Marine graphic descriptors

Sea Temperature, Newfoundland and Labrador Shelves

Graphic thumbnail: sea temperature, Newfoundland and Labrador Shelves

This graph displays sea temperatures around Newfoundland (Bonavista) and Labrador (Seal Island) from 1950 to 2005. The water temperatures at both sites were very similar, fluctuating around 2 degrees Celsius, with no apparent trend up to 1990. Both locations experienced peaks of approximately 3 degrees Celsius in 1965, and lows of approximately 1 degree Celsius in 1984 and 1990. Since 1990, the temperature at both locations has been increasing steadily, reaching nearly 3 degrees Celsius in 2005.

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Sea temperature, Pacific Coast

Graphic thumbnail: sea temperature, Pacific Coast

This series of graphs shows the mean annual temperature for three locations on the Pacific Coast of British Columbia. On each graph, annual values are plotted and a horizontal line shows the average sea temperature for the reference period 1961 to 1991. At the first location, Langara Island (North Coast/Hecate Strait), the average sea temperature was just below 9 degrees Celsius. At the second location, Amphitrite Point (West Coast of Vancouver Island), the average sea temperature was 10.5 degrees Celsius. At the third location, Departure Bay (Strait of Georgia), the average sea temperature was 11.4 degrees Celsius. At all three locations, temperatures in most years before 1978 were below the average (with an exception of warmer temperatures grouped around 1940), while most years after 1978 have had warmer than average sea temperatures.

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Dissolved oxygen in the St. Lawrence Estuary

Graphic thumbnail: dissolved oxygen in the St. Lawrence Estuary

This graph displays the percentage saturation of dissolved oxygen in the St. Lawrence Estuary from 1930 to 2008. A horizontal line at 30% marks the critical oxygen concentration threshold. Samples in the earlier part of the period of record were only occasionally below this level, but samples from the early 1980s to the late 2000s were all well below this threshold, with dissolved oxygen levels being stable at around 20% saturation since 2000. There are no data points from 1936 to 1959 and from the mid 1970s to 1981.

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Seasonal change in zooplankton bloom, Strait of Georgia

Graphic thumbnail: seasonal change in zooplankton bloom, Strait of Georgia

This graph shows the date of peak bloom of zooplankton in the Strait of Georgia. Points representing annual dates of the blooms are plotted and two trend lines are shown for an earlier and a later set of years. First, from 1968 to 1996, the date of peak bloom advanced from approximately May 13th to April 24th. The values over these years were determined by back-calculation. Second, from 2002 to 2005, the date of peak bloom advanced steadily and at a more rapid rate than during the earlier time period, changing from approximately April 7th to March 10th. The values over these later years were determined by direct observation.

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Decline in krill in the western North Atlantic and Scotian Shelf

Graphic thumbnail: decline in krill in the western North Atlantic and Scotian Shelf

This graph shows an overall declining trend in the mean number of krill (log x+1) per 3 cubic metres of filtered seawater from in the western North Atlantic and Scotian Shelf from 1961 to 2008, with change mainly occurring in recent years. In 1961 the mean number of krill was 6.3. Annual values fluctuated until 1978, with a peak in 1975 of 11.6 krill, and low points of about 4 krill in two years during this period. Overall, there was no clear trend in krill abundance from 1961 to 1978. No data are available from 1979 through 1990. From 1991 to 2008 the mean number of krill declined sharply and steadily from about 6 to a value of below 1 in 2008.

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Population trend for northern shrimp and four of their predators

Graphic thumbnail: population trend for northern shrimp and four of their predators

These four graphs show the population of northern shrimp from 1976 to 2000, compared against four of its predators. The shrimp population (measured as an index of catch per unit effort, abbreviated as CPUE) decreased over the first ten years, from approximately 0.5 to 0.2 CPUE in the period from 1976 to 1985. After 1985 the population increased, reaching a high of 1.0 CPUE in 2000, the last year for which data are presented. The datasets for the four predators are all based on research surveys. Three of the northern shrimp’s predators (all fish species) declined, while snow crab, an invertebrate, increased with increasing shrimp populations.

Each graph is described in the following set of points:

  1. Redfish abundance fluctuated widely until 1985, with peaks of over 2 tonnes and lows of about 0.6 tonnes. After 1985 redfish abundance dropped to below 0.5 tonnes and, from 1992 to 2000, declined to annual measurements of zero to slightly above zero tonnes. The graph includes the shrimp population trend, showing that shrimp abundance increased rapidly, coinciding with the period of sharp declines of redfish.
  2. Atlantic cod abundance fluctuated between 1 and 2.5 tonnes from 1983 to 1991, then rapidly declined to around zero tonnes in annual surveys from 1994 to 2000. The graph includes the shrimp population trend, showing that shrimp abundance increased rapidly, coinciding with the period of sharp declines of Atlantic cod.
  3. Skate abundance increased from 1981 to 1984, reaching a peak of nearly 15 kilograms per tow. The population then declined over the next 10 years to 2 kilograms per tow in 1994, remaining close to this value from 1994 to 2000. The graph includes the shrimp population trend, showing that shrimp abundance increased rapidly, coinciding with the period of sharp declines of skate.
  4. Snow crab abundance fluctuated over the period of measurement, with overall higher values since 1990. Prior to that time, annual surveys resulted in measurements varying between about 3 and 12 kilograms per trap. After 1990, measurements were between 12 and 15 kilograms per trap. The graph includes the shrimp population trend, showing that snow crabs did not undergo a decline as did the fish predators of shrimp.

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Diet of thick-billed murre at Coats and Digges Islands

Graphic thumbnail: diet of thick-billed murre at Coats and Digges Islands

This graph shows the percent of the diet of thick-billed murres that was composed of Arctic cod and of capelin over the period 1981 to 2007. The diet composition fluctuated from year to year, with Arctic cod gradually declining in importance in the diet and capelin gradually increasing. From 1981 to 1990, Arctic cod consistently made up the majority of the diet. By 1997, capelin had replaced Arctic cod as the main component in the diet of thick-billed murres. An inset map shows the location of Coats and Digges Islands north of Hudson Bay.

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Marine mammals

Graphic thumbnail: marine mammals

This graphic shows the populations of seven species of marine mammals in locations along Canada’s coasts over a range of time periods. A separate line graph is shown for each of the seven locations, which are indicated on a central locator map. Overall, the graphs show increasing populations of marine mammals.

Each graph is described in the following set of points:

  1. Bowhead whales in the Beaufort Sea, 1978 to 2001. At the beginning of this period, the population was around 4,000 whales. Since then, the population generally increased, with a count of more than 10,500 whales in 2001.
  2. Harp seal populations in the Gulf of St. Lawrence from 1952 to 2009. Populations declined slowly from 2.7 million seals in 1954 to 1.9 million seals in 1970. From 1970 to 2009 the population increased, reaching 6.9 million in 2009.
  3. Sable Island grey seal pups from 1962 to 1997. In 1962 there was a low of fewer than 1000 pups; however, the number of pups increased exponentially over the study period, reaching more than 25,000 pups by 1997.
  4. Resident killer whale populations of northern and southern B.C. The northern population (north of central Vancouver Island) increased from 120 whales in 1974 to 220 whales by 2004. The southern population (southern B.C. coast, including Georgia Strait and Puget Sound) did not show the same increase, fluctuating in the range of 70 to 100 whales, with no clear overall trend, from 1974 to 2008.
  5. Sea otters off Vancouver Island from 1977 to 2008. Numbers of otters increased from 100 in 1977 to more than 2,700 otters in 2008.
  6. Steller sea lion population off the central coast of B.C. from 1913 to 2005. The population declined from 13,000 in 1913 to 7,000 in 1961. After 1961, the population began to increase, reaching 28,000 by 2005.
  7. Harbour seal population off Haida Gwaii, B.C. The historical reconstruction of harbour seal populations shows a cycling population with a high of 80,000 seals in 1890 and lows of approximately 10,000 seals in 1917 and 1970. Population estimates from the mid 1980s to 2009 are based on surveys. Harbour seals increased in abundance after about 1970, with the trend showing signs of leveling off in the last decade, with approximately 100,000 seals in 2009.

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Marine Fisheries

Graphic thumbnail: marine Fisheries

This graphic shows the populations of five species of fish in locations along Canada’s east and west coasts over a range of time periods. A separate line graph is shown for each of the five locations, which are indicated on a central locator map. Overall, the graphs show strongly declining fish populations.

Each graph is described in the following set of points:

  1. Spawning biomass of “Grand Bank” Atlantic cod from 1960 to about 2008. The population showed large variations, including a high of more than 120,000 tonnes in 1965 and a low of 10,000 tonnes in 1957, increasing again to 80,000 tonnes in the early 1980s. By the early 1990s biomass values below 10,000 tonnes were consistently recorded.
  2. Atlantic salmon returning to a Bay of Fundy river from the early 1960s to 2002. There was a peak of approximately 5,000 salmon returning in 1965. Following the 1960s, numbers were mainly in the range of 1,000 to 2,000 until the early 1990s, when they decreased and leveled off at approximately 100 salmon.
  3. Percent survival of wild coho in the Strait of Georgia from 1986 to 2006. Survival rates were about 12% in the first two years, rose to 18% in 1988, and then declined fairly steadily to 2% in 2006.
  4. Sockeye returning to Barkley Sound from 1970 to 2006. The number of sockeye fluctuated over a range from lows of approximately 300,000 to peaks of up to 1,800,000 sockeye, with below-average peak-year returns from the mid 1990s to 2006.
  5. Pre-fishery biomass of herring on the central coast of B.C., from 1950 to 2009. Biomass of herring fluctuated from year to year, generally within a range of about 30,000 to 60,000 tonnes, with peaks as high as almost 80,000 tonnes (1950) and an outlying low value of less than 20,000 tonnes in the late 1960s. In the last decade, however, the pattern changed, with biomass declining steadily to less than 10,000 tonnes in 2009.

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Fish length at age 5, Scotian Shelf

Graphic thumbnail: fish length at age 5, Scotian Shelf

This graph shows the change in length of four species of fish at age 5 years from 1970 to 2002. Annual average lengths are plotted and trend lines are shown for each fish species. All species – cod, haddock, pollock, and silver hake – had decreasing trends over this period. The average length of pollock at age five decreased from approximately 67 centimetres in 1970 to approximately 51 centimetres in 2000. Cod average length decreased from approximately 57 centimetres in 1970 to approximately 46 centimetres in 2000. Haddock average length decreased from approximately 67 centimetres in 1970 to approximately 51 centimetres in 2000. Silver hake average length decreased from approximately 39 centimetres in 1970 to approximately 32 centimetres in 2000.

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