SAMPLING LARVAL FISHES WITH A NIGHTLIGHT LIFT-NET IN TROPICAL INSHOREWATERS

The applicability of a nightlight lift-net for sampling ichthyoplankto n assemblages was evaluated in inshore habitats off southwestern Puert o Rico. The effects of lunar periodicity, habitat, light duration, and gear type (nightlight vs. plankton tow) were investigated. Overall, 3 6 piscine taxa were collected with the nightlight lift-net from inshor e habitats (i.e. coral reef, mangroves, seagrass bed, sand flat). Larv al fishes (80.6%), particularly clupeids (Jenkinsia spp. and Harengula spp,), were the predominant developmental stage collected. Juvenile a nd adult fishes accounted for 14.7% and 4.7% of the catch, respectivel y. Nightlight collections showed marked patterns in larval fish abunda nce during different lunar phases with peak catchability occurring dur ing the new moon phase. New moon samples accounted for 65.7% of all la rvae collected during the complete lunar cycle. Significant lunar effe cts were observed in coral reef, seagrass bed, and sand flat habitats. No lunar related trends were observed in mangrove cay or nearshore ma ngrove habitats. Spatial patterns in nightlight catches were present w ith many taxa showing significant differences in abundance among habit ats sampled. During lunar periodicity trials, catches were highest in the seagrass bed and coral reef habitats. Taxonomic diversity was grea test in seagrass bed and coral reef habitats with 16 and 11 taxa, resp ectively. Low abundance and taxonomic diversity characterized mangrove cay and nearshore mangrove habitats; however, increases in taxonomic diversity were observed during a fall survey of nearshore mangrove hab itats. Light duration experiments indicated that larval abundance incr eased with increasing sampling duration and maximum catch per unit tim e was obtained at 10 min. Longer and shorter durations resulted in low er catch per unit effort and greater coefficients of variation. Trends in species composition and development stage were detected among nigh tlight lift-net and plankton net-tow methods.