Evaluating Adverse Environmental Impacts by Cooling-Water System Entrainment at a California Power Plant

“…Larval Sebastes are very difficult to visually identify to the species level [17,18,19,20,21,22]. Perhaps 5 or 6 of the 59 rockfish species expected to occur in the vicinity of DCPP can be identified at the early larval stage to the species level [22]: aurora rockfish (S. aurora), shortbelly rockfish (S. jordani), cowcod (S. levis), blue rockfish (S. mystinus), bocaccio (S. paucispinis), and stripetail rockfish (S. saxicola).…”