scholarly journals Spatial variance of mobile aquatic organisms: capelin and cod in Newfoundland coastal waters

1997 ◽  
Vol 352 (1353) ◽  
pp. 633-642 ◽  
Author(s):  
John K. Horne ◽  
David C. Schneider
Keyword(s):  
Time Scales ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Aquatic Organisms ◽  
Spatial Variance ◽  
Individual Organism ◽  
Commercial Population ◽  
Population Sizes ◽  
Passive Tracers

Spatial variance in the distribution of aquatic mobile organisms differs from that of passive tracers such as phytoplankton or water temperature. On average, spatial variance of phytoplankton scales with sample unit as L 2 or equivalently with frequency as f −2 . Limited evidence suggests that spatial variance in the distribution of mobile organisms is concentrated at relatively small scales, with little increase over larger scales: spatial variance scales as f −1 or less. We investigated whether spatial variance in distributions of a mobile predator, Atlantic cod ( Gadus morhua ), and a schooling prey, capelin ( Mallotus villosus ), also scale with frequency as f −1 . Acoustic surveys showed that at short time scales spatial variance in cod and capelin densities, as measured by spectral density, peaked at various scales ranging from 20 m to 10 km. At longer time scales, spatial variance of cod scaled as f −1.08 at resolutions finer than 90 m, while scaling as f −0.18 at coarser scales. Spatial variance of capelin scaled as f −1.1 at resolutions finer than 400 m, while scaling as f −0.20 at coarser scales. Spatial variance plots of krill and marine birds showed similar transitions from shallow to steep scaling. Shoaling, schooling and the aggregative response by predators to concentrations of prey were three processes hypothesized to influence spatial variance in distributions of mobile organisms. Numerical experiments showed that shoaling injects variance at large to intermediate scales, resulting in scalings flatter than f −1 . Additional experiments showed that schooling produces a transition from shallow to steep scaling as frequency increases. Spatial variance patterns in cod density were not due to aggregative responses by the predator to concentrations of capelin— there was no association, on average, at resolution scales from 20 m to 10 km. Exponent values for aquatic or terrestrial mobile organisms are predicted to be approximately two at the scale of an individual organism, 0.2 at scales that contain aggregations, and two at scales larger than that of populations. These findings suggest that relations between mobile organisms and large scale habitat variables will be difficult to detect, that stratified survey designs used to estimate commercial population sizes will be inefficient, and that rates of interaction between predator and prey will be underestimated if local observations are averaged over the spatial scale of the population.

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.

Mixing and migration of overwintering Atlantic cod (Gadus morhua) stocks near the mouth of the Gulf of St. Lawrence

1999 ◽  
Vol 56 (10) ◽  
pp. 1873-1881 ◽  
Author(s):  
S E Campana ◽  
G A Chouinard ◽  
J M Hanson ◽  
A Fréchet
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fishing Effort ◽  
Trace Element Composition ◽  
Eastern Canada ◽  
Management Area ◽  
Elemental Fingerprint ◽  
And Migration ◽  
Southern Flank

Millions of Atlantic cod (Gadus morhua) migrate distances of up to 500 km each fall to aggregate together in a small overwintering area off eastern Canada. Synoptic research vessel surveys carried out each January between 1994 and 1997 documented dense aggregations of cod along both flanks of the Laurentian Channel in each year, with estimated biomasses exceeding 100 000 metric tons. Using the trace element composition of the otolith ("otolith elemental fingerprint") as a natural tag, we found members of four populations to be present on the overwintering grounds in significant numbers, yet large-scale mixing among the populations was minimal. Individual trawl samples were often composed of a single population, suggesting that population integrity was maintained at a scale of <20 km. Cod from the southern Gulf of St. Lawrence dominated the population composition along the southern flank of the Channel, while cod from the northern Gulf dominated the northern flank; the distributions of both of these populations extended well to the east of their summer habitats and were remarkably similar across years. There was no evidence of large-scale mixing across the Channel. In light of the substantive migration of northern Gulf cod into the management area for the southern Newfoundland population, fishing effort off southern Newfoundland has the potential to reduce the size of the northern Gulf population.

Recruitment to Northwest Atlantic Cod (Gadus morhua) and Haddock (Melanogrammus aeglefinus) Stocks: Influence of Stock Size and Climate

1987 ◽  
Vol 44 (1) ◽  
pp. 26-39 ◽  
Author(s):  
J. Anthony Koslow ◽  
Keith R. Thompson ◽  
William Silvert
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Reproductive Output ◽  
Atlantic Cod ◽  
Low Frequency ◽  
Melanogrammus Aeglefinus ◽  
Northwest Atlantic ◽  
Biological Variables ◽  
Low Frequency Variability ◽  
Haddock Melanogrammus Aeglefinus

Year-class success of both Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) stocks in the northwest Atlantic exhibits large-scale coherence and low-frequency variability with apparent periodicities of 10–20 yr. Several physical and biological variables in the region exhibit similar large-scale coherence and apparent periodicity. Multiple regression analysis indicates that year-class success in northwest Atlantic cod stocks tends to be associated with large-scale meteorological patterns and offshore winds. Recruitment to most haddock stocks from the Scotian Shelf to Georges Bank is negatively associated with abundance of 0-group mackerel, which may be due to predation over winter and/or to a combination of environmental features including sea-surface temperature, large-scale atmospheric pressure systems, and freshwater outflows. Statistical analyses often did not define a unique set of variables that best predicted fishery recruitment due to widespread intercorrelations among environmental processes and the likelihood that not all relevant processes entered directly into the analyses. There is little evidence that stock reproductive output during the study period was significantly related to year-class success.

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.

scholarly journals Catch-and-release of Atlantic cod (Gadus morhua): post-release behaviour of acoustically pretagged fish in a natural marine environment

2015 ◽  
Vol 72 (2) ◽  
pp. 252-261 ◽  
Author(s):  
Keno Ferter ◽  
Klaas Hartmann ◽  
Alf Ring Kleiven ◽  
Even Moland ◽  
Esben Moland Olsen
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Sublethal Effects ◽  
Atlantic Cod ◽  
Small Scale ◽  
Marine Environments ◽  
Vertical Movements ◽  
Catch And Release ◽  
Diel Vertical Migrations ◽  
In The Wild

Studying the sublethal effects of catch-and-release (C&R) is challenging, as there are several potential sources of bias. For example, if behavioural alterations immediately after the release event are to be studied, separation of tagging effects from actual C&R effects is required, which is a challenge in the wild, particularly in marine environments. To investigate the effects of C&R on Atlantic cod (Gadus morhua) in their natural environment, 80 cod were caught in fyke nets, fitted with acoustic transmitters, and released. After recovery from tagging and handling for at least 14 days, nine individuals were recaptured and released at least once during experimental angling, following best release practice. All cod survived the C&R event and did not show any large-scale behavioural changes (i.e., changes in diel vertical migrations). However, analysis of small-scale vertical movements showed that three individuals underwent short-term alterations (e.g., reduced or increased swimming activity). This study showed that pretagging fish with acoustic transmitters before experimental angling is an option when investigating fish behaviour immediately after the release event in marine environments. Moreover, release guidelines for cod should be developed, as cod can recover quickly if caught in shallow waters (<20 m) and properly handled and released.

Spatiotemporal variations in juvenile mortality and cohort strength of Atlantic cod (Gadus morhua) off Newfoundland and Labrador

2020 ◽  
Vol 77 (3) ◽  
pp. 625-635
Author(s):  
Fan Zhang ◽  
Rick M. Rideout ◽  
Noel G. Cadigan
Keyword(s):  
Newfoundland And Labrador ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Survival Rates ◽  
Mortality Rates ◽  
Spatiotemporal Variations ◽  
Juvenile Mortality ◽  
Modelling Framework ◽  
Fish Recruitment

Juvenile mortality is an important factor affecting the spatiotemporal dynamics of fish recruitment, but estimation of the spatiotemporal variations in juvenile mortality rates remains challenging. We developed a state-space metapopulation dynamics model to simultaneously estimate spatiotemporal variations in juvenile mortality rates and cohort strength and applied this general modelling framework to data from multiple surveys for juvenile (ages 2–5) Atlantic cod (Gadus morhua) stocks off Newfoundland and Labrador (NL). We found large-scale synchronized dynamics of decreasing juvenile mortality rates and increasing cohort strength from offshore surveys off eastern and southeastern NL, suggesting improving reproduction and survival rates for juvenile cod. No synchronized patterns of juvenile mortality rates and cohort strength were detected for cod stocks off southern and western NL, indicating more complex cod population spatial structures in those areas. Our study demonstrates the potential of juvenile mortality to cause temporally variable and spatially synchronized dynamics of fish recruitment, and the spatial patterns of juvenile mortality and cohort strength indicate some potential mismatch between cod population structure and current management units off NL.

Chemical–environment interactions affecting the risk of impacts on aquatic organisms: A review with a Canadian perspective — interactions affecting vulnerability

2008 ◽  
Vol 16 (NA) ◽  
pp. 19-44 ◽  
Author(s):  
Catherine M. Couillard ◽  
Simon C. Courtenay ◽  
Robie W. Macdonald
Keyword(s):  
Large Scale ◽  
Municipal Wastewater ◽  
Environmental Changes ◽  
Environmental Variability ◽  
Atlantic Cod ◽  
Aquatic Organisms ◽  
The Body ◽  
Toxic Chemicals ◽  
Aquatic Species ◽  
Species Vulnerability

Environmental change can increase the vulnerability of aquatic species to toxic chemicals by challenging an organism’s aptitude to respond to chemicals or to repair toxic injury or by modifying animal behaviours like migration or predation. On the other hand, xenobiotics may affect the capacity of aquatic species to adapt to environmental challenges that come with change (e.g., pathogens, temperature). Across Canada we have identified a number of circumstances where chemicals and environmental variability have likely worked together to affect vulnerability of aquatic organisms. For example in the Maritimes, exposure to municipal wastewater or bleached kraft pulp mill effluent altered immune function in bivalves and increased their risk of developing haemocytic neoplasia, a disease known to cause high mortality. Northwest Atlantic cod stocks have experienced large-scale changes in environment and exhibit marked seasonal cycles in energy reserves. The risk associated with subsequent redistribution of persistent chemicals in the body together with nutritional deficiency is presently under evaluation since it could affect the recovery of these endangered stocks. In the Great Lakes, the introduction of an invasive fish species, the alewife, modified the diet of salmonids, which led to a deficiency of the vitamin thiamine in eggs causing early mortality. Contaminants may interact with thiamine deficiency and thus critically impair recruitment of salmonids. Viewing the risks presented by toxic chemicals from the point of view of species vulnerability, offers managers opportunities to mitigate such risks, for example, through habitat, ocean and fisheries management. Further research is needed to develop biomarkers of vulnerability, identify most vulnerable life stages and populations, to understand the interactions between global environmental changes, nutritional status, pathogens and toxic chemicals, and to develop integrated approaches to manage vulnerability of aquatic ecosystems to toxic chemicals.

scholarly journals Recolonization history and large-scale dispersal in the open sea: the case study of the North Atlantic cod, Gadus morhua L.

2008 ◽  
Vol 94 (2) ◽  
pp. 315-329 ◽  
Author(s):  
CHRISTOPHE PAMPOULIE ◽  
MAGNÚS ÖRN STEFÁNSSON ◽  
THÓRA DÖGG JÖRUNDSDÓTTIR ◽  
BRET S. DANILOWICZ ◽  
ANNA KRISTÍN DANÍELSDÓTTIR
Keyword(s):  
North Atlantic ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
The North ◽  
Open Sea ◽  
The North Atlantic

Local-Scale versus Large-Scale Factors Affecting Recruitment

1991 ◽  
Vol 48 (6) ◽  
pp. 1003-1006 ◽  
Author(s):  
Edward B. Cohen ◽  
David G. Mountain ◽  
Robert O'Boyle
Keyword(s):  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Scale Effects ◽  
Melanogrammus Aeglefinus ◽  
Data Set ◽  
Factors Affecting ◽  
Scale Factors ◽  
Haddock Melanogrammus Aeglefinus ◽  
Recruitment Time

Recent analyses of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) stocks in the northwest Atlantic have indicated that large-scale factors (several hundred to thousands of kilometres) dominate over effects operating on more local scales (10 to a few hundred kilometres} in determining recruitment patterns for these stocks. Adding additional years and additional stocks to the data set, the recruitment time series for cod and haddock have been reexamined. A first differencing technique was used to remove trends in the data. The results indicate that while large-scale effects probably do affect recruitment, the dominant factors are operating on more local scales and correlations are strongest for neighboring stocks.

scholarly journals Long-term shift in coastal fish communities before and after the collapse of Atlantic cod (Gadus morhua)

2015 ◽  
Vol 73 (5) ◽  
pp. 1415-1426 ◽  
Author(s):  
J. Scott P. McCain ◽  
Deneen J. Cull ◽  
David C. Schneider ◽  
Heike K. Lotze
Keyword(s):  
Fish Community ◽  
Large Scale ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Substantial Reduction ◽  
Fish Communities ◽  
Coastal Habitat ◽  
Coastal Fish ◽  
Before And After

Abstract The collapse of the Northwest Atlantic cod (Gadus morhua) stocks in the early 1990s led to widespread ecological changes offshore. Changes in coastal fish communities are less known, largely due to the lack of historical records and long-term, standardized research surveys in coastal ecosystems. We aimed to overcome this with a unique dataset known as the Fleming survey. From 1959 to 1964, a systematic beach-seine survey was conducted to examine juvenile cod abundance in 84 bays (42 of which were consistently sampled and therefore analysed) along the east coast of Newfoundland. In addition to cod, all other fish collected in the seines were recorded. These surveys were repeated from 1992 to 1996 after the cod collapse, and document a substantial reduction in a dominant inshore species—juvenile Atlantic cod. We show that total fish abundance declined significantly with the decrease of cod, whereas Shannon diversity and species evenness significantly increased. Species richness increased in some regions but decreased in others. We also found significant changes in the composition of the fish community likely due to a combination of release from predation from fewer large cod feeding in inshore areas as well as a release from competition from fewer juvenile cod occupying the coastal habitat. Region and the presence of vegetated habitats also significantly influenced the fish community. This study shows a strong reorganization of coastal fish communities after a large-scale fisheries collapse with implications for ecosystem-based and cross-ecosystem management.

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