RECRUITMENT, GROWTH, MORTALITY AND ORIENTATION PATTERNS OF BALANUS-TRIGONUS (CRUSTACEA, CIRRIPEDIA) DURING SUCCESSION ON FOULING PLATES

Succession studies on artificial substrates in the Bay of Santa Marta, Colombian Caribbean showed Balanus trigonus (Darwin) as one of the mo re prominent members of the fouling community. This fact prompted the interest for a closer examination of its biology. Four aspects were to uched upon: recruitment, growth and mortality rates, and orientation w ith respect to the horizon line. Two hypotheses were tested. First, th at orientation of individuals was random within the orientation range observed during succession, and second, that there was no relationship between orientation and age of the individuals. Larvae settling was f ound to occur throughout the year but with a well delimited peak in th e dry season (January to April). The availability of competent larvae is reflected in the abundance of the species during succession. Growth and mortality proceed rapidly. Maximal growth (6.2 mm average carino- rostral distance) is reached in 20 weeks after settlement. Mortality i s substantial: 50% of recruits, on average, died after 3-4 weeks from settlement. Orientation at settlement was found to be not random: for instance, 64% of individuals orientated between 0 degrees-60 degrees f rom the horizon. With age the orientation patterns at settlement chang ed statistically. Biological and ecological implications of these find ings are discussed and comparisons made with other studies. It is conc luded that Balanus trigonus could act as a model species for latitudin al comparisons in view of its wide distribution, adaptability and sess ile habit.