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Grifoll M.,Polytechnic University of Catalonia | Grifoll M.,Center Internacional dInvestigacio Dels Recursos Costaners | Aretxabaleta A.L.,Integrated Statistics | Espino M.,Polytechnic University of Catalonia | Espino M.,Center Internacional dInvestigacio Dels Recursos Costaners
Journal of Geophysical Research C: Oceans | Year: 2015

Cross and along-shelf winds drive cross-shelf transport that promotes the exchange of tracers and nutrients to the open sea. The shelf response to cross-shelf winds is studied in the north shelf of the Ebro Delta (Mediterranean Sea), where those winds are prevalent and intense. Offshore winds in the region exhibit strong intensities (wind stress larger than 0.8 Pa) during winter and fall. The monthly average flow observed in a 1 year current meter record at 43.5 m was polarized following the isobaths with the along-shelf variability being larger than the cross-shelf. Prevalent southwestward along-shelf flow was induced by the three-dimensional regional response to cross-shelf winds and the coastal constraint. Seaward near-surface velocities occurred predominantly during offshore wind events. During intense wind periods, the surface cross-shelf water transport exceeded the net along-shelf transport. During typically stratified seasons, the intense cross-shelf winds resulted in a well-defined two-layer flow and were more effective at driving offshore transport than during unstratified conditions. While transfer coefficients between wind and currents were generally around 1%, higher cross-shelf transfer coefficients were observed in the near-inertial band. The regional extent of the resulting surface cold water during energetic cross-shelf winds events was concentrated around the region of the wind jet. Cross-shelf transport due to along-shelf winds was only effective during northeast wind events. During along-shelf wind conditions, the transport was estimated to be between 10 and 50% of the theoretical Ekman transport. © 2015. American Geophysical Union. All Rights Reserved.


Risch D.,Integrated Statistics | Clark C.W.,Cornell University | Dugan P.J.,Cornell University | Popescu M.,Cornell University | And 2 more authors.
Marine Ecology Progress Series | Year: 2013

Passive acoustic monitoring (PAM) is a rapidly growing field, providing valuable insights in marine ecology. The approach allows for long-term, species-specific monitoring over a range of spatial scales. For many baleen whales fundamental information on seasonal occurrence and distribution is still missing. In this study, pulse trains produced by the North Atlantic minke whale, a highly mobile and cryptic species, are used to examine its seasonality, diel vocalization patterns and spatial distribution throughout the Stellwagen Bank National Marine Sanctuary (SBNMS), USA. Three and a half years (2006, 2007 to 2010) of near continuous passive acoustic data were analyzed using automated detection methods. Random forests and cluster analyses grouped pulse trains into 3 main categories (slow-down, constant and speed-up), with several subtypes. Slow-down pulse trains were the most commonly recorded call category. Minke whale pulse train occurrence was highly seasonal across all years. Detections were made from August to November, with 88% occurring in September and October. No detections were recorded in January and February, and only few from March to June. Minke whale pulse trains showed a distinct diel pattern, with a nighttime peak from approximately 20:00 to 01:00 h Eastern Standard Time (EST). The highest numbers of pulse trains were detected to the east of Stellwagen Bank, suggesting that minke whales travel preferably in deeper waters along the outer edge of the sanctuary. These data show that minke whales consistently use Stellwagen Bank as part of their migration route to and from the feeding grounds. Unlike other baleen whales in this area they do not appear to have a persistent year-round acoustic presence. © Inter-Research 2013 · www.int-res.com.


Warden M.L.,Integrated Statistics | Haas H.L.,National Oceanic and Atmospheric Administration | Rose K.A.,Louisiana State University | Richards P.M.,National Oceanic and Atmospheric Administration
Ecological Modelling | Year: 2015

Incidental mortality from commercial fishing operations can alter the demography and distribution of affected species. Population assessments for long-lived, wide-ranging species such as sea turtles may need to include a spatial component and a consideration of the affected life stages. We used a spatial matrix population projection model to examine the impact of federally authorized incidental fishing mortality on a simulated Northwest Atlantic loggerhead sea turtle population. We projected the population for 100 years, simulating fisheries bycatch mortality through removals from the population that were directed toward specific spatial units or life stages. We kept removals constant across years for most simulations. We incorporated demographic information in the removals by using reproductive values to estimate adult-equivalent turtles, which we compared with removing individual turtles. Removals made in terms of adult equivalents had identical population impacts for all removal schemes (80% population decline after 40 years). Removals made in terms of individuals had the greatest impact if weighted toward the adult life stage (89% population decline after 40 years) and the least impact if weighted toward the youngest life stage (78% population decline after 40 years). Differences in impact between spatially directed removals were attributed to unequal stage distributions between regions. Because the population impact of loggerhead mortality depends on the affected life stage, the monitoring of population-level impacts is more reliable if authorized incidental take is specified and monitored by life stage or by adult equivalents. © 2014 Elsevier B.V.


Risch D.,Integrated Statistics | Siebert U.,University of Veterinary Medicine Hannover | Van Parijs S.M.,National Oceanic and Atmospheric Administration
Behaviour | Year: 2014

Information on individual calling behaviour and source levels are important for understanding acoustically mediated social interactions of marine mammals, for which visual observations are difficult to obtain. Our study, conducted in the Stellwagen Bank National Marine Sanctuary (SBNMS), located in the Gulf of Maine, USA, used passive acoustic arrays to track North Atlantic minke whales and assess the sound production behaviour of individuals. A total of 18 minke whales were acoustically tracked in this study. Individual calling rates were variable, with a median intercall interval (ICI) of 60.3 s. Average source levels (SLrms) for minke whales pulse trains ranged between 164 and 168 dB re 1 μPa, resulting in a minimum detection range of 0.4-10.2 km for these calls in this urban, coastal environment. All tracked animals were actively swimming at a speed of 5.0 ± 1.2 km/h, which matches swimming speeds of migrating minke whales from other areas and confirms SBNMS as part of the migration route of this species in the Western North Atlantic. Tracked minke whales produced 7 discrete call types belonging to 3 main categories, yet no individual produced all call types. Instead, minke whales produced 2 multisyllabic call sequences (A and B) by combining 3-4 different call types in a non-random order. While 7 of the tracked individuals produced calling pattern A, 10 whales used calling pattern B, and only 1 animal combined call types differently. Animals producing different call sequences were in acoustic range of one another on several occasions, suggesting they may use these sequences for mediating social interactions. The fact that the same calling patterns were shared by several individuals suggests that these patterns may contain information related to sex, age or behavioural context. © Copyright 2014 Denise Risch et al.


Smith T.D.,World Whaling History | Reeves R.R.,Okapi Wildlife Associates | Josephson E.A.,Integrated Statistics | Lund J.N.,New Bedford Whaling Museum
PLoS ONE | Year: 2012

American whalemen sailed out of ports on the east coast of the United States and in California from the 18th to early 20th centuries, searching for whales throughout the world's oceans. From an initial focus on sperm whales (Physeter macrocephalus) and right whales (Eubalaena spp.), the array of targeted whales expanded to include bowhead whales (Balaena mysticetus), humpback whales (Megaptera novaeangliae), and gray whales (Eschrichtius robustus). Extensive records of American whaling in the form of daily entries in whaling voyage logbooks contain a great deal of information about where and when the whalemen found whales. We plotted daily locations where the several species of whales were observed, both those caught and those sighted but not caught, on world maps to illustrate the spatial and temporal distribution of both American whaling activity and the whales. The patterns shown on the maps provide the basis for various inferences concerning the historical distribution of the target whales prior to and during this episode of global whaling. © 2012 Smith et al.


Risch D.,Integrated Statistics | Corkeron P.J.,Northeast Fisheries Science Center | Ellison W.T.,Marine Acoustics Inc. | van Parijs S.M.,Northeast Fisheries Science Center
PLoS ONE | Year: 2012

The effect of underwater anthropogenic sound on marine mammals is of increasing concern. Here we show that humpback whale (Megaptera novaeangliae) song in the Stellwagen Bank National Marine Sanctuary (SBNMS) was reduced, concurrent with transmissions of an Ocean Acoustic Waveguide Remote Sensing (OAWRS) experiment approximately 200 km away. We detected the OAWRS experiment in SBNMS during an 11 day period in autumn 2006. We compared the occurrence of song for 11 days before, during and after the experiment with song over the same 33 calendar days in two later years. Using a quasi-Poisson generalized linear model (GLM), we demonstrate a significant difference in the number of minutes with detected song between periods and years. The lack of humpback whale song during the OAWRS experiment was the most substantial signal in the data. Our findings demonstrate the greatest published distance over which anthropogenic sound has been shown to affect vocalizing baleen whales, and the first time that active acoustic fisheries technology has been shown to have this effect. The suitability of Ocean Acoustic Waveguide Remote Sensing technology for in-situ, long term monitoring of marine ecosystems should be considered, bearing in mind its possible effects on non-target species, in particular protected species.


Jech J.M.,National Oceanic and Atmospheric Administration | Stroman F.,Integrated Statistics
Aquatic Living Resources | Year: 2012

Atlantic herring (Clupea harengus) in the offshore regions of the Gulf of Maine migrate each fall from their feeding grounds to the northern portion of Georges Bank to spawn. The Northeast Fisheries Science Center's (NEFSC) herring acoustic survey has taken advantage of this behavior by conducting systematic surveys of the pre-spawning fish each year since 1999. Multi-frequency acoustic and midwater trawl data were collected along transects oriented perpendicular to bathymetric contours. Acoustic backscatter was analyzed to describe the aggregative patterns (e.g., size, location in the water column, and spatial and temporal distribution) of Atlantic herring during these surveys and regression trees were used to examine the aggregation characteristics. The positional variables of distance to spawning grounds and vertical location in the water column were the primary characteristics for describing pre-spawning aggregations. Secondary to these were the temporal variables of diel and survey timing, and the morphological characteristic of aggregation area. Lower numbers of aggregations were observed close to the herring spawning grounds but with higher acoustic energy than larger numbers of aggregations observed further from the spawning grounds but smaller in size and lower in acoustic energy. Most aggregations were in the lower portion of the water column, but those that were in the upper portion of the water column had higher acoustic energy. Consistently throughout the decade, 90% or more of herring aggregations were located within 40 nautical miles of their spawning grounds. The regression tree method provided valuable insight to the data series where it highlighted spatial and temporal patterns and was an effective way to quantitatively summarize relationships. © EDP Sciences, IFREMER, IRD 2012.


Press Y.K.,Integrated Statistics | Mcbride R.S.,National Oceanic and Atmospheric Administration | Wuenschel M.J.,National Oceanic and Atmospheric Administration
Journal of Fish Biology | Year: 2014

Winter flounder Pseudopleuronectes americanus were collected at monthly intervals from December 2009 to May 2011, to describe the pattern and seasonality of oocyte development, including: (1) the group-synchronous transition from primary to secondary oocytes that initiates immediately after spawning, (2) the slow (months) development of vitellogenic oocytes followed by the rapid (weeks) maturation of oocytes, (3) the synchronous nature of mature oocytes ovulating, but the discrete releases of benthic eggs in batches, (4) the protracted (months) degradation of postovulatory follicles and (5) the occurrence of follicular atresia. Although fish were collected across only c. 2° latitudinal range, the spawning season was c. 1 month later in the Gulf of Maine (GOM) than on Georges Bank and in southern New England. This is probably due to lower temperatures in the GOM. These stock-specific data regarding the time course of oogenesis are of practical value. This information is discussed in relation to measuring and interpreting elements of reproductive potential such as maturation, skipped spawning and fecundity, the response of reproductive traits by this widely distributed species to changing climate and the response by this common, marine-estuarine species to urbanization, particularly environmental pollutants and dredging. © Published 2014.


Interactions between sea turtles and northwestern Atlantic trawl fisheries are of global concern, and the National Marine Fisheries Service is considering expanding bycatch reduction regulations, including deployment of turtle excluder devices (TEDs). To inform bycatch mitigation strategies, the number of loggerhead sea turtle (Caretta caretta) interactions was estimated for US Mid-Atlantic bottom trawl fisheries for fish and scallops. A generalized additive model of interactions was developed using 1994-2008 Northeast Fisheries Observer Program data from trawl fisheries that were not required to deploy TEDs. Predicted loggerhead interaction rates were applied to 2005-2008 commercial fishing data to estimate the number of interactions for the trawl fleet. For trawl fisheries in which TEDs were required, an experimentally-determined TED exclusion rate (97%) was applied to estimate the number of loggerheads that were excluded by TEDs. Latitude, depth, and sea surface temperature (SST) were associated with the interaction rate. Average annual interactions for 2005-2008 were estimated at 292 (CV 0.13, 95% CI 221-369) loggerheads, with an additional 61 (CV 0.17, 95% CI 41-83) excluded by TEDs. The interaction rate was highest south of latitude 37°N in waters <50. m deep with SST >15. °C; interaction magnitude in terms of adult equivalents was highest at latitude 37-39°N, depth <50. m, and SST >15. °C. Predicted average annual loggerhead interactions decreased compared to 1996-2004, likely due to decreased commercial fishing effort in high-interaction areas. Additional sea turtle conservation measures can be informed by the high-interaction-rate and -magnitude areas identified through this analysis. © 2011 Elsevier Ltd.


Bisack K.D.,National Oceanic and Atmospheric Administration | Magnusson G.,Integrated Statistics
North American Journal of Fisheries Management | Year: 2014

Marine mammal stock assessments provide information that is valuable to public sector management and the private fishing sector; however, data are costly to collect. The precautionary approach, which is widely used in fishery and marine mammal management, advocates a conservative management decision with priority to the resource when there is uncertainty regarding the impact on the resource from human activity. The potential biological removal (PBR) control rule of the U.S. Marine Mammal Protection Act explicitly incorporates uncertainty in input variables into the determination of allowable levels of human-induced mortality for a stock. Less uncertainty results in higher PBR values for a given stock level. Variations in government funding levels can disrupt the scientific data collection that is necessary for PBR calculation. We present an economic net benefit framework that examines the indirect value of information from marine mammal stock assessments to the commercial fishing industry. Using the harbor porpoise Phocoena phocoena and the U.S. Atlantic sink gill-net fishery as a case study, we estimated the difference between total public sector data collection costs and total private sector benefits from increased profits. Net benefits represent a measure of the value of information to society, while the difference in profits measures the value of the information to the private sector. Several results are forthcoming. First, the optimal allocation of funding showed that abundance surveys are a more cost-effective means to reduce uncertainty in PBR input variables than increasing observer coverage of the fishing industry. Second, for all levels of PBR in this empirical example, total benefits to the private sector for a higher PBR exceeded the costs of collecting additional scientific data to increase the precision of input variables and thus increase PBR. Since net benefits are positive, the private sector may consider funding of scientific data collection for marine mammals as a way to reduce uncertainty, thereby allowing a higher PBR value.Received March 19, 2013; accepted November 14, 2013. © 2014 © American Fisheries Society 2014.

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