CalCOFI Reports, Vol. 27, 1986 - California Cooperative Oceanic ...

BAILEY ET AL.: FORECASTING HAKE RECRUITMENTCalCOFI Rep., Vol. XXVII, 198635 -30 -RESULTS AND DISCUSSIONThe California Fish and Game trawl surveys forSAN FRANCISCOpelagic fish resources were not targeting on juvenile- hake, but their incidental catches of 0-age hake appearto be useful in forecasting year-class strength of this- species. Figure 3 demonstrates the relationship betweencatches of 0-age hake in the surveys and yearclassstrength as determined by cohort analysis. Duringthe interval from 1965 to 1981, five large year classes- of hake appeared in the population (1967, 1970, 1973,1977, and 1980). These five year classes were also themost abundant as 0-age juveniles monitored by thesurveys.The surveys apparently are not accurate in orderingthe rank of strong year classes when compared with resultsof the cohort analysis. For example, 0-age hakewere more abundant in the 1973 surveys than in the1970 surveys, but the cohort analysis indicated that the1970 year class was stronger than the 1973 year class.Predicting strong year classes is important, but in amanagement context it is equally important to recognizeyear-class failure; in this analysis all weak yearI l l I , , , classes were accurately indicated by the surveys.125 120 115 Since the cohort analysis extends only to the 1981year class, we can use the 0-age catches in the surveysto forecast the relative recruitment strengths of theFigure 2. Locations of catches of 0-age hake in midwater trawls of the CaliforniaDepartment of Fish and Game used in this study, 1965-84.1.0 -0.5.67 7073807-77840c.-.-30 -20 -10 -67--.I70 77784lln n nnn -n-nn2.5 - -702.0 - -1.5 -1.0 -0.5 -677773--Figure 3. Catch per unit effort (CPUE;n fln nlln -n -0- " and percent occurrence (mid-YEAR CLASSof 0-age hake in rnidwater trawlsurveys compared with year-classstrength determined by cohort analysis(bottom).111