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

THE ACCUMULATION OF FISH DEBRIS IN CERTAINCALlFORMlA COASTAL SEDIMENTSANDREW SOUTARScripps Institution of OceanographyLa Jolla, CaliforniaThe fact that the remains of fish, such as scales andbones, are found in coastal marine sediments should,perhaps, not come as a surprise. Well preserved fishremains have been found in California marine sedimentaryformations from Upper Cretaceous throughPliocene times. Furthermore, scales and bones of variousspecies were reported in the surf ace sedimentsof the Catalina Channel by David (1947).This paper presents some of the results of an initialattempt to study the distribution of fish remainsat depth in the sediment. The discussion is limited tocertain aspects of the distribution of fish scales. Themain purpose of the paper is to point out the existenceof material which could allow the introduction of arelatively long-time perspective into the character ofthe fisheries and oceanographic conditions off California.The sediments used in the study were collectedfrom the Santa Barbara Basin, off Santa Barbara,California. The basin has an oval configuration withthe long axis parallel to shore. The sill depth is 475meters and the area encompassed below sill depth is600 km2. The oxygen concentration at sill depth isabout 0.4 ml/l. The oxygen concentration in thenear-bottom water falls to 0.0 ml/l in the middle ofthe basin at 580 meters, (Emery, 1960). The floor ofthis basin is an exception to usual basin floors. Herebottom-living animals and their sediment mixing effectshave been consistently excluded by the virtualabsence of oxygen in the bottom water. This anoxicwater forms from the consumption of dissolved oxygenin the bacterial decomposition of organic matter, andthe restriction of vertical circulation in the bottomwaters. Thus sediments falling to the floor of thebasin accumulate undisturbed and in serial order.There is evidence of occasional disturbance, but it isestimated that this amounts to a few percent of thetotal length. There are, however, slump or turbiditelayers which constitute about ten percent of the corelength. These are easily recognized by a marked colorcontrast at various levels in the cores.Undisturbed sediments such as these provide an excellentframework for the study of ocean history. Theabsence of mechanical disruption allows the preservationof delicate organic remains such as the fish scalesseen in Figure 1. The absence of mechanical disruptionalso preserves lithologic patterns. Major lithologicpatterns, if they exist, allow physical correlationbetween adjacent cores. In addition if annual variationsexist in the supply of certain components ofa. b. C.FIGURE 1.Representative fish scales found in the Santa Barbara Basin sediments.a. Pacifi: hake, 72 centimeters below surface.b. Pacific sardine, 89 centimeters below surface.c. Northern anchovy, 79 centimeters below surface.( 1% 1