Yellowtail Rockfish Research Articles

Energetics of early development in the viviparous yellowtail rockfish

Total mean gestation period of all female yellowtail rockfish Sebastes flavidus, from fertilization to parturition, was 29.2 days. Hatching occurred 23 days after fertilization, followed by 6 days of larval incubation. Eggs varied in dry mass and energy content with lipid concentrations contributing the greatest amount of energy per egg. The endogenous energy of the yolk and oil globule declined throughout gestation resulting in limited yolk and oil reserves at parturition.

Energetics of early development in the viviparous yellowtail rockfish

Total mean gestation period of all female yellowtail rockfish Sebastes flavidus, from fertilization to parturition, was 29.2 days. Hatching occurred 23 days after fertilization, followed by 6 days of larval incubation. Eggs varied in dry mass and energy content with lipid concentrations contributing the greatest amount of energy per egg. The endogenous energy of the yolk and oil globule declined throughout gestation resulting in limited yolk and oil reserves at parturition.

Lipid class composition of the viviparous yellowtail rockfish over a reproductive cycle

Triacylglycerols (TAG) were the dominant lipids in liver tissue of both sexes of the viviparous yellowtail rockfish Sebastes flavidus during the spring and summer when greatest feeding occurred. Significant declines in liver TAG during the winter corresponded to increased concentrations of polar lipids (PL), the main component of cell membranes. Elevated PL in female livers relative to those of males preceded the period of ovarian enlargement and may be attributed to the production of vitellogenin. During late vitellogenesis and gestation, ovaries contained significantly elevated concentrations of PL, TAG, and cholesterol. Since yellowtail rockfish are highly fecund and viviparous, large quantities of ovarian PL are required for proliferation of the cell membranes in developing larval tissues. TAG accumulated in ovaries in lower concentrations than PL and were likely metabolized as the main source of energy during gestation. This pattern of ovarian PL concentrations exceeding those of TAG and the presence of oil globules, may be unique to highly fecund, viviparous teleosts and signify an alternative profile to those previously documented for oviparous species. Testes at maximum IG were only 7% of maximum ovarian size, composed of mainly PL, and lacked a defined lipid dynamic pattern across the reproductive cycle.

Lipid class composition of the viviparous yellowtail rockfish over a reproductive cycle

Lipid class composition of the viviparous yellowtail rockfish over a reproductive cycle

Polymerase chain reaction‐restriction fragment length polymorphism analysis of mitochondrial rRNA genes from yellowtail rockfish

A 1600 base pair region of the mitochondrial rRNA genes from 74 yellowtail rockfish, collected from three north‐east Pacific localities, was amplified via PCR. RFLP analysis yielded a total of 33 restriction sites allowing examination of 139 base pairs or 0·8% of the mtDNA molecule. Essentially no variation was detected within or among the three populations.

Polymerase chain reaction–restriction fragment length polymorphism analysis of mitochondrial rRNA genes from yellowtail rockfish

Polymerase chain reaction–restriction fragment length polymorphism analysis of mitochondrial rRNA genes from yellowtail rockfish

Metabolic costs of viviparity in yellowtail rockfish,Sebastes flavidus

We estimated the energy utilized by developing embryos and larvae of yellowtail rockfish,Sebastes flavidus, by determining the routine metabolic rate of adult females throughout gestation and subtracting the mean metabolic rate of non-gestating fish. The pattern of maternal oxygen consumption during gestation was such that metabolic demands did not become significantly elevated until intra-ovarian embryos had hatched and larvae were being incubated (i.e. 24–28 d post-fertilization). Metabolic rates of females in this latter stage of gestation were 82% higher than spent females and 101% higher than those of non-reproductive males. We determined that 0.08996 cal embryo-1 was consumed during gestation as compared to the change in energy content of embryos from fertilization to birth which was 0.08690 cal embryo-1. The difference between the energy consumed and the energy lost during the 29 d gestation period indicated that extra embryonic sources contributed only 3.4% or 0.00306 cal embryo-1 of the energy utilized after fertilization. Our observations agree with previous work which determined that embryos and larvae ofS. flavidus are primarily lecithotrophic and that the relatively high fecundity ofS. flavidus coupled with a small egg size, rapid embryogenesis and brief gestation period characterize this species as a relative r-strategist within a genus whose species range broadly over the ‘K end’ of the r-K continuum.

Matrotrophic viviparity in the yellowtail rockfish Sebastes flavidus

A capacity for matrotrophic viviparity was established in the yellowtail rockfish Sebastes flavidus (Teleostei: Scorpaeniformes). The incorporation of radiolabel into embryos from [14C]phosphatidylcholine present in the maternal serum during gestation provided the first in vivo demonstration of matrotrophy of phospholipid for any viviparous teleost and of any nutrient for a member of the genus Sebastes. Radiolabel content increased as embryos progressed through ontogeny. Serum proteins of 170 kDa, present in vitellogenic and embryogenic females, but not in earlier stages, in immature females or in males, indicated the presence of vitellogenin in pregnant females and, thus, the potential for matrotrophic supplementation to yolk sequestered before fertilization. The retention of higher molecular mass proteins and highly phosphorylated proteins and the maintenance of total protein content in yolk during early to mid embryogenesis argue for exogenous maternal supply during gestation. As ovarian development proceeded from the oocyte through successive embryonic stages, the distribution of yolk proteins shifted from higher (67&shy;97 kDa) to lower molecular masses (<70 kDa). The results of these experimental studies corroborate data from field investigations showing that yellowtail rockfish can matrotrophically supplement embryo nutrients obtained before fertilization. Thus, yellowtail rockfish represent a teleost species positioned within the viviparity continuum and not at its extremes.

Temporal and Spatial Variation in Fecundity of Yellowtail Rockfish

Abstract Fecundities of the commercially important yellowtail rockfish Sebastes flavidus were compared to determine interannual variability and geographic variation, which will assist in stock assessment, characterization, and management. Gravimetrically estimated fecundities were compared in 1985–1991 between California, the southern extent of the species' distribution, and coastal waters of Washington, near the center of the species' abundance, where yellowtail rockfish are most heavily fished. California yellowtail rockfish were older, smaller in weight and length, and had smaller mesenteric fat deposits and more extensive disease and parasite pathologies than Washington fish. Egg production of this comparatively fecund viviparous fish increased linearly and sigmoidally with body weight and length, and asymptotically with age. Significant interannual differences were found in fecundities of young fish ( age 14) or in ...

A Predation Bioassay to Quantify the Ecological Significance of Sublethal Responses of Juvenile Chinook Salmon (Oncorhynchus tshawytscha) to the Antisapstain Fungicide TCMTB

The lumber protection antisapstain fungicide 2-(thiocyanomethylthio)benzothiazole (TCMTB) is leached by rainfall from treated wood awaiting shipment from outdoor lumber storage facilities. Stormwater discharges of this pesticide into estuarine reaches of the Fraser River, British Columbia, have raised concern about toxic effects on juvenile salmon rearing in this habitat. Simulated stream flow conditions were used to expose underyearling chinook salmon (Oncorhynchus tshawytscha) to a sublethal (10 μg∙L−1) concentration of TCMTB. Equal numbers of fin-clipped control and exposed fish were subsequently transferred to a vertically stratified (fresh over seawater) 15 500-L outdoor tank where they were challenged with the combined stressors of salinity and the presence of a marine predator (yellowtail rockfish (Sebastes flavidus)). After 5 d under these simulated estuarine conditions, survivors were enumerated. Chinook salmon that had been exposed to the toxicant were consumed in preference to the control group by a factor of 5.5:1. Inasmuch as predator avoidance represents the successful integration of appropriate biochemical, physiological, and behavioural responses, the predator bioassay provides an ecologically relevant technique to determine the significance to survival of the complex multifactorial interactions of individually "sublethal" stressors.

Behavioural approaches to demonstrate the ecological significance of exposure of juvenile Pacific salmon (genus Oncorhynchus) to the antisapstain fungicide TCMTB

Simulated stream conditions were used to expose underyearling Pacific salmon (genus Oncorhynchus) to sublethal doses of TCMTB (2-thiocyanomethylthio) benzothiazole; a fungicide used by the lumber industry to protect against discolouration by sapstain fungi. Observed changes in schooling, swimming, and respiration were studied in more detail utilizing progressively more complex and ecologically relevant experimental designs. Laboratory troughs (600 litre) were used to quantify innate shelter-seeking behaviour and susceptibility to predation during salinity stress. Swimming speed, schooling behaviour and responses to salinity and hypoxia were studied in a 4500-litre Water Column Simulator under vertically stratified conditions (fresh water overlying sea water). Finally a similarly stratified 15,500-litre outdoor tank was designed to compare susceptibility to predation during a volitional salinity challenge. Relative to controls, TCMTB-exposed underyearling salmon exhibited a reduction in cover response, were slower to seek shelter from bright light, were more erratic in their swimming behaviour and more likely to be eaten by marine predators. Videotape analyses confirmed that TCMTB reduced exploratory behaviour and swimming speed under both normoxic and hypoxic conditions in the WCS. The ecological consequences of these overt behavioural changes were experimentally linked to a clear increase in risk from predation by yellowtail rockfish (Sebastes flavidus) inhabiting the marine zone below the halocline of the 15,500-litre tank. These techniques illustrate our most recent efforts to correlate cumulative sublethal physiological stress with ecologically meaningful behavioural dysfunction.

Lipid Dynamics in Relation to the Annual Reproductive Cycle in Yellowtail Rockfish (Sebastes flavidus)

In yellowtail rockfish (Sebastes fiavidus), lipids that accumulated in mesenteries and liver during the summer and early fall upwelling were subsequently translocated to developing ovaries during late fall and winter. Tissue and serum lipids were assessed by stage of ovary maturation from fish collected monthly over six annual reproductive cycles (1985–91) from Cordell Bank, a seamount off central California. Lipids were primarily transported to ovaries prior to fertilization. Energetic lipids (triglycerides, nonesterified fatty acids) were maximal in serum during yolk accumulation stages and declined significantly during embryonic stages. Between fertilization and parturition, lipid and protein content of ovaries declined by about 21%, a value approaching the minimum for lecithotrophy (i.e. ovoviviparity). During gestation, however, serum phospholipids and calcium (vitellogenin surrogate) were significantly elevated relative to male levels, suggesting matrotrophic contributions. A reproductive mode that is primarily lecithotrophic but supplemented by maternal inputs during embryogenesis would be beneficial to viviparous fishes of the California coast. This strategy may optimize reproduction by coupling the disparate times of food abundance and gestation, yet allow for provision of nutrients late in the reproductive cycle should they be available.

Parasites of yellowtail rockfish, Sebastes flavidus (Ayres, 1862) (Pisces: Teleostei), from the Pacific coast of North America as potential biological tags for stock identification

We assessed the value of parasites of yellowtail rockfish, Sebastes flavidus (Pisces: Teleostei), as biological tags on the Pacific coast of North America. Of the 25 parasite species found, only Microcotyle sebastis (Monogenea: Microcotylidae) showed a latitudinal cline. Prevalence of this flatworm increased from 0–10% in samples from central British Columbia, to 80 and 100% in the California and Oregon samples, respectively. Mean intensity also increased from north to south. The results indicate that stock assessments for yellowtail rockfish, which treat the coastal population as five stocks from central British Columbia to northern California, can assume that harvests in one area will have little short-term impact on distant areas.

Chromatophoromas and Related Hyperplastic lesions in Pacific rockfish ( Sebastes spp.)

Pacific rockfish were sampled from Cordell Bank, off central California, from 1985 to 1990. Hyperplastic and neoplastic lesions, involving dermal chromatophores, were observed in five species; yellowtail rockfish ( Sebastes flavidus), bocaccio ( S. paucispinis), olive rockfish ( S. serranoides), widow rockfish ( S. entomelas), and chilipepper rockfish ( S. goodei). Yearly prevalences were highest, but static, in S. pancipinis, while prevalences in S. flavidus have risen steadily. The majority of lesions were black, but white, red, orange, yellow, and mixed color variants were also seen. Lesions were found in skin, fins, lips, gingiva, longue, urogenital papilla, and in the conjunctira and cornea of the eye. Flat lesions were consistent with either melanophore (black), erythrophore (red), or xanthophore (yellow) hyperplasia. Neoplastic lesions included melanophoromas, amelanotic melanophoromas, xanthophoromas, erythrophoromas, and mixed chromatophoromas. Electron microscopy did not reveal the presence of viruses and the etiology of the lesions has not been determined.

Reproductive performance of yellowtail rockfish,Sebastes flavidus

Reproductive performance of yellowtail rockfish,Sebastes flavidus

Age Validation and Revised Natural Mortality Rate for Yellowtail Rockfish

Abstract Oxytetracycline (OTC) injections were used in a mark-recapture study undertaken to validate the otolith method of age determination for yellowtail rockfish Sebastes flavidus. Otoliths from recaptured fish were broken across the focus and burned to enhance the contrast of features in the internal structure. The number of opaque and translucent zones laid down in the otolith after the deposition of the fluorescent OTC mark at the time of tagging agreed with the number of years (up to four) that the fish had been at liberty. These results validate the annual pattern of banding in otoliths of fish of ages 8–34 years. A larger sample of fish aged by this technique indicated an instantaneous natural mortality rate (M) of 0.07, a value only 28% of the estimate presently used for stock assessment and management of yellowtail rockfish.

Restricted Year-Class Structure and Recruitment Lag within a Discrete School of Yellowtail Rockfish

Observations of a school of adult yellowtail rockfish Sebastes flavidus over an 11-year period in southeastern Alaska revealed negligible recruitment as the school dwindled in numbers and remaining individual fish grew in size.

The Taxonomic Status of Sarcotaces komaii and Sarcotaces verrucosus (Copepoda: Phylichthyidae) and Host-Parasite Relationships between Sarcotaces arcticus and Sebastes spp. (Pisces)

Five species of rockfish (Sebastes spp.) were examined off southeast Alaska for Sarcotaces arcticus (Copepoda). Only Sebastes ciliatus was infected. Sarcotaces were compared to those found in 7 species of Sebastes collected off California and those from Molva dypterygia collected off Norway. As a result of these comparisons it is suggested that Sarcotaces komaii be synonymized with S. arcticus. It is possible that S. arcticus is synonymous with Sarcotaces verrucosus. Studies on aspects of the host-parasite relationship indicated that younger fish have a higher prevalence of infection and more multiple infections. There is no host-parasite size relationship. Seventy-five percent of the female parasites were associated with males, 85% had eggs and 10% nauplius larvae. Females ranged in size from 20 to 50 mm. Smaller specimens were represented by degenerated cysts. There was no indication of parasite-induced host mortality. The absence of infection in some species may be more a result of the hosts' natural history and geographic distribution than parasite specificity. In the course of a study on nearshore demersal fishes off southeast Alaska, numerous individuals from 5 species of rockfish (Sebastes) were examined for Sarcotaces (Copepoda: Phylichthyidae). Only Sebastes ciliatus was found to harbor Sarcotaces. This copepod, Sarcotaces arcticus Collett, 1874, was compared to specimens recovered from incidental collections of Sebastes spp. off southern and northern California. This report discusses some aspects of the host-parasite relationship between S. arcticus and S. ciliatus and suggests changes in the taxonomic status of Sarcotaces komaii Shiino, 1953. MATERIALS AND METHODS Five Sebastes spp. were collected off southeast Alaska from June to August 1981. Specimens were collected at 0 to 30 m by spear using SCUBA and hook-andline and at 80 to 120 m by longline and a jigging machine. Sebastes spp. (number hosts necropsied): S. ciliatus (411); Sebastes brevispinis (90); Sebastes ruberrimus (141); Sebastes entomelas (125); and Sebastes melanops (797). Hosts were aged by otolith ring count. The text will refer to small and large populations of S. ciliatus. The small populations are fish between 140 to 340 mm (3 to 12 yr old) and the large between 350 to 500 mm (12 to 27+ yr old). Although there is some overlap, the large populations were usually found in deeper water than the small. Comparisons between samples were standardized for host size, sex, Received 5 September 1984; revised 6 November 1985; accepted 10 December 1984. * School of Fisheries and Sciences, University of Alaska, Juneau, Alaska 99801. t School of Fisheries, University of Washington, Seattle, Washington 98195. seasons and depth of collection. Hence, not all comparisons have the same sample sizes. Infected Sebastes spp. off California included (host, number infected, collection, location, date): Sebastes auriculatus, 7, Tiburon, Sept. 1980; S. entomelas, 2, Moss Landing, Aug. 1982 and, 1, Point Pinos, Oct. 1982; Sebastes flavidus, 4, Moss Landing, June 1983; Sebastes melanops, 2, Monterey Bay, June 1982; S. rubrivinctus, 1, Bodega Bay, May 1981; Sebastes semicinctus, 1, Los Angeles, June 1982; and Sebastes serranoides, 2, Farallon Island, June 1981. The Molva dypterygia was collected by Dr. Bjmrn Berland, Zoological Laboratory, Bergen, Norway in September 1970. The tissues containing the Sarcotaces specimens were rehydrated in glycerine in March 1984. The northeastern Pacific Sarcotaces were compared to these specimens because the type specimen of S. arcticus was described from M. dypterygia (as Molva abyssorum) off Norway. Linear regression was used to assess the host-parasite size relationship and comparison between percentages to test prevalence of infections (Bailey, 1974). Parasites were formalin fixed at necropsy. Specimens to be examined by scanning electron microscopy were prepared by routine methods and examined on a NANOLAB 7 (SEM). All measurements were taken from formalin fixed specimens. The taxonomy of the Sebastes spp. is from Eschmeyer et al. (1983).

Comparative biochemical studies of carotenoids in fishes. XXVII. Stereochemical investigation of carotenoids from yellow-tail rocfish Sebastes flavidus.

The carotenoids in the integuments of yellow-tail rockfish Sebastes flavidus were investigated from the stereochemical points of view. Tunaxanthin fraction was found to be a mixture of three stereoisomers, tunaxanthin C (1), tunaxanthin D (2), and tunaxanthin J (3). Furthermore (6R, 6'R)-e, e-carotene-3, 3'-dione (4), (6R, 6'S;meso)-e, e-carotene-3, 3'-dione (5), and (6S, 6'S)-e, e-carotene-3, 3'-dione (6) Were also isolated.

Identification of Pacific Rockfish (Sebastes) Species by Isoelectric Focusing

Isoelectric focusing (IEF) is currently the most reliable method available for the identification of fish species. The high resolution of this method usually allows discrimination between even closely related species. One genus, the Sebastes, does present a problem however. Using both low and high resolution, IEF is unable to differentiate several species. Disc electrophoresis, used in an AOAC official final action method, does not differentiate the rockfish reliably. Using IEF, identical protein patterns were obtained for Pacific Ocean perch (Sebastes alutus), Bocaccio rockfish (S. paucispinis), and yelloweye rockfish (S. ruberrimus). A second group, comprised of silvergray rockfish (S. brevispinis), yellowtail rockfish (S. flavidus), black rockfish (S. melanops), and canary rockfish (S. pinniger), also has identical protein patterns. Widow rockfish (S. entomelas) and chilipepper rockfish (S. goodei) each had a unique pattern, different from the above 2 groups and from each other. The actual taxonomic relationships of these rockfish species are not clear and further work with IEF may help in this regard. Users of IEF and disc electrophoresis for identification purposes should be aware of this problem when working with the Sebastes.