Research Document - 2011/054
State of physical, biological, and selected fishery resources of Pacific Canadian marine ecosystems in 2010
By W.R. Crawford and J.R. Irvine (editors)
Abstract
The near-record high number of returning Sockeye Salmon to the Fraser River was the good news story for 2010. Approximately 30 million adults returned, and of these about 17 million were headed for Shuswap Lake. These returns contrast with 2009 when fewer than 2 million sockeye migrated back to the Fraser. With such wide changes between years it is difficult to predict returns for 2011 with high certainty. The DFO prediction for 2011 is between 1.0 and 12 million (10% and 90% probabilities) if the low recent productivity persists. If on the other hand salmon have the long-term average productivity seen last year and in previous decades, between 1.7 and 15 million sockeye are predicted to return.
The story was reversed for Humboldt squid. Squid were found in record-high numbers in summer 2009 along the west coast, but in 2010 not even one was observed in British Columbia waters. Several causes have been proposed, but none proven.
The year 2010 started with extreme El Niño weather along the west coast, with strong southerly winds bringing warm, fresh ocean waters to the Oregon and British Columbia coast. These winds weakened in April and by summer the winds blew much more strongly than normal from the north, upwelling cool salty water along the outer coast. Waters of the Strait of Georgia shifted from cool to normal or even warm in 2010. La Niña conditions of late 2010 and early 2011 were linked to stronger westerly winds in the Pacific Ocean and cooler ocean waters along the coast. Overall the cool conditions prevailed in 2010, and this year was the third consecutive year with cooler than normal ocean temperatures along the Pacific Canadian coast.
Over the past decade and a half both the Pacific Decadal Oscillation and ENSO (El Niño – La Niña) have shifted phase together and reinforced the impact of each one on west coast ocean temperature. Whereas in the 1990s scientists would attribute changes in ocean temperatures and species compositions to changes in PDO or ENSO, they have recently been able to use these indices almost interchangeably in local waters to link physical changes in the ocean to shifts in abundance of one or several marine species.
Scientists monitor abundance and species of plankton in local waters to determine the quantity and quality of prey for larger species. Phytoplankton can be tracked by measuring chlorophyll in the ocean. Summer 2010 chlorophyll concentrations were often low in the southern Strait of Georgia and Juan de Fuca Strait, while fall chlorophyll concentrations were higher in Juan de Fuca Strait and slightly lower in the Strait of Georgia compared with previous years. The timing of the spring bloom in the Strait of Georgia is considered important for juvenile herring and salmon survival. Numerical models suggest that this bloom occurred in mid-April in 2010, compared to March to early April for most years. Bloom timing depends on local winds and cloud cover. A study of Rivers Inlet of Central BC discovered the spring bloom could be blown completely out of this short inlet by outflow winds. Its late development in 2009 could have been due to these winds. Studies of impacts of this outflow on local sockeye juveniles are ongoing.
Zooplankton species tend to shift from cold-water to warm-water types with corresponding shifts in local ocean temperature. Monthly surveys found the 2010 composition of cold-water copepods (a type of zooplankton) off Oregon was 4th highest in 15 years of observations. However, the species richness, which usually correlates with ocean temperature, was also high in 2010. These contrasting observations might be attributed to a warm ocean waters in winter and cool summer of 2010. Similar surveys in British Columbia observed more cold-water copepods species.
Recent surveys found the that biomass of Pandalus jordani shrimp off central west coast Vancouver Island had increased in 2008, 2009, and 2010 from very low levels during 2004-2007. Such increases appear related to colder waters in 2006, 2007, and 2008 during the larval stages of the shrimp (this species has a 2-yr time lag from hatch to recruitment at age 2) and to low abundances of Pacific hake (a potential shrimp predator) in May surveys in 2008, 2009, and 2010. This survey in May also provides insight into populations of resident flatfish, such as sole, Pacific cod, halibut, and arrowtooth flounder. Biomass trends of key flatfish indicator species all increased in 2010, as did the biomass of the “cold water indicator” species walleye pollock.
Offshore Pacific hake (Merluccius productus) is a trans-boundary stock that exhibits seasonal migratory behavior, ranging from offshore and generally southern waters during the winter spawning season to coastal areas between northern California and northern British Columbia from spring to fall. In 2011, spawning biomass is estimated to have rebounded rapidly from a low in 2007 based on the strength of recent year classes (2005, 2006 and particularly 2008). However, estimates of spawning biomass are highly uncertain. The most recent coast-wide survey in 2009, using ship-based sonar sampling, was difficult to interpret due to large numbers of Humboldt squid among the hake.
Coastwide, herring adult biomass is generally low in all areas except the Strait of Georgia, where the stock remains somewhat high due to its near-record high biomass several years ago and indications of strong returns in 2011. Sardine numbers went from zero to many thousands of tonnes in the 1990s, but have declined since 2006. Eulachon have experienced long-term declines in many rivers throughout their distribution from California to Alaska. Indices of eulachon abundance in central and southern British Columbia rivers remain at low levels. COSEWIC recently assessed eulachon, and designated stock from some BC rivers as Threatened and in others as Endangered.
The abundance of albacore tuna in BC coastal waters in 2010 was the second highest since 1990, and those caught were in cooler water than in previous years.
Counts of seabirds in Pacific Rim Marine Reserve on the west coast of Vancouver Island revealed many species increased in number over the past five years. However, on Triangle Island where seabird breeding depends critically on ocean conditions in April, the mean growth rate for chicks of Cassin’s auklet was extremely low in 2010 – in fact, the lowest in the 15-year time series by quite a wide margin. This poor growth is linked to late arrival of spring weather.
A Pacific North Coast Integrated Management Area (PNCIMA) Groundfish overview revealed several general trends. Gadoid (Pacific Cod, Walleye Pollock, Pacific Hake) stocks are stable or increasing. Most rockfish species are at low abundance with some being listed as Special Concern or Threatened by COSEWIC. Flatfish stocks appear to be stable. Sablefish stocks appear to be stable at low abundance. Lingcod and Elasmobranch (e.g. Spiny Dogfish) stocks appear stable.
Sockeye ocean survival was high for stocks in Barkley Sound on the west coast of Vancouver Island, attributed to cool ocean waters when they entered the ocean two years earlier. An assessment of ~60 years of escapement and catch data of five salmon species to the central and north coast suggests that Pink Salmon, with significant increases in escapements, are doing relatively well. Coho and Chinook Salmon are doing relatively poorly - declines over the time series were significant for Coho Salmon catches, escapements, and returns; and for Chinook Salmon catches and returns. A different picture can emerge from shorter-term studies. For example, the Chinook Abundance Index for stocks between SE Alaska and Oregon has increased and declined over 10 to 15 year cycles since 1979, and this index is presently increasing from a low in 2008.
The numbers of some baleen whales have increased following the end of whaling in the 1960s. Humpback whales are now most frequently sighted. Fin, blue and sei whales are observed much less frequently.
Oxygen concentrations in bottom waters at 150 metres depth in late summer dropped to lowest observed values in 2006 and 2009 off southwest Vancouver Island. Normal concentrations were observed in 2010. Lower oxygen concentrations were observed off the coast of Oregon and Washington in most summers since 2002, perhaps due to stronger upwelling winds there in summer.
Finally, biophysical features and human uses on the BC coast are illustrated by 260 new maps prepared by the BC Marine Conservation Analysis Project Team.
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