Patterns of larval-stage connectivity of Atlantic cod (Gadus morhua) within the Gulf of Maine in relation to current structure and a proposed fisheries closure

2016 ◽  
Vol 74 (1) ◽  
pp. 20-30 ◽  
Author(s):  
J. H. Churchill ◽  
J. P. Kritzer ◽  
M. J. Dean ◽  
J. H. Grabowski ◽  
G. D. Sherwood
Keyword(s):  
Larval Stage ◽  
Large Scale ◽  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Larval Transport ◽  
Spatially Explicit ◽  
Closed Area ◽  
Spawning Stock ◽  
Juvenile Habitat

The decline of the Atlantic cod, Gadus morhua, stock in the Gulf of Maine to a historically low biomass has been coupled with a severe contraction in spatial range. The stock is now largely concentrated in the western Gulf of Maine. This erosion of spatial stock structure may be a factor-inhibiting recovery of Gulf of Maine cod. However, recent efforts to rebuild anadromous forage fish in the coastal Maine region coupled with the proposed creation of a new Eastern Maine Closed Area (EMCA), sited where localized depletion of the cod stock has been especially severe, might enable reestablishment of lost spatial structure of Gulf of Maine cod. We carried out larval transport modeling to examine the potential benefit of recovered cod spawning in the EMCA through supplying larvae to suitable juvenile settlement areas in the Gulf of Maine coastal zone and in the Cashes Ledge Closed Area (CLCA) in the central Gulf of Maine. The results indicate that an appreciable fraction of the larvae spawned in the EMCA are retained, to an age of settlement capability, in the coastal Maine region. Spawning in the EMCA may thus be a contributor of juveniles to a local, eastern Gulf of Maine, cod sub-stock. The results further indicate that spawning in the EMCA may supply a substantial subsidy of larvae to suitable juvenile habitat in the western Gulf of Maine and the CLCA. Protection of spawning stock in the EMCA may thus provide demographic benefits for the wider Gulf of Maine cod stock. Patterns of larval-stage connectivity between various potential spawning regions (including the EMCA) and areas of suitable juvenile habitat exhibit considerable interannual variability, which is predominantly linked to variability in the large-scale Gulf of Maine circulation. This result underscores the value of spatially explicit management as a means of fostering the recovery of the Gulf of Maine cod stock.

The influence of spatially variable and connected recruitment on complex stock dynamics and its ecological and management implications

2019 ◽  
Vol 76 (6) ◽  
pp. 937-949 ◽  
Author(s):  
Lisha Guan ◽  
Yong Chen ◽  
James A. Wilson ◽  
Timothy Waring ◽  
Lisa A. Kerr ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Temporal Trends ◽  
Substantial Reduction ◽  
Management Implications ◽  
Agent Based ◽  
Stock Biomass ◽  
Spawning Stock ◽  
The Individual

To evaluate the influence of spatially variable and connected recruitments at spawning component scale on complex stock dynamics, a typical agent-based complex stock was modeled based on the Atlantic cod (Gadus morhua) stock in the Gulf of Maine. We simulated three scenarios with different degrees of connectivity (i.e., individual exchange) between the spatially variable recruitments of 36 spawning components within four subpopulations under the stock. Subsequently, the temporal trends were compared for different scenarios in age-1 recruitment, spawning stock biomass, and local depletion proportion of the overall complex stock and the individual subpopulations. Results show that increased recruitment connectivity from 0.1–0.2 to 0.6–0.8 between various components tends to increase the productivity and stability of a complex stock at local and global scales and reduce the proportion of depleted components due to overfishing. Moreover, depletions of less productive components may occur without a substantial reduction in the overall complex stock biomass and recruitment.

Advances in Fish Tagging and Marking Technology

2012 ◽  
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Stock Identification ◽  
Quality Of Data ◽  
Mark Recapture ◽  
International Industry ◽  
Research Initiatives

<i>Abstract</i>.—In the Gulf of Maine region, Atlantic cod <i>Gadus morhua</i>, are managed as three separate stocks: in U.S. waters, the Gulf of Maine (5Y) and Georges Bank (5Z) stocks and in Canadian waters, the Bay of Fundy stock (4X). The Northeast Regional Cod Tagging Program (NRCTP), a large-scale, international collaborative tagging program, was initiated in 2003 and provides the first region-wide, international snapshot of cod movements, mixing, and growth across all three management areas. As the 2008 stock assessment of Atlantic cod was approaching, these mark–recapture data (114,473 tag releases and >6,500 recaptures) were being analyzed for stock identification purposes. Analysis of raw and weighted data indicate exchanges between different areas which are likely related to spawning behavior, maturation, and environmental conditions. Two core assumptions when defining a stock are that (1) the stock is self-sustaining and that (2) neighboring stocks exist in isolation; the migration patterns observed in the current study may substantially violate both assumptions. With additional ongoing assessments into spatial variation in key life history characteristics of growth and natural mortality, the NRCTP exemplifies the role of conventional mark–recapture data in the complex process of stock identification. The geographic scale and quality of data collected during the NRCTP also confirm the value of international, industry-science collaborative research initiatives; involving this data in both stock assessments and future management initiatives is rewarding to the ~250 commercial and recreational fishermen who tagged cod for this program.

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.

An "experiment" on effort allocation of fishing vessels: the role of interference competition and area specialization

2007 ◽  
Vol 64 (2) ◽  
pp. 304-313 ◽  
Author(s):  
Jan-Jaap Poos ◽  
Adriaan D Rijnsdorp
Keyword(s):  
North Sea ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Seasonal Pattern ◽  
Interference Competition ◽  
Catch Rate ◽  
The North ◽  
Closed Area ◽  
Fishing Vessels ◽  
The North Sea

A temporarily closed area established to protect spawning Atlantic cod (Gadus morhua) in the North Sea allowed us to study the response of the Dutch beam trawl fleet exploiting common sole (Solea solea) and plaice (Pleuronectes platessa). A number of vessels left the North Sea 1 month earlier than the normal seasonal pattern. The vessels that continued fishing in the North Sea were concentrated in the remaining open areas. In the first week after the closure, the catch rate decreased by 14%, coinciding with an increase in crowding of 28%. Area specialisation affected the response of individual vessels because vessels without prior experience in the open areas showed a larger decline in catch rate compared with vessels that previously fished in these open areas and were more likely to stop fishing during the closed period. The decrease in catch rate in response to the increase in competitor density allowed us to estimate the strength of the interference competition.

Automated monitoring of a large-scale cod (Gadus morhua) migration in the open sea

2002 ◽  
Vol 59 (12) ◽  
pp. 1845-1850 ◽  
Author(s):  
Luc A Comeau ◽  
Steven E Campana ◽  
Martin Castonguay
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Seasonal Migration ◽  
Migration Routes ◽  
Eastern Canada ◽  
Migration Patterns ◽  
Migration Timing ◽  
Open Sea ◽  
And Migration

The migration patterns of marine fishes are poorly known, in part owing to the technical limitations associated with tracking the movements of animals in deep water. Here we document a large-scale, directed, migration of Atlantic cod (Gadus morhua) off eastern Canada. Our approach was based on the acoustic tagging of 126 fish and the deployment of 69 subsurface receivers, stretching over a 160-km distance along the edge of the Laurentian Channel. After 1 year of automated recording, we found that 65% of the fish migrated out of coastal waters in two distinct runs during the summer–autumn period. The offshore-migrating fish overwintered in deep Laurentian Channel waters, returning inshore in April. Individual migration routes and migration timing were variable, indicating that the cod did not aggregate in large schools during the seasonal migration events.

Oxidative stress, DNA damage and p53 expression in the larvae of atlantic cod (Gadus morhua) exposed to ultraviolet (290–400 nm) radiation

2001 ◽  
Vol 204 (1) ◽  
pp. 157-164 ◽  
Author(s):  
M.P. Lesser ◽  
J.H. Farrell ◽  
C.W. Walker
Keyword(s):  
Oxidative Stress ◽  
Dna Damage ◽  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Growth Arrest ◽  
Individual Performance ◽  
Cellular Growth ◽  
Pyrimidine Dimer ◽  
Uvb Radiation

Decreases in stratospheric ozone levels from anthropogenic inputs of chlorinated fluorocarbons have resulted in an increased amount of harmful ultraviolet-B (UVB, 290–320 nm) radiation reaching the sea surface in temperate latitudes (30–50 degrees N). In the Gulf of Maine, present-day irradiances of ultraviolet-A (UVA, 320–400 nm) radiation can penetrate to depths of 23 m and UVB radiation can penetrate to depths of 7–12 m, where the rapidly developing embryos and larvae of the Atlantic cod (Gadus morhua) are known to occur. Laboratory exposures of embryos and larvae of Atlantic cod to ultraviolet radiation (UVR) equivalent to a depth of approximately 10 m in the Gulf of Maine resulted in significant mortality of developing embryos and a decrease in standard length at hatching for yolk-sac larvae. Larvae at the end of the experimental period also had lower concentrations of UVR-absorbing compounds and exhibited significantly greater damage to their DNA, measured as cyclobutane pyrimidine dimer formation, after exposure to UVB radiation. Larvae exposed to UVB radiation also exhibited significantly higher activities and protein concentrations of the antioxidant enzyme superoxide dismutase and significantly higher concentrations of the transcriptional activator p53. p53 is expressed in response to DNA damage and can result in cellular growth arrest in the G1- to S-phase of the cell cycle or to programmed cell death (apoptosis). Cellular death caused by apoptosis is the most likely cause of mortality in embryos and larvae in these laboratory experiments, while the smaller size at hatching in those larvae that survived is caused by permanent cellular growth arrest in response to DNA damage. In addition, the sub-lethal energetic costs of repairing DNA damage or responding to oxidative stress may also contribute to poor individual performance in surviving larvae that could also lead to increases in mortality. The irradiances of UVB radiation that elicit these responses in cod larvae can occur in many temperate latitudes, where these ecologically and commercially important fish are known to spawn, and may contribute to the high mortality of cod embryos and larvae in their natural environment.

The role of spawning stock in formation of recruitment of northeast atlantic cod Gadus morhua

2006 ◽  
Vol 46 (1) ◽  
pp. 74-82 ◽  
Author(s):  
V. M. Borisov ◽  
A. A. Elizarov ◽  
V. D. Nesterov
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Northeast Atlantic ◽  
Spawning Stock

The influence of forage fish abundance on the aggregation of Gulf of Maine Atlantic cod (Gadus morhua) and their catchability in the fishery

2014 ◽  
Vol 71 (9) ◽  
pp. 1349-1362 ◽  
Author(s):  
David E. Richardson ◽  
Michael C. Palmer ◽  
Brian E. Smith
Keyword(s):  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Distribution Patterns ◽  
Fish Populations ◽  
Dependent Data ◽  
Forage Fish ◽  
Catch Per Unit Effort ◽  
Sand Lance ◽  
Unit Effort

Shifts in the distribution and aggregation patterns of exploited fish populations can affect the behavior and success of fishermen and can complicate the interpretation of fisheries-dependent data. Starting in 2006, coinciding with an increase in sand lance (Ammodytes spp.) abundance, Gulf of Maine Atlantic cod (Gadus morhua) concentrated on Stellwagen Bank, a small (405 km2) underwater plateau located in the southwestern portion of the larger (52 461 km2) stock area. The cod fishery in turn concentrated on Stellwagen Bank. Specifically, the proportion of Gulf of Maine cod landings caught in a single 10-minute square area (260 km2) encompassing the tip of Stellwagen Bank increased from 12% in 2005 to 45% in 2010. An increase in landings per unit effort in the fishery coincided with the concentration of the fleet on Stellwagen Bank. Overall, both fisheries-independent and fisheries-dependent data indicate that an increase in sand lance abundance resulted in cod aggregating in a small and predictable area where they were easily caught by the fishery. More broadly, this work illustrates how changes in the distribution patterns of fish and fisherman can decouple trends in abundance and fisheries catch per unit effort.

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.

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