Johannes (1978) emphasizes avoiding predation and invokes data (largely 

 anecdotal) to suggest that eggs are cast into local current gyres that often 

 return to the same island or, at least, to the same general locality and not 

 necessarily to far distant shores. There were some data to suggest that this 

 was so when Johannes (1978) postulated the role of local currents in recolonization 

 (Jones, 1968; Sale, 1970; Watson and Leis, 1974; Lobel and Reaka, 1977; and 

 since then Leis, 1982). More convincing data have now been provided by Lobel 

 and Robinson (1983) that current gyres do develop off the big island of Hawaii 

 twice each year and, importantly, coincide with the two major seasonal spawning 

 peaks for many of the coral reef fishes in Hawaii (Jones, 1968; Sale, 1970). 

 Lobel and Robinson, using radio-tracked drogues, found circulation times of 7- 

 14 days (offshore and return inshore) and evidence for at least two cycles. 

 Thus, there would be time for eggs and larvae to develop to a sufficient size 

 to settle onto the reef after initially being advected away from the reef. 

 However, it should be emphasized that in multiple releases of drogues, some 

 returned close to the inshore release site, but others drifted off and even 

 headed toward the island of Molokai. Furthermore, as Barlow (1981) emphasizes, 

 even if major seasonal spawnings at Hawaii do coincide with the weakest offshore 

 currents and the presence of local gyres (Watson and Leis, 1974) which might 

 favor recolonization, spawning nevertheless continues in many species at other 

 times of the year when currents would not favor recolonization, but rather long- 

 range dispersal . 



Duration of Larval Life 



Certainly if long-range dispersal is to be invoked, as for example Barlow 

 (1981) suggests occurs for those coral reef species that have managed to cross 

 the Indo-Pacific barrier (see Rosenblatt and Walker, 1963), then the length of 

 larval life must be long. An alternative tactic for long-range dispersal would 

 invoke rafting of juveniles or adults, a requirement if the larval phase is of 

 short duration (< 20-30 days). How long, then, are larvae advected at sea? 



By comparing spawning dates with recruitment dates, larval duration has 

 been estimated to vary among coral reef species from a week to several months 

 (Randall, 1961; Moran and Sale, 1977; Johannes, 1980). Over the last few years, 

 the otolith daily aging technique has allowed direct estimation of the age of 

 individual larvae (Brothers and McFarland, 1981). The results to date indicate 

 that larval duration does vary from weeks to months in different species 

 (Ralston, 1976; Brothers, et al . , 1983; Victor, 1983a_; and Brothers and Thresher, 

 1985). The duration within a species is often variable, as it is in marine 

 invertebrates (Scheltema, 1968, 1971), but some species have very restricted 

 lengths of larval life, the cause of which is unknown (Brothers and McFarland, 

 1981). For the 115 species of Pacific coral reef fishes studied, Brothers and 

 Thresher (1985) obtained otolith ages for settlement (the so-called settlement 

 check mark; see Brothers and McFarland, 1981; Brothers, et al . , 1983; Victor, 

 1983b_) that range from 15 to 82 days. In some labrids, it can be a week (Victor, 

 1983b), and in grunts settlement always occurs at about 15 days (McFarland, 

 1982J. These pelagic periods favor only short-range dispersal. But, some 

 labrids can have larval durations up to 50 days (Brothers, et al . , 1983), which 

 would allow for long-range dispersal. 



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