CalCOFI: Climate, ecosystem & fishery relationships in the California Current
Tony Koslow, Scripps Institution of Oceanography, University of California, SD, La Jolla, CA 92093
jkoslow@ucsd.edu.
The California Cooperative Oceanic Fisheries Investigations (CalCOFI) program was initiated in 1949 in
response to the collapsing Pacific sardine fishery. It is a partnership of Scripps Institution of
Oceanography, committed to oceanographic and climate research, and the state and federal agencies
responsible for fishery management. From the outset it has been committed to an ecosystem approach
to fisheries in the California Current. Since 1984, quarterly cruises have been conducted covering at least
six transects from the US/Mexico border to north of Pt Conception and extending from the 35-50 m
isobath to several hundred miles offshore. Traditional measurements include temperature, salinity,
nutrients, chlorophyll, and oxygen from a CTD casts to 500 m, and zooplankton and ichthyoplankton
from net tows. More recently the California Current Ecosystem Long-Term Ecological Research program
and other funding sources have supplemented these with measurements of phytoplankton pigment
types, pico-, nano, micro- and mesozooplankton, seabirds, marine mammals, and the micronekton.
Today, CalCOFI truly samples the marine ecosystem from ‘winds to whales.’
CalCOFI data have been critical to our understanding of climate impacts in the California Current,
ranging from studies of interannual (e.g. ENSO) to decadal (i.e. the PDO and NPGO) and longer-term
climate change impacts.
The ichthyoplankton data comprise the best taxonomically-resolved CalCOFI data set. Recent principal
component (PC) analysis of this data set provided insight into the assemblage structure of the diverse
fish community of the California Current, the internal and external influences on these assemblages, and
potential ecological indicators. PC 1, which explained 20.5% of the variance of the data set, was
dominated by 24 mesopelagic taxa from 8 families and included migrators, non-migrators, planktivores
and piscivores. All were closely correlated with each other and with decadal-scale changes in midwater
oxygen concentration. It is hypothesized that declining oxygen and a shoaling oxygen minimum zone
compresses available habitat for the mesopelagic fauna, leads to a shoaling of the deep scattering layer
and renders this fauna more vulnerable to visual predators. The total mesopelagic fish fauna has
contracted 38% from periods of high to low oxygen concentration. The total biomass of vertically
migratory mesopelagic fishes has ranged from 5 – 8-fold higher than that of small pelagic planktivores
(northern anchovy + Pacific sardine) in the California Current, and their food consumption is estimated
to be 2 -3-fold higher.
PC 2 explained 12.4% of the variance of the data set and was dominated by 6 out of 7 of the most
abundant taxa in the ichthyoplankton data set, five of which are noted for their northerly or cool-water
affinity: northern anchovy, Pacific hake, Sebastes spp., the myctophid Stenobrachius leucopsarus and the
bathylagid Leuroglossus stilbius. Pacific sardine, which is favored by relatively warm conditions, loaded
highly but with opposite sign to the others. The group is comprised predominantly of pelagic species,
including several species of Sebastes commonly found in midwater. PC 2 was negatively correlated with
near-surface temperature conditions.
PC 3 explained 6.8% of the variance of the data set and was dominated by coastal species with generally
warm-water affinities, including tonguefish (Symphurus atricaudus), blacksmith (Chromis punctipinnis),
Pacific barracuda (Sphyraena argentea), cuskeels (Ophidion scrippsae, Chilara taylori), blennies,
(Hypsoblennius spp.), sciaenids, and sand dabs (Citharichthys spp.). This group was favored by warmwater conditions.
PC 2 and PC 3 correspond closely with the northerly and southerly/coastal larval assemblages previously
defined with recurrent group analysis on the basis of their spatial co-occurrence (Moser et al. 1987). The
temporal coherence of these ‘habitat’/biogeographic-based assemblages indicates broad environmental
forcing of assemblages sharing spatial habitat. These larval fish assemblages may thus serve as multidimensional ecosystem indicators of environmental change.
There were generally positive correlations between mesopelagic fishes and key pelagic species: Pacific
hake, northern anchovy, Pacific mackerel (Scomber japonicus), and horse mackerel (Trachurus
symmetricus). Both mesopelagic and pelagic groups were generally correlated significantly with key
ocean indices, such as the MEI, PDO, and NPGO. Correlations were generally positive with the MEI and
PDO and negative with the NPGO, indicating that warm conditions with reduced upwelling were
generally favorable. The consistent positive correlations among potential competitors, predators and
prey indicate bottom-up forcing. The strong coherent response of the mesopelagic fishes to changing
oxygen conditions indicates that this group may be a sensitive ecological indicator for deoxygenation, a
key change predicted by several climate models.