Virginia Marine Resources Commission

Newport News, VA, United States

Virginia Marine Resources Commission

Newport News, VA, United States
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The Virginia Marine Resources Commission this week released the results of the 2017 Blue Crab Winter Dredge Survey, which shows a 31 percent increase in adult female crabs and forecasts another year of improved harvests. This is the highest level of adult, spawning-age females recorded in the survey's 28-year history.

Schaffler J.J.,Old Dominion University | Schaffler J.J.,Virginia Marine Resources Commission | Miller T.J.,University of Maryland Center for Environmental Science | Jones C.M.,Old Dominion University
Transactions of the American Fisheries Society | Year: 2014

The Atlantic Menhaden Brevoortia tyrannus is an important component of the estuarine and nearshore fish assemblages in the mid-Atlantic region. It serves as a forage species for many piscivorous fish, birds, and marine mammals as well as being subject to an important commercial fishery. Currently there is concern over low standing stocks and recruitment, yet few studies have addressed those concerns. We evaluated the effectiveness of using an otolith chemistry approach to identify juvenile menhaden nursery areas throughout the Chesapeake Bay over 2 years. If successful, an otolith chemistry approach is capable of addressing a number of hypotheses regarding the source and fate of recruits in a stock. We found multiple unique otolith chemistry signatures in menhaden collected in the Chesapeake Bay. Overall correct classification was 85% for the 2005 cohort and 95% for the 2006 cohort. The ratios of most trace element: Ca and stable isotope ratios were different among areas. In addition to spatial differences, both seasonal and annual temporal variation was present in the otolith chemistry. However, a discriminant function that included temporal variation resulted in reduced prediction accuracy (overall errors increased 7-10%). We found that our classification function, which was developed for multiple cohorts, can successfully predict group membership. We recommend additional evaluation of this strategy because of its potential application to data-poor stocks. Our data show that juvenile menhaden in the Chesapeake Bay can be reliably discriminated based on otolith chemistry signatures and that this approach can be used to critically evaluate the nursery contributions of the bay to the coastal adult stock of menhaden.Received July 11, 2013; accepted January 21, 2014. © 2014 © American Fisheries Society 2014.

Ashford J.,Old Dominion University | Jones C.,Old Dominion University | Fegley L.,Annapolis flyer cab | O'reilly R.,Virginia Marine Resources Commission
Transactions of the American Fisheries Society | Year: 2010

Marine recreational surveys often intercept fishers at public access sites to address identification error and recall bias in data reported by telephone, then calculate catch as the product of the effort reported by telephone and the catch rate recorded at public access sites. However, fishers using private access are left out of the public access frame. In a survey of the recreational catch of blue crabs Callinectes sapidus in Maryland and Virginia, we compared catch calculated using catch rates from public access surveys with catch estimated from catch data reported by telephone to see whether there was evidence of public access bias. We found no identification error by blue crab fishers. However, fishers interviewed by telephone reported that 61-83% of trips were made from private access sites, and relative to catch data reported by telephone the estimates of catch calculated using catch rates were at least 25-63% larger. Catch data reported by telephone followed a delta distribution and avoided (1) the cost of complementary public access surveys, (2) incompatibilities between the public access and telephone frames, and (3) inefficient estimators of variance. We suggest estimating catch using catch data reported by telephone and tested independently for identification and recall bias via a public access survey. © by the American Fisheries Society 2010.

Hoover R.R.,Center for Quantitative Fisheries Ecology | Hoover R.R.,Virginia Marine Resources Commission | Jones C.M.,Center for Quantitative Fisheries Ecology
Marine Ecology Progress Series | Year: 2013

Life history scans of fish otoliths are bringing new insight into the structure, connectivity, and movement of fish populations. Data obtained from such scans, however, possess in-herent limitations that have not yet been fully addressed or understood. For example, several investigators have noted delays in otolith elemental uptake that do not appear to reflect habitat exposure. We hypothesized that the 3-dimensional structure of otoliths may produce sampling artifacts in the results obtained from laser ablation scans. To test this hypothesis, we sampled sagittal otoliths from juvenile Atlantic croaker Micropogonias undulatus with laser ablation inductively coupled plasma mass spectrometry to obtain elemental molar ratios of a common environmental marker (barium). We ablated 2 trenches of different depths on each otolith and performed spectral analyses on the data to investigate the effects of ablation depth, including differences in the periodicities and temporal variability between trenches. The mean barium concentration between the 2 trenches was significantly different (t = 114.25, p < 0.0001). From shallow to deep trenches, variance decreased; the standard error about the means was reduced from 0.609 to 0.086. Peaks in spectral density, which estimate the ingress timing for this species, were shifted in absolute value an average of 32 d. Our results highlight the necessity of considering depth of laser ablation when conducting life history scans. © Inter-Research 2013.

Hyun S.-Y.,University of Massachusetts Dartmouth | Cadrin S.X.,University of Massachusetts Dartmouth | Roman S.,Virginia Marine Resources Commission
Fisheries Research | Year: 2014

Fishermen reported that Georges Bank yellowtail flounder (Limanda ferruginea) migrated to deeper waters during 2000-2004 and 2006-2010. To test this hypothesis, we analyzed fishery data from otter trawl vessels targeting a mixed groundfish complex over the 10 year period, using a statistical linear model with catch-per-unit-effort weighted depth as the response variable, and abiotic (e.g., bottom water temperature) and biotic (e.g., skate and dogfish catch) data as predictor variables. We considered mixed as well as fixed effect models to account for dependence or correlation in catches among hauls within a trip. Yellowtail flounder shifted to deeper waters during the 10 years. Bottom water temperature had a greater influence on the movement than the distribution of skate or dogfish. Optimal water temperature was about 6.8 °C from the fixed effect model and about 7.1 °C from the mixed effect model. Skate distribution affected yellowtail flounder depth more than dogfish distribution. The mixed effect model was more parsimonious than the fixed effect model, although the latter fitted the data better and performed better under cross validation. © 2014 Elsevier B.V.

Westhoff J.T.,Tennessee Technological University | Westhoff J.T.,University of Missouri | Watts A.V.,Tennessee Technological University | Watts A.V.,Virginia Marine Resources Commission | Mattingly H.T.,Tennessee Technological University
Aquatic Conservation: Marine and Freshwater Ecosystems | Year: 2013

Artificial refugia have been implemented in freshwater and marine systems to increase structural complexity and achieve a variety of fisheries management goals. The use of artificial refuge to promote coexistence between an invasive species and a native species has not been widely studied but may serve as a viable management option. Range expansion of the invasive western mosquitofish, Gambusia affinis, across the Barrens Plateau of Tennessee has contributed to local extirpations of the native Barrens topminnow, Fundulus julisia, from parts of its historic range. Recent laboratory and field observations suggest that young topminnows may be vulnerable to injury from, or predation by, mosquitofish in the wild. In this study, an artificial refuge was tested in the laboratory and in situ to determine if it could increase survival, growth, or recruitment of juvenile topminnows exposed to mosquitofish. Adult topminnows and small mosquitofish caused negligible mortality to juvenile topminnows regardless of refuge presence in the laboratory trial. However, topminnow 20-day survival in the presence of large mosquitofish was 13% when refuge was present and 7% when refuge was absent. Juvenile topminnow growth did not differ among treatments indicating that the addition of refuge or the type of potential antagonist did not significantly affect topminnow growth. Field trial results showed no statistical differences in the number of juvenile topminnows captured at sites with refuges and those without, except during July sampling. In both trials, juvenile topminnows were observed to use the refuges, but no evidence exists that would indicate refuges are a feasible management tool for promoting the coexistence of topminnows with mosquitofish. © 2012 John Wiley & Sons, Ltd.

Jiao Y.,Virginia Polytechnic Institute and State University | O'Reilly R.,Virginia Marine Resources Commission | Smith E.,Virginia Polytechnic Institute and State University | Orth D.,Virginia Polytechnic Institute and State University
ICES Journal of Marine Science | Year: 2016

In many marine fisheries assessments, population abundance indices from surveys collected by different states and agencies do not always agree with each other. This phenomenon is often due to the spatial synchrony/asynchrony. Those indices that are asynchronous may result in discrepancies in the assessment of temporal trends. In addition, commonly employed stock assessment models, such as the statistical catch-at-age (SCA) models, do not account for spatial synchrony/asynchrony associated with spatial autocorrelation, dispersal, and environmental noise. This limits the value of statistical inference on key parameters associated with population dynamics and management reference points. To address this problem, a set of geospatial analyses of relative abundance indices is proposed to model the indices from different surveys using spatial hierarchical Bayesian models. This approach allows better integration of different surveys with spatial synchrony and asynchrony. We used Atlantic weakfish (Cynoscion regalis) as an example for which there are state-wide surveys and expansive coastal surveys. We further compared the performance of the proposed spatially structured hierarchical Bayesian SCA models with a commonly used Bayesian SCA model that assumes relative abundance indices are spatially independent. Three spatial models developed to mimic different potential spatial patterns were compared. The random effect spatially structured hierarchical Bayesian model was found to be better than the commonly used SCA model and the other two spatial models. A simulation study was conducted to evaluate the uncertainty resulting from model selection and the robustness of the recommended model. The spatially structured hierarchical Bayesian model was shown to be able to integrate different survey indices with/without spatial synchrony. It is suggested as a useful tool when there are surveys with different spatial characteristics that need to be combined in a fisheries stock assessment. © 2016 International Council for the Exploration of the Sea 2016. All rights reserved.

Harding J.M.,Virginia Institute of Marine Science | Mann R.,Virginia Institute of Marine Science | Southworth M.J.,Virginia Institute of Marine Science | Wesson J.A.,Virginia Marine Resources Commission
Journal of Shellfish Research | Year: 2010

The Piankatank River is a trap-type estuary on the western shore of Chesapeake Bay that has been managed for seed oyster production since 1963. Market oyster production in the river is minimal. Repletion efforts include shell planting and seed removal. We describe sequential changes in population demographics and habitat in relation to repletion activities on eight Piankatank River public oyster reefs from 1998 through 2009. Two reef groups (northern and southern) may be distinguished by density (oysters/m 2), biomass (g dry tissue weight), and shell volume (L/m 2) data. Age-at-length relationships were estimated from demographic data using a quadratic model. Observed mortality rates were high, and age 3+ oysters were essentially absent. A strong recruitment signal was observed in 1999 and 2002. Between 1998 and 2009, about 30% of the live oysters in the river were harvested as seed, corresponding to ∼7.5% of the total shell base in an average year. Typically, for every 5 bushels of shell planted, 1 bushel of seed was harvested (20% return). Even with shell planting (∼10 L/m 2/y), the river shell budget showed a deficit with respect to the accretion rate required to balance sea level rise and natural degradation processes. During the study period, the mean river recruit-to-stock ratio was ∼4. The unusual and consistently high recruit-to-stock ratios suggest that management for modest continuous seed removal may be accomplished without shell planting. Annual stock assessment to identify low recruitment years is recommended as a method to adjust annual seed harvest quotas.

Southworth M.,Virginia Institute of Marine Science | Harding J.M.,Virginia Institute of Marine Science | Wesson J.A.,Virginia Marine Resources Commission | Mann R.,Virginia Institute of Marine Science
Journal of Shellfish Research | Year: 2010

We describe oyster population trends in the Great Wicomico River, VA, from 2009 through 2009 using quantitative fishery independent survey data collected using a stratified random design. The seven public reefs examined cover a total of 2.8 × 105 m2 and vary in individual size from 1.36 × 104 to 7.16 × 104 nr. The river is functionally divided by a sand spit into upriver and downriver regions. Oyster densities on the upriver reefs were typically an order of magnitude higher than densities on the downriver reefs within the same time period. Throughout the system, the highest observed densities were coincident with high annual recruitment events (2002, 2006). Recruitment events were usually followed by high mortality, with small percentages of the population reaching ≥3 y of age. A predictive stockrecruit relationship is absent; rather, population demographics appear to be dominated by periodic high recruitment events. In the absence of seed removal, biomass maxima follow 12 y after recruitment maxima. Standing stock for the system varied between 1.56 × 106 g and 3.63 × 107 g in 2005 and 2006. Year-specific age-at-length relationships were estimated from demographics data. Length demographics were recast as age demographics to estimate mortality. Observed proportional mortality between young of the year and age 2 oysters was approximately 0.88 for the 2006-y class, which is slightly higher than the 0.620.71 observed for the 2007-y class. The ability to estimate age specific mortality accurately allows the construction of shell (habitat) budgets for the individual reef systems. The Great Wicomico oyster population appears to be maintained by episodic and extraordinary recruitment in the face of high mortalitythe latter driven by disease (predominantly Perkinsus marinus) epizootics. The shell resource is modest, equivalent to little more than a monolayer several centimeters thick. Over short timescales (years), the available shell resource oscillates in concert with mortality. The shell accretion rate on upriver reefs is consistently 45 times greater than that observed on downriver reefs. Periodic modest shell planting has maintained the habitat base (the shell resource) throughout the system over decadal scales.

Jiao Y.,Virginia Polytechnic Institute and State University | Smith E.P.,Virginia Polytechnic Institute and State University | O'Reilly R.,Virginia Marine Resources Commission | Orth D.J.,Virginia Polytechnic Institute and State University
ICES Journal of Marine Science | Year: 2012

Non-stationarity in the natural mortality of many species has been discussed among research scientists, but no generally applicable models/methods have been developed where a statistical catch-at-age (SCA) model framework is used. Using the Atlantic weakfish (Cynoscion regalis) fishery as an example, several SCA models are developed to assess the population dynamics, then compared. Models used included (i) an SCA with constant natural mortality, (ii) an SCA with unknown natural mortality, but with a hierarchical prior distribution from a mixture of distributions based on life-history information, (iii) an SCA with age-specific unknown natural mortality, (iv) an SCA with time-varying natural mortality, following a random-walk process, and (v) an SCA with age-specific time-varying natural mortality. The last two models imply that the population dynamics are not stationary. A Bayesian approach was used to estimate parameters, and performance of the models was compared through goodness-of-fit and the retrospective patterns of the models. A simulation study was then conducted to test the uncertainty resulting from model selection, the efficiency of using the best model selected based on deviance information criterion, and whether changes in natural mortality could be detected. An SCA with time-varying natural mortality, following a random-walk process, is proposed for the example fishery here. The estimated non-stationary temporal patterns in natural mortality were linked further to climateocean oscillation indices, to diagnose possible mechanisms/linkages to these temporal variations in natural mortality. © 2011 International Council for the Exploration of the Sea. Published by Oxford University Press. All rights reserved.

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