Larval durations and recruitment patterns of two Caribbean gobies (Gobiidae): contrasting early life histories in demersal spawners

Two demersally-spawning fishes were selected to examine the relationship between adult spawning strategies and the early life histories of larvae and juveniles. Although the Caribbean gobies, Coryphopterus glaucofraenum Gill and Gnatholepis thompsoni Jordan are common, co-occurring constituents of nearshore coral reefs, relatively little is known about the early life history and recruitment of their pelagic larvae to the reef environment. To examine patterns of recruitment, recently settled juveniles (7.5 to 16 mm standard length, SL) were censused and collected biweekly from reefs of Barbados, West Indies, during the spring recruitment peak for 3 yr (March to June 1990 to 1992). Otolith analyses were used to determine larval durations and to back-calculate settlement patterns and spawning dates. G. thompsoni spent more than twice as long in the plankton (60 d) than did C. glaucofraenum (27 d). Variation in larval duration of G. thompsoni [coefficient of variation (CV) = 22.4%; durations up to 112 d] was significantly greater than that of C. glaucofraenum (CV=9.4%), which suggests that G. thompsoni has a greater capacity for delaying settlement and metamorphosis. Estimated size at settlement for G. thompsoni (SL = 8.4 mm) was significantly larger than for C. glaucofraenum (SL = 6.4 mm), but post-settlement growth rates were virtually identical (0.21 to 0.22 mm d-a). Settlement of both gobies occurred predominantly around the third quarter moon (ca. Day 21 to 22), but there was much greater spread in the settlement of C. glaucofraenum. Back-calculated spawning frequency for C. glaucofraenum was not closely linked to the lunar cycle, whereas spawning of G. thompsoni occurred more frequently during the third quarter moon. These observations demonstrate that two confamilial demersal spawners may have larvae with contrasting life history traits which can influence patterns of juveCommunicated by J. R Grassle, New Brunswick S. Sponaugle ([]) 9 R. K. Cowen Marine Sciences Research Center, State University of New York, Stony Brook, New York 11794-5000, USA nile recruitment. A secondary peak in larval duration of G. thompsoni approximately 1 mo after the major mode (Day 87) suggests that if settlement does not occur two lunar cycles after hatching, G. thompsoni larvae may delay settlement until the following third quarter moon. This coupling suggests that settlement during a particular lunar phase may be advantageous for new recruits, and the capacity to delay metamorphosis may enable tighter synchronization to the lunar cycle.