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

~~~REPORTS VOLUME XI, 1 JULY 1963 TO 30 JUNE 1966 39FIGURE 8. Scale from E. australis of standard length 75 mm taken inJune, with third zone of crowded striae forming at the anterior edge(from Blackburn 19500).1950 a); the embedded anterior portion is shownuppermost. The striae on the anterior portion aresemi-concentric ; they run parallel to the anterioredge of the scale and obliquely towards the lateraledges. In the region where they lie parallel to theedge, bands of widely spaced striae alternate withbands of narrowly spaced striae, in a way reminiscentof a salmonoid scale pattern.It can be shown that this pattern is annud, andthat the period at which the striae become mostcrowded is in winter. For instance, Figure 6 shows aMarch scale on which the striae are becoming crowdedalong the anterior edge, and Figure 7 shows a Novemberscale on which a similar zone of crowdedstriae has been succeeded by one of widely spacedstriae. A similar comparison may be made for theoutermost zone of crowded striae in Figure 8 (June)and Figure 9 (October). Further information wasgiven by Blackburn (1950 a). Each zone of crowdedstriae was therefore considered to represent one winterof life, with very few exceptions. Other apparentlyperiodic features of the scale pattern might havebeen used, but were not, to indicate the age (e.g.,the zones of interrupted, branched, or fragmentedstriae which occur more or less parallel to the scalesides).Table 1, from Blackburn (1950 a), shows the frequencyof occurrence of different numbers of winter“rings” (zones of crowded striae) in successivelength-groups of fish; the lengths are standardlengths, snout tip to end of body excluding caudalfin (this applies to all lengths mentioned in thispaper); 4.5 ern means 45 to 49 mm inclusive, andother length-groups likewise. Table 1 gives a generalidea of the growth-rate of the Victorian E. australis;FIGURE 9. Scale from E. australis of standard length 81 mm token inOctober, with third zone of crowded striae completely formed andsucceeded by a zone of more widely spaced striae (from Blackburn19500).TABLE 1ENGRAULIS AUSlRALE, VICTORIAN SPECIMENS, RECORDED BYNUMBER OF ANNUAL (WINTER) SCALE-RINGS AND STANDARDLENGTH OF FISH; FOR FURTHER EXPLANATION SEE TEXT. (FROMBLACKBURN 1950~1).-~ __ -~~ -4.55.05.56.06.57.07.58.08.59.09.510.010.511 .o11.50Ring!1Ring2lings_-__42135343710621_____-__3lings4lings_-___-_-___.1618151513515lings’otd-371747484653272726464037224-it is shown below that the fish are hatched in summer,so they are about 0.5 year old at the first ring, 1.5years at the second, etc.More precise information was obtained by calculatingthe successive intermediate lengths of the fish(Ll, La, etc.) at the times when the successive zonesof crowded striae (first, second, etc.) were completed.Such calculations required knowledge of the relationshipbetween the fish-length and the radius of thescale selected for measurement, which was investigatedempirically as shown in Figure 10. Fish-lengthand scale-radius increase in direct proportion onlyabove a fish-length of 60 mm ; at fish-lengths between35 and 60 mm the scales, which may have one or twocomplete winter zones, grow faster than the fish.The calculations of L1, La. etc., were described by4 50