|Feeding habits of larval and juvenile skipjack tuna|
Aoki, M. (1999). Feeding habits of larval and juvenile skipjack tuna. Bull. Inst. Oceanic Res. & Develop., Tokai Univ. 20: 173-185
In: Bulletin of Institute of Oceanic Research and Development. Tokai University. Tokai University. Institute of Oceanic Research and Development: Shimizu. ISSN 0289-680X, more
We conducted this study of the feeding habits of juvenile skipjack tuna, Katsuwonus pelamis, based on 456 specimens obtained from the stomachs of adult fish caught by pole and lines in the waters of Mariana and Caroline Islands from the years 1965 ~ 1985.We noted that the relative growth of feeding and digestive organs (mouth width, length of stomach, intestine, rectum and pyloric ceaca, etc.) compared to body length changed markedly from the postlarval stage to juvenile stage. The allometry of the filtering area (F) to body length (BL) in the juvenile stage was expressed as F = 3.047BL - 4.569.The composition of stomach contents of juveniles skipjack consisted of 62% fish larvae, 36% crustaceans and 2% cephalopods in number, and also 90%, 4% and 6% in weight, showing the dominancy o fish larvae as prey. Copepods are also recognized to be important food items for smaller juveniles (20 ~ 60mm in length) of this species.Base on the relationships between opened mouth width, gill-raker gap, prey width and body length, juvenile skipjack was found to show a tendency for a marked increase in the range of prey sizes with growth. A feeding strategy such as this seems to benefit the rapid growth of juvenile skipjack tuna.