POSTLARVAL AND JUVENILE SCOMBRIDS CAPTURED IN LIGHT TRAPS - PRELIMINARY-RESULTS FROM THE CENTRAL GREAT-BARRIER-REEF LAGOON

Light traps were used to catch post-larval and juvenile scombrids from the coastal waters of the central Great Barrier Reef. A total of 200 scombrid larvae and juveniles, representing at least six taxa, were ca ught during sampling periods October to January, 1988-1990. The indivi duals captured in the light traps provided unique specimens of small S comberomorus, Cybiosarda elegans, Euthynnus affinis and Thunnus specie s from this area. Comparison of size-frequencies showed that light tra ps collected larger individuals than did a standard trawl net. A multi -gear sampling strategy, utilizing both towed nets and light traps, wo uld provide a more complete description of the distribution and abunda nce patterns of small scombrids than either technique in isolation. Sc ombrid abundances were highly variable, with a maximum catch of 13 fis h in a single trap in an hour. A single station on a single night acco unted for almost 50% of the scombrids captured in 1988. This patch, wh ich consisted of Scomberomorus and Thunnus species, was coherent over at least 1 km. All scombrid species were relatively abundant at statio ns 16-24 km from the coast. This corresponded to the position of a coa stal boundary layer in the area-the significance of this boundary laye r to the distributions of small scombrids is not yet known. Light trap s, which can simultaneously sample large volumes of water over a range of spatial scales, may prove a cost-effective and efficient way of sa mpling post-larval and juvenile scombrids.