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Newport News, VA, United States

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.

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.

Jiorle R.P.,Virginia Marine Resources Commission | Jiorle R.P.,University of Florida | Trowbridge C.D.,University of Oregon | McAllen R.,University College Cork
Biology and Environment | Year: 2016

The fully marine Lough Hyne in south-west Ireland was designated a marine nature reserve in 1981 because of its high species and habitat diversity as well as intense fishing pressure. Considerable research has described the fish species in the Lough, their behaviour and distributions. Following the population demise of purple urchins in the Lough, the fish communities inhabiting the shallow sublittoral zone, particularly benthic and hyperbenthic fishes, which could be potential predators of sea urchins, were characterised. Three sites were chosen in different parts of Lough Hyne that historically supported dense urchin populations. In August to September 2014, fish density was estimated by snorkel surveying 50m band transects, noting water depth, habitat type and the number of fish by family for each 5m section. The two-way factorial survey design included time of day (morning, midday, late afternoon) and tide (high vs low) as factors with six surveys per transect. Numerically, gobies were the most abundant benthic to hyperbenthic fish in the shallow subtidal habitats; wrasses were the second most abundant. While all factors of site, tide, time and weather had significant effects on fish densities, site was most significant. This pattern indicated that gobies and wrasses were distributed more according to habitat type than small-scale depth and temporal variations, but further work should be done to elucidate nocturnal-diurnal effects and large-scale, seasonal effects. In the absence of direct evidence of predation effects before and after 1981, coupled with observational and/or gut content data, the role of fish predation as the major causal mechanism of urchin demise in the Lough was not supported. © ROYAL IRISH ACADEMY.

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.

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