Tiburon Laboratory. Southwest Fisheries Science Center National Marine Fisheries Service. NOAA 3150 Paradise Drive. Tiburon. California 94920 Age, Growth, and Potential Yield for Shortbelly Rockfish Sebastes jordan; Abstract.Shortbelly rockfish Sebastes jordani is an abundant species that could support a large commercial fishery off central California. Prior studies of shortbelly rockfish growth were based on age data obtained from scales or whole otoliths. We show that broken and burnt otoliths provide reliable ages that are substantially different than those derived from previous methods. This new information was used to update estimates of the von Bertalanffy growth curve parameters, the natural mortality rate, and potential yield. We found that shortbelly rockfish live for up to 22 years. Males grew more slowly and reached a smaller maximum size than females. Estimates of natural mortality from three predictive models ranged from 0.212 to 0.378 for males and 0.203 to 0.437 for females. Assuming Mis 0.20-0.35 and using biomass estimates from hydroacoustic surveys, we estimated that potential yield in the Ascension Canyon-Farallon Islands area ranges from 13,400 to 23,500 metric tons.

This study was undertaken to resolve problems in age determination of sablefish (Anoplopoma fimbria). Aging of this species has been hampered by poor agreement (averaging less than 45%) among age readers and by differences in assigned ages of as much as 15 years.Otoliths from fish that had been injected with oxytetracycline (OTC) and that had been at liberty for known durations were used to determine why age determinations were so difficult and to help determine the correct aging procedure. All fish were sampled from Oregon southwards, which represents the southern part of their range. The otoliths were examined with the aid of image processing.Some fish showed little or no growth on the otolith after eight months at liberty, whereas otoliths from other fish grew substantially. Some fish lay down two prominent hyaline zones within a single year, one in the summer and one in the winter. We classified the otoliths by morphological type and found that certain types are more likely to lay down multiple hyaline zones and other types are likely to lay down little or no zones. This finding suggests that some improvement could be achieved by detailed knowledge of the growth characteristics of the different types.This study suggests that it may not be possible to obtain reliable ages from sablefish otoliths. At the very least, more studies will be required to understand the growth of sablefish otoliths.

Otoliths from blue rockfish (Sebastes mystinus), were aged by using a combination of surface and break-and-burn methods. The samples were collected between 1978 and 1998 off central and northern California. Annual growth increments in the otoliths were validated by using edge analysis for females up to age 23 and for males to age 25. The first annual growth increment was identified by comparing the diameter of the otolith from fish known to be one year old collected in May (when translucent zone formation was completed) to the mean diameter of the first translucent zone in the otoliths from older fish. Our estimated maximum ages of 44 years for males and 41 years for females were much older than those reported in previous studies. Von Bertalanffy growth models were developed for each sex. Females grew faster and reached larger maximum length than males. The growth models were similar to those generated in other studies of this species in southern and central California. Fish from northern and central California had similar maximum sizes, maximum ages, an growth model parameters.

The Cobb Seamount was discovered in 1950 by the crew of the fishery research vessel John N . Cobb (Anonymous, 1950). This submerged volcanic mountain (Budinger, 1967) is located approximately 280 nautical miles (nmi) off the southern Washington coast and comes to within 50 meters of the sea surface. At the 200-m isobath, its area is approximately 32 nmi2 (Budinger, 1967). Various efforts have been made t o study the biological, oceanographic, and geologic characteristics of the seamount since its discovery (Budinger, 1967; Birkland, 1971; Dower et al., 1992), but these efforts have been somewhat limited in scope and duration. The studies have shown that the seamount has concentrations of commercially valuable species including rockfishes (genus Sebastes). Most of the information about commercial fishing operations on the seamount is anecdotal and speculative, primarily because the seamount is located outside the Exclusive Economic Zone (EEZ) and therefore fishing vessels operating there are not subject to fishing regulations or routine sampling. What is known, however, is that bottom trawl, midwater trawl, gill net, and longline fishing has occurred at various times. Foreign and domestic fleets have fished on the Cobb Seamount from a t least the mid 1960’s (Sasaki, 1986). Most of the fishing operations appear to have been aimed a t several species of rockfish. Sasaki (1986) suggests that prior to 1985, there was intense fishing pressure on the seamount by the Japanese fishing fleet. In 1985, a few fishermen from Oregon attempted to trawl on the Cobb Seamount but were unsuccessful. It is not known why these efforts failed. Little fishing activity is believed to have occurred on Cobb Seamount between 1985 and September 1991. In 1991, fishermen from Oregon and Washington returned to Cobb Seamount; this time they were successful. This success drew the attention of fishery managers because fish caught outside the EEZ are not regulated by the west coast Fisheries Management Plan governing nearshore stocks. Because of the regulatory problems presented by this new fishery, port samplers were instructed to give a high priority to sampling of landings from Cobb Seamount in part as an effort to identify any unusual characteristics which might make landings identifiable. In this paper we present some of the unique characteristics of the fish populations found on Cobb Seamount, particularly widow rockfish (S. entomelas). This seamount is isolated enough from coastal fish populations so that recruitment dynamics, density dependent growth, and bioenergetic studies could provide valuable new insights into fisheries biology.

Shortbelly rockfish Sebastes jordani is an abundant species that could support a large commercial fishery off central California. Prior studies of shortbelly rockfish growth were based on age data obtained from scales or whole otoliths. We show that broken and burnt otoliths provide reliable ages that are substantially different than those derived from previous methods. This new information was used to update estimates of the von Bertalanffy growth curve parameters, the natural mortality rate, and potential yield. We found that shortbelly rockfish live for up to 22 years. Males grew more slowly and reached a smaller maximum size than females. Estimates of natural mortality from three predictive models ranged from 0.212 to 0.378 for males and 0.203 to 0.437 for females. Assuming M is 0.20-0.35 and using biomass estimates from hydroacoustic surveys, we estimated that potential yield in the Ascension Canyon-Farallon Islands area ranges from 13,400 to 23,500 metric tons.