VARIATION IN THE CONDITION FACTORS OF CALIFORNIA PELAGIC FISHES AND ASSOCIATED ENVIRONMENTAL-FACTORS

Time series of condition factors for mackerel, Scomber japonicus, jack mackerel, Trachurus symmetricus, and northern anchovy, Engraulis mord ax, stocks in the Southern California region were compared with time s eries of oceanographic indices to develop hypotheses concerning physic al environmental forcing of the population dynamics and energetics of small pelagic fishes. Mackerel and jack mackerel condition factor time series showed decade-scale variation, whereas those of anchovy showed coherent fluctuations for 1 to 2 years. Mackerel, and to a lesser ext ent jack mackerel, condition factors were correlated with proxy indice s of alongshore advection (sea level), offshore advection (Ekman trans port), ambient temperature (shore station temperature), and ambient sa linity (shore station salinity). The condition factor of anchovy was m uch less correlated with environmental variables. Multiple regression analyses which included sea level, upwelling and salinity proxies expl ained 80% (33%) of the variance in the annual (monthly) condition fact or of mackerel. The first-order variation in condition factors of mack erel and jack mackerel suggests that they are responding to very large -scale perturbations of the California Current system which are at lea st partially described by variations in sea level. The population size of mackerel is apparently also responding to these large-scale pertur bations, making it difficult to isolate environmental dependence of co ndition factors from density dependence. The second-order variation is more regional in nature and unexpectedly it appears to be associated with upwelling in the Baja California region.