Aspects of the Life Histories of Pinkrose Rockfish (Sebastes simulator) and Swordspine Rockfish (Sebastes ensifer) with Notes on the Subgenus Sebastomus

Abstract

The rockfishes, genus Sebastes, form an extremely speciose group that often dominates the fish assemblages of California reefs between depths of 30 and 300 m (Love et al. 2002). The genus is divided into a number of subgenera (estimated at between 13 and 15, Hyde and Vetter 2007) among which the subgenus Sebastomus is particularly well characterized by congruencies in both morphology and genetics (Chen 1971; Rochas-Olivares et al. 1999; Hyde and Vetter 2007). In general, species in this subgenus are relatively small (to a maximum of 56 cm total length) (Table 1) and all are benthic or epibenthic (Love 2011). In addition, with the exception of Sebastes helvomaculatus, all of the North American species are relatively warm-water, and most are rare or absent from waters north of central California (Table 1). The basic biology and ecology of most of the Sebastomus living in the northeastern Pacific (i.e., with ranges extending at least into California waters) have been fairly well documented (summarized in Love et al. 2002; Love 2011; Fields 2016). The main exception was Sebastes simulator, the pinkrose rockfish, and to a lesser extent, Sebastes ensifer, the swordspine rockfish, whose life histories, were poorly understood. In this paper, we report on a number of aspects on the biology of S. simulator, provide supplementary data on the biology of Sebastes ensifer, and update basic information on all species in the subgenus Sebastomus. We collected specimens by hook-and-line from southern California waters (primarily from the northern Channel Islands), immediately placed them on ice aboard a research vessel, and then froze them in the lab for later examination. All specimens were measured [standard (SL), fork (FL), and total (TL) length] to the nearest millimeter and most were weighed (to the nearest 0.1 g). All lengths are reported as TL. We used sagittal otoliths for age determinations; these were removed and stored dry in coin envelopes. For age determinations, each otolith was glued to a wooden block, placed on a Bueller Isomet low-speed saw and a 0.05-cm wafer was cut from it, using two diamond-edge blades separated by a stainless-steel shim. Before reading, the wafers were slightly burned over an alcohol lamp. The wafers were then placed in a water-filled, blackbottomed watch glass and examined under a dissecting microscope. All wafers were read twice by M. Love. When reading did not agree, the otoliths were read again. The value of two coincident readings was accepted as the best estimate of age. We judged that the otoliths of about 5% of the specimens were unreadable due to poorly developed annuli. Lengths at ages were estimated by direct observation of otolith annuli and by using the von Bertalanffy growth model: