Abstract
Characteristics of the life history of the coral reef‐dwelling cardinalfish Siphamia tubifer , from Okinawa, Japan, were defined. A paternal mouthbrooder, S. tubifer , is unusual in forming a bioluminescent symbiosis with Photobacterium mandapamensis . The examined S. tubifer ( n = 1273) ranged in size from 9·5 to 43·5 mm standard length ( L S ), and the minimum size at sexual maturity was 22 mm L S . The number of S. tubifer associated during the day among the spines of host urchins was 22·9 ± 16·1 (mean ± s.d .; Diadema setosum ) and 3·6 ± 3·2 ( Echinothrix calamaris ). Diet consisted primarily of crustacean zooplankton. Batch fecundity (number of eggs; F B ) was related to L S by the equations: males (fertilized eggs) F B = 27·5 L S − 189·46; females (eggs) F B = 31·3 L S − 392·63. Individual mass ( M ; g) as a function of L S was described by the equation: . Growth, determined from otolith microstructure analysis, was described with the von Bertalanffy growth function with the following coefficients: L ∞ = 40·8 mm L S , K = 0·026 day −1 and t 0 = 23·25 days. Planktonic larval duration was estimated to be 30 days. The age of the oldest examined individual was 240 days. The light organ of S. tubifer , which harbours the symbiotic population of P. mandapamensis , increased linearly in diameter as S. tubifer L S increased, and the bacterial population increased logarithmically with S. tubifer L S . These characteristics indicate that once settled, S. tubifer grows quickly, reproduces early and typically survives much less than 1 year in Okinawa. These characteristics are generally similar to other small reef fishes but they indicate that S. tubifer experiences higher mortality.