The Wahle Lab

 

 
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Darling

Marine

Center

 

Wahle Lab                                                                                                            n

 

 

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Current Graduate Students

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Skylar Bayer

Degree: PhD

Institution:   University of Maine

Year completed:  in progress

Current Position: Student

Contact info:  Skylar.Bayer@maine.edu

  Population density and flow impacts on scallop reproductive ecology

I am researching the biology, reproduction and recruitment of P. magellanicus that will aid in managing this fishery and provide a broader understanding of the reproductive biology of free-spawning marine animals. My thesis work will be based on both field and lab experimentation and observation of the effects of population density and flow on scallop fertilization success.

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Morgan Brunbauer

Degree:  M.Sc. Marine Biology

Institution:   University of Maine

Year completed:  in progress

Current Position: Student

Contact info:  Morgan_Brunbauer@umit.maine.edu

  Experimental Fishery for Female Deep-sea red crabs

The deep-sea red crab Chaceon quinquedens is found in the continental slope waters off the northeastern coast of the United States; and has been exploited since the early 1970's.  Historically, only the largest of the males have been harvested in the fishery but recently an experimental fishing permit has been obtained to exploit females.  There is also great uncertainty about the sustainability of current and proposed fishing efforts because many aspects of the crab's biology and life history stages are poorly understood.  With funding provided by the New England Red Crab Harvester's Association a two year tagging study will be done to pave the way for future growth and movement models.  My possible Master's thesis topics include larval behavior and development under different temperature regimes, reproductive biology of female crabs, movement patterns of tagged crabs, and / or designing a habitat model based on depth, sex ratios, abundances, and average size.  All of these topics could provide critical information needed for improved management and sustainability of the fishery.

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Past Graduate Students

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Charlene Bergeron

Degree:   M.Sc. Marine Biology

Institution:  University of Maine

Year completed:  2011

Current Position: technician Wahle Lab

Contact info: Charlene.Bergeron@maine.edu

Developing Region-specific Growth Models for the American Lobster

Following the fate of cohorts in crustacean populations is complicated by the fact that with no morphological features such as growth rings to chronicle age there is no way to age them. Understanding the size-age relationship and its variability is therefore critical for population studies. This is especially true for the American lobster, the most valuable single species fishery in New England and Atlantic Canada. Growth data for wild lobster populations are derived from two sources – size frequency distributions of early juveniles and tagging of older juveniles and adults. We aim to integrate growth data from these two sources to develop growth models for lobsters in the three regions of contrasting oceanography, from the Bay of Fundy to the southern New England shelf. Data from long-term monitoring and tagging programs will be used to parameterize different growth models. Approaches used in modeling the data will include length-frequency analysis, the von Bertalanffy growth function, and probabilistic stepwise growth curves.

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Mahima Jaini

Degree:   M.Sc. Marine Biology

Institution:  University of Maine

Year completed:  2011

Current Position:  Teacher

Contact info:  Mahima_Jaini@umit.maine.edu

   Environmental forcing of American lobster settlement: the role of temperature, wind and egg production

My master’s research utilizes the ability of satellite data to provide time and space patterns of important oceanographic properties to quantify the link between the environment and American lobster settlement. Coherence in the settlement index time series for spatially different survey sites indicate large scale environmental forcing in lobster larval supply to inshore nursery grounds. I am testing the spatial correlation of lobster settlement with environmental variables (such as Sea Surface Temperature and Wind) found over the Gulf of Maine and neighboring shelf waters for the duration of the planktonic larval phase of lobsters. Settlement data used in the analysis will be from three of the longest lobster settlement index time series (18-20 years) from oceanographically contrasting segments of the coast; the mouth of the Bay of Fundy, the central Gulf of Maine and Rhode Island. Remotely sensed data on SST and wind will be from satellite derived sources provided by the Andrew Thomas Lab, University of Maine, Orono. Results will contribute to the application of environmental satellite data in a coupled biophysical model that is providing new insights for fishery scientists into lobster larval transport and population connectivity.

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Victoria Burdett-Coutts

Degree: M.Sc. Marine Biology

Institution:  Memorial University

Year completed:  2010

Current Position: 

Contact info: 

Larval Supply, Settlement, and Recruitment of America lobster, Homarus americanus

My thesis contains three studies on the American lobster, Homarus americanus. Two took place in Bonne Bay, Newfoundland and a third used a long-term young-of-year (YoY) recruitment index from New England, USA.  In the first study, planktonic larval and benthic suction sampling along the Bonne Bay estuary indicated larval concentrations were consistently highest at the mouth of the bay, with a more dramatic drop in density from early to late stages than reported elsewhere.  The second study evaluated the spatial scale of correlations between YoY recruitment and older juvenile densities at some 70 sampling sites in New England.  Strong correlations at even the finest scale (meters), along with behavioral experiments, suggest postlarvae preferentially settle among resident conspecifics.  The third study compared fishers’ local knowledge of lobster hatching and nursery locations in Bonne Bay against ground-truth data collected by fishery-dependent and -independent surveys.  Fishers accurately identified hatching but not nursery locations in the bay.

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Curt Brown

Degree: M.Sc. Marine Biology; M.A. Marine Policy

Institution:  University of Maine

Year completed:  2007

Current Position:  Technician, Gulf of Maine Research Institute / Lobsterman

Contact info:  Curtis_Brown@umit.maine.edu

Spatial Patterns of Predation on the American Lobster along New England’s Biogeographic Transition Zone

Our understanding of the spatial and temporal variability in the strength of predator-prey interactions and their demographic effects are poor for subtidal marine taxa largely because of the small scale and short term of most ecological experiments.  In this thesis I investigated how the interaction between the American lobster, Homarus americanus, and its predators varies over New England’s biogeographic transition zone, a region encompassing one of the steepest latitudinal gradients in sea surface temperature on earth. A comparison of tethering experiments conducted in 2000 to those done in 2004 and 2005 indicated a decline in predation rates on juvenile lobsters in Rhode Island and an increase in Maine. Video monitoring indicated that visitation and attack rates of fish had declined in Rhode Island, while attacks by crabs (Cancer irroratus and C. borealis) had become a significant agent of mortality in Maine. Surveys suggest a recent recruitment pulse of crabs has elevated mortality risk for juvenile lobsters in the Gulf of Maine. We also conducted lab experiments to compare fish and crabs with respect to their ability to subdue lobster prey, both on and off tether.  Laboratory results suggest that while fish predation is greater during daylight hours, crab predation is greater at night. Taken together these results may have important implications for fishery models and management plans that assume spatially invariant rates of natural mortality. This may be especially true for species spanning ecologically heterogeneous regions and biogeographic transition zones.

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Julien Gaudette

Degree:  M.Sc. Biology

Institution:  Universite Laval, Quebec

Year completed:  2005

Current Position:  Invertebrate Biologist, Department of Fisheries and Oceans, St.Andrews, NB, Canada

Contact info:  Julien.Gaudette@dfo-mpo.gc.ca

Reproductive Dynamics of Depleted Sea Urchin Populations

How populations respond to large scale depletion is poorly understood in marine systems. Free-spawners – organisms that broadcast their gametes into the water - may be particularly vulnerable to the extent spawning and fertilization depend on population density.  During the winter and spring of 2002 and 2003, we used time-integrated fertilization assays to monitor sperm availability in three populations of the green sea urchin Strongylocentrotus droebachiensis in Maine: a naturally occurring population of > 40,000 urchins and two smaller groups (< 1,000) of transplanted urchins isolated from other aggregations. Episodes of sperm release coincided in two populations 10 km apart, suggesting that urchins were responding to a widespread environmental signal. We observed significant lunar periodicity in sperm release events for both of these populations. However, extensive spawning as shown by fertilization rates near 100% and a dramatic drop in gonad mass only occurred in the large natural population around the onset of thermal stratification and the spring phytoplankton bloom. By contrast, in the two small populations we observed low fertilization rates and little or no change in gonad mass. We speculate that a subset of males in these populations responded to a common external spawning signal, but that mass spawning is more likely to occur in large, dense populations where sperm concentrations reach high enough levels to trigger spawning in less responsive urchins.

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