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Bivalve molluscs record histories of individual growth as alternating periods of activity (shell deposition) and inactivity (growth cessation marks) within their multilayered shells, and in some species, as alternating sublayers with different morphology. Shell growth patterns reflect tidal, daily, and seasonal cycles of key environmental parameters, such as submergence and temperature, which influence physiology (e.g., feeding, respiration, metabolic rates, and reproductive cycles). Knowledge of the periodicity of formation of various structures within the shell enables researchers to place a calendar across the growth history of an animal knowing only the date of collection. In turn, this enables both the determination of age (essential in studies of population dynamics) and the assessment of how bivalve populations responded to known environmental events, be they anthropogenic or natural, after the event has occurred. Seasonal microstructural shell growth patterns of six common bivalve species living in fresh (Corbicula fluminea O. F. Muller, 1774), brackish (Rangia cuneata G. B. Sowerby I, 1832), lower estuarine (Geukensia demissa Dillwyn, 1817), coastal (Mytilus edilis Linnaeus, 1758 and Mya arenaria Linnaeus, 1758), and continental shelf (Spisula solidissima Dillwyn, 1817) habitats in the mid-Atlantic region of the United States are documented using optical and scanning electron microscopy based on collections in the late 1980s. Some of the works have been published previously, but the results for each of the six species are combined and summarized in one volume as a guide to the seasonal shell microstructure for some common bivalves in New Jersey waters. The utility of shell growth pattern analysis in environmental impact assessments and population dynamics studies is evaluated within each habitat and example applications are provided. Although the results reported here were from studies conducted over 30 y ago, they represent collectively a contribution to our knowledge of molluscan shell microstructure that remain relevant today and are published as a coherent monograph before they are lost as so many other important unpublished works have been as time ran out on aging authors before they could relay the precious secrets they uncovered over the years. KEY WORDS: bivalve, shell, microstructure, environmental assessment, population dynamics, INTRODUCTION Studies of environmental stress in aquatic and marine environments are frequently based on expensive faunal surveys, bioassay work, or a combination of approaches. Such a research program can be [...]

We utilized aerial images and employed photogrammetric methodologies to collect standardized lengths of Steller sea lions (Eumetopias jubatus) terrestrially hauled out. We conducted comparisons among all site types and separately for rookery and haulout site-types between the two distinct population segments (DPSs; eastern and western) and two broad regions within the western DPS experiencing contrasting population abundance trends. An observed adult female index was created from measurements of reproductive females--in the presence of a pup or juvenile--and was applied as a model constraint for 'adult females'. We fitted a finite mixture distribution model to the length-frequency data to estimate the proportion population for three delineated age-sex classes (juveniles, adult females, and adult males) and mean length for juveniles and adult males. Estimated proportions reflected what we expected; however, the broad region within the western DPS exhibiting substantial population declines had greater proportion of all age-sex classes on rookery sites than increasing broad region. Adult sea lions were significantly shorter in the eastern DPS than the western area, providing further evidence of morphological differences between the DPSs. We also introduce a less resource-demanding method for estimating population demographics, and potentially vital rates, for pinnipeds across a vast geographic range. Nous avons utilise des images aeriennes et des methodes photogrammetriques pour obtenir des longueurs normalisees d'otaries de Steller (Eumetopias jubatus) echouees en milieu terrestre. Nous avons effectue des comparaisons entre tous les types de sites et, pour les differents types de roqueries et d'echoueries, entre deux segments de population distincts (SPD est et ouest) et deux grandes regions dans le SPD ouest presentant des tendances contraires d'abondance de la population. Un indice de femelles adultes observees a ete cree a partir des mesures de femelles reproductrices (en presence d'un veau ou d'un juvenile) et a ete applique comme contrainte du modele pour les << femelles adultes >>. Nous avons cale un modele de melange fini aux donnees de frequences des longueurs pour estimer la proportion de la population pour trois classes d'ages selon le sexe (juveniles, femelles adultes et males adultes) et la longueur moyenne pour les juveniles et les males adultes. Les proportions estimees refletent ce qui etait prevu, bien que la grande region du SPD ouest qui presentait des baisses significatives de la population soit caracterisee par de plus grandes proportions de toutes les classes d'ages selon le sexe dans les sites de roquerie que la grande region presentant une augmentation de l'abondance. Les otaries adultes etaient significativement plus courtes dans le SPD est que dans le SPD ouest, une autre indication de la presence de differences morphologiques entre les SPD. Nous presentons egalement une methode peu couteuse en termes de ressources pour estimer la demographie des populations et, potentiellement, des indices vitaux relatifs aux pinnipedes a l'interieur d'une vaste aire geographique. [Traduit par la Redaction], Introduction The Steller sea lion (Eumetopias jubatus) inhabits the North Pacific rim from Japan to California. Alaskan Steller sea lion population abundance estimates were well documented since the 1950s (Trites [...]

One focus of mitigation for Steller sea lion (Eumetopias jubatus) declines in Alaska has been to restrict commercial fishery activity around sea lion rookeries and haul-outs. However, a variety of statistical hypothesis tests have failed to relate sea lion population metrics to fish and fishing variables, prompting speculation that regulations may be unwarranted. In this study, we use simulation to show that standard hypothesis tests often have overstated power to detect a relationship between Steller sea lion vital rates and fish or fishing variables. The power and utility of hypothesis tests largely depend on choosing appropriate dependent and independent variables. In particular, pup counts were the most effective for diagnosing fecundity effects, and successive ratios of adult counts were the most effective for diagnosing survival effects. Fish relative abundance was the most effective independent variable, with other choices (e.g., fishery catch) often resulting in misleading inferences. We argue that Bayes factors are best suited for characterizing the relationship between fish abundance and Steller sea lion vital rates and that existing evidence does not preclude a strong relationship between sea lion fecundity and the availability of commercially harvested fish stocks. Un des axes d'intervention pour contrer les baisses d'abondance des otaries de Steller (Eumetopias jubatus) en Alaska a consiste a restreindre les activites de peche commerciale autour des roqueries et echoueries d'otaries. Divers tests statistiques n'ont toutefois pas permis de relier des parametres relatifs a la population d'otaries a des variables associees aux poissons ou a la peche, ce qui remet en question la pertinence de la reglementation. Nous nous servons des simulations pour montrer que la puissance des tests d'hypothese standards pour detecter un eventuel lien entre les indices vitaux des otaries de Steller et des variables associees aux poissons ou a la peche est souvent surestimee. La puissance et l'utilite des tests statistiques dependent en bonne partie du choix des variables dependantes et independantes. En particulier, le nombre de veaux etait la variable la plus efficace pour deceler des effets sur la fecondite et les rapports successifs du nombre d'adultes constituaient la variable la plus efficace pour deceler des effets sur la survie. L'abondance relative des poissons etait la variable independante la plus efficace, d'autres choix (p. ex. les prises de peche) se traduisant souvent par des inferences trompeuses. Nous arguons que les facteurs de Bayes se pretent le mieux a la caracterisation du lien entre l'abondance des poissons et les indices vitaux des otaries de Steller, et que les donnees disponibles n'excluent pas la presence d'un fort lien entre la fecondite des otaries et la disponibilite de stocks de poissons faisant l'objet d'une exploitation commerciale. [Traduit par la Redaction], Introduction In 1990, the Steller sea lion (SSL; Eumetopias jubatus), the largest of the otariid pinnipeds and a prodigious piscivore, was listed as a 'Threatened' species range-wide under the US [...]

The recovery plan for Steller sea lions (SSL; Eumetopias jubatus) suggests critical habitat should be enhanced to incorporate the spatio-temporal variation in dynamic oceanographic features that influence the prey and survival of SSL. It is necessary, therefore, to determine which features affect SSL. Demographics for sub-regions of the endangered, western stock of SSL were examined with respect to corresponding average, maximum, and variance of chlorophyll-α data (SeaWIFS), a proxy for primary productivity. Overall, SSL trends (2000-2008) and pup productivity (1999-2009) were related to maximum values of chl-α in critical habitat. Additionally, conditions in critical habitat appeared worse in areas of decline (i.e., dispersed patterns of chl-a hotspots and greater distances from SSL sites to productive areas). Although there may be a low feasibility of mitigating the effects of dynamic features on the recovery of SSL, the interactive effects of primary productivity and other stressors should be investigated for safeguarding their prey., Introduction From the late 1970s through the 1990s, the endangered, western distinct population segment (wDPS) of Steller sea lions (SSL; Eumetopias jubatus), which occurs west of 144°W (Cape Suckling, AK, [...]

Abstract: Steller sea lion (Eumetopias jubatus (Schreber, 1776)) populations have had differing dynamics in different regions of Alaska over the past 30 years. The western population (west of 144°W, near [...]

Abstract--Survey- and fishery-derived biomass estimates have indicated that the harvest indices for Pacific cod (Gadus macrocephalus) within a portion of Steller sea lion (Eumetopias jubatus) critical habitat in February and [...]

ABSTRACT - In April 1990, the Steller sea lion, Eumetopias jubatus, was listed as threatened under the U.S. Endangered Species Act by emergency action. Competitive interactions with the billion-dollar Alaska [...]

Walleye pollock (Theragra chalcogramma) is the single most abundant fish species in the Bering Sea and comprises the bulk of the commercial catch. Juvenile pollock are an important forage fish for older pollock, other fish, marine mammals, and birds. We examine the interaction between cannibalism, climate variability, and related patterns in physical transport. Our analysis of adult and juvenile pollock abundance and distribution time series, ocean current modelling studies, and information on climate variability indicates that cannibalism is a major determinant of interannual recruitment variability. In turn, the intensity of cannibalism appears to be dependent on the degree of spatial separation of adults and juveniles. Strong year classes occur when juvenile pollock are transported inshore and away from adults in spring – conditions typical of warm years. In cold years, transport is reduced and juveniles remain on the outer shelf in proximity to adults. Co-occurring distribution patterns of adults and juveniles resulting from these conditions lead to potentially increased cannibalism and subsequent weak year classes. [ABSTRACT FROM PUBLISHER]