scholarly journals Abundance and distribution of Atlantic cod (Gadus morhua) in a warming southern New England

2020 ◽  
Vol 118 (2) ◽  
pp. 145-156
Author(s):  
Joseph A. Langan ◽  
M. Conor McManus ◽  
Douglas R. Zemeckis ◽  
Jeremy S. Colli
Keyword(s):  
New England ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Southern New England ◽  
Abundance And Distribution

Fish Catches and Long-Term Tidal Cycles in Northwest Atlantic Fisheries: A Nonlinear Regression Approach

1987 ◽  
Vol 44 (11) ◽  
pp. 1890-1897 ◽  
Author(s):  
Paul Cabilio ◽  
David L. DeWolfe ◽  
Graham R. Daborn
Keyword(s):  
New England ◽  
Nonlinear Regression ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Significant Negative Correlation ◽  
Clupea Harengus ◽  
Atlantic Menhaden ◽  
Melanogrammus Aeglefinus ◽  
Grand Banks

Selected long-term fisheries catch data from the New England – Fundy area and the Grand Banks were examined for concordance between changes in fish catches and the 18.6-yr nodal cycle of the tides using a nonlinear regression model. Significant positive correlations were found for Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), alewife (Alosa pseudoharengus), Atlantic herring (Clupea harengus harengus), and scallop (Placopecten magellanicus), with lag times that are biologically appropriate for the time from hatching to recruitment into the fishery. A significant negative correlation with the nodal cycle was evident for Atlantic menhaden (Brevoortia tyrannus), for which this area constitutes the most northerly part of its range. Cod catches on the Grand Banks showed no correlation with the nodal cycle. It is suggested that the correlations between the nodal cycle and the changes in fish catches are caused by correlated changes either in sea surface temperature or in productivity resulting from changes in the degree of vertical mixing.

Production Responses for Multi-species Fisheries

1981 ◽  
Vol 38 (11) ◽  
pp. 1393-1404 ◽  
Author(s):  
R. J. Agnello ◽  
L. G. Anderson
Keyword(s):  
New England ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Clupea Harengus ◽  
Categorical Variables ◽  
Melanogrammus Aeglefinus ◽  
Target Species ◽  
Northwest Atlantic ◽  
Fisheries Economics ◽  
Log Linear

Production equations are estimated for five major species of fish harvested in the Northwest Atlantic including Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), flounder (Pleuronectiformes), redfish (Sebastes marinus), and herring (Clupea harengus) using data collected by the International Commission for the Northeast Atlantic Fisheries from 1960 to 1974. A log-linear regression specification is used in which the relationship between catch of a vessel and several factors including days fished and vessel characteristics is estimated simultaneously. Vessel characteristics are represented as (0, 1) categorical variables, and include a variable indicating the target species designated by the caption. Various settings for the target species variables allow the estimated equation to represent either a by-catch or target catch equation. The production parameters estimated by the regressions are used to analyze the effects of current quotas set by the New England Fisheries Management Council. For some fleets we find a likelihood of idle capacity given the current quotas.Key words: fisheries economics, multi-species harvesting, Northwest Atlantic fisheries

Spawning of Atlantic cod (Gadus morhua) in the northern Gulf of St. Lawrence: a study of adult and egg distributions and characteristics

1997 ◽  
Vol 54 (1) ◽  
pp. 198-210 ◽  
Author(s):  
P Ouellet ◽  
Y Lambert ◽  
M Castonguay
Keyword(s):  
Gadus Morhua ◽  
Developmental Stages ◽  
Atlantic Cod ◽  
Relative Proportion ◽  
Class Strength ◽  
Acoustic Surveys ◽  
Abundance And Distribution ◽  
Trawl Catches ◽  
Dominant Influence

From 1993 to 1995, Atlantic cod (Gadus morhua) egg abundance and distribution, fisheries acoustic surveys, and analysis of trawl catches provided evidence of spawning for the northern Gulf of St. Lawrence cod stock at the same location off Newfoundland's west coast. From the relative proportion of spent fish and various developmental stages of cod eggs, spawning could not have started before the end of March or early April. Spawning started while cod were in dense shoals following a prespawning migration from Cabot Strait. Larger cod started to spawn earlier than smaller cod. In May 1994, cod dispersed soon after spawning began, and most of the spawning activity probably occurred as the fish migrated and scattered within the northern Gulf. Stage I cod eggs were distributed throughout the water column but higher concentrations were observed within the cold (<0°C) layer of the Gulf each year. We propose that water temperature could have a dominant influence on determination of year-class strength in the northern Gulf via its effect on egg development and survival.

scholarly journals Validation of a hidden Markov model for the geolocation of Atlantic cod

2017 ◽  
Vol 74 (11) ◽  
pp. 1862-1877 ◽  
Author(s):  
Chang Liu ◽  
Geoffrey W. Cowles ◽  
Douglas R. Zemeckis ◽  
Steven X. Cadrin ◽  
Micah J. Dean
Keyword(s):  
Markov Model ◽  
New England ◽  
Hidden Markov Model ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Hidden Markov ◽  
Data Depth ◽  
Environmental Data ◽  
Additional Species ◽  
Modified Method

Models developed to geolocate individual fish from data recorded by electronic tags often require major modification to be applied to new regions, species, or tag types due to variability in oceanographic conditions, fish behavior, and data resolution. We developed a model for geolocating Atlantic cod (Gadus morhua) off New England that builds upon an existing hidden Markov model (HMM) framework and addresses region- and species-specific challenges. The HMM framework contains a likelihood model that compares tag-recorded environmental data (depth, temperature, tidal characteristics) with those derived from an oceanographic model and a behavior model that constrains the horizontal movement of the fish. Validation experiments were performed on stationary tags, double-electronic-tagged fish (archival and acoustic tags), and simulated tracks. Known data, including fish locations and activity metrics, showed good agreement with those estimated by the modified approach and improvements in performance of the modified method over the original. The modified geolocation approach will be applicable to additional species and regions to obtain valuable movement information that is not typically available for demersal fishes.

scholarly journals Impacts of seasonal stock mixing on the assessment of Atlantic cod in the Gulf of Maine

2014 ◽  
Vol 71 (6) ◽  
pp. 1443-1457 ◽  
Author(s):  
Jie Cao ◽  
Samuel B. Truesdell ◽  
Yong Chen
Keyword(s):  
New England ◽  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Stock Assessment ◽  
Critical Role ◽  
Seasonal Migration ◽  
Assessment Model ◽  
Complex Population ◽  
Stock Mixing

Atlantic cod (Gadus morhua) in the Northwest Atlantic off New England and southern Atlantic Canada exhibit a complex population structure. This region has three independently assessed stocks [Georges Bank, Gulf of Maine (GOM), and the 4X stock], all of which are known to mix with each other. Assessments of these stocks, however, assume no interpopulation mixing. Using simulations, we evaluated impacts of ignoring mixing resulting from seasonal migrations on the GOM assessment. The dynamics of the three stocks were simulated according to different scenarios of interstock mixing, and a statistical catch-at-age stock assessment model was fitted to the simulated GOM data with and without mixing. The results suggest that, while mixing causes measurable bias in the assessment, under the conditions tested, this model still performed well. Of the bias that does exist, spawning-stock biomass estimates are relatively sensitive to mixing compared with estimates of recruitment and exploitation rate. The relative timing of seasonal migration of the three stocks plays a critical role in determining the magnitude of bias. The scale and trends among years in the bias were driven by how representative the catch and survey data were for the GOM stock; this representation changed with the mixing rates.

scholarly journals Stock structure of Atlantic cod (Gadus morhua) in West Greenland waters: implications of transport and migration

2004 ◽  
Vol 61 (6) ◽  
pp. 972-982 ◽  
Author(s):  
Marie Storr-Paulsen ◽  
Kai Wieland ◽  
Holger Hovgård ◽  
Hans-Joachim Rätz
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Stock Structure ◽  
West Greenland ◽  
The Past ◽  
Migration Behaviour ◽  
And Migration ◽  
Abundance And Distribution ◽  
Icelandic Waters

Abstract Atlantic cod in West Greenland waters have varied greatly in abundance and distribution in the past decades. Strong year classes yielded good catches inshore and offshore in the late 1980s, but since then cod have been nearly absent offshore and the inshore fishery has been depressed, though there has been a small increase inshore over the past few years. Different components contribute to the Greenland cod stock, and re-analysed tagging experiments indicate that migration behaviour differs between them. Inshore cod are sedentary, with almost no migration between different fjord systems. In contrast, there are many cases of alongshore migration of cod tagged on the offshore fishing banks. Further, observations have been made of occasional migrations from offshore to inshore, notably so in years of good recruitment originating from Icelandic waters.

scholarly journals Measurements of acoustic backscatter and density of captive Atlantic cod with synchronized 300-kHz multibeam and 120-kHz split-beam echosounders

2009 ◽  
Vol 66 (6) ◽  
pp. 1303-1309 ◽  
Author(s):  
Christopher W. D. Gurshin ◽  
J. Michael Jech ◽  
W. Huntting Howell ◽  
Thomas C. Weber ◽  
Larry A. Mayer
Keyword(s):  
Gadus Morhua ◽  
Gulf Of Maine ◽  
Atlantic Cod ◽  
Management Strategies ◽  
Acoustic Backscatter ◽  
Standard Sphere ◽  
Factors Affecting ◽  
Acoustic Data ◽  
Nylon Mesh ◽  
Abundance And Distribution

Abstract Gurshin, C. W. D., Jech, J. M., Howell, W. H., Weber, T. C., and Mayer, L. A. 2009. Measurements of acoustic backscatter and density of captive Atlantic cod with synchronized 300-kHz multibeam and 120-kHz split-beam echosounders. – ICES Journal of Marine Science, 66: 1303–1309. Effective management strategies for Atlantic cod (Gadus morhua) in the Gulf of Maine require stock assessments based on accurate estimates of its abundance and distribution. If multibeam echosounders are to provide data for such estimates, the relationship between acoustic backscatter and fish biology must be better understood. Working towards this goal, a series of acoustic measurements was made using a 120 kHz, split-beam echosounder (Simrad EK60) and a 300 kHz, multibeam echosounder (Kongsberg EM3002). The transducers from both systems were fixed to a platform over a submerged 98 m3 cage made of 5 cm stretched-nylon mesh. After standard-sphere calibrations, the cage was stocked with live, mature Atlantic cod, with a mean total length of 80.7 cm (range: 51.5–105.0 cm). The echosounders synchronously collected acoustic data, while the cod were monitored with two underwater video cameras. Cod were incrementally removed from the cage to provide a time-series of acoustic backscatter at four densities (n = 128, 116, 66, and 23). Backscatter measurements of cod are compared between echosounders and over time, and the factors affecting the acoustically derived density estimates are discussed. The benefits and limitations of the EM3002 are highlighted.

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