Large-scale Analysis of Atlantic Nova Scotia American Lobster (Homarus americanus) Landings with Respect to Habitat, Temperature, and Wind Conditions

1994 ◽  
Vol 51 (6) ◽  
pp. 1308-1321 ◽  
Author(s):  
Christiane Hudon
Keyword(s):  
Nova Scotia ◽  
Large Scale ◽  
Coastal Upwelling ◽  
Thermal Characteristics ◽  
Homarus Americanus ◽  
American Lobster ◽  
Cumulative Number ◽  
Northern Cape ◽  
Definition Of ◽  
Homogeneous Regions

American lobster (Homarus americanus) landings per unit of habitat, calculated for 25 statistical districts (SD) of Atlantic Nova Scotia (N.S.), were consistently higher in northern Cape Breton (SD 1–7) and southwestern N.S. (SD 32–34) than from the eastern (SD 15–18) and southern (SD 22–31) shores. Analyses suggest that changes in lobster populations of Atlantic N.S. take place over distances in the order of 100 km and over periods of about 5 yr and that lobster abundance is not limited by habitat availability. Five large homogeneous regions subject to similar historical landing trends could be identified on the basis of their thermal characteristics. Regions of lowest lobster landings (SD 8–31) are oriented in the axis of dominant southwest winds, which generate coastal upwelling, resulting in the lowest cumulative number of degree-days and a high year-to-year variability. Conversely, the high landings recorded in southwestern N.S. can be related to warm and stable temperature conditions, allowing lobsters to enhance yearly thermal gains via winter migrations into deep (> 100 m), warm Slope water. The definition of homogeneous regions characterized by common historical landing trends and thermal regime suggests that lobster abundance in Atlantic N.S. is ultimately controlled by large-scale oceanographic processes.

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.

Relationship Between Destructive Grazing by the Sea Urchin, Strongylocentrotus droebachiensis, and the Abundance of American Lobster, Homarus americanus, on the Atlantic Coast of Nova Scotia

1981 ◽  
Vol 38 (11) ◽  
pp. 1339-1349 ◽  
Author(s):  
W. G. Wharton ◽  
K. H. Mann
Keyword(s):  
Population Structure ◽  
Nova Scotia ◽  
Sea Urchins ◽  
Atlantic Coast ◽  
Homarus Americanus ◽  
Strongylocentrotus Droebachiensis ◽  
American Lobster ◽  
History Of ◽  
Kelp Bed ◽  
The Relationship

Relationships between percentage cover of macroalgae, population structure of sea urchins (Strongylocentrotus droebachiensis), and the history of the lobster fishery were examined at nine sites distributed along the Atlantic coast of Nova Scotia from Guysborough County in the northeast to Pubnico in the southwest. At Pubnico there was dense algal cover and a small number of urchins living in crevices, and at Cape Sable there was an area of transition, but at all other sites there were urchin-dominated barren grounds. When the population structure of the urchins was compared with that previously observed in St. Margaret's Bay before, during, and after destruction of beds of kelp (Laminaria spp. and Agarum) by overgrazing, it was concluded that kelp bed destruction occurred on the coast north of Halifax prior to 1970, and on the coast south of Halifax after 1970. From the records of American lobster (Homarus americanus) catches it was concluded that a critical decline in catches at each site occurred a few years after kelp bed destruction. Information from various sources is synthesized into a coherent theory of the relationship between lobsters, other predators, sea urchins, and kelp.Key words: lobsters, Homarus americanus; sea urchins, Strongylocentrotus droebachiensis; destructive grazing, kelp, Laminaria, Agarum

scholarly journals Examining Scale Dependent Environmental Effects on American Lobster (Homarus americanus) Spatial Distribution in a Changing Gulf of Maine

2021 ◽  
Vol 8 ◽  
Author(s):  
Jamie Behan ◽  
Bai Li ◽  
Yong Chen
Keyword(s):  
Spatial Distribution ◽  
Species Distribution ◽  
Environmental Variables ◽  
Large Scale ◽  
Gulf Of Maine ◽  
Homarus Americanus ◽  
American Lobster ◽  
Sediment Grain Size ◽  
Scale Models ◽  
Spatial Nonstationarity

The Gulf of Maine (GOM) is a highly complex environment and previous studies have suggested the need to account for spatial nonstationarity in species distribution models (SDMs) for the American lobster (Homarus americanus). To explore impacts of spatial nonstationarity on species distribution, we compared models with the following three assumptions : (1) large-scale and stationary relationships between species distributions and environmental variables; (2) meso-scale models where estimated relationships differ between eastern and western GOM, and (3) finer-scale models where estimated relationships vary across eastern, central, and western regions of the GOM. The spatial scales used in these models were largely determined by the GOM coastal currents. Lobster data were sourced from the Maine-New Hampshire Inshore Bottom Trawl Survey from years 2000–2019. We considered spatial and environmental variables including latitude and longitude, bottom temperature, bottom salinity, distance from shore, and sediment grain size in the study. We forecasted distributions for the period 2028–2055 using each of these models under the Representative Concentration Pathway (RCP) 8.5 “business as usual” climate warming scenario. We found that the model with the third assumption (i.e., finest scale) performed best. This suggests that accounting for spatial nonstationarity in the GOM leads to improved distribution estimates. Large-scale models revealed a tendency to estimate global relationships that better represented a specific location within the study area, rather than estimating relationships appropriate across all spatial areas. Forecasted distributions revealed that the largest scale models tended to comparatively overestimate most season × sex × size group lobster abundances in western GOM, underestimate in the western portion of central GOM, and overestimate in the eastern portion of central GOM, with slightly less consistent and patchy trends amongst groups in eastern GOM. The differences between model estimates were greatest between the largest and finest scale models, suggesting that fine-scale models may be useful for capturing effects of unique dependencies that may operate at localized scales. We demonstrate how estimates of season-, sex-, and size- specific American lobster spatial distribution would vary based on the spatial scale assumption of nonstationarity in the GOM. This information may help develop appropriate local adaptation measures in a region that is susceptible to climate change.

scholarly journals Modelling ocean acidification effects with life stage-specific responses alters spatiotemporal patterns of catch and revenues of American lobster, Homarus americanus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Travis C. Tai ◽  
Piero Calosi ◽  
Helen J. Gurney-Smith ◽  
William W. L. Cheung
Keyword(s):  
Climate Change ◽  
Ocean Acidification ◽  
Large Scale ◽  
Life Stage ◽  
Homarus Americanus ◽  
Minimum Size ◽  
Future Climate Change ◽  
American Lobster ◽  
Fishing Pressure ◽  
Size Limits

AbstractOcean acidification (OA) affects marine organisms through various physiological and biological processes, yet our understanding of how these translate to large-scale population effects remains limited. Here, we integrated laboratory-based experimental results on the life history and physiological responses to OA of the American lobster, Homarus americanus, into a dynamic bioclimatic envelope model to project future climate change effects on species distribution, abundance, and fisheries catch potential. Ocean acidification effects on juvenile stages had the largest stage-specific impacts on the population, while cumulative effects across life stages significantly exerted the greatest impacts, albeit quite minimal. Reducing fishing pressure leads to overall increases in population abundance while setting minimum size limits also results in more higher-priced market-sized lobsters (> 1 lb), and could help mitigate the negative impacts of OA and concurrent stressors (warming, deoxygenation). However, the magnitude of increased effects of climate change overweighs any moderate population gains made by changes in fishing pressure and size limits, reinforcing that reducing greenhouse gas emissions is most pressing and that climate-adaptive fisheries management is necessary as a secondary role to ensure population resiliency. We suggest possible strategies to mitigate impacts by preserving important population demographics.

Biological reference points for American lobster (Homarus americanus) populations: limits to exploitation and the precautionary approach

2004 ◽  
Vol 61 (8) ◽  
pp. 1392-1403 ◽  
Author(s):  
Michael J Fogarty ◽  
Louise Gendron
Keyword(s):  
United States ◽  
Egg Production ◽  
Large Scale ◽  
Abiotic Factors ◽  
Homarus Americanus ◽  
The United States ◽  
Reference Points ◽  
Population Increase ◽  
American Lobster ◽  
Precautionary Approach

Large-scale changes in American lobster (Homarus americanus) landings and abundance have been documented in both Canada and the United States over the last several decades. The spatial coherence of these changes suggests the importance of common environmental and fishery-related factors operating over broad areas in the western North Atlantic. Changes in both biotic and abiotic factors have been hypothesized to underlie the recent increases in lobster production. Area expansion of lobsters to previously unoccupied or low-density areas appears to be an important element of the population increase. Here, we review biological reference points applied to American lobster populations in the United States and Canada. Egg production per recruit models have been used to specify limit reference points (F10% in the United States) or target reference points (increasing egg production per recruit to twice its 1995 level in Canada). Surplus production and yield-per-recruit models have also been employed to provide qualitative management guidelines. We describe sources of uncertainty in the development of biological reference points for American lobster based on dynamic pool models in relation to the precautionary approach. Finally we consider auxiliary indicators and reference points with potential application to lobster stocks.

Temperature and Lobster, Homarus americanus, Yield Relationships

1991 ◽  
Vol 48 (11) ◽  
pp. 2073-2082 ◽  
Author(s):  
A. Campbell ◽  
D. J. Noakes ◽  
R. W. Elner
Keyword(s):  
Nova Scotia ◽  
New Brunswick ◽  
East Coast ◽  
Homarus Americanus ◽  
Fishing Effort ◽  
Sea Surface ◽  
Time Series Models ◽  
American Lobster ◽  
Sea Temperature ◽  
Survival And Growth

Commercial landings of American lobster (Homarus americanus) have increased dramatically in many areas along the east coast of Canada since the late 1970's. Average annual sea surface temperatures (SST) were analysed to test if lobster landings were related to changes in the marine environment. Time series models were fitted to lobster landings and SST data from Maine (USA), Halifax County (Nova Scotia), and Charlotte County (New Brunswick). Including temperature in the models improved forecasting ability for lobster catches for Maine and Halifax but not Charlotte. In Maine, lobster landings in year t were related to SST in year t. In Halifax, however, landings were related to SST in the previous 4 yr but not by SST of the current year. Lower fishing effort levels for Halifax compared with Maine probably extended the yield from strong year-classes through a number of years. We surmise that an increase in sea temperature near Halifax during the early 1980's increased the survival and growth rates of lobster juveniles. This provided a strong pulse of recruits to the fishery throughout coastal Nova Scotia during the mid- to late 1980's. Similar increases in temperature and landings were not observed for Maine and Charlotte.

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

A survey of parasites of the American lobster, Homarus americanus (Crustacea: Decapoda), from the Canadian Maritimes

1986 ◽  
Vol 64 (9) ◽  
pp. 1998-2003 ◽  
Author(s):  
John Brattey ◽  
Alan Campbell
Keyword(s):  
Nova Scotia ◽  
Continental Shelf ◽  
Parasite Species ◽  
Homarus Americanus ◽  
Coastal Areas ◽  
Parasite Fauna ◽  
American Lobster ◽  
Stock Discrimination ◽  
High Prevalence ◽  
Size Groups

Examination of 885 lobsters (Homarus americanus) trapped in five areas of the Canadian Maritimes during 1980–1982 revealed four parasite species: Porospora gigantea (Apicomplexa: Sporozoea), Polymorphus botulus (Acanthocephala: Palaeacanthocephala), Hysterothylacium sp. (Nematoda: Secernentea), and Stichocotyle nephropis (Platyhelminthes: Trematoda). The prevalence and abundance of each parasite species did not differ significantly (p > 0.05) between lobster sexes or size groups. Lobsters in each area were characterized by a high prevalence of P. gigantea (43.6 to 84.2%) and low prevalences of P. botulus (1.3 to 9.9%) and Hysterothylacium sp. (1.1 to 5.6%). Stichocotyle nephropis was found in one lobster from German Bank. The parasite fauna were similar throughout the areas sampled, which suggests that the data were of little value for lobster stock discrimination. However, lobsters probably acquired P. botulus in the shallow coastal areas where the primary hosts of this parasite occur; therefore, the presence of P. botulus in lobsters from inshore and offshore areas south and southeast of Nova Scotia suggests some mixing between coastal lobsters and those on the continental shelf.

Aspects of Larval American Lobster (Homarus americanus) Ecology in St. Georges Bay, Nova Scotia

1982 ◽  
Vol 39 (8) ◽  
pp. 1117-1129 ◽  
Author(s):  
Gareth C. Harding ◽  
W. Peter Vass ◽  
Ken F. Drinkwter
Keyword(s):  
Nova Scotia ◽  
Large Scale ◽  
Homarus Americanus ◽  
Small Scale ◽  
Langmuir Circulation ◽  
Survival Estimate ◽  
Larval Production ◽  
Stage 1 ◽  
Surface Drift ◽  
Probability Of Capture

Lobster larvae first appeared in the neuston of St. Georges Bay, N.S., in 1978 on June 22 at a surface temperature of 12.5 °C. Abundances ranged from 0 to 243 × 103 larvae∙km−2 throughout the larval season with a seasonal average of 22.9 ± 37.9 × 103 larvae∙km−2 for the entire bay. Larval production in the bay equals the highest values reported in the literature for individual stations in nearby western Northumberland Strait. We derive the first survival estimate from larval stage 1 to recruits entering the fishery of 0.2–0.4%. On average 81.4, 14.1, and 4.5% of the larvae were caught within the upper 30-cm, 30- to 70-cm, and 70- to 110-cm levels beneath the sea surface, respectively. This daytime distribution of lobster larvae in the upper 110 cm is modified by cloud cover. The adult distribution in the bay and wind-driven surface drift are believed to be the two main causes of the observed large-scale horizontal patchiness. Lobster larvae have a significantly high probability of capture by our nets if patches of floating seaweed are encountered. A hypothesis is proposed that the observed small-scale patchiness of both larvae and weed is caused by Langmuir circulation.Key words: lobster larvae, Homarus americanus, ecology, Langmuir circulation, recruitment, survival, Nova Scotia

Reproductive Potential of Three American Lobster (Homarus americanus) Stocks in the Canadian Maritimes

1983 ◽  
Vol 40 (11) ◽  
pp. 1958-1967 ◽  
Author(s):  
A. Campbell ◽  
D. G. Robinson
Keyword(s):  
Nova Scotia ◽  
Egg Production ◽  
Reproductive Potential ◽  
Homarus Americanus ◽  
Curvilinear Relationship ◽  
Bay Of Fundy ◽  
American Lobster ◽  
Female Size ◽  
New Information ◽  
Stock Recruitment

New information on female size at maturity, fecundity, and relative egg production per recruit is presented for American lobsters (Homarus americanus) from three areas in the Canadian Maritimes. Based on pleopod examination, sizes at 50% maturity for females were estimated at 108.1 mm carapace length (CL) from the Fundy area (Bay of Fundy and southwestern Nova Scotia), at 92.5 mm CL from eastern Nova Scotia, and at 78.5 mm CL from Northumberland Strait. There was a curvilinear relationship between the number of eggs per female and CL. An egg-per-recruit model predicted that in all three areas the second and third molt groups beyond the legal minimum recruit size contribute the most to egg production under current exploitation rates. Lobsters in Northumberland Strait and eastern Nova Scotia produce up to 30–50% of their eggs at sizes smaller than those at which females from the Bay of Fundy start to produce eggs. Although the stock–recruitment relationships for H. americanus are unknown, the egg-per-recruit assessment suggests that all three areas would benefit in egg production increases by increasing minimum legal recruit size by one molt increment.

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