CalCOFI Reports, Vol. 11, 1967 - California Cooperative Oceanic ...

SUMMARY OF BIOLOGICAL INFORMATION ON THE NORTHERN ANCHOVYENGRAULIS MORDAX GIRARDJOHN 1. BAXTERMarine Resources OperationsCalifornia Department of Fish and GameTerminal Island, CaliforniaINTRODUCTIONThe northern anchovy has long been recognized asone of the most abundant fishes in the northeasternPacific Ocean and a sizable latent resource (Croker,1942; Chapman, 1942). In recent years the anchovypopulation has increased dramatically. Egg and larvasurveys by the U.S. Bureau of Commercial Fisheriesshow that the population trebled between 1951 and1958 and has increased even further since (Ahlstrom,1965). Despite its great abundance the anchovy hasnever been the object of a large-scale fishery.DISTRIBUTIONAdult northern anchovies occur from the QueenCharlotte Islands, British Columbia to Cape SanLucas, Baja California. They are most commonfrom about San Francisco to Magdalena Bay,chiefly in coastal waters. Eggs and larvae have beentaken as far as about 300 miles offshore.Hubbs (1925) described a separate subspecies (E.nz. nanzis) which inhabits San Francisco Bayand tolerates much-reduced salinities. In both meanand modal number of vertebrae the bay subspecieshas two fewer than the ocean subspecies. It is a muchsmaller fish, the largest found by Hubbs measured 99nim TL. Its head averages longer, the body deeperand more compressed. The early development is alsoapparently more accelerated and transformation frompostlarval to juvenile stages occurs at a much smallersize.Similar brackish-water forms also are known forthe European anchovy (E. encrasicholus) and Australiananchovy (E. australis) (Blackburn, 1950).SubpopulationsMcHugh (1951) delineated three northern anchovysubpopulations on the basis of differences in numbersof dorsal, anal, and pectoral fin rays; vertebrae;and gill rakers. The three subpopulations occur fromBritish Columbia to central California, off southernCalifornia and northern Baja California, and offcentral and southern Baja California.Miller (1956), on the basis of age and size compositionsof central and southern California commercialand live bait catches, aerial surveys. and sea surveys,gave possible evidence of "local" stocks of fish.Work currently is underway by the U.S. Bureauof Commercial Fisheries using serological techniquesto delineate possible genetically distinct stocks ofnorthern anchovies.HabitatAnchovies are pelagic schooling fishes, generallyfound in coastal waters. During recent years, theiroffshore occurrence has expanded markedly as thepopulation has increased. Like their cogeners, northernanchovies exhibit some seasonal movements. Duringfall and winter they apparently move offshoreand return inshore in spring. Fall surveys by theDepartment's R/V ALASKA indicate that anchoviesoccur well below the surface during the day and moveto the upper layers of the ocean at night. The Europeananchovy (E. encrasicholus) makes similar diurnalmovements at this time of year. Off the coastnear Santa Barbara during November, 1964, anchovieswere noted on the depth recorder in a thinband along the bottom during the day, but at nightthey rose toward the surface to form a band 20 to50 feet thick. Our sampling also indicates that largefish are less available in inshore waters during winter.During periods of warmer-than-average water temperatures,adult anchovies become less available inthe inshore waters. Fish-of-the-year apparently toleratesomewhat higher water temperatures than adults.Our sampling program has shown that 0-age-groupfish predominate in inshore live bait catches duringperiods of warm water. During the 1957-59 "warmwateryears" our research vessel surveys showed thatlarge anchovies no longer frequented inshore areasbut were more numerous offshore. While live baitfishermen were experiencing difficulty in catchinglarge fish, T-essels conducting seismic oil explorationoccasionally were killing large anchovies well offshorefrom usual areils of abundance.On Department sea surreys for the years 1955through October, 1964, samples of anchovies werecaught in water temperatures ranging from 8.5" to25.0"C. between northern California and MagdalenaBay, Baja California (Table 1). Of 617 samplescaught where surface temperatures mere recorded,75.9 percent of the catches occurred in waters havingsurface temperatures between 14.5" and 20.0"C.Off California and northern Baja California (northof lat. 31"N.) 340 samples were taken in temperaturesranging from 8.5" to 21.5"C. Of these, 72.5percent occurred between 14.5' and 18.5"C. Offcentral and southern Baja California 277 anchovysamples were taken in water temperatures rangingfrom 13.0" to 25.O0C., 65.0 percent between 17.0"and 21.5'C.