Evidence for inshore spawning of northern Atlantic cod (Gadus morhua) in Trinity Bay, Newfoundland, 1991-1993

1997 ◽  
Vol 54 (S1) ◽  
pp. 177-186 ◽  
Author(s):  
R K Smedbol ◽  
J S Wroblewski
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Northern Atlantic ◽  
Trinity Bay

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.

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.

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.

Movements of farmed and wild Atlantic cod (Gadus morhua) released in Trinity Bay, Newfoundland

1996 ◽  
Vol 124 (4) ◽  
pp. 619-627 ◽  
Author(s):  
J. S. Wroblewski ◽  
R. K. Smedbol ◽  
C. T. Taggart ◽  
S. V. Goddard
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Trinity Bay

Temporal changes in harvesting dynamics of Canadian inshore fisheries for northern Atlantic cod, Gadus morhua

2000 ◽  
Vol 57 (4) ◽  
pp. 805-814 ◽  
Author(s):  
Jeffrey A Hutchings ◽  
Mark Ferguson
Keyword(s):  
Gadus Morhua ◽  
Atlantic Cod ◽  
Fishing Effort ◽  
Temporal Changes ◽  
Catch Rate ◽  
Fish Stock ◽  
Small Fish ◽  
Trap Design ◽  
Northern Atlantic ◽  
Unreported Catches

We quantified temporal changes in catch rate, fishing effort, and catch misreporting for two sectors of the fixed-gear fishery for Newfoundland's northern Atlantic cod, Gadus morhua, from 1980 to 1991, the year preceding the stock's commercial fishing moratorium. Over the 12-year period, fishermen reported catch rate declines of 40 and 75% in the trap and gillnet fisheries, respectively, associated with significant increases in nominal fishing effort. Additional changes to effort included smaller gillnet and trap mesh sizes, larger traps, longer soak times, and modifications to trap design to increase catch retention probabilities. Compared with the early 1980s, unreported catches among inshore fishermen may have trebled by the late 1980s and early 1990s due to longer gillnet soak times, increased gear selectivity for small fish, and declining availability of fish of marketable size. These patterns in harvesting dynamics are consistent with the hypothesis that the decline of northern cod was gradual and that increased rates of catch misreporting contributed to increases in fishing mortality. The concomitants of declining fixed-gear catch rate, increasing quantitative and qualitative fishing effort, increased selectivity for smaller fish, and increasing levels of unreported catches may represent general correlates of imminent fish stock collapses.

Observations of Adult Atlantic Cod (Gadus morhua) Overwintering in Nearshore Waters of Trinity Bay, Newfoundland

1994 ◽  
Vol 51 (1) ◽  
pp. 142-150 ◽  
Author(s):  
J. S. Wroblewski ◽  
Wade L. Bailey ◽  
Kristine A. Howse
Keyword(s):  
Minimum Distance ◽  
Short Range ◽  
Gadus Morhua ◽  
Atlantic Cod ◽  
Nearshore Zone ◽  
Island Region ◽  
Northern Cod ◽  
Near Shore ◽  
Surgical Implantation ◽  
Trinity Bay

In the Random Island region of Trinity Bay, Newfoundland, individual adult Atlantic cod (Gadus morhua) with surgically implanted sonic transmitters were repeatedly relocated during the winter of 1990–91. Cod remained near shore, where seawater temperatures were as low as −1.5 °C. These fish did not move in the fall to offshore continental shelf waters as do most northern cod, nor did they move into the deeper waters of Trinity Bay that were slightly warmer than those in the nearshore zone. Of 12 cod released with transmitters in the fall and early winter, two were caught by local inshore fishermen the following spring, providing evidence that adult cod that overwinter nearshore become available to the spring inshore fishery. Another three were caught within a year of release. One fish was hooked in Fortune Bay on the southern coast of Newfoundland, having traveled a minimum distance of 305 nautical miles. These results demonstrate that northern cod can survive the surgical implantation of transmitters for at least a year and that this method is a valid technique for studying the behavior of northern cod. The main limitation to our sonic tracking was the relatively short range of signal reception (<1 nautical mile).

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