American lobster: persistence in the face of high, size-selective, fishing mortality — a perspective from the southern Gulf of St. Lawrence

2018 ◽  
Vol 75 (12) ◽  
pp. 2401-2411 ◽  
Author(s):  
Michel Comeau ◽  
J. Mark Hanson
Keyword(s):  
Gadus Morhua ◽  
Fishery Management ◽  
Atlantic Cod ◽  
Adult Population ◽  
Homarus Americanus ◽  
Snow Crab ◽  
American Lobster ◽  
High Survival ◽  
Size Limit ◽  
The 1960S

The American lobster (Homarus americanus) population in southern Gulf of St. Lawrence has long been subjected to high exploitation, and yet its population is currently at a high and increasing abundance level. The lobster fishery management is based on effort-control, with a short season, mandatory release of egg-bearing females, and strict enforcement of regulations. Another important factor is the high survival of lobster returned to the water. The combination of a minimum legal size limit and either an upper size limit for females or an effective size limit due to entrance-ring size on the traps has resulted in a slot fishery after which the larger, most fecund animals have low vulnerability to the fishery. These efforts to protect large individuals have had a positive effect on lobster larval production, which may lead to even higher adult population numbers. Comparisons with the management of snow crab (Chionoecetes opilio) and Atlantic cod (Gadus morhua) quota-based fisheries were made to try to explain the different trajectories that these three species’ populations have taken since the 1960s.

Using acoustic telemetry to observe the effects of a groundfish predator (Atlantic cod, Gadus morhua) on movement of the American lobster (Homarus americanus)

2013 ◽  
Vol 70 (11) ◽  
pp. 1625-1634 ◽  
Author(s):  
Marissa D. McMahan ◽  
Damian C. Brady ◽  
Diane F. Cowan ◽  
Jonathan H. Grabowski ◽  
Graham D. Sherwood
Keyword(s):  
Home Range ◽  
Behavioral Response ◽  
Acoustic Telemetry ◽  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Homarus Americanus ◽  
American Lobster ◽  
Habitat Area ◽  
Predation Rates

American lobster (Homarus americanus) landings have more than quadrupled in the last two decades (1990–2010), coinciding with the collapse of Gulf of Maine groundfish fisheries such as Atlantic cod (Gadus morhua). Recently there has been speculation that the release of lobster from predatory control may have resulted in both lower predation rates and increased foraging areas. We used fine-scale acoustic telemetry within a 200 m × 250 m field enclosure to test the hypothesis that cod induce lobsters to decrease movement and seek refuge. We found a large amount of variation in the behavioral response of individual lobsters to predators; however, the addition of cod into the enclosure reduced maximum daily home range area and significantly reduced the distance traveled from shelter habitat area for all individuals. When predators were removed from the enclosure, lobsters responded by increasing home range area and significantly increasing the distance traveled from shelter habitat area. These results represent the first experimental evidence for American lobster range contraction and subsequent expansion in the presence and absence of cod, respectively.

scholarly journals Climate impacts on the Gulf of Maine ecosystem

Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Andrew J. Pershing ◽  
Michael A. Alexander ◽  
Damian C. Brady ◽  
David Brickman ◽  
Enrique N. Curchitser ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Algal Species ◽  
Homarus Americanus ◽  
Climate Impacts ◽  
Clupea Harengus ◽  
Calanus Finmarchicus ◽  
American Lobster ◽  
Surface Salinity

The Gulf of Maine has recently experienced its warmest 5-year period (2015–2020) in the instrumental record. This warming was associated with a decline in the signature subarctic zooplankton species, Calanus finmarchicus. The temperature changes have also led to impacts on commercial species such as Atlantic cod (Gadus morhua) and American lobster (Homarus americanus) and protected species including Atlantic puffins (Fratercula arctica) and northern right whales (Eubalaena glacialis). The recent period also saw a decline in Atlantic herring (Clupea harengus) recruitment and an increase in novel harmful algal species, although these have not been attributed to the recent warming. Here, we use an ensemble of numerical ocean models to characterize expected ocean conditions in the middle of this century. Under the high CO2 emissions scenario (RCP8.5), the average temperature in the Gulf of Maine is expected to increase 1.1°C to 2.4°C relative to the 1976–2005 average. Surface salinity is expected to decrease, leading to enhanced water column stratification. These physical changes are likely to lead to additional declines in subarctic species including C. finmarchicus, American lobster, and Atlantic cod and an increase in temperate species. The ecosystem changes have already impacted human communities through altered delivery of ecosystem services derived from the marine environment. Continued warming is expected to lead to a loss of heritage, changes in culture, and the necessity for adaptation.

scholarly journals Non-linearity in stock–recruitment relationships of Atlantic cod: insights from a multi-model approach

2019 ◽  
Vol 77 (4) ◽  
pp. 1492-1502 ◽  
Author(s):  
Camilla Sguotti ◽  
Saskia A Otto ◽  
Xochitl Cormon ◽  
Karl M Werner ◽  
Ethan Deyle ◽  
...  
Keyword(s):  
Environmental Variables ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Fish Stock ◽  
Recovery Potential ◽  
Stock Recruitment ◽  
Model Approach ◽  
Non Parametric

Abstract The stock–recruitment relationship is the basis of any stock prediction and thus fundamental for fishery management. Traditional parametric stock–recruitment models often poorly fit empirical data, nevertheless they are still the rule in fish stock assessment procedures. We here apply a multi-model approach to predict recruitment of 20 Atlantic cod (Gadus morhua) stocks as a function of adult biomass and environmental variables. We compare the traditional Ricker model with two non-parametric approaches: (i) the stochastic cusp model from catastrophe theory and (ii) multivariate simplex projections, based on attractor state-space reconstruction. We show that the performance of each model is contingent on the historical dynamics of individual stocks, and that stocks which experienced abrupt and state-dependent dynamics are best modelled using non-parametric approaches. These dynamics are pervasive in Western stocks highlighting a geographical distinction between cod stocks, which have implications for their recovery potential. Furthermore, the addition of environmental variables always improved the models’ predictive power indicating that they should be considered in stock assessment and management routines. Using our multi-model approach, we demonstrate that we should be more flexible when modelling recruitment and tailor our approaches to the dynamical properties of each individual stock.

scholarly journals Estimating and mitigating the discard mortality of Atlantic cod (Gadus morhua) in the Gulf of Maine recreational rod-and-reel fishery

2016 ◽  
Vol 73 (9) ◽  
pp. 2342-2355 ◽  
Author(s):  
Connor W. Capizzano ◽  
John W. Mandelman ◽  
William S. Hoffman ◽  
Micah J. Dean ◽  
Douglas R. Zemeckis ◽  
...  
Keyword(s):  
Best Practice ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Related Factors ◽  
Discard Mortality ◽  
Recreational Fishery ◽  
Receiver Array ◽  
Management Plans

Abstract In recent years, the recreational contribution to the total catch of Atlantic cod (Gadus morhua) in the Gulf of Maine (GOM) has increased with recreational discards outnumbering recreational landings by 2:1. However, the discard mortality (DM) rate of cod released in the recreational fishery remains poorly understood, thus contributing to the uncertainty in stock assessments and fishery management plans. The current study examined the capture-related factors most detrimental to cod DM in the GOM recreational rod-and-reel fishery. Atlantic cod (n = 640; 26.0–72.0 cm) were angled from June–October 2013 on southern Jeffreys Ledge in the western GOM using fishing gear representative of the local recreational fishery. A subset (n = 136) was also tagged with pressure-sensing acoustic transmitters before being released into an acoustic receiver array (n = 31) deployed to monitor survival up to 94 days. To properly model DM up to the fishery-wide level, all cod were visually assessed for capture-related injuries according to a four-level injury score index. Mean tackle-specific DM rates of 15.4 and 21.2% were estimated for bait- and jig-captured cod, respectively, with an overall 16.5% mean DM rate for the 2013 GOM recreational cod fishery. Twenty-nine cod tagged with acoustic transmitters were identified as dead, where the majority (∼90%) died within 16 h post-capture. Upon evaluation with a specifically adapted parametric survival analysis, greater incidence of mortality was attributed to the capture and handling process (rather than release) for moderately and severely injured cod. Based on the capture-related factors associated with the highest injury rates, we recommend minimizing fight and handling times, avoiding areas with small cod, educating inexperienced anglers, and favouring bait over jigs to mitigate mortality. Results will continue to inform the development of fishery management plans and enhance survival through dissemination of “best practice” techniques to fishery stakeholders.

Recruitment overfishing reference point for the American lobster, Homarus americanus

1997 ◽  
Vol 48 (8) ◽  
pp. 1029 ◽  
Author(s):  
G. P. Ennis ◽  
M. J. Fogarty
Keyword(s):  
Median Survival ◽  
Reference Point ◽  
Egg Production ◽  
Adult Population ◽  
Homarus Americanus ◽  
Reference Points ◽  
American Lobster ◽  
Survival Ratio ◽  
Low Level ◽  
Exploitation Rate

A 21-year series of annual estimates of egg production and recruitment in a Newfoundland lobster population indicates similar asymptotic relationships for recruitment to the fishery and to the adult population, both derived from legal stock estimates. Lines with slopes equal to the 90th-percentile and median survival ratios drawn through the origin of the egg production–adult recruitment scatterplot were examined as potential recruitment overfishing reference points for the Arnold’s Cove lobster stock. If the inverse of the estimated lifetime egg production per recruit (E/R) for a given exploitation rate exceeds the slope of the selected reference point, the risk of recruitment overfishing is high. For the Arnold’s Cove stock, the E/R level at a nominal 90% exploitation rate is estimated at 4.2% of the unfished population, compared with 2.5% for the overfishing reference point corresponding to the median survival ratio. Female lobsters at Arnold’s Cove mature at sizes below the minimum legal size, providing a buffer against high exploitation rates. Small, scattered refugia of large lobsters could also help to explain how heavily exploited populations of this species persist at such a low level of egg production.

scholarly journals Effects of closing bottom trawling on fisheries, biodiversity, and fishing communities in a boreal marine ecosystem: the Hawke Box off Labrador, Canada

2017 ◽  
Vol 74 (9) ◽  
pp. 1490-1502 ◽  
Author(s):  
Kate Kincaid ◽  
George Rose
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Marine Ecosystem ◽  
Snow Crab ◽  
Offshore Area ◽  
Seasonal Snow ◽  
Management Measure ◽  
Relative Production ◽  
Fishery Data ◽  
Demersal Species

The Hawke Box is an offshore area (8610 km2) of the boreal Northwest Atlantic that at the request of local fishers was closed to trawling and gillnetting in 2003, but remained open to seasonal snow crab (Chionocetes opilio) pot fishing. Closure was a precautionary management measure primarily to sustain the crab fishery and secondarily to conserve cod known to aggregate there. Fall (1996–2013) and spring (1996–2003, 2015) surveys indicated that biological community assemblages changed significantly before–after and inside–outside the closure (PERMANOVA P < 0.01). Crab fishery data (1996–2013) indicated that landings and relative production declined throughout the region after closure, but was significantly more outside than inside. Atlantic cod (Gadus morhua) increased inside and outside the closure, and several other demersal species increased significantly more inside. The Hawke Box provides a unique boreal area for the study of restrictions on trawling and gillnetting in an area with historically strong fisheries, restrictions that are strongly supported by local fishers. The overall evidence suggests that within a decade the Hawke Box has benefited fisheries communities, fisheries production, and biodiversity conservation.

Can Atlantic cod (Gadus morhua) recover? Exploring trophic explanations for the non-recovery of the cod stock on the eastern Scotian Shelf, Canada

2005 ◽  
Vol 62 (7) ◽  
pp. 1474-1489 ◽  
Author(s):  
Alida Bundy ◽  
L Paul Fanning
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Snow Crab ◽  
Forage Fish ◽  
Scotian Shelf ◽  
The Poor ◽  
Mass Balance Models ◽  
Average Condition ◽  
High Predation ◽  
High Predation Pressure

The Atlantic cod (Gadus morhua) stock on the eastern Scotian Shelf collapsed in 1993. Over a decade later, in spite of a fisheries moratorium on cod fishing, this stock is at an all-time low. In parallel with the collapse of the cod stock, the abundance of large cod prey, including forage fish, shrimp, and snow crab, has greatly increased. The key question, which we explore using trophic mass-balance models, is what processes are preventing cod from recovering on the eastern Scotian Shelf? Cod were split into large and small cod. Modelling results indicate high predation pressure on small cod. In addition, small cod compete with the abundant forage fish for decreasing prey, and are in below-average condition. Large cod incur high, but unidentified, mortality that we suggest is derived from the poor condition of small cod carried through to adulthood. As a consequence of the removal of cod by fishing and an ensusing trophic cascade, eastern Scotian Shelf cod are trapped in a vicious circle: their abundance is being kept low by predation, causing an abundance so low that cod cannot compete for prey with their exceptionally abundant competitors. Furthermore, these competitors may also prey on younger stages of cod.

Re-evaluating Atlantic cod mortality including lobster bycatch: where could we be today?

2020 ◽  
Vol 77 (6) ◽  
pp. 1049-1058 ◽  
Author(s):  
Robert Boenish ◽  
Yong Chen
Keyword(s):  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Homarus Americanus ◽  
Small Scale ◽  
Stock Biomass ◽  
Stock Assessments ◽  
Spawning Stock ◽  
Assessment Bias ◽  
Related Mortality

Full accounting of fisheries mortality is one of the most tractable ways to improve stock assessments. However, it can be challenging to obtain in cases when missing catch comes from small-scale nontarget fisheries unrequired to report incidental catch. Atlantic cod (Gadus morhua) in the Gulf of Maine (GoM), USA, once served as a regionally important fishery, but has been serially depleted to <5% of historic spawning stock biomass. Recent management efforts to rebuild GoM cod have largely failed. We test the hypothesis that unaccounted bycatch of Atlantic cod in the Maine American lobster (Homarus americanus) fishery is a substantial missing piece in the GoM Atlantic cod assessment. We integrated multiple scenarios of hind-casted discards into the two accepted regional cod assessment models from 1982 to 2016. Incorporation of discards improved the assessment bias for both models (10%–15%), increased estimates of spawning stock biomass (4%), and decreased estimates of fishing mortality (9%). A novel evaluation of longitudinal model bias suggests that alternative modelling approaches or specifications may be warranted. We highlight the importance of accounting for all fishery-related mortality and the need for methods to deliver more comprehensive estimates from both target and nontarget fisheries.

Reconciling overfishing and climate change with stock dynamics of Atlantic cod (Gadus morhua) over 500 years

2004 ◽  
Vol 61 (9) ◽  
pp. 1553-1557 ◽  
Author(s):  
G A Rose
Keyword(s):  
Little Ice Age ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Ice Age ◽  
Production Model ◽  
Late 20Th Century ◽  
Climate Effects ◽  
Lower Productivity ◽  
History Of ◽  
The 1960S

To examine overfishing and climate effects on depleted cod (Gadus morhua) stocks, a surplus production model based on reconstructions of cod catch in Newfoundland was used to describe biomass dynamics from 1505 to 2004. Productivity parameters r (population growth rate) and K (carrying capacity) were assigned by fitting model to survey biomass. Assumptions of fishery-only influences inferring constant, random, or depensatory parameters fared poorly (did not mimic history), as did climate influences indexed by tree ring growth. However, a model using both climate and depensation fared well, mimicking much documented history of Newfoundland cod, including declines during the Little Ice Age (mid- to late 19th century) and the stock collapses of the late 20th century, with a good fit to recent scientific surveys (r2 = 0.80). This model suggests temporal differentiation between fishing and climate effects, including (i) declines during the Little Ice Age (1800–1880) caused by lower productivity, (ii) collapses in the 1960s caused by overfishing, (iii) collapses in the late 1980s caused by both, and (iv) rebuilding now hindered by depensatory effects of low numbers.

American lobster dynamics in a brave new ocean

2013 ◽  
Vol 70 (11) ◽  
pp. 1612-1624 ◽  
Author(s):  
Robert S. Steneck ◽  
Richard A. Wahle
Keyword(s):  
North Atlantic ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Homarus Americanus ◽  
Lifetime Reproductive Success ◽  
Larval Size ◽  
The North ◽  
The Us ◽  
The Future ◽  
Consequences Of Disease

Dynamic food webs and climate are changing lobster ecology and management. American lobsters (Homarus americanus) evolved in the North Atlantic under conditions of intense predation from large finfish such as Atlantic cod (Gadus morhua). Lobster’s relatively extended brood period and large larval size result in high per capita pelagic phase survival, which, coupled with settlement habitat selection for predator refugia, contributes to the species’ high lifetime reproductive success. However, the western North Atlantic is an extremely low diversity ecosystem prone to booms and busts. Extirpation of coastal predators released past constraints on lobster population growth such that lobster landings increased three- to five-fold since 1980 in Canada and the US. Climate change may stress lobsters in some regions and enhance stocks elsewhere, but it also facilitates warm-water species distribution shift northward. As lobster population densities and water temperatures increase, so do risks and consequences of disease. In the future we must expect the unexpected. “Equilibrium” conditions on which traditional fisheries management depends simply do not exist. This creates new challenges for managing this species regionally and into the future.

Sign in / Sign up

Export Citation Format

Share Document