Dispersal of Homarus americanus Larvae in the Gulf of Maine from Browns Bank

1988 ◽  
Vol 45 (3) ◽  
pp. 416-425 ◽  
Author(s):  
Gareth C. Harding ◽  
Ronald W. Trites
Keyword(s):  
Nova Scotia ◽  
Gulf Of Maine ◽  
Stage Iv ◽  
Homarus Americanus ◽  
Seasonal Migration ◽  
Ecological Traits ◽  
Growth And Survival ◽  
Larval Recruitment ◽  
Surface Drifter ◽  
Planktotrophic Larvae

Studies of larval lobster (Homarus americanus) distribution off southwestern Nova Scotia during the summers of 1977 and 1978, were used to estimate an average larval recruitment or production of 1918 and 5284 stage IV lobsters per square kilometre per year inshore and offshore, respectively. Results indicate that the offshore may contribute up to 97% of the larval recruits for the entire southwestern Nova Scotia region. Current patterns and velocities of 3–16 cm∙s−1 were estimated from surface drifter returns within the Gulf of Maine. Limits of larval dispersion are estimated from surface currents in the region and the physiological and ecological traits of the larval lobster. Offshore lobsters could make an important contribution to recruitment not only off southwestern Nova Scotia but in the entire eastern sector of the Gulf of Maine to Casco Bay. Larval dispersal provides another line of evidence that the Gulf of Maine area represents one lobster recruitment center. Our results are consistent with the idea that ontogenic seasonal migration of female lobsters has evolved to locate planktotrophic larvae in warmer shoal areas where growth and survival is optimal and from which ocean currents subsequently disperse a large portion of these larvae to settle over highly productive juvenile grounds.

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

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.

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.

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.

Neustonic postlarval American lobsters, Homarus americanus, in the western Gulf of Maine: spatial and interannual variations

2000 ◽  
Vol 57 (4) ◽  
pp. 755-765 ◽  
Author(s):  
Lewis S Incze ◽  
Peter Aas ◽  
Terri Ainaire ◽  
Marcia Bowen
Keyword(s):  
New Hampshire ◽  
Gulf Of Maine ◽  
Stage Iv ◽  
Homarus Americanus ◽  
Seasonal Abundance ◽  
Interannual Variations ◽  
Distributed Source ◽  
High Recruitment ◽  
Benthic Population

We examined the seasonal abundance of postlarval (PL) (stage IV) American lobsters, Homarus americanus, from neuston samples from 1989 to 1995 at Johns Bay, Maine, and Seabrook, New Hampshire, located 150 km apart in the western Gulf of Maine. The postlarval season at these sites began between approximately days of the year 180 and 210 and ranged from about 35 to 70 days in duration. Within years, start and end dates were similar for the two sites. Maximum concentrations from single tows exceeded 100 PL·1000 m-2, but 85% or more of the positive tows had concentrations <15 PL·1000 m-2 and more than half had <5 PL·1000 m-2. These concentrations occurred at high levels of the stock, were the source for continued high recruitment in the 1990s, and thereby form a benchmark for future measurements. Only one of the seven years showed a major decline in seasonal abundance, and it occurred at both sites. Of the remaining years, three had nearly identical integrated abundances at both sites (approximately 200 PL· 1000 m-2·year-1). A survey in the western Gulf of Maine caught postlarvae out to 56 km offshore at concentrations similar to the coastal samples, indicating a broadly distributed source of potential recruits to the benthic population.

Predicting bycatch hotspots based on suitable habitat derived from fishery-independent data

2020 ◽  
Vol 641 ◽  
pp. 159-175
Author(s):  
J Runnebaum ◽  
KR Tanaka ◽  
L Guan ◽  
J Cao ◽  
L O’Brien ◽  
...  
Keyword(s):  
Habitat Suitability ◽  
Mixed Model ◽  
Linear Mixed Model ◽  
Gulf Of Maine ◽  
Homarus Americanus ◽  
Management Tool ◽  
American Lobster ◽  
Suitable Habitat ◽  
Climate Conditions ◽  
Suitability Index

Bycatch remains a global problem in managing sustainable fisheries. A critical aspect of management is understanding the timing and spatial extent of bycatch. Fisheries management often relies on observed bycatch data, which are not always available due to a lack of reporting or observer coverage. Alternatively, analyzing the overlap in suitable habitat for the target and non-target species can provide a spatial management tool to understand where bycatch interactions are likely to occur. Potential bycatch hotspots based on suitable habitat were predicted for cusk Brosme brosme incidentally caught in the Gulf of Maine American lobster Homarus americanus fishery. Data from multiple fisheries-independent surveys were combined in a delta-generalized linear mixed model to generate spatially explicit density estimates for use in an independent habitat suitability index. The habitat suitability indices for American lobster and cusk were then compared to predict potential bycatch hotspot locations. Suitable habitat for American lobster has increased between 1980 and 2013 while suitable habitat for cusk decreased throughout most of the Gulf of Maine, except for Georges Basin and the Great South Channel. The proportion of overlap in suitable habitat varied interannually but decreased slightly in the spring and remained relatively stable in the fall over the time series. As Gulf of Maine temperatures continue to increase, the interactions between American lobster and cusk are predicted to decline as cusk habitat continues to constrict. This framework can contribute to fisheries managers’ understanding of changes in habitat overlap as climate conditions continue to change and alter where bycatch interactions could occur.

Effect of Temperature on the Behavior of Stage IV American Lobster (Homarus americanus) Larvae

2015 ◽  
Vol 34 (2) ◽  
pp. 545-554 ◽  
Author(s):  
Melanie Chiasson ◽  
Gilles Miron ◽  
Dounia Daoud ◽  
Martin D. Mallet
Keyword(s):  
Stage Iv ◽  
Homarus Americanus ◽  
Effect Of Temperature ◽  
American Lobster

Spatial and Temporal Overlap of the American Lobster (Homarus americanus) and Sea Scallop (Placopecten magellanicus) as Related to the impact of Inshore Scallop Dragging

1992 ◽  
Vol 49 (7) ◽  
pp. 1486-1492 ◽  
Author(s):  
D. L. Roddick ◽  
R. J. Miller
Keyword(s):  
Nova Scotia ◽  
Homarus Americanus ◽  
Fishing Effort ◽  
The Other ◽  
American Lobster ◽  
Placopecten Magellanicus ◽  
Time And Space ◽  
Sea Scallop ◽  
The Impact ◽  
Temporal Overlap

Assessment of the damage of one fishery by another requires knowledge of the overlap, in time and space, of the damaging fishing effort and the abundance of the damaged species, as well as a measure of the rate of damage. This approach was used to measure the impact of inshore scallop dragging on lobsters in Nova Scotia. Areas of reported co-occurrence of lobster and scallop grounds were surveyed by divers to determine the extent of overlap. Only 2 of 52 sites surveyed had lobsters on scallop grounds that could be dragged. Divers surveyed one site six times during 1987 and 1988 and found lobsters most abundant during August and September. Only 2% of the lobsters in the path of scallop drags were either captured or injured. The estimated value of lobsters destroyed by dragging for scallops during periods of peak lobster abundance was minor: $757 at one site and $176 at the other. Restricting dragging to periods of low lobster abundance significantly reduces this cost.

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