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COSEWIC assessment and update status report on the Atlantic Cod in Canada

Newfoundland & Labrador Population

Cod in this population combine the stocks identified for management purposes by DFO as:  (1) Northern Labrador cod (NAFO Divisions 2GH; (2) "Northern" cod, i.e., those found off southeastern Labrador, the Northeast Newfoundland Shelf, and the northern half of Grand Bank (NAFO Divisions 2J3KL); and (3) Southern Grand Bank cod (NAFO Divisions 3NO).  Temporal trends in abundance for each of these stocks are presented separately in APPENDIX 1.

Calculated from the means for each of its constituent stocks (APPENDIX 1), generation time is estimated to be 11.0 years for this Population, yielding a three-generation time period of 33 years.  Abundance data represent the sum of the VPA estimates of mature population size for each of the stocks included in this population.  The time period for which data were available for both stocks was 1962 to 2001.  These are the data included here for the purpose of estimating rates of population decline.

Within the northern cod stock, there are limited temporal data that allow one to evaluate trends in abundance for cod found in inshore waters.  These data include:  DFO research surveys conducted annually (except 1999) since 1996 over an area of 6,400 square nautical miles; hydro-acoustic surveys of cod in Smith Sound, Trinity Bay, conducted by George Rose (Memorial University of Newfoundland) since 1995; DFO-sponsored sentinel survey catch rate data obtained by fishers; and local knowledge of fish harvesters.  According to DFO's inshore survey data, catch rates of cod aged 5 years and older show an overall decline (correlation coefficient between log(catch rate) and year is negative) between 1996 and 2002 (Lilly et al. MS2003, unpublished data presented at the DFO Zonal Assessment Meeting, 20 February 2003).  Hydro-acoustic estimates of cod biomass in Smith Sound (where the largest spawning component of northern cod is now located), including data obtained in January 2003, also have declined in recent years, according to George Rose (personal communication, DFO Zonal Assessment Meeting, 20 February 2003).  Sentinel survey gillnet catch rates throughout the inshore waters of northeastern Newfoundland in 2001 and 2002 were either the lowest or second lowest since the beginning of the fisher-conducted surveys in 1995 (DFO 2002; Jarvis and Dalley MS2003, unpublished data presented at the DFO Zonal Assessment Meeting, 20 February 2003).  Sentinel survey linetrawl catch rates for Trinity and Bonavista Bays in 2001 were the lowest in the time series (DFO 2002).  Ninety-five percent of fish harvesters who responded to a questionnaire sent to Professional Fish Harvesters Committees along the northeast coast of Newfoundland reported that the Sentinel catch rates corresponded closely with trends in cod abundance observed by fish harvesters (Jarvis and Stead 2001).  In 2002, a majority of fish harvesters reported that commercial catch rates and sounder recordings were the same as or lower than they were in 2001, that the amount of bait fish present in 2002 was the same as or less than that in 2001, and that cod were in average to good condition in 2001 (Jarvis and Dalley MS2003, unpublished data presented at the DFO Zonal Assessment Meeting, 20 February 2003; see also Jarvis and Stead 2001).

Irrespective of the estimated age at maturity or data source, the 3-generation decline experienced by the Newfoundland & Labrador Population was 97% (Figures 6 and 7).

Age at maturityGeneration
time (yr)

Data Source

Data type

Time period

Rate of change
unfished state11.0VPAnumber of individuals1968-2001−97%

Area of occupancy for this population declined from approximately 365,000 km2 in the early 1960s to approximately 290,000 km in recent years, a decline of roughly 21% (Smedbol et al. 2002).

 

Laurentian North population

Cod in this population combine the stocks identified for management purposes by DFO as (1) St. Pierre Bank (NAFO Division 3Ps) and (2) Northern Gulf of St. Lawrence (NAFO Divisions 3Pn4RS).  Temporal trends in abundance for each of these stocks are presented separately in APPENDIX 1.

Calculated from the means for each of its constituent stocks (APPENDIX 1), generation time is estimated to be 10 years for this Population, yielding a three-generation time period of 30 years.

Abundance data represent the sum of the VPA estimates of mature population size for each of the stocks included in this population.  The time period for which data were available for both stocks was 1974 to 2001.  These are the data included here for the purpose of estimating rates of population decline.

Figure 6.  Temporal variation in the estimated number of mature individuals in two cod stocks in the Newfoundland and Labrador population.

 

Figure 6.  Temporal variation in the estimated number of mature individuals in two cod stocks in the Newfoundland & Labrador population.  Data for northern cod (NAFO Divisions 2J3KL) and southern Grand Bank cod (Divisions 3NO) are shown in panel (a).  The combined data for the population are shown in panel (b).

Figure 7.  Plot of loge (abundance, Nt) versus time (t, in years) for the Newfoundland & Labrador population. 


Figure 7.  Plot of loge (abundance, Nt) versus time (t, in years) for the Newfoundland & Labrador population.  The line represents the linear regression equation of ln(Nt) = 232.19 − 0.11t (r2 = 0.77, p<0.0001).  Based on this equation, the rate of decline of the Newfoundland & Labrador population over the three-generation time period of 33 years is (1−exp(−0.11*33))*100, which equals 97%.

The Laurentian North population has declined 81% over the past three generations.  This trend is driven primarily by the decline experienced by the Northern Gulf stock (3Pn4RS).  By comparison, the St. Pierre Bank stock (3Ps) has changed relatively little since 1974 (Figure 8).

Age at maturityGeneration
time (yr)

Data Source

Data type

Time period

Rate of change
unfished state10VPAnumber of individuals1974-2001−81%

Area of occupancy data for this population overlap only for the years 1991 to 2001.  During this period, area of occupancy declined marginally from approximately 96,000 km2 to approximately 89,000 km2, a decline of roughly 7% (Smedbol et al. 2002).

Figure 8.  Temporal variation in the estimated number of mature individuals in two cod stocks in the Laurentian North population. 


Figure 8.  Temporal variation in the estimated number of mature individuals in two cod stocks in the Laurentian North population.  Data for northern Gulf cod (NAFO Divisions 3Pn4RS) and St. Pierre Bank cod (Subdivision 3Ps) are shown in panel (a).  The combined data for the population are shown in panel (b).

 

Maritimes population

Cod in this population combine the stocks identified for management purposes by DFO as:  (1) Southern Gulf of St. Lawrence (NAFO Division 4T); (2) Cabot Strait (NAFO Division 4Vn); (3) Eastern Scotian Shelf (NAFO Divisions 4VsW); (4) Bay of Fundy/Western Scotian Shelf (NAFO Division4X); and (5) cod found on the Canadian portion of Georges Bank (NAFO Division 5Zej,m).  Temporal trends in abundance for each of these stocks are presented separately in APPENDIX 1.

Calculated from the means for each of its constituent stocks (APPENDIX 1), generation time is estimated to be 9 years for this population, yielding a three-generation time period of 27 years.

Abundance data represent the sum of the VPA estimates of mature population size for each of the stocks included in this population.  The time period for which data were available for most stocks was 1974 to 1997 (this being the last year in which a VPA was conducted for Eastern Scotian Shelf cod).  These are the data included here for the purpose of estimating rates of population decline.

The Maritimes population has declined 14% over the past three generations.  However, there is some discordance in the temporal trends among the stocks in this population (Figure 9).  The dominant stock in this population (Southern Gulf; 4T) was actually at higher levels in 1997 than it was in 1974.  By contrast, Eastern Scotian Shelf cod (4VsW) is (in 2002) at historically low levels, according to the research survey indices, which are not part of the present calculation.

Age at maturityGeneration
time (yr)

Data Source

Data type

Time period

Rate of change
unfished state9VPAnumber of individuals1974-1997−14%

Area of occupancy for this population declined from approximately 179,000 km2 in the early 1970s to approximately 140,000 km2 , in recent years, a decline of roughly 22% (Smedbol et al. 2002).


Figure 9.  Temporal variation in the estimated number of mature individuals in cod stocks in the Maritimes population.


Figure 9.  Temporal variation in the estimated number of mature individuals in cod stocks in the Maritimes population.  Data for individual stocks, as identified in the status report, are shown in panel (a).  The combined data for the population are shown in panel (b).

Figure 10.  Temporal variation in the estimated number of mature individuals in the Northern Labradorcod stock (NAFO Divisions 2GH)


Figure 10.  Temporal variation in the estimated number of mature individuals in the Northern Labradorcod stock (NAFO Divisions 2GH).