Application of SWAN+ADCIRC to tide-surge and wave simulation in Gulf of Maine during Patriot's Day storm

The southern coast of the Gulf of Maine in the United States is prone to flooding caused by nor＇easters. A state-of-the-art fully-coupled model, the Simulating WAves Nearshore （SWAN） model with unstructured grids and the ADvanced CIRCulation （ADCIRC） model, was used to study the hydrodynamic response in the Gulf of Maine during the Patriot＇s Day storm of 2007, a notable example of nor＇easters in this area. The model predictions agree well with the observed tide-surges and waves during this storm event. Waves and circulation in the Gulf of Maine were analyzed. The Georges Bank plays an important role in dissipating wave energy through the bottom friction when waves propagate over the bank from offshore to the inner gulf due to its shallow bathymetry. Wave energy dissipation results in decreasing significant wave height （SWH） in the cross-bank direction and wave radiation stress gradient, which in turn induces changes in currents. While the tidal currents are dominant over the Georges Bank and in the Bay of Fundy, the residual currents generated by the meteorological forcing and waves are significant over the Georges Bank and in the coastal area and can reach 0.3 m/s and 0.2 m/s, respectively. In the vicinity of the coast, the longshore current generated by the surface wind stress and wave radiation stress acting parallel to the coastline is inversely proportional to the water depth and will eventually be limited by the bottom friction. The storm surge level reaches 0.8 m along the western periphery of the Gulf of Maine while the wave set-up due to radiation stress variation reaches 0.2 m. Therefore, it is significant to coastal flooding.

Can back-calculated lengths based on otoliths measurements provide reliable estimates of Atlantic halibut(Hippoglossus hippoglossus)growth in the Gulf of Maine (U.S.A.)?

Atlantic halibut(Hippoglossus hippoglossus,Linnaeus,1758)are a data-poor stock within the waters of the United States.This study evaluated the use of otolith measurements to back-calculate lengths of Atlantic halibut at previous ages.Back-calculations have proven useful for estimating length at age and growth rates of other species.To the best knowledge of the authors,this study is the first to document the use of this method for Atlantic halibut.Otolith back-calculations rely on a few key assumptions,such as proportionality of fish length and otolith length,which are not always met.This study shows that backcalculations using the Fraser-Lee method can provide reasonable estimates of Atlantic halibut length at previous ages,especially when samples from young halibut are included to improve estimates of the intercept of the linear regressions.Based on back-calculated estimates,female and male halibut in the Gulf of Maine showed different growth rates after age five.There was no evidence of changes in growth rates over an approximately 15 year time period.Halibut caught in the Gulf of Maine and on the neighboring Scotian Shelf showed some differences in growth rates;however,the results did not support strong conclusions about differences between the two regions as the direction of the differences was not consistent between the sexes and previous tagging studies have shown extensive movement between the two areas.The finding of reasonably accurate back-calculated lengths at previous ages is important for this data-poor species,as back-calculations increase the amount of information that can be obtained from otoliths.

Sensitivity study of coastal plumes

A three-dimensional numerical model of the coastal plume in an ideal basin for the western Gulf of Maine of USA, based on the observations, was configured to examine the dynamical properties under the spring riverine, tidal, and wind forcing. The purpose of this paper is to reveal possible effects of different factors on the coastal plume. The control run with a sloping bottom mimicking the western Gulf of Maine reproduced a southward advection speed of 14 km/d, consistent with the observed speed of 13.3 km/d. The plume evolutions due to the two typical wind forcing, upwelling favourable (wind from north) and downwelling favourable (wind from south). were simulated to explain the observations during the spring of 1993. A systematic sensitivity study was also conducted on the following themes: model parameters. dynamic processes, and topography effect.

Developing a longline/jig sentinel survey program for an area with limited monitoring and fishing efforts

Areas,such as coastal eastern Gulf of Maine(GOM),perceived to have low density of target fish species and having high density fixed gear,are often subject to low fishing pressure and not well monitored.This can lead to a shortage of information regarding the fine scale dynamics of groundfish populations.Sentinel surveys are commonly developed for such areas with little monitoring and commercial fishing activity as a cost effective way to collect relevant data for monitoring the dynamics of fish stocks.In this study,we outline an approach that utilizes information from other survey programs and pilot study for designing a survey that satisfies both the wish of fishermen participants to contribute their knowledge and experience in determining groundfish abundance and distribution and the statistical rigor required for stock assessments.Through an analysis of spatial and density distribution of groundfish populations based on data from pilot seasons of the sentinel survey and other monitoring programs,we designed a survey that has good spatial and temporal coverage and captures the spatial variability in species composition and size structure of key species.The spatially explicit data collected in the program can contribute to a better understanding of groundfish stock status in the eastern GOM.The approach,although developed for the coastal eastern GOM,is also applicable to other areas with similar issues.