Dispersal of American Lobsters, Homarus americanus, Tagged Off Southern Nova Scotia

1989 ◽  
Vol 46 (11) ◽  
pp. 1842-1844 ◽  
Author(s):  
Alan Campbell
Keyword(s):  
Nova Scotia ◽  
Continental Shelf ◽  
Continental Slope ◽  
Gulf Of Maine ◽  
Homarus Americanus ◽  
Georges Bank ◽  
Scotian Shelf ◽  
Long Distance ◽  
German Bank ◽  
Long Distance Movement

Of the 5281 American lobsters (Homarus americanus) tagged and released off McNutt Island, South Nova Scotia, during 1983–87, 15.8% were captured within 3 yr of release. Although most immature (99%) and mature (86%) lobsters were caught < 18.5 km from release, mature lobsters moved a greater mean distance (25.8 km) than immature lobsters (3.6 km). Of the lobsters that moved > 30 km eight moved south to the continental slope near Browns Bank and 11 moved west of Cape Sable to the inshore areas of southwestern Nova Scotia, the midshore area of German Bank and offshore to Browns Bank and Georges Bank. This and other studies of tagged lobsters indicate that there is some movement of lobsters east and west of the Cape Sable area, the southern tip of Nova Scotia, suggesting some mixing between lobster stocks off eastern Nova Scotia and southwestern Nova Scotia. The long distance movement and mixing of mature lobsters suggests that attempts to use tagging information in locating biological boundaries between lobster stocks in the Gulf of Maine, adjoining Continental Shelf, Scotian Shelf and inshore areas of southwestern Nova Scotia and southern end of eastern Nova Scotia may be a difficult task.

Movements of Tagged American Lobsters, Homarus americanus, off Southwestern Nova Scotia

1985 ◽  
Vol 42 (2) ◽  
pp. 229-238 ◽  
Author(s):  
Alan Campbell ◽  
Aivars B. Stasko
Keyword(s):  
Nova Scotia ◽  
Continental Shelf ◽  
Carapace Length ◽  
Gulf Of Maine ◽  
Homarus Americanus ◽  
Long Distance ◽  
Mature Adults ◽  
Straight Line ◽  
Straight Line Distance ◽  
Long Distance Movement

A total of 4304 American lobsters (Homarus americanus) were tagged and released in inshore areas off southwestern Nova Scotia and on northwest Browns Bank during June–August 1975. Of the 424 lobsters recaptured within 5.4 yr of release, 385 had known recapture locations. For all release areas the average straight-line distance traveled by mature ([Formula: see text]carapace length) lobsters (15.6 km) was significantly greater than for immature (59–94 mm carapace length) lobsters (4.7 km). Most (69.3%) of the immature lobsters (N = 212) were recaptured less than 18.5 km (10 naut mi) from the release sites; for mature lobsters (N = 173) this percentage was 40.5%. Previous tagging studies off southwestern Nova Scotia revealed little evidence of long-distance movement; our study, however, shows that mature lobsters can move long distances. Many (19.7%) of the mature lobsters were recaptured more than 92.6 km (50 naut mi) from the release sites. The overall direction of travel was south, in both an east and west direction, with many lobsters moving greater than 50 km from coastal Nova Scotia and Browns Bank into the Gulf of Maine and to the slopes of the continental shelf. Thirteen lobsters moved from Browns Bank to inshore areas of southwestern Nova Scotia. The evidence of the long-distance interchange of a portion of the mature adults between southwestern Nova Scotia and the adjoining continental shelf suggests that lobsters in these areas could belong to a single stock.

Genetic relationships among subpopulations of the American lobster (Homarus americanus) as revealed by random amplified polymorphic DNA

1997 ◽  
Vol 54 (8) ◽  
pp. 1762-1771 ◽  
Author(s):  
G C Harding ◽  
E L Kenchington ◽  
C J Bird ◽  
D S Pezzack ◽  
D C Landry
Keyword(s):  
Nova Scotia ◽  
Gulf Of Maine ◽  
Genetic Relationships ◽  
Random Amplified Polymorphic Dna ◽  
Preliminary Investigation ◽  
Homarus Americanus ◽  
Past Century ◽  
Georges Bank ◽  
The Past ◽  
Significant Difference

Random amplified polymorphic DNA (RAPD) profiles were used in a preliminary investigation of the genetic relationships among American lobsters (Homarus americanus) from the ecologically disparate and geographically separate regions of the southern Gulf of St. Lawrence, a bay off southwestern Nova Scotia, and a deep-sea canyon off Georges Bank. Phenotypic analyses of the RAPD bands showed no significant difference between samples caught at these three geographic locations. Lobsters from the Gulf of Maine, collected inshore from Lobster Bay, Nova Scotia, and offshore from Georges Bank, were genetically the most similar (D = 0.002), whereas Gulf of St. Lawrence lobsters were about three times as genetically distant from these two subpopulations (D = 0.005-0.006). However, FST values at each RAPD band ranged from <0.000 to 0.073, indicating that lobsters at these three locations are not genetically isolated. The number of migrants needed to account for this observed level of genetic differentiation could be as few as five animals in each generation. The present findings should not have been surprising given the enormous potential for larval dispersal, the wide ranging movements of adult lobsters within each region, and the level of anthropogenic interference through both displacement of larvae and adults over the past century in the name of conservation, particularly adults released into the Gulf of Maine.

Factors Influencing the Size of American Lobster (Homarus americanus) Stocks Along the Atlantic Coast of Nova Scotia, Gulf of St. Lawrence, and Gulf of Maine: A New Synthesis

1983 ◽  
Vol 40 (2) ◽  
pp. 168-184 ◽  
Author(s):  
Gareth C. Harding ◽  
Ken F. Drinkwater ◽  
W. Peter Vass
Keyword(s):  
Nova Scotia ◽  
Gulf Of Maine ◽  
Rapid Development ◽  
Atlantic Coast ◽  
Homarus Americanus ◽  
American Lobster ◽  
Georges Bank ◽  
Larval Recruitment ◽  
Larval Stages ◽  
Recruitment Failure

The general aspects of fluctuating American lobster (Homarus americanus) stocks are considered in an attempt to identify common principles controlling lobster populations in the Gulf of Maine, Gulf of St. Lawrence, and the Atlantic coast of Nova Scotia. Inshore fishing mortality is known to be precariously high in both Canadian and American waters yet only in the central Northumberland Strait region and along the Atlantic coast of Nova Scotia are stocks experiencing steep declines. Existing regulations allow fishing of lobsters well below the size at which maturity can be expressed. In western and central Northumberland Strait female lobsters are not protected by the 'berried' law because of the timing of the fishing season. Climatic change, expressed as sea-surface temperature, is closely associated with the success of lobster recruitment in the Gulf of Maine, but nowhere else. Huntsman's hypothesis that warm surface water of sufficient duration is essential for the successful completion of the larval stages of the lobster is found to have wide application. Warmer waters are also found to have a preponderance of plankton in the size categories required for feeding by the first two larval stages. Both the southern Gulf of St. Lawrence and the southwestern Gulf of Maine, including Georges Bank, are believed to be prolific nursery grounds for the early larval lobsters because warm water with plenty of food stimulates rapid development and settling. We calculated that larvae released on Georges Bank supply recruits to southern Nova Scotia, Bay of Fundy, and Maine, whereas some larvae from the southern Gulf of St. Lawrence are thought to settle as far as Cape Breton Co., N.S., and before the closure of the Strait of Canso, Guysborough Co., N.S. The past importance of lobster recruitment to the Atlantic coast of Nova Scotia through the Strait of Canso is estimated to have been as high as 60% of the average landings in Chedabucto Bay during the 11 best years of this fishery. The failure of the Atlantic coast lobster fishery off Nova Scotia is believed to have been initiated by a larval recruitment failure caused by the synchronous closure of the Strait of Canso and the start of a general climatic cooling. Possibly a critical temperature was reached along the Atlantic coast of Nova Scotia in the 1950s below which larval survival is much reduced by the shortened season. Reduced lobster abundance along the Atlantic coast of Nova Scotia may have contributed to the imbalance in the benthic ecosystem in which an uncontrolled urchin population consumed the kelp beds and until recently greatly reduced the primary production input to the system.Key words: American lobster, Homarus americanus; stocks, recruitment, ecology, larval transport

scholarly journals Seasonal trends and phenology shifts in sea surface temperature on the North American northeastern continental shelf

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Andrew C. Thomas ◽  
Andrew J. Pershing ◽  
Kevin D. Friedland ◽  
Janet A. Nye ◽  
Katherine E. Mills ◽  
...  
Keyword(s):  
Surface Temperature ◽  
Continental Shelf ◽  
Sea Surface Temperature ◽  
North American ◽  
Gulf Of Maine ◽  
Sea Surface ◽  
Scotian Shelf ◽  
Seasonal Differences ◽  
Study Region ◽  
The North

The northeastern North American continental shelf from Cape Hatteras to the Scotian Shelf is a region of globally extreme positive trends in sea surface temperature (SST). Here, a 33-year (1982–2014) time series of daily satellite SST data was used to quantify and map spatial patterns in SST trends and phenology over this shelf. Strongest trends are over the Scotian Shelf (&gt;0.6°C decade–1) and Gulf of Maine (&gt;0.4°C decade–1) with weaker trends over the inner Mid-Atlantic Bight (~0.3°C decade–1). Winter (January–April) trends are relatively weak, and even negative in some areas; early summer (May–June) trends are positive everywhere, and later summer (July–September) trends are strongest (~1.0°C decade–1). These seasonal differences shift the phenology of many metrics of the SST cycle. The yearday on which specific temperature thresholds (8° and 12°C) are reached in spring trends earlier, most strongly over the Scotian Shelf and Gulf of Maine (~ –0.5 days year–1). Three metrics defining the warmest summer period show significant trends towards earlier summer starts, later summer ends and longer summer duration over the entire study region. Trends in start and end dates are strongest (~1 day year–1) over the Gulf of Maine and Scotian Shelf. Trends in increased summer duration are &gt;2.0 days year–1 in parts of the Gulf of Maine. Regression analyses show that phenology trends have regionally varying links to the North Atlantic Oscillation, to local spring and summer atmospheric pressure and air temperature and to Gulf Stream position. For effective monitoring and management of dynamically heterogeneous shelf regions, the results highlight the need to quantify spatial and seasonal differences in SST trends as well as trends in SST phenology, each of which likely has implications for the ecological functioning of the shelf.

Advancing an Ecosystem Approach in the Gulf of Maine

2012 ◽  
Keyword(s):  
Large Scale ◽  
Gulf Of Maine ◽  
Critical Role ◽  
Monitoring Program ◽  
Ecosystem Dynamics ◽  
Georges Bank ◽  
Scotian Shelf ◽  
Monitoring Programs ◽  
Zooplankton Dynamics ◽  
Biological Environment

<i>Abstract</i>.—Zooplankton communities perform a critical role as secondary producers in marine ecosystems. They are vulnerable to climate-induced changes in the marine environment, including temperature, stratification, and circulation, but the effects of these changes are difficult to discern without sustained ocean monitoring. The physical, chemical, and biological environment of the Gulf of Maine, including Georges Bank, is strongly influenced by inflow from the Scotian Shelf and through the Northeast Channel, and thus observations both in the Gulf of Maine and in upstream regions are necessary to understand plankton variability and change in the Gulf of Maine. Large-scale, quasi synoptic plankton surveys have been performed in the Gulf of Maine since Bigelow’s work at the beginning of the 20th century. More recently, ongoing plankton monitoring efforts include Continuous Plankton Recorder sampling in the Gulf of Maine and on the Scotian Shelf, U.S. National Marine Fisheries Service’s MARMAP (Marine Resources Monitoring, Assessment, and Prediction) and EcoMon (Ecosystem Monitoring) programs sampling the northeast U.S. Continental Shelf, including the Gulf of Maine, and Fisheries and Oceans Canada’s Atlantic Zone Monitoring Program on the Scotian Shelf and in the eastern Gulf of Maine. Here, we review and compare past and ongoing zooplankton monitoring programs in the Gulf of Maine region, including Georges Bank and the western Scotian Shelf, to facilitate retrospective analysis and broadscale synthesis of zooplankton dynamics in the Gulf of Maine. Additional sustained sampling at greater-than-monthly frequency at selected sites in the Gulf of Maine would be necessary to detect changes in phenology (i.e. seasonal timing of biological events). Sustained zooplankton sampling in critical nearshore fish habitats and in key feeding areas for upper trophic level organisms, such as marine mammals and seabirds, would yield significant insights into their dynamics. The ecosystem dynamics of the Gulf of Maine are strongly influenced by large-scale forcing and variability in upstream inflow. Improved coordination of sampling and data analysis among monitoring programs, effective data management, and use of multiple modeling approaches will all enhance the mechanistic understanding of the structure and function of the Gulf of Maine pelagic ecosystem.

Evidence of Migration and Homing of Lobsters (Homarus americanus) on the Scotian Shelf

1986 ◽  
Vol 43 (11) ◽  
pp. 2206-2211 ◽  
Author(s):  
D. S. Pezzack ◽  
D. R. Duggan
Keyword(s):  
Return Migration ◽  
Release Site ◽  
Homarus Americanus ◽  
Winter Period ◽  
Scotian Shelf ◽  
Long Distance ◽  
Initial Release

In the Browns Bank region of the Scotian Shelf between June 1982 and December 1983, 6285 tagged lobsters (Homarus americanus) were released. Of the 2486 lobsters recaptured, 361 were recaptured more than once. Eight lobsters released in late May to mid-July were recaptured the following spring and summer, with at least one intervening recapture in the fall–winter period. Five of the eight lobsters showed homing tendencies. Two lobsters made long-distance (> 200 km) return migrations, three made short (50–100 km) return migrations, and three moved long distances but did not return. One lobster at large 6 mo and four at large 22–34 mo made long-distance return migrations, moving over 200 km and returning to within 9–42 km of the initial release site. The data indicate that some lobsters undertake long-distance return migration, which returns the lobsters to specific sections of the Shelf.

scholarly journals Interaction between the Tidal and Seasonal Variability of the Gulf of Maine and Scotian Shelf Region

2016 ◽  
Vol 46 (11) ◽  
pp. 3279-3298 ◽  
Author(s):  
Anna Katavouta ◽  
Keith R. Thompson ◽  
Youyu Lu ◽  
John W. Loder
Keyword(s):  
Gulf Of Maine ◽  
Circulation Model ◽  
Surface Current ◽  
Maximum Speed ◽  
Georges Bank ◽  
Scotian Shelf ◽  
Linear Superposition ◽  
Dynamical Interaction ◽  
The North ◽  
Shelf Region

AbstractAs part of a broader study of ocean downscaling, the seasonal and tidal variability of the Gulf of Maine and Scotian shelf, and their dynamical interaction, are investigated using a high-resolution (1/36°) circulation model. The model’s seasonal hydrography and circulation, and its tidal elevations and currents, are compared with an observed seasonal climatology, local observations, and results from previous studies. Numerical experiments with and without density stratification demonstrate the influence of stratification on the tides. The model is then used to interpret the physical mechanisms responsible for the largest seasonal variations in the M2 surface current that occur over, and to the north of, Georges Bank. The model generates a striation pattern of alternating highs and lows, aligned with Georges Bank, in the M2 surface summer maximum speed in the Gulf of Maine. The striations are consistent with observations by a high-frequency coastal radar system and can be explained in terms of a linear superposition of the barotropic tide and the first-mode baroclinic tide, generated on the north side of Georges Bank, as it propagates into the Gulf of Maine. The seasonal changes in tidal currents in the well-mixed area on Georges Bank are due to a combination of increased sea level gradients, and lower vertical viscosity, in summer.

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