Outcome of an inshore spawning event by northern Atlantic cod (Gadus morhua) at a low stock level

1998 ◽  
Vol 55 (10) ◽  
pp. 2283-2291 ◽  
Author(s):  
R K Smedbol ◽  
D C Schneider ◽  
J S Wroblewski ◽  
D A Methven
Keyword(s):  
Gadus Morhua ◽  
Direct Evidence ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Spawning Aggregation ◽  
Stock Level ◽  
Egg Density ◽  
Northern Atlantic ◽  
Northeast Coast ◽  
Trinity Bay

A large spawning aggregation of northern Atlantic cod (Gadus morhua) was discovered in a fjord of Trinity Bay, Newfoundland, in April 1995, 3 years after the collapse of this stock and 1 year after the last offshore spawning aggregation was recorded. We hypothesized that spawning by this aggregation would increase the abundance/density of eggs and settled 0-group juveniles above the level of spawning in the bay during recent years. Data from 1995 were compared with ichthyoplankton and postsettlement juvenile surveys conducted in recent years. Egg density was significantly higher in 1995 than the pooled average of two recent years (1991 and 1993). The hypothesized increase in numbers of postsettlement age 0 fish was tested at three different spatial scales: the entire northeast coast of Newfoundland, individual bays, and areas within Trinity Bay. There was no detectable increase in catches of settled age 0 juveniles at any spatial scale. Consequently, while this large spawning aggregation produced locally high egg concentrations, it did not lead to a detectable increase in abundance of newly settled age 0 juveniles in coastal nursery areas. This study did not provide any direct evidence for an increase in recruitment in the inshore region due to the spawning output of locally abundant spawners in Trinity Bay.

Isolation or metapopulation: whence and whither the Smith Sound cod?

2011 ◽  
Vol 68 (1) ◽  
pp. 152-169 ◽  
Author(s):  
George A. Rose ◽  
R. John Nelson ◽  
Luiz G.S. Mello
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Genetic Data ◽  
Spawning Aggregation ◽  
Genetic Isolation ◽  
Coastal Fisheries ◽  
Data History ◽  
Northern Atlantic ◽  
First Maturity ◽  
Year 2000

In April 1995, a spawning aggregation of “northern” Atlantic cod ( Gadus morhua ) (10 000 t) appeared in Smith Sound, Newfoundland, growing to 26 000 t by year 2000. The origin of the founder year classes (primarily the 1990 and 1992 year classes) and potential for expansion remains controversial, with genetic isolation used to justify reopenings of coastal fisheries. We investigated the origin using historical, demographic, and genetic data. History provided no evidence of large aggregations before 1995. Demographics in the early 1990s suggested few spawners in Smith Sound, but many in the adjacent Bonavista Corridor. The strong 1990 year class was not evident until 1995 and the strong 1992 year class until 1997 (both age 5 and first maturity). Genetic study of six microsatellite loci from 791 cod from overwintering aggregations in Smith Sound and offshore regions indicated little to no differentiation (FST) among southern groups (Smith Sound, Bonavista Corridor, Halibut Channel). These results provide a perspective that these groups comprise a metapopulation and that the Smith Sound aggregation arose not from self-recruitment but immigration. By 2009, the aggregation had dispersed, with large concurrent increases in the Bonavista Corridor.

scholarly journals Regional variation in otolith geochemistry of juvenile Atlantic cod (Gadus morhua) in coastal Newfoundland

2016 ◽  
Vol 73 (10) ◽  
pp. 1507-1519 ◽  
Author(s):  
Ryan R.E. Stanley ◽  
Claudio DiBacco ◽  
Simon R. Thorrold ◽  
Paul V.R. Snelgrove ◽  
Corey J. Morris ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Environmental Variability ◽  
Atlantic Cod ◽  
Environmental Influence ◽  
Spatial Scales ◽  
Early Life History ◽  
Otolith Chemistry ◽  
Geographic Patterns ◽  
Assignment Success ◽  
Scale Classification

We examined spatial variation in otolith geochemistry as a natural tag in juvenile Atlantic cod (Gadus morhua) to resolve geographic patterns during early life history. Individuals from 54 inshore sites spanned five embayments in eastern Newfoundland. Otolith composition differed at all spatial scales and related inversely to spatial scale. Classification analysis revealed increasing discrimination at coarser spatial scales: site (26%–58%), bay (49%), and coast (76%). Assignment success declined by ∼10% per added site with increasing sampling sites per bay, demonstrating fine-scale (<100 km) variation. When we partitioned environmental variability from observed otolith chemistry using predictive models, assignment success improved by 56%, 14%, and 5% for site, bay, and coast, respectively. Our results demonstrate environmental influence on spatial structure of otolith chemistry and illustrate the importance of resolving baseline variability in otolith chemistry when conducting assignment tests. Collectively, our results describe the potential utility of juvenile otolith composition in evaluating contributions of subpopulations to the Northwest Atlantic cod stock and highlight important limitations imposed by environmental variation at scales less than 100 km.

Small-scale temporal and spatial variation in Atlantic cod (Gadus morhua) life history

2003 ◽  
Vol 60 (9) ◽  
pp. 1111-1121 ◽  
Author(s):  
Tara M McIntyre ◽  
Jeffrey A Hutchings
Keyword(s):  
Body Mass ◽  
Life Histories ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Gonadosomatic Index ◽  
Small Scale ◽  
Hepatosomatic Index ◽  
Georges Bank ◽  
High Fecundity

Life histories of Atlantic cod (Gadus morhua) from the Gulf of St. Lawrence south to Georges Bank differ significantly through time and space. Within the Southern Gulf, fecundity per unit body mass differed by more than 40% over short (2 years) and long (42–45 years) periods of time. Significant variation in size-specific fecundity is also evident among populations: Southern Gulf cod produce almost 30% more eggs per unit body mass than those on Georges Bank, whereas fecundity of Scotian Shelf cod is almost half that of cod in Sydney Bight. Compared with those on Georges Bank, Southern Gulf cod life histories are characterized by high fecundity, late maturity, high gonadosomatic index, and large eggs. Relative to the influence of body size, neither temporal nor spatial differences in fecundity can be attributed to physiological condition, as reflected by liver weight, hepatosomatic index, and Fulton's K. Delayed maturity and higher reproductive allotment among Southern Gulf cod can be explained as selection responses to slower growth, higher prereproductive mortality, and fewer lifetime reproductive events. Patterns of covariation in heritable, fitness-related traits suggest the existence of adaptive variation and evolutionarily significant units at spatial scales considerably smaller than the species range in the Northwest Atlantic.

Survival of Northern Atlantic Cod (Gadus morhua) Eggs and Larvae when Exposed to Ice and Low Temperature

1992 ◽  
Vol 49 (12) ◽  
pp. 2588-2595 ◽  
Author(s):  
Paul F. Valerio ◽  
Sally V. Goddard ◽  
Ming H. Kao ◽  
Garth L. Fletcher
Keyword(s):  
Low Temperature ◽  
Newfoundland And Labrador ◽  
Direct Contact ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Ice Crystals ◽  
Freeze Resistance ◽  
Northern Cod ◽  
Northern Atlantic ◽  
Eggs And Larvae

Freeze resistance of eggs and larvae of Atlantic cod (Gadus morhua) from the northern cod stock was investigated to determine whether ice contact could affect survival during the spring spawning season off Newfoundland. Egg and larval homogenates did not appear to contain antifreeze proteins (mean freezing points −0.78 and −0.88 °C, respectively). However, cod eggs did not freeze at −1.8 °C in icy aerated seawater, could be undercooled to −4.0 °C in ice, and froze at temperatures between −4.1 and −1 7 °C; freeze resistance depended on the integrity of the chorion. Larvae withstood undercooling to −1.8 °C, provided they were not brought into direct contact with ice crystals, if directly touched with ice, larvae froze at −1.36 °C (feeding stage) or −1.34 °C (yolk-sac), approximately 0.5 °C lower than would be expected from the freezing temperatures of their body fluids. The nature of their external epithelium and delayed development of sensitive gill structures below 0 °C may contribute to larval freeze resistance. Cod eggs and larvae are found in spring off Newfoundland and Labrador, when sea temperatures can be as low as −1.8 °C and ice cover extensive. While cod eggs are remarkably freeze resistant, such environmental conditions may cause freezing mortalities in larval cod.

scholarly journals Otolith chemistry and redistributions of Northern cod: evidence of Smith Sound – Bonavista Corridor connectivity

2018 ◽  
Vol 75 (12) ◽  
pp. 2302-2312 ◽  
Author(s):  
Victoria Neville ◽  
George Rose ◽  
Sherrylynn Rowe ◽  
Robyn Jamieson ◽  
Glenn Piercey
Keyword(s):  
Oxygen Isotope ◽  
Gadus Morhua ◽  
Direct Evidence ◽  
Atlantic Cod ◽  
Otolith Chemistry ◽  
Stable Oxygen Isotope ◽  
Metapopulation Structure ◽  
Northern Cod ◽  
Stable Oxygen ◽  
Placentia Bay

Stable oxygen isotope assays of otoliths (δ18Ooto) from migrant Atlantic cod (Gadus morhua Linnaeus, 1758) that overwintered in Smith Sound, Newfoundland, during 1995–2006 differed from those of nonmigrating summer residents and cod from Placentia Bay and Halibut Channel but did not differ from those of cod from the adjacent offshore Bonavista Corridor in summer. All fish sampled were of the 1990 year class (founder of the Smith Sound aggregation) at ages 8–10 years. Hence, overwintering Smith Sound and summering Bonavista Corridor cod likely experienced similar temperatures and salinities in each year of life, representing different migration stages of an intermixed group. Moreover, predictions of δ18Ooto from near-bottom ocean temperatures and salinities differed between inshore and offshore sites and, in general, matched observed signatures of inshore and offshore cod. The Bonavista Corridor cod, however, were an exception, having δ18Ooto signatures suggestive of inshore exposure. Our findings provide direct evidence of metapopulation structure in the Northern cod and are consistent with offshore rebuilding having been spurred by dispersal of cod from inshore Smith Sound.

Depth-dependent vertebral number of Atlantic cod (Gadus morhua) on the Magdalen Shallows and Scotian Shelf: stock mixing or microgeographic trends within populations?

2000 ◽  
Vol 57 (12) ◽  
pp. 2393-2401 ◽  
Author(s):  
D P Swain ◽  
K T Frank
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Spatial Scales ◽  
Relative Length ◽  
Scotian Shelf ◽  
Age Classes ◽  
Vertebral Number ◽  
Size At Age ◽  
Stock Mixing ◽  
Summer Feeding

We examined spatial variation in the vertebral number of Atlantic cod (Gadus morhua) during the summer feeding season in the southern Gulf of St. Lawrence and on the Scotian Shelf. Mean vertebral number increased significantly with depth in the southern Gulf and on the northeastern Scotian Shelf but not on the southwestern Scotian Shelf. In the southern Gulf, where sampling was most extensive, mean vertebral number increased steadily as depth increased from 25 m to over 175 m. Mean vertebral number was also strongly related to relative length within age-classes, with the larger fish at age having more vertebrae. However, the association between vertebral number and depth could not be attributed to confounding between depth and size at age. These results indicate either unexpected mixing between neighbouring cod populations or unexpected structure at fine spatial scales within cod populations.

Movements of Atlantic Cod (Gadus Morhua) Within the Spring Thermocline in Trinity Bay, Newfoundland

1995 ◽  
Vol 75 (2) ◽  
pp. 265-284 ◽  
Author(s):  
J.S. Wroblewski ◽  
Sally V. Goddard ◽  
R. Kent Smedbol ◽  
Wade L. Bailey
Keyword(s):  
Surface Waters ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Antifreeze Protein ◽  
Early Spring ◽  
Subzero Temperature ◽  
Cold Adapted ◽  
Protein Levels ◽  
Trap Fishery ◽  
Trinity Bay

Using depth-telemetering, sonic tags orally inserted into the stomachs of Gadus morhua (Pisces: Gadiformes) found over-wintering in Trinity Bay, Newfoundland, the movements of individual fish were observed as surface waters warmed in early spring. Physiological measurements (antifreeze protein levels in the blood) indicate that many cold-adapted, bay cod change their thermal regime at this time. Fish acclimatized to subzero water temperatures enter the newly-formed thermocline and become available to a cod trap fishery. Most sonically-tagged fish resided in 0–1°C waters along the shoreline. Tracking data confirmed indications from declining antifreeze protein levels that cold-adapted cod, having moved into shallow waters in early spring, do not return to deeper, subzero-temperature waters for any appreciable time. At night some cod swam pelagically near the surface. Fish moved at times in the same direction as the tidal current, but ground speeds were several times greater than current velocities. Nocturnal pelagic swimming was also observed during the summer when temperatures within the thermocline exceeded 10°C.

Cods for sale Do we know what we are buying?

DNA Barcodes ◽  
2015 ◽  
Vol 3 (1) ◽  
Author(s):  
Christian Lambarri ◽  
Héctor Espinosa ◽  
Armando Martínez ◽  
Ariana Hernández
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
The United States ◽  
High Rate ◽  
Coi Gene ◽  
High Price ◽  
Blue Shark ◽  
Salted Fish ◽  
Northern Atlantic ◽  
Near Threatened

AbstractThe Atlantic Cod Gadus morhua is fished in Northern Atlantic and Arctic waters. In Mexico cod is imported from Norway and the United States, and is traditionally eaten at Christmas and Easter. In Mexico City several stores sell dry-salted cod, but due to the high price of the imported Atlantic Cod, other fish species are sold. In this project we examined six samples of dried-salted fish from different stores and used DNA barcoding of the COI gene to corroborate the identity of the product sold as Atlantic Cod. Barcoding revealed that only two of the six samples (33%) were Atlantic cod, with two being Ling, one Alaska Pollock, and one Blue Shark. The high rate of mislabeling (67%) is a major concern. It is especially worrying that Blue Shark is being sold as Atlantic cod, since the Blue Shark is listed as a near-threatened species by the IUCN. We must be aware of the damages that overexploitation and uninformed consumption cause to cod and shark populations. There needs to be stricter policing of seafood product labeling in México.

Overwintering of Adult Northern Atlantic Cod (Gadus morhua) in Cold Inshore Waters as Evidenced by Plasma Antifreeze Glycoprotein Levels

1994 ◽  
Vol 51 (12) ◽  
pp. 2834-2842 ◽  
Author(s):  
Sally V. Goddard ◽  
J. S. Wroblewski ◽  
C. T. Taggart ◽  
K. A. Howse ◽  
W. L. Bailey ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Antifreeze Glycoproteins ◽  
Cold Temperatures ◽  
Antifreeze Glycoprotein ◽  
Trap Fishery ◽  
In The Wild ◽  
History Of ◽  
Inshore Waters ◽  
Trinity Bay

Adult Atlantic cod (Gadus morhua) are known to produce antifreeze glycoproteins in response to cold temperatures. Our laboratory studies demonstrated that blood plasma levels in adult cod were positively correlated with the number of days they spent in subzero water. Between April 1991 and June 1993, we monitored concentrations of antifreeze glycoproteins in the plasma of late juvenile and adult cod in Trinity Bay, Newfoundland, and used the results to estimate how long cod had been exposed to low water temperatures. A consideration of these data in conjunction with detailed temperature profiles of the area taken over the course of the study allowed us to deduce the distribution of cod in relation to the temperature field. This study provides evidence that (1) blood antifreeze glycoprotein levels can be used to deduce the recent thermal history of cod in the wild and (2) after their inshore summer feeding period, considerable numbers of adult cod overwintered inshore in Trinity Bay in subzero water, producing antifreeze glycoproteins as temperatures fell below 0 °C. From May onwards, "cold-adapted" cod moved into warming surface waters, where they became available to an early inshore trap fishery.

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