DAILY GROWTH INCREMENTS IN OTOLITHS FROM 

 LARVAL AND ADULT FISHES 



Edward B. Brothers,^ Christopher P. Mathews,^ and Reuben Lasker^ 



ABSTRACT 



Daily growth increments have been found in otoliths offish larvae. The daily nature of these layers 

 was verified by examining larval fish of known age reared in the laboratory. A simple technique for 

 observing these marks is described and can be used on otoliths from larvae and adults. This provides 

 a convenient method for determining early growth in fishes and is particularly useful for fishes which 

 do not lay down annual or seasonal rings. 



The use of otoliths in age determination (by 

 means of annual marks) is well known. The 

 techniques used have been described by Williams 

 and Bedford (1974) and Blacker (1974). Recently 

 Pannella (1971) has suggested that daily marks 

 may be formed in the sagittae (the otoliths used 

 almost universally in age determinations) of some 

 temperate species, while in 1974 Pannella 

 claimed to have detected them in a number of 

 tropical species. He also studied the temperate 

 species — silver hake, Merluccius bilivoaris; red 

 hake, Urophycis chuss; Atlantic cod, Gadus mor- 

 hua; and winter flounder, Pseudopleuronectes 

 americanus — in greater detail in this latter pa- 

 per. For some of these temperate species, particu- 

 larly for the first, Pannella was able to show that 

 there were fortnightly, monthly, and annual pat- 

 terns. The annual marks detected in the conven- 

 tional way were shown to contain about 365 daily 

 units. Pannella used acetate replicas of ground 

 otoliths which had been previously etched with 

 HCl. Pannella's work appears to justify the fol- 

 lowing conclusions: 



1 . Daily increments^ occur in certain temperate 

 fish, e.g., M. bilinearis. 



2. Periodic variations in increment thickness 

 occur with fortnightly, monthly, and annual 

 frequencies in this species. 



'Scripps Institution of Oceanography, La Jolla, CA 92038; 

 present address: Langmuir Laboratory, Section of Ecology and 

 Systematics, Cornell University, Ithaca, NY 14853. 



^Department of Fisheries, Escuela Superior de Ciencias 

 Marinas, University of Baja California A.P. 453, Ensenada, 

 B.C., Mexico. 



^Southwest Fisheries Center, National Marine Fisheries Ser- 

 vice, NOAA, P.O. Box 271, La Jolla, CA 92038. 



■•The smallest visible concentric layers seen in an otolith. 



3. Structural units that are similar to those 

 shown to be daily in their occurrence in tem- 

 perate species are also found in some 

 tropical species. 



Pannella (1974) was careful to explain that the 

 marks present in otoliths of tropical fish that ap- 

 peared to be annual on the basis of conventional 

 criteria could be deceptive. He suggested that by 

 analogy with temperate species, certain struc- 

 tures found in otoliths of tropical fish were also 

 daily in occurrence. Although he found spawning 

 marks, he did not find any seasonal or winter 

 growth checks in the otoliths of tropical fish. In 

 view of Pannella's expressed skepticism about the 

 formation of annual marks and his tentative con- 

 clusions, further evidence is needed that daily 

 increments occur in tropical fish. Furthermore, no 

 one appears so far to have attempted to apply this 

 method of age determination to larval fish, yet it is 

 in this last area that the most accurate and useful 

 results might be expected. Pannella (1974) com- 

 mented on the great regularity of the presumably 

 daily marks near the center of the otoliths of both 

 tropical and temperate fish. In these portions of 

 the otoliths, no superposition of more complex 

 patterns (e.g., 14 day, 28 day) were found. 



It is the object of this paper to show that 1) true 

 daily increments are found in the otoliths of the 

 larvae of several species, and that daily marks 

 may be used to determine the ages of larval fish 

 with great accuracy and precision, at least for 

 approximately the first 100 days of life; and 2) in 

 adults offish from a variety of habitats, including 

 tropical waters, daily increments may be proven 

 to exist, and so to confirm Pannella's work. 



Manuscript accepted July 1975. 



FISHERY BULLETIN: VOL. 74, NO. 1. 1976. 



