Abstract

The vertical distribution of fish larvae from the southwest coast of Puerto Rico were described from samples collected during two cruises, Feb/95 and May/96 along three meridional (North-South) transects (67°00'; 67°03; and 67°06 W) running perpendicular to the coastline off La Parguera. The shelf-edge (SE-13) and three offshore positions (OC-17, OC-29 and OC-46) were occupied along each transect, for a total of 12 stations per cruise. These stations were sampled in vertically stratified, step-oblique tows at three discrete depths (surf 0-20, mid 21-40 and deep 41-60 meters) within the surface mixed layer using a 1 m2 Tucker Trawl fitted with three 202 im mesh nets and standard flow meters. Conductivity, temperature, depth, and chlorophyll-a concentrations were measured using a CID profiler with an integrated fluorometer. Water column densityprofiles at the different stations for February and May cruises showed permanent stratification with well developed pycnoclines associated with increasing salinity and a decline of water temperature with depth.\A total of 15, 638 fish larvae representing 82 families were identified during the study. Pre-flexion coral reef fish larvae did not show any statistically significant pattem of abundance in their vertical distribution within the surface mixed layer. Only a few families at post-flexion stage showed statistically significant differences of abundance between depths, or between day and night samplings. While a more comprehensive vertical sampling program based on a larger number of samples may be required to provide definitive conclusions on reef fish vertical distributions for some taxa, some trends were apparent. Abundance of oceanic type larvae, such as myctophids, gonostomatids and photichtyids increased with depth, as well as coral reeffish larvae of the Gobiidae and Scaridae families. Conversely, Clupeifonnes, Pomacentridae, Haemulidae and Holocentridae were more abundant at shallower depths within the surface mixed layer. Lutjanidae were found mostly in mid water. The level of taxonomic analysis (Family) used in the present study may have masked species-specific trends in vertical distribution. Furthermore, patchiness was relatively high, and imposed a large margin of variability in mean abundance at each depth.

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