Impact of Climate on Distribution and Migration of North Atlantic Fishes George Rose, Memorial University, NL Canada

Table of Contents A few platitudes Brief history of the North Atlantic Where are the fish? “Grouping” analysis of species “Event” analysis: the warming “Species” analysis: capelin “Ripple” effects: food webs

Fish distributions and migrations NOT random the result of evolution of the physiology of the species “tuned to the particular biotic and abiotic environment of the stock” variable at several time scales early indicator of ecosystem change “On the cod highway”

Migration links Abiotic: depth temp salinity currents oxygen Biotic: fishing prey predators density- dependence spawning feeding juvenile Environmental unit

History of North Atlantic

Long-term climate change

Most North Atlantic species have Pacific origins (Ekman, 1953) The gadoids are likely the only major fish group whose evolutionary center is the North Atlantic

Where are the fish?

# of species with latitude in N. Atlantic (data from Briggs, 1974; Cech, 2000)

Sea temperatures in mid-Atlantic (data from Ekman, 1953)

Depth: Number of species in the North Atlantic (data from Challenger cruise, 1800s) Depth

Number of species at depth in North Atlantic (from 150 species documented in this study)

Lower and upper temperature limits: cumulative # of species

Spawning temperature limits

Spawning salinity limits

“Grouping” analysis All North Atlantic Species - catalogued 146

Can species be grouped into response categories? Feeding period requirements (temperature, depth) Spawning requirements (temperature, salinity, depth, timing)

Warmer Shallower Principle Components 1: Min and Max depth 2: Min and Max temperature

Salinity Deeper Spawning Components 1: salinity 2: depth 3: temp, timing

General limits: F1 with pop’n doubling time

Spawning limits: PCs and pop’n doubling time (depth,temp,timing)

“Event” analysis

An old problem “there have been certain periods of years in northern seas with higher temperatures and simultaneously increasing occurrence of southern species, for instance in the years of about , , , and 1920-” Rollefsen and Taning, 1948

A warm water “event” in the north Atlantic (or thereabouts)

According to Taning, 1948 “Simultaneous with this scarcity of ice in the waters around Iceland the winters have been exceedingly mild, especially during February and March, when the mean temperature was some 4 to 7 o C above the normal” “This increase of the surface temperature has amounted to about o above the normal”

Annual air temperature St. John’s, NL Godthab, Greenland Akureyi, Iceland Bodo, Norway

The warm 1930s mid- N. Atl.

Species distribution changes (data from Saemundsson, 1932; Taning, 1948; Fridriksson, 1948; Rollefsen, 1948; others)

Norwegian skrei fishery landings, Lofoten (N) and More (S) (data from Nakken, 1994)

No warming: No fish change Warming: fish change 1920s

Species analysis

A keystone species: Capelin

The dispersal of capelin from their north Pacific origin (from Vilhjalmsson, 1994)

Present distribution of capelin (from Vilhjalmsson, 1994)

Documented capelin shifts

Extension of capelin spawning grounds from cold period ( ) to warm period ( ); from Vilhjalmsson 1997 cold warm

Capelin: distance moved and temperature change

Capelin: distance moved and persistence

Ripple effects

North Atlantic food web

Capelin is key to: Many fishes (e.g., cod, greenland halibut, salmon, charr, winter flounder) Seabirds Marine Mammals

Templeman, 1948, on Newfoundland caplin “not only does it provide the nourishment on which the great bulk of inshore running codfish recover condition in June and July after spawning, but it is very likely in the main responsible for the attraction of the huge shoals of cod to the coast”

Extension of capelin spawning grounds from cold period ( ) to warm period ( ); from Vilhjalmsson 1997 cold warm

Extension of cod spawning grounds from cold period ( ) to warm period ( ); from Vilhjalmsson 1997 cold warm

Capelin movements late 1980s Northern cod movements early 1990s Grand Banks Hamilton Bank Flemish Cap

Cod and capelin on Newfoundland shelf in early 1990s (from O’Driscoll & Rose, 2001)

Effects of lack of capeln: weight of cod in winter: Iceland data from Vilhjalmsson, 2002

Northern cod liver index and capelin availability (from Rose & O’Driscoll, 2002)

Cod stock historical range and biomass (from Robichaud & Rose, in press)

Conclusions Distribution changes important - early indicator of ecosystem change Response differences (pelagics faster; demersals slower, some maybe not at all) Capelin fast - “canary in the mine” Ripple effects: capelin changes affect many species