Aspects of the biology of the butterfish, coridodax pullus (Forster)

Abstract

Odax vittatus Richardson, 1843 is synonymized with Coridodax pullus (Forster, 1801). C. pullus, the butterfish, is described and its meristic variation in fin rays, scale rows and vertebrae is shown to have significant negative correlation with sea surface temperature. Seasonal changes in gut depot fat, gut weight as a percentage of the body weight and the length/weight relationship are outlined and interpreted along with the gonad cycle as part of the reproductive cycle. Total fecundity, relative fecundity and numbers of ova released at each spawning are estimated. Butterfish ova were artificially fertilized, reared under different conditions and a photographic record of development from the first cleavage to the two week old post-larva was made. Changes in the length/weight relationship with age and sex were investigated and attempts were made to elucidate age and growth by means of scale reading. Finally, feeding of the butterfish, a herbivore, and effects of infestation by the parasites Codonophilus lineatus (?) Miers (Isopoda) and Caligus brevis Shiino (Copepoda) are discussed.