Maturity, Spawning Omission, and Reproductive Complexity of Deepwater Rockfish

Abstract

Reproductive parameters are critical components of stock assessment models that directly influence estimates of the stock biomass of mature females and significantly impact the determination of catch levels for many federally managed fish species. There are few data available concerning the reproductive biology of deepwater rockfish species in the Gulf of Alaska, which are suspected to have complex life histories that include viviparity, increasing productivity with age, abortive maturity, and spawning omission. The objective of this study was to examine the reproductive biology of female Shortraker Rockfish Sebastes borealis, Rougheye Rockfish S. aleutianus, and Blackspotted Rockfish S. melanostictus within the Gulf of Alaska. The reproductive development stage was examined for samples collected opportunistically throughout the year from a variety of scientific platforms and charter vessels in 2008–2014. Rougheye Rockfish and Shortraker Rockfish were found to be seasonal synchronous spawners, with the onset of development occurring in the later summer months and parturition taking place from March through May. The fork length at 50% maturity (L₅₀) was similar for Rougheye Rockfish (L₅₀ = 45.0 cm) and Blackspotted Rockfish (L₅₀ = 45.3 cm), but the age at 50% maturity (A₅₀) was younger for Rougheye Rockfish (A₅₀ = 19.6 years) than for Blackspotted Rockfish (A₅₀ = 27.4 years). The L₅₀ for Shortraker Rockfish was 49.9 cm, but this species could not be reliably aged. In all three species, there were individuals undergoing abortive maturity and skipped spawning. Skipped spawning rates ranged from 37.4% (95% confidence interval [CI] = 29.9–44.9%) for Rougheye Rockfish to 93.9% (95% CI = 90.0–97.3%) for Blackspotted Rockfish; Shortraker Rockfish had an intermediate skipped spawning rate of 60.0% (95% CI = 49.2–70.8%). The results from this study will advance our knowledge of the reproductive biology of these species and will aid in ensuring that the most appropriate data are utilized in their stock assessments.

Received August 17, 2016; accepted January 18, 2017 Published online March 24, 2017

ACKNOWLEDGMENTS

I acknowledge the many individuals and agencies that contributed samples to this project, including B. Knoth, R. Swanson, D. Jones, C. Rooper, P. Spencer, T. Tenbrink, M. Martin, M. Zimmermann, D. Hanselman, D. Urban, K. Spalinger, A. Ellsworth, the North Pacific Groundfish Observer Program, and the ADFG. I thank the NMFS-AFSC Age and Growth Laboratory for providing age and growth data for Rougheye Rockfish and Blackspotted Rockfish; P. Hulson for assisting with statistical analyses; and the crew of the F/V Gold Rush, including B. Ashley, D. Ashley, and M. Smith, for assisting in sample collection during charter operations.