scholarly journals Identifying the distribution of Atlantic cod spawning using multiple fixed and glider-mounted acoustic technologies

2019 ◽  
Vol 76 (6) ◽  
pp. 1610-1625 ◽  
Author(s):  
Douglas R Zemeckis ◽  
Micah J Dean ◽  
Annamaria I DeAngelis ◽  
Sofie M Van Parijs ◽  
William S Hoffman ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Fishery Management ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Temporal Distribution ◽  
Management Actions ◽  
Spawning Site ◽  
Management Measures ◽  
Fish Spawning ◽  
Spatio Temporal

Abstract Effective fishery management measures to protect fish spawning aggregations require reliable information on the spatio-temporal distribution of spawning. Spawning closures have been part of a suite of fishery management actions to rebuild the Gulf of Maine stock of Atlantic cod (Gadus morhua), but difficulties remain with managing rebuilding. The objective of this study was to identify the spatial and temporal distribution of cod spawning during winter in Massachusetts Bay to improve our understanding of cod spawning dynamics and inform fisheries management. Spawning was investigated in collaboration with commercial fishermen during three winter spawning seasons (October 2013–March 2016) using acoustic telemetry and passive acoustic monitoring equipment deployed in fixed-station arrays and mounted on mobile autonomous gliders. Tagged cod exhibited spawning site fidelity and spawning primarily occurred from early November through January with a mid-December peak and some inter-annual variability. The spatial distribution of spawning was generally consistent among years with multiple hotspots in areas >50 m depth. Current closures encompass most of spawning, but important areas are recommended for potential modifications. Utilizing multiple complementary technologies and deployment strategies in collaboration with commercial fishermen enabled a comprehensive description of spawning and provides a valuable model for future studies.

scholarly journals Spawning site fidelity by Atlantic cod (Gadus morhua) in the Gulf of Maine: implications for population structure and rebuilding

2014 ◽  
Vol 71 (6) ◽  
pp. 1356-1365 ◽  
Author(s):  
Douglas R. Zemeckis ◽  
William S. Hoffman ◽  
Micah J. Dean ◽  
Michael P. Armstrong ◽  
Steven X. Cadrin
Keyword(s):  
Population Structure ◽  
Site Fidelity ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Scientific Uncertainty ◽  
Spawning Site ◽  
Metapopulation Structure ◽  
Spawning Sites

Rebuilding the Gulf of Maine stock of Atlantic cod (Gadus morhua) has been much slower than expected. An important source of scientific uncertainty contributing to the difficulties in managing rebuilding has been the lack of understanding of cod population structure. Previous research indicates that the stock functions as a metapopulation that is made up of multiple subpopulations and many finer-scale spawning components. This study investigated fine-scale, multiyear spawning site fidelity by a spring-spawning component of Atlantic cod in the western Gulf of Maine. Movements of acoustically tagged cod (n = 63) with respect to a known spawning site were tracked using passive acoustic telemetry. A large proportion (38–67%) of tagged cod exhibited spawning site fidelity between 2010 and 2012. After adjusting for fishing mortality, natural mortality, and skipped spawning, the estimated rate of spawning site fidelity ranged between 47 and 95% in 2011. Multiyear spawning site fidelity was also observed, with individuals being tracked for up to four consecutive spawning seasons. Spawning site fidelity serves as one of the multiple mechanisms that contribute to the formation and maintenance of the observed metapopulation structure. Spawning site fidelity also reduces the reproductive connectivity among spawning sites, thus delaying both recolonization of abandoned spawning sites and stock rebuilding. Future stock assessment models and fishery management plans that incorporate the metapopulation structure of cod in the Gulf of Maine are expected to be more effective at preventing continued declines in spawning diversity and promoting rebuilding.

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.

The relative importance of sub-populations to the Gulf of Maine stock of Atlantic cod

2019 ◽  
Vol 76 (6) ◽  
pp. 1626-1640 ◽  
Author(s):  
Micah J Dean ◽  
Scott P Elzey ◽  
William S Hoffman ◽  
Nicholas C Buchan ◽  
Jonathan H Grabowski
Keyword(s):  
Fishery Management ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Large Fraction ◽  
Fish Population ◽  
Training Data ◽  
Population Difference ◽  
Management Measures ◽  
Spawning Stock ◽  
Management Plans

Abstract Discriminating among sympatric sub-populations is critical not only for the investigation of fish population structure, but also for effective fishery management. The Gulf of Maine stock of Atlantic cod contains two genetically distinct sub-populations whose spawning grounds overlap in space, but not season. Lack of a practical tool for discriminating between these spring and winter spawners has thus far prevented addressing metapopulation structure in stock assessments and fishery management plans. To address this issue, we developed a simple approach to discriminate between the sympatric sub-populations that relies on internal otolith structures. Using a logistic regression model fit to training data (n = 577) and evaluated through cross-validation, we correctly classified individuals with 81% accuracy and predicted the overall sub-population mixture within 1%. Applying the model to a broader population dataset (n = 1642) revealed that spring-spawned cod are more concentrated within closed fishing areas and therefore experience a lower mortality rate. However, despite dominating older age classes and comprising a large fraction of the spawning stock, these spring cod contribute little to recruitment. This apparent sub-population difference in the stock–recruitment relationship has important consequences for assessment models and the success of management measures designed to rebuild the stock.

Discrimination of wild and farmed Atlantic cod (Gadus morhua) based on morphology and scale-circuli pattern

2011 ◽  
Vol 68 (9) ◽  
pp. 1928-1936 ◽  
Author(s):  
Ingebrigt Uglem ◽  
Marius Berg ◽  
Rebecca Varne ◽  
Rune Nilsen ◽  
Jarle Mork ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Temporal Distribution ◽  
Ecological Impacts ◽  
Farmed Fish ◽  
In The Wild ◽  
Computer Based ◽  
Spatio Temporal ◽  
Discrimination Methods

Abstract Uglem, I., Berg, M., Varne, R., Nilsen, R., Mork, J., and Bjørn, P. A. 2011. Discrimination of wild and farmed Atlantic cod (Gadus morhua) based on morphology and scale-circuli pattern. – ICES Journal of Marine Science, 68: 1928–1936. To evaluate the spatio–temporal distribution and ecological impacts of escaped farmed Atlantic cod (Gadus morhua), it is necessary that escapees can be traced in the wild. To do this, simple, reliable, and fast methods for determining the origin of cod are required. The aim of this proof-of-concept study was to evaluate whether simple analyses of scales and body morphology can distinguish between wild and farmed cod. Digital images of fish and scales from adult cod from two farms, and wild cod caught near these farms, were analysed by computer-based image analyses. By combining mean breadth of circuli and length-adjusted scale radius in a discriminant analysis, 86 and 80% of wild and farmed fish, respectively, were correctly classified. Moreover, using three simple morphometric measures representing dorsal fin size, neck curvature, and length of lower jaw, 100 and 95% of wild and farmed cod, respectively, were classified correctly. To validate these discrimination methods further, an expanded analysis of additional farmed and wild cod populations is required. The results pave the way for the development of a reliable and standardized methodology for classification of the origin of cod caught in the wild.

Seasonal movements and connectivity of an Atlantic cod (Gadus morhua) spawning component in the western Gulf of Maine

2017 ◽  
Vol 74 (6) ◽  
pp. 1780-1796 ◽  
Author(s):  
Douglas R. Zemeckis ◽  
Chang Liu ◽  
Geoffrey W. Cowles ◽  
Micah J. Dean ◽  
William S. Hoffman ◽  
...  
Keyword(s):  
Population Structure ◽  
Data Storage ◽  
Gadus Morhua ◽  
Fishery Management ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Movement Patterns ◽  
Seasonal Movements ◽  
Spawning Sites

Abstract Movement patterns of marine fishes can have considerable impacts on their population dynamics. A thorough understanding of fish movements is therefore required for informing stock identification, stock assessment, and fishery management. This study investigated the seasonal movements and connectivity of a spring-spawning component of Atlantic cod (Gadus morhua) in the western Gulf of Maine. From 2010 through 2013, spawning cod were sampled within an inshore spawning closure and tagged with conventional tags (n = 2368), acoustic transmitters (n = 106), and archival data storage tags (n = 266). Acoustic receivers were deployed on three inshore spawning sites to test for connectivity among sites. Data from archival tags were used to describe seasonal habitat occupancy and movement patterns via geolocation to statistical areas. Tagging data indicated that cod were primarily residential in the western Gulf of Maine, moving inshore to spawn during the spring (April–July), followed by an offshore migration to their feeding grounds for summer and fall. Cod generally inhabited waters from 45 to 175 m, with the deep offshore basins (>150 m) serving as overwintering habitat. Occupied water temperatures ranged from 4.0 to 13.3 °C, with the coldest temperatures experienced from March through July and the warmest temperatures experienced from September through January. Results provided evidence of spawning site fidelity and connectivity among spawning sites, with some fish visiting multiple spawning sites within or between years. The movements observed during and after the spring-spawning season serve as important mechanisms influencing metapopulation dynamics in the Gulf of Maine region, including both fine- and broad-scale population structure. The improved understanding of cod movement patterns will assist fishery managers in developing management plans, including spawning protection measures, and help to address remaining uncertainties with respect to cod population structure in the Gulf of Maine and other regions.

scholarly journals Density-independent and density-dependent factors affecting spatio-temporal dynamics of Atlantic cod (Gadus morhua) distribution in the Gulf of Maine

2018 ◽  
Vol 75 (4) ◽  
pp. 1329-1340 ◽  
Author(s):  
Zengguang Li ◽  
Zhenjiang Ye ◽  
Rong Wan ◽  
Kisei R Tanaka ◽  
Robert Boenish ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Temporal Dynamics ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Cumulative Distribution ◽  
Distribution Area ◽  
Science Center ◽  
Empirical Cumulative Distribution Function ◽  
Density Dependent ◽  
Spatio Temporal

Abstract Due to strong spatial interplays between intraspecific interactions and environmental forcing, both density-dependent and density-independent processes can affect spatio-temporal dynamics of fish populations in a spatially explicit fashion. To this end, this study investigated the underlying mechanisms of spatio-temporal dynamics of Atlantic cod (Gadus morhua) in the Gulf of Maine (GoM). Based on the data from the Northeast Fisheries Science Center (NEFSC) bottom-trawl surveys in spring and fall from 1982 to 2013, empirical cumulative distribution function (ECDF) curves and geographic distribution indices were used to examine the species–environment and abundance–occupancy relationship, respectively. Then, a variable-coefficient generalized additive model was constructed to quantify the simultaneous effects of environmental variables and population size on the spatio-temporal dynamics of cod distribution. Area occupied remained relatively high through the late 1990s, but underwent a pronounced contraction into the western GoM (WGoM) for the reminder of the time-series. The model results suggest that the spatio-temporal dynamics of GoM cod have been driven by complex interactions of density-dependent and density-independent factors over the past three decades. Better knowledge of these dynamics can improve our understanding of the causality of abundance–occupancy and species–environment relationships and help to reduce error estimates for survey-based indices.

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 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.

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.

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