Lunar and seasonal patterns in fecundity of an indeterminate, multiple-spawning surgeonfish, the yellow tang Zebrasoma flavescens
Reproduction was investigated in relation to lunar and annual cycles in a population of yellow tang Zebrasoma flavescens, a popular aquarium species commercially harvested in Hawaii. Lunar periodicity was determined to be an inherent characteristic of reproduction; peaks in mean daily egg production, female gonado-somatic index (IG) and the fraction of females with eggs were observed at the full moon of each sampled month. An increase in the fraction of late-stage vitellogenic oocytes within the ovaries was also observed at the full moon. Reproductive effort peaked in the late spring and summer as indicated by high values of mean daily egg production, female IG and the recorded incidence of females spawning for at least two consecutive days. Mean daily egg production and IG of monthly samples were lowest in November to February, although some level of egg production continued throughout the year. Large individual variation in batch fecundity was observed, with a range from 44 to > 24 000 eggs per female produced on a single sampling date. Smaller females, 80–120 mm standard length (LS), produced limited numbers of eggs, while females ≥ 120 mm LS were capable of maximal egg production (> 20 000 eggs per batch). In contrast to trends observed in many fish species, no significant relationship between batch fecundity and adult LS > 120 mm was observed in female Z. flavescens. An estimate of annual fecundity (mean ±s.e. 1 055 628 ± 120 596 eggs) was also generated using a simple model of the lunar variability in egg production. This study illustrates the importance of accounting for potential variation in egg production over time, especially with respect to diel and lunar cycles, in the design of reproductive studies of multiple-spawning fishes. Greater insight into the environmental factors that regulate reproductive activity may be gained by determining the relative reproductive investment allocated at each spawning event. The ability to estimate annual fecundity for more multiple-spawning species will facilitate examination of the effects of fishing on the reproductive characteristics of these populations and permit examination of life-history evolution across a broader suite of fishes.
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annual and batch fecundity;
Document Type: Regular Paper
Hawaii Cooperative Fishery Research Unit, University of Hawaii, 2538 The Mall, Edmondson 165A, Honolulu, HI 96822, U.S.A.
Finfish Department, Oceanic Institute, Makapuu Point, 41-202 Kalanianaole Highway, Waimanalo, HI 96795, U.S.A.
Publication date: 2010-04-01