A light trap design for stratum-specific sampling of reef fish larvae

The vertical distribution of late stage reef fish larvae may potentially influence their dispersal, recruitment success and energetic expenditure during the recruitment process. To date, methods of examining the vertical distribution of reef fish larvae either under-sample late stage individuals, or are incapable of discretely sampling the water column. The aim of this study was to develop a light trap able to sample a narrow depth range enabling fine scale patterns of vertical distribution to be examined. The experimental traps radiated light in a relatively narrow beam with a maximum vertical angle of radiation of 7.5°, indicating that the traps could be placed 4.8 m apart and still sample discrete depth strata. Their catch efficiency was similar to conventional light traps, indicating that they are adequate sampling units. Preliminary data showed that most families are more abundant near the surface, although many have significant numbers of individuals lower in the water column. Some families (inc. Apogonidae) occurred in higher abundance at greater depths. Our experimental light traps permit increased resolution of the vertical distribution of late stage larval reef fishes in the field.