Pacific halibut Hippoglossus stenolepis of known age were used to create a reference chronology of radiocarbon levels for the years 1944-1981. Levels of radiocarbon in Pacific halibut otoliths pre-1958 were among the lowest reported to date, but radiocarbon levels increased dramatically post-1960. Subsequently, this reference chronology was used to validate ages determined using the standard break and burn and surface ageing technique. These older fish were collected at a later date but were born during this period of rapidly increasing radiocarbon levels. Otolith cores were compared to the reference chronology based upon the presumed birth year determined from annulus counts and year of capture. The ages derived from both break and burn and surface ageing methods were determined to be accurate. # 2004 The Fisheries Society of the British Isles
The hypothesis was tested that the sagittae of age 2 year Pacific halibut Hippoglossus stenolepis are interchangeable, by analysing whole-otolith preparations for element-to-calcium ratios of 10 trace metals ( 7 Li, 25 Mg, 55 Mn, 56 Fe, 60 Ni, 63 Cu, 66 Zn, 88 Sr, 138 Ba and 208 Pb) and carbon and oxygen stable isotope ratios (d 13 C and d 18 O). After detrending for significant (a ¼ 0Á05) relationships between elemental concentration and otolith mass, significant (paired t-tests, P < 0Á01) asymmetry was detected in d 13 C and d 18 O, and 88 Sr: 48 Ca. Right (smaller) sagittae exhibited higher d 13 C and d 18 O, and lower 88 Sr: 48 Ca, than left sagittae. Significant (a ¼ 0Á05) left-right differences were not detected in the remained trace metals. Given that sagittae are the same size at hatch and diverge as H. stenolepis age, the larger otolith is presumably biased towards later-accreted carbonate. Estuarine-reared flatfish probably exhibit more pronounced dissimilarities than observed here, given greater environmental variability in such habitats relative to coastal halibut nurseries, and the importance of salinity and temperature in regulating elemental uptake.Journal compilation # 2008 The Fisheries Society of the British Isles No claim to original US government works
a b s t r a c tStable isotope studies are increasingly important for understanding past environmental and cultural developments along the North Pacific Rim. In this paper, we present methods for using Pacific cod (Gadus macrocephalus) otoliths as a paleothermometer using a case study from Kodiak Island, Alaska. The results of this study indicate that Pacific cod otoliths record variable paleoenvironmental conditions during the Little Ice Age. The broad distribution of Pacific cod and success in using the otoliths as a paleothermometer makes this method widely applicable to researchers working throughout the northern Pacific Rim.
Previous studies of polyandry and population genetics in garter snakes have been hampered by the limited number of available microsatellite markers. Here we report another six dinucleotide microsatellite markers, doubling the number of previously available loci. The majority of the loci exhibit utility across a broad geographical range for the common garter snake and also cross‐amplify effectively in samples from two other Thamnophis species.
The effect of glycerin storage on the bomb radiocarbon content of otoliths was determined experimentally. Storage in either pre‐ or post‐bomb glycerin had no detectable effect on the bomb radiocarbon content of either pre‐ or post‐bomb otoliths. Therefore bomb‐dated age validation studies need not be restricted to freshly‐collected samples or dry otoliths, implying that the large numbers of glycerin‐archived otoliths around the world are suitable for age validation studies using bomb radiocarbon.
Sagittal otoliths from juvenile Pacific halibut (Hippoglossus stenolepis) of known age were used to create a bombproduced radiocarbon reference chronology for the eastern Bering Sea (EBS) by fitting a coupled-function model to ⌬ 14 C values from each specimen's birth year. The newly created EBS reference chronology was then compared with a reference chronology previously created for Pacific halibut from the Gulf of Alaska (GOA). Adult Pacific halibut age-validation samples from the EBS were also analyzed for 14 C and modeled to validate age-estimation accuracy. A Bayesian model was developed and Markov chain Monte Carlo simulation was used to estimate model parameters and adult Pacific halibut ageing bias. Differences in reference chronologies between ocean basins were reflected in a large deviance information criterion (⌬DIC) between models, supporting the hypothesis that two separate coupled-function models were required to adequately describe the data, one each for the EBS and GOA. We determined that regionally specific GOA and EBS oceanography plays a considerable role in the ⌬ 14 C values and must be taken into consideration when selecting a reference chronology for bomb-produced 14 C age-validation studies. The age-validation samples indicated that the current ageing methodology used in Pacific halibut assessments is accurate and has provided accurate age assignments for Pacific halibut in the EBS.Résumé : Des otolites sagittaux de flétans du Pacifique (Hippoglossus stenolepis) juvéniles d'âges connus ont été utilisés pour établir une chronologie de référence au radiocarbone dérivé d'explosions pour la mer de Behring orientale (EBS) en calant un modèle de fonctions couplées sur les valeurs de ⌬ 14 C pour l'année de naissance de chaque spécimen. Cette nouvelle chronologie de référence pour l'EBS a ensuite été comparée à une chronologie de référence déjà établie pour le flétan du Pacifique du golfe d'Alaska (GOA). Des échantillons de validation de l'âge de flétans du Pacifique adultes de l'EBS ont également été analysés pour le 14 C et modélisés pour en valider l'exactitude des estimations de l'âge. Un modèle bayésien a été mis au point et une simulation de Monte Carlo par chaîne de Markov a été utilisée pour estimer les paramètres de modèle et le biais associé à la détermination de l'âge de flétans du Pacifique adultes. Des différences des chronologies de référence entre les deux bassins océaniques se reflétaient par une grande variation du critère d'information associé à la somme des carrées des écarts (⌬DIC) entre les modèles, appuyant l'hypothèse voulant que deux modèles de fonctions couplées distincts soient nécessaires pour décrire adéquatement les données, soit un modèle pour l'EBS et un autre pour le GOA. Nous avons établi que l'océanographie régionale respective du GOA et de l'EBS joue un rôle important dans la détermination des valeurs de ⌬ 14 C et doit être prise en compte dans la sélection d'une chronologie de référence pour les études de validation des âges reposant sur le 14 C dérivé d'explosion...
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