Temporal Coupling of Production and Recruitment of Larvae of a Caribbean Reef Fish

Abstract

Variation in larval recruitment is thought to have profound effects on the structure of coral reef fish communities, and planktonic processes often are cited as the major factor controlling the temporal and spatial patterns of such recruitment. We looked at the relationship between temporal patterns of larval production and settlement of planktonic larvae of the Caribbean damselfish Stegastes partitus at one site and attributed any differences to processes acting in the plankton. In doing so we assumed that the pattern of production we observed was representative of the regime that produced fish that settled in the study area. We monitored spawning and larval recruitment continuously for 3 yr. Both spawning and settlement followed (unimodal) lunar cycles, and both activities spanned °3 wk of the lunar month. Although the form of the average settlement cycle matched that of the average production cycle, monthly settlement episodes were shorter and (slightly) more variably timed than equivalent production episodes. Although monthly variability in the magnitude of settlement was fourfold greater than corresponding variability in the magnitude of larval production, monthly settlement success did not vary in an extreme manner. There was no significant correlation between the magnitude of larval production in a month and of settlement the following month. Daily growth increments in the otoliths of settlers indicated that (1) larvae were °5 wk old at settlement, (2) there was low overall variability in age at settlement, (3) there were no differences between the ages of settlers arriving early and late in the monthly settlement period, and (4) age variability among settlers collected on the same day was not different from that among settlers collected on different days. Hence, the basic lunar periodicity of settlement is determined by the periodicity of production of relatively fixed—age settlers. Planktonic processes enhance the temporal variability of settlement, principally by affecting the magnitude of settlement events, but also by influencing the duration and precise timing of monthly settlement episodes. Planktonic processes also determine that most of a month's successful settlers arrive (and are produced) over a few consecutive days and mix cohorts of larvae that are produced on different days. We conclude that the timing and magnitude of settlement are strongly influenced by both production and planktonic processes, and the latter only partly decouple settlement and production.