SOUTAR and ISAACS: ABUNDANCE OF PELAGIC FISH 



Table 2. — Derived-age' frequency of Pacific sardine, northern 

 anchovy, and Pacific hake scales in sediment of the Santa Bar- 

 bara and Soledad Basins. 



'The derived age is an estimate of age based on the measurement of scale 

 width. The scale width is a more reliable feature of sedimented scales than 

 is the scale length as, for example, in the case of the sardine the exposed 

 "wing" of the scale is often separated The scale width is converted to an 

 estimate of standard length and the estimate of standard length is con- 

 verted to an age estimate by the growth curve. 



uration of the northern anchovy. Considering 

 that 50% of the anchovy mature in 2 to 3 yr (Clark 

 and Philhps, 1952), then the derived-age fre- 

 quency of the anchovy scales (Table 2) suggests 

 that for Santa Barbara 35% and for Soledad 24% 

 of the contributing anchovy are mature. 



No direct population estimates are available for 

 the Pacific hake; however, larval abundances 

 thought to be proportional to the adult biomass 

 have been provided.^ In view of the estimate that 

 54% or more of the scale information in the sedi- 

 ment is derived from hake less than one year old, a 

 proportional relationship between larval abun- 

 dance and scale deposition might be anticipated. 

 However, this comparison for the inshore region of 

 southern California and southern Baja California 

 from 1950 to 1965 indicates a non-systematic rela- 

 tionship (Table 5). One explanation of the incon- 

 sistency may be that between 1950 and 1965 the 

 inshore larval populations were generally low and 

 had no strong trend. It should also be noted that 

 the inshore and total abundances are in them- 

 selves not entirely consistent, and, in fact, the 

 total larval abundances tend toward an inverse 

 relationship with the scale-deposition rate. 



Information on the spawning population of the 

 Pacific saury for the period 1950 to 1966 has been 

 reported (Smith et al., 1970). Comparison of the 

 spawning biomass and the scale-deposition rate 

 (Table 6) indicates a sparse but sensible relation. 



Egg abundances and catch information for the 

 Pacific mackerel which could reflect the popula- 



tion are available, but the extremely low rate of 

 scale deposition for this species limits an evalua- 

 tion (Table 7). 



The generally consistent relationships between 

 the available estimates of pelagic fish populations 

 and scale deposition provide an entree into the 

 past. Such relationships are perhaps not un- 

 reasonable considering the strategic location of 

 the basins adjacent to major spawning grounds. 

 The short time over which population estimates 

 and scale-deposition rates may be compared in the 

 case of the anchovy, hake, saury, and mackerel is 

 presently a limitation; nevertheless, relative 

 measures of high and low spawning biomass may 

 be made from the sedimentary information. The 

 record for the Pacific sardine, however, should be 

 amenable to direct interpretation in terms of 

 year-class size and projected biomass, with the 

 exception perhaps of those times when scale dep- 

 osition far exceeds our experience. 



Consideration of the scale record (Figure 5) as a 

 population record affords a fascinating look into 

 the flow of ocean life at the higher trophic level. 

 The historical decline of the sardine, seen in per- 

 spective, appears as a subdued finale to a move- 

 ment that had begun in 1890, thirty years before 

 the inception of the fishery, and this movement in 

 turn belongs to a theme extending into the mil- 

 lennia (Soutar and Isaacs, 1969). Levels of year- 

 class success in excess of 10^° fish occurring in the 

 late 1930's, which are historically considered im- 

 pressive, appear in broader context to be at most 

 moderate. Even higher levels of success suggested 

 by the sedimentary record between 1855 and 1865 

 afforded insufficient reserve against a precipitous 

 and natural decline. Nor can the virtual absence of 

 the sardine from the waters off Alta California be 



Table 3. — Comparison of Pacific sardine population (Murphy, 

 1966) and scale-deposition rate in the Santa Barbara Basin 

 sediment.' 



^Smith, P.E. CalCOFI— the first twenty-five years. Unpubl. 

 manuscr. 



'The Spearman rank-correlation coefficient between the 2-yr and older 

 biomass and the scale-deposition rate is 0.81 , n = 6; and for the 2-yr-old 

 year class and the scale-deposition rate Is 0.99, n = 6. While these are 

 highly suggestive of a significant relationship, no probabilities are as- 

 signed due to inherent autocorrelation in these series. 

 ^Incomplete data. 



263 



