__ REPRINT FROM Calif. Fish and Game 59(3) : 191-195. 1973. INCONSISTENCIES IN LOCATING THE FIRST ANNULUS OF PACIFIC SARDINES' MAKOTO KIMURA National Marine Fisheries Service La Jolla, California 92037 A special scale r e a d i n g session d e s i g n e d to b r i n g t o g e t h e r o l d a n d n e w scale readers t o compare t h e c r i t e r i a f o r estimating t h e f i r s t annulus i n sardine scales &,), e x a m i n e d scales collected f r o m t h e 1941 t h r o u g h 1962 sardine landings. Estimates of 1 1 b y t h e o r i g i n a l readers w e r e consistently l o w e r t h a n those o f t h e n e w e r readers. The r e p o r t e d increase i n Pacific sardine l e n g t h a t t h e f o r m a t i o n of first annulus a p pears to b e due t o a change i n t h e o l d e r reader's c r i t e r i a f o r t h e posit i o n o f t h e f i r s t annulus. I n addition, t h e r e w a s a g r a d u a l r e p l a c e m e n t o f t h e o l d e r readers b y n e w e r ones w h o consistently r e a d h i g h e r a n d thus o v e r e s t i m a t e d 11. Hence, it a p p e a r s t h a t t h e r e was n o r e a l change i n sardine g r o w t h r a t e s d u r i n g these years. INTRODUCTION W a l f o r d a n d Mosher (1943a, 1943b) validated t h e use of scales f o r estimating the age of t h e Pacific sardine a n d set criteria f o r t h e scale annulus. I n 1960, I suspected the sardine scale readers were not strictly following the criteria in locating the first or innermost annulus. The radius of this a n n u l u s is used to estimate the L, (defined as ( i ) ) the calculated length of t h e fish a t the end of the first year of life ( M a r r 1 9 6 0 ) , or ( i i ) the calculated length of the fish a t the time of formation of t h e r i n g in the first year of life ( P h i l l i p s 1948a). F r o m information obtained on the time of a n n u l u s formation on known-age sardine ( K i m u r a a n d Sakagawa 1972) the second definition is recommended. The L1 is one of the basic measurements f o r estimating growth ( P h i l l i p s 1948b). It has also been used as a p a r a m e t e r t o separate subpopulations ( F e l i n 1954) , a n d to support certain hypothesis a b o u t the population ( M a r r 1 9 6 0 ) . The importance of the p a r a m e t e r warr a n t e d t h a t a s t u d y be made to determine if scale readers were changing L1 estimates by mislocation of the first annulus. P r e l i m i n a r y analysis of the scale-age d a t a a n d rereads of a random number of scales f o r the 1941-42 through 1961-62 seasons indicated t h a t the only conclusive way to settle the matter was by direct comparison of scale reading between the original scale readers a n d t h e readers then in tenure. This report describes the results of the comparative scale reading. MATERIALS AND METHODS On March 25-29, 1963, the three original scale readers a n d t h e circa 1963 scale readers met a t Hopkins Marine Station, Monterey, California, to determine whether the l a t t e r readers were following the original Accepted for publication March 1973. ( 191 1 192 CALIFORNIA FISH AND GAME readers’ criteria i n reading Pacific sardine scales. Since the three original readers h a d been away f r o m such work f o r so long, certain steps were taken to ensure their ability to read scales i n the same way as they d i d d u r i n g their tenure. F o r practice they were sent, 4 months before the formal meeting, 100 scale slides which each h a d read a n d recorded d u r i n g his tenure. They also practiced as a g r o u p prior to t h e formal meeting, a n d a test was carried out f o r consistency in aging with 60 slides selected f r o m t h e 1 9 4 1 4 2 t h r o u g h 1 9 4 3 4 4 season. They agreed a b o u t 88% of t h e time, which compared favorably to t h e 80-90% agreement when they were i n tenure. T h e 1963 readers d i d not practice b u t were told to read in t h e same m a n n e r as they were doing. A t the formal meeting each reader read independently t h e same preselected scales f r o m 105 scale samples of fish taken i n t h e S a n Pedro, California, fishery. The pre-selected scales were those selected originally by the historical scale readers ( a s recorded on scale cards) a n d were distinguished f r o m t h e others f o r the present test b y encircling with a glass-marking pen. The remaining scales on t h e slide were l e f t i n view to aid each reader i n his evaluation of t h e annulus. Other test scale readings included individual readings on t h e same slides b u t each individual selec+g a scale of his choosing, two-separate g r o u p readings on the same slides, a n d a final reading whereby all seven readers together read a series of slides. All showed the same t r e n d a s is described f o r the test i n the present report. A f t e r viewing the scale on a scale projector, the reader recorded the r a d i i of all annuli, a n d also the margin of the scale on a scale card. The reader went through the same procedure f o r each of the 105 slides; five slides f o r each of t h e 21 seasons f r o m 1 9 4 1 4 2 t h r o u g h 1961-62, the same method used a n d described b y F e l i n a n d Phillips (1948). T h e back-calculated lengths of the fish a t various annuli were obtained w i t h a nomograph by the method of Phillips (1948a). The average L1values were calculated f o r t h e original a n d t h e 1963 readers, respectively, a n d the results compared. T h e average Ll’s f r o m the historical data used to prepare the age a n d length reports f o r t h e Pacific sardine reported by Wolf (1961) were also calculated f o r comparison. RESULTS A graphic comparison of L1 estimations by seasons f o r both g r o u p s of readers a n d the historical readers shows t h a t the L1estimates of t h e original readers were consistently lower t h a n those of the 1963 readers 1 ( F i g u r e 1).The historical average L h a d a positive t r e n d w i t h time b u t t h e other two d i d not. DISCUSSION A comparison of the scale readings shows t h a t t h e 1963 scale readers were not following the criteria of the original readers. Therefore, the average L1 values which were used as a basic measurement f o r estim a t i n g growth, to separate subpopulations, a n d t o s u p p o r t certain hypothesis about the population needed to be reexamined. F o r example, M a r r (1960) f o u n d a positive t r e n d with time i n the L1values f o r t h e year-classes 1934 t h r o u g h 1955 f o r the fishery a t S a n Pedro. H e assumed t h a t the increase in length of L was caused by biological o r 1 LOCATING FIRST ANNULUS cn Q W 2 0 cn 194 CALIFORNIA FISH AND GAME environmental factors which affected the Pacific sardine ; but, this s t u d y indicates t h e change in L1 was the result of scale reader bias. The consensus of opinions among scale workers is t h a t consistency among a g r o u p of readers, or t h e presence of experienced readers guarantee results comparable to past results, However, there were two experienced readers present a t the time the historical L1 estimation began its a b r u p t increase in t h e mid-1940’s. The present s t u d y indicates t h a t while t h e 1963 readers were consistent among themselves, their criteria were inconsistent with those of the original readers. K i m u r a a n d Sakagawa (1972) concluded on t h e basis of a comparison of L1 of known age sardine with the average L1 of fish aged by t h e early a n d recent scale readers t h a t the early readers’ L1 estimations were closer to t h a t obtained f r o m the known age fish. T h e results obtained here indicate a need f o r some k i n d of s t a n d a r d or length-by-age values to serve as a reference to the readers i n obtaini n g back-calculated length measurements. A suggested s t a n d a r d is a series of random, stratified-by-age scales, i.e., 0-, I-, II-, III-, . . . n-year-old fish scales, preferably selected f r o m the time period when t h e validators of t h e scale (otolith a n d a n y other bony structures used i n a g i n g ) method were i n tenure, or were used by the validators as t h e basis of their study. F o r the sake of simplifying comparative readings a n d as assurance t h a t the same scale will be read a t all times, the initial readers of the s t a n d a r d series of slides should circle t h e selected scale w i t h a marking pen. Similarly, the slides read routinely d u r i n g a season should also be circled by the initial reader so t h a t both a reader a n d the checker can be certain to have examined t h e same scales. The presence of such a set of s t a n d a r d slides probably would ( i ) assure continuity i n the m a n n e r of the scale interpretation by t h e original validators of the scale or a n y other method used i n estimating fish age, ( i i ) counteract a n d monitor the effect of dominance of a n y individual scale reader, a n d ( i i i ) deter the occurrence of similarly costly mistakes a s illustrated i n this study. CONCLUSIONS T h e circa 1963 scale readers have not been reading like the original readers and, apparently, have not been following the same criteria i n estimating t h e L1.The L1 value change i n time resulted f r o m scalereader subjectivity a n d was not caused by biological or environmental factors. ACKNOWLEDGMENTS My thanks to the original scale readers, Dr. L. A. W a l f o r d , Mr. K. H. Mosher, a n d M r . J. B. Phillips, a n d to t h e 1963 scale readers, Miss A. E. D a u g h e r t y , Mr. H. H y a t t , a n d Mr. R. S. Wolf, f o r participating i n the scale-reading workshop. The editorial assistance of staff members of the National Marine Fisheries Services, a n d t o a number of other staff members of the same organization who gave their time as ‘‘sounding b o a r d s ” a r e acknowledged. RFRNE EE E CS Felin, Frances E. 1954. Population heterogeneity in the Pacific pilchard. Fish Wildl. Sew., Fish. Bull. 8 6 ( 5 4 ) : 201-225. U.S. LOCATING FIRST ANNULUS 195 Felin, Frances E. and Julius B. Phillips. 1948. Age and length composition of the sardine catch off the Pacific coast of the United States and Canada 1941-42 through 1 9 4 6 4 7 . Calif. Div. Fish and Game, Fish Bull. (69) : 122 p. Kimura, Makoto and Gary T. Sakagawa. 1972. Observations on scale patterns and growth of the Pacific sardine reared in the. labpratory. Fish. Bull., U.S. 70( 3 ) : 1,043-1,052. Rlarr, J o h n C. 1960. The causes of major variations in t h e catch of the Pacific sardine, Sardinops caertclea ( G i r a r d ) . Proceedings F A 0 World Sci. Meet. Biology of Sardines and Related Species, Rome, 14-21 September 1 9 5 9 ; 667-791. Phillips, Julius B. 1948a. Comparison of calculated fish lengths based on scales from different body areas of the sardine, Sardinops caerulea. Copeia, 1948, 2 : 94-106. 1948b. Growth of the sardine, Sardinops caerulea, 1941-42 through 1 9 4 8 4 7 . Calif. Div. Fish and Game, Fish Bull. (71) : 33 p. Walford, Lionel A. and Kenneth M. Mosher. 1943a. Studies on the Pacific pilchard or sardine (Sardinops caerulea) 2. Determination of t h e age of juveniles by scales and otoliths. U.S. Fish Wildl. Serv. Spec. Sci. Rep. 21, 2 9 p. (Reissued in Spec. Sci. Rep. Fish. 15 : 31-95,1950.) 1943b. Studies on the Pacific pilchard or sardine (Sardinops caerulea). 3. Determination of age of adults by scales and effect of environment on first year’s growth a s i t bears on age determination. U.8. F i s h Wildl. Serv. Spec. Sci. Rep. 21, 29 p. (Reissued in Spec. Sci. Rep. Fish. 15 : 96-131, 1950.) Wolf, Robert S. 1961. Age composition of the Pacific sardine 1932-1960. U.S. Fish Wildl. Serv. Res. Rep. 53, 36 p. . .