The striped bass (Morone saxatilis) is an economically and ecologically important finfish species along the Atlantic seaboard of the United States. Recent stock assessments in Chesapeake Bay (U.S.A.) indicate that non-fishing mortality in striped bass has increased since 1999, concomitant with very high (>50%) prevalence of visceral and dermal disease caused by Mycobacterium spp. Current fishery assessment models do not differentiate between disease and other components of non-fishing mortality (e.g., senescence, predation); therefore, disease impact on the striped bass population has not been established. Specific measurement of mortality associated with mycobacteriosis in wild striped bass is complicated because the disease is chronic and mortality is cryptic. Epidemiological models have been developed to estimate disease-associated mortality from cross-sectional prevalence data and have recently been generalized to represent disease processes more realistically. Here, we used this generalized approach to demonstrate disease-associated mortality in striped bass from Chesapeake Bay. To our knowledge this is the first demonstration of cryptic mortality associated with a chronic infectious disease in a wild finfish. This finding has direct implications for management and stock assessment of striped bass, as it demonstrates population-level negative impacts of a chronic disease. Additionally, this research provides a framework by which disease-associated mortality may be specifically addressed within fisheries models for resource management.

Large-scale research on the environmental, biological, and anthropogenic drivers of fish distributions, abundances, and community structure can identify patterns and trends within systems, provide mechanistic insight into ecosystem functioning, and contribute to ecosystembased fisheries management. This study synthesized 10 yr of extensive fisheries-independent bottom trawl data (2002 to 2011) to evaluate drivers of demersal fish community structure in Chesapeake Bay, the largest estuary in the United States. Changes in community composition were assessed using constrained correspondence analysis. Also, aggregate community metrics (species richness, Simpson diversity, and catch-per-unit-effort [CPUE] of species groups) were modeled using generalized additive models. Five species (Atlantic croaker, white perch, spot, striped bass, and summer flounder) accounted for > 75% of the total trawled biomass. The demersal fish community was primarily structured by the latitudinal salinity gradient that largely differentiated anadromous fishes from coastal shelf spawning species and elasmobranchs, with low overall CPUE and richness in mesohaline waters. Low dissolved oxygen concentrations (below ~4 mg l −1 ) greatly suppressed CPUE and diversity metrics and appeared to displace fish biomass toward the northern and southern edges of the bay's mainstem channel. Water temperature and month strongly influenced the seasonal dynamics of community composition and metrics. Community composition and biomass shifted after 2007, with a substantial decline in annual CPUE of some species groups. Recruitment and fishing indices for the dominant species were the best predictors of the interannual patterns in community metrics, outperforming various other climatic and biological annual-scale covariates.

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Striped bass (Morone saxatilis) in the Chesapeake Bay are currently experiencing a very high prevalence of mycobacteriosis associated with newly described Mycobacterium species, Mycobacterium pseudoshottsii and M. shottsii. The ecology of these mycobacteria outside the striped bass host is currently unknown. In this work, we developed quantitative real-time PCR assays for M. pseudoshottsii and M. shottsii and applied these assays to DNA extracts from Chesapeake Bay water and sediment samples, as well as to tissues from two dominant prey of striped bass, Atlantic menhaden (Brevoortia tyrannus) and bay anchovy (Anchoa mitchilli). Mycobacterium pseudoshottsii was found to be ubiquitous in water samples from the main stem of the Chesapeake Bay and was also present in water and sediments from the Rappahannock River, Virginia. M. pseudoshottsii was also detected in menhaden and anchovy tissues. In contrast, M. shottsii was not detected in water, sediment, or prey fish tissues. In conjunction with its nonpigmented phenotype, which is frequently found in obligately pathogenic mycobacteria of humans, this pattern of occurrence suggests that M. shottsii may be an obligate pathogen of striped bass.Mycobacteriosis is a common disease affecting a large variety of wild and aquacultured fishes worldwide (9). Chronic disease is most commonly observed and is characterized by granulomatous inflammation that may affect all host tissues. External clinical signs include scale loss, dermal ulceration, spinal defects, emaciation, and ascites (5,6,16,25,31).Mycobacteriosis in Chesapeake Bay striped bass (Morone saxatilis) was first observed in 1997 from histologic findings of acid-fast bacilli in granulomatous lesions (W. Vogelbein, unpublished data). Since the initial finding, surveys have demonstrated a very high prevalence of this disease in Chesapeake Bay striped bass, exceeding 50% in many samples (8,17). Concomitantly with detection of high prevalence, tag recapture analysis has indicated that natural, nonfishing mortality of Chesapeake Bay striped bass has increased since 1999 (13), and modeling of apparent prevalence data has indicated that some mortality is associated with disease (8). Because the striped bass is an ecologically and economically important finfish along the U.S. Atlantic coast, the high prevalence of this disease creates considerable concern about the continuing health of the resource.Mycobacteriosis of fishes has traditionally been considered to be caused by Mycobacterium marinum, M. fortuitum, or M. chelonae; however, the recognized diversity of Mycobacterium spp. infecting fishes has increased markedly in recent years (9).To date, neither M. fortuitum nor M. chelonae have been isolated from internal tissues of striped bass in the Chesapeake Bay, and M. marinum has been cultured from only a small fraction (3%) of fish (20). Instead, a variety of slow-growing mycobacteria have been isolated, dominated by the recently described species M. pseudoshottsii and M. shottsii (9,(20)(21)(22). The 16S rRNA gene sequenc...

Abstract-A hierarchical Bayesian approach was used to model the spatiotemporal habitat distribution of spiny dogfish (Squalus acanthias) of both sexes (adults) caught during trawl surveys conducted by the Northeast Area Monitoring and Assessment Program in inshore coastal waters between New England and North Carolina during [2007][2008][2009][2010][2011][2012][2013]. The best model for predicting catch per unit of effort (CPUE) for this species includes the following relevant variables: bathymetry, sea surface temperature, salinity, chlorophyll-a (chl-a) concentration, season and time of survey, and a random spatial effect for both sexes. Predicted CPUE was related to depth for both sexes; females occurred in shallower waters than those in which males occurred. Also, more females than males were predicted to occur in warmer, less saline and more productive (higher chl-a concentration) waters. Seasonality and time of predicted CPUE indicated that the abundance of females was higher in inshore coastal waters in the spring and in the morning, and the abundance of males was greater in the afternoon and in the fall in the same area. Collectively, these results provide information that enhances our understanding of differences in habitat selection and spatiotemporal distribution of the 2 sexes of this species-information that can help to modify present management strategies for the U.S. Atlantic fishery.The spiny dogfish (Squalus acanthias) is a small shark commonly found in oceanic and coastal temperate waters throughout the world, at depths less than 900 m (Compagno et al., 2005;Dell'Apa et al., 2015). The species is sexually dimorphic; adult females, on average, are larger than adult males (Nammack et al., 1985). Moreover, aggregations of adult individuals are segregated by sex and size (Ford, 1921;Shepherd et al., 2002;Dell'Apa et al., 2014)-a common occurrence with elasmobranchs (Springer, 1967; Sims, 2005). Sexual segregation can be the effect of social segregation, in which the interaction between the sexes is limited by behavioral differences between the sexes, or it can be the effect of habitat segregation, in which the 2 sexes use habitats with different physical and environmental characteristics. Social segregation and habitat segregation can also occur simultaneously for the two sexes and can lead to differences in spatial distribution and habitat associations between the sexes (Wearmouth and Sims, 2008). Additionally, sexual dimorphism may influence feeding habits in live-bearing elasmobranchs (Sims, 2005), resulting in the 2 sexes having evolved specific physiological requirements that have led to differences in diet and prey preferences (Ruckstuhl and Clutton-Brock, 2005). Consequently, the 2 sexes may occupy different habitats characterized by different prey compositions and thus reduce intraspecific competition (Sims, 2005).For commercially important species, such as the spiny dogfish (Lack, 2006;Dell'Apa et al., 2013), predicting abundance and identifying habitat associations in response to enviro...